Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
METHOD AND APPARATUS FOR ADJUSTING PRESS
OPERATING CONDITIONS DEPENDING UPON DIES USED
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates in general to a
pressing machine, and more particularly to a method and an
apparatus for adjusting the operating conditions of a press
on the basis of information of the machine and the dies
used.
Discussion of the Prior Art
There has been widely used a press wherein a
pressing operation such as a drawing operation is effected
such that upper and lower dies removably installed on the
machine are moved towards and away from each other. On some
pressing machines of this type, the operating conditions may
be changed or adjusted depending upon the specific. set of
dies used. In a single-action press constructed as shown in
Figs. 1 and 2, for example, a drawing operation on a
workpiece or blank in the form of a metal strip or sheet is
performed by an upper die 18 and a lower punch 12 while the
blank is held by means of a pressure ring 30 in cooperation
with the upper die 18. In this type of press, pressure
control valves 46 and 84, a servomotor 60 and other
components are provided to adjust the operating conditions
such as the pneumatic pressures Pa and Pb of pneumatic
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cushioning cylinder 42 and counterbalancing cylinder 80, and
distance h associated with a die-height adjusting mechanism
52. The pressure Pa of the cushioning cylinder 42 influences
the holding force to be applied to the pressure ring 30, and
the distance h influences the pressing force to be applied
to the blank.
In a double-action press as shown in Figs. 12-14,
the holding force is applied to the blank through a pressure
ring 156 attached to an outer slide 160, and the pressing
force is applied to the blank through a punch 162 fixed to
an inner slide 164 and a lower die 152 disposed on a bolster
154. In this double-action press, too, the operating
conditions such as a pneumatic pressure Pe of a cylinder 184
which influences the holding force must be suitably adjusted
so as to avoid the cracking and wrinkling of a product
formed from the blank. The operating conditions to be
adjusted also include a distance ha associated with a
die-height adjusting mechanism 172.
The holding force and the pressing force which
assure an adequate pressing operation without cracking
and/or wrinkling of the products obtained differ depending
upon the specific machine and the specific die set used on
the machine. More specifically, the weights of the upper die
18, 162 and the pressure ring 30, 156 which cooperate with
the lower die 12, 152 to constitute a die set vary from one
die set to another. Therefore, it is necessary to suitably
adjust the pressure Pa, Pe and the distance h, ha, for
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example, depending upon the specific die set. Further, the
pressure-receiving areas of the cylinders 42, 184, and the
sliding resistance and rigidity values of the machine
components differ from one machine to another. Therefore,
the operating conditions such as the optimum pressure Pa, Pe
and distance h, ha for assuring an adequate pressing
operation are generally determined or established by a
trial-and-error procedure, namely, by performing test
operations on the press to be used for production.
If the optimum pneumatic pressure Pa, Pe and
distance h, ha for example are determined beforehand for
different die sets during test operations on trial or test
presses used for testing the individual die sets, the
above-indicated trial-and-error procedure on the production
press can be eliminated. As indicated above, however, the
individual production presses have different operating
characteristics, such as different pressure receiving areas
of the cushioning cylinder 42, and different sliding
resistance and 'rigidity values of the various components.
Thus, the adjustment of the operating conditions according
to the known or predetermined optimum values is not
practically satisfactory for the individual pressing
machines in general.
Further, the adjustment of the operating
conditions according to the predetermined optimum values is
likely to cause cracking and/or wrinkling of the product
obtained by a pressing operation. This drawback is
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considered to arise from factors which relate to the
properties of the blank such as elongation and surface
roughness, and an amount of a lubricating oil deposited on
the surface of the blank. Namely, even if the pressing
operation is performed with the same blank holding force,
the sliding resistance between the blank and the dies may
fluctuate due to different properties of the individual
blanks, which lead to different tensile forces acting on the
different blanks during a drawing operation, for example.
Although the material and thickness of the blank are taken
into account when the optimum holding force is determined
for each die set, the chemical composition and the thickness
of the blank in the form of a metal strip prepared by
rolling generally vary within certain ranges of tolerances.
Further, a variation in the amount of deposition of the
lubricating oil on the surface of the blanks is inevitable.
Thus, there exist various fluctuating factors relating to
the manufacturing process of the blanks, which cause
different physical properties of the blanks.
The above analysis may suggest a necessity of
determining the optimum pneumatic pressure Pa of the
cushioning pneumatic cylinder 42, for example, by a
trial-and-error procedure. In this respect, the relationship
between the optimum pressure Pa and the optimum holding
force on one machine is usually different from that on
another machine. This means, the same amount of adjustment
of the pneumatic pressure Pa is not necessarily adequate or
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sufficient to remove the same degree of cracking or
wrinkling of the product. Accordingly, the adjustment is
troublesome and time-consuming even for an experienced or
skilled user or operator of the pressing machine. This is
particularly so, on the double-action press in which the two
or more cylinders 184 are used to adjust the blank holding
force.
As described above, the known pressing machines
require cumbersome and time-consuming trial-and-error
procedure and a high level of skill for adjusting the
operating conditions such as the pneumatic pressure Pa
depending upon the specific die set, and are not capable of
producing desired articles of manufacture with highly
consistent quality.
A further study of the pressing operations on the
pressing machines as described above suggests a problem that
the blanks or products formed from the blanks are likely to
easily crack or suffer from similar defects after a
relatively Long continuous pressing job in which a given
pressing cycle is repeated on a large number of blanks which
are successively loaded on the machine. This problem is
considered to occur due to a rise in the temperature of the
die set by heat generated due to sliding resistance of the
blank which is moved between and in contact with the lower
and upper dies in the process of a pressing operation such
as a drawing operation. The temperature of the die set rises
as the number of the pressing cycles performed increases. As
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the temperature of the die set rises, the property of the
oil lubricating the die set, characteristics of the die set
and the friction characteristics of the blanks tend to vary,
while the volatility of the lubricating oil increases.
Consequently, the sliding resistance of the blanks with
respect to the die set increases, causing an increase in the
tensile force acting on the blanks during the drawing
operation, and leading to easy occurrence of cracking or
other defects of the formed products. The increase in the
sliding resistance also accelerates the wearing of the die
set, and shortens the life of the die set.
An analysis of the relationship between a sliding
resistance of a blank or workpiece and the amount of heat
generated by the sliding resistance indicates that an amount
of heat Qo generated by a grinding operation is expressed by
the following equation (a):
Qo = Ft~(Va~Vb)~T ................. (a)
where, Ft: tangential grinding resistance
z: grinding time
Va: peripheral speed of a grinding wheel
Vb: speed of movement of a workpiece to be
ground
In view of the above, the tangential sliding
resistance in the case of a drawing operation performed on a
blank on a press can be expressed as (u + r)~F(t), where
represents a sliding resistance determined by the surface
roughness of the die set and the blank and the lubricating
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condition, and r represents a resistance to a bend-back
action of the blank due to a bead in the blank holding
portion (pressure ring) of the die set, while f(t)
represents a surface pressure of the blank holding portion.
Hence, an amount of heat Qs generated in the blank holding
portion is expressed by the following equation (b):
Qs = (u + r)~f(t)~W~w ............. (b)
where, W: amount of tangential movement of the blank
w: width of the blank
W = a(u + r)~If(t)dt ............... (c)
Therefore, the amount of heat Qs generated by the
sliding resistance of the blank with respect to the die set
is expressed by the following equation (d):
Qs = (u + r)2~f(t)~If(t)dt~w ........... (d)
On the other hand, the tensile force Te acting on
the blank during the drawing operation is expressed by the
following equation (e):
Te (u + r)~f(t) ................... (e)
The above equation (e) indicates that the tensile
force Te increases with an increase in the sliding
resistance a due to the temperature rise of the die set and
the change in the lubricating condition of the blank, even
if the surface pressure f(t) is held constant. Thus, the
product formed from the blank tends to crack as the
temperature of the die rises. It will be apparent from the
above equation (d) that the amount of heat Qs also increases
with an increase in the sliding resistance u. Accordingly,
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There exists a vicious circle in which the temperature of
the die set further rises, which in turn causes a further
increase in the sliding resistance
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to
provide a method and apparatus for automatically adjusting a
holding force to be applied to blanks during a pressing job
on a pressing machine.
In accordance with an aspect of the present invention,
there is provided a method for automatically adjusting a
holding force to be applied to blanks during a pressing job
on a pressing machine. The holding force is produced by a
fluid-actuated cylinder. The method comprises the steps of
counting the number of pressing cycles which have been
performed on successive blanks; and adjusting a fluid
pressure of the fluid-actuated cylinder to adjust the
holding force such that the fluid pressure which determines
the holding force decreases with an increase in the counted
number of the pressing cycles which have been performed on
successive blanks during the pressing job.
In accordance with another aspect of the present
invention, there is provided an apparatus for automatically
adjusting a holding force to be applied to blanks during a
pressing job on a pressing machine. The holding force is
produced by a fluid-actuated cylinder. The apparatus
comprises adjusting means for adjusting a fluid pressure of
the fluid-actuated cylinder to adjust the holding force;
counting means for counting the number of pressing cycles
which have been performed on successive blanks during the
pressing job; and control means for controlling the
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adjusting means so that the fluid pressure which determines
the holding pressure and which is adjusted by the adjusting
means decreases with an increase in the number of pressing
cycles counted by the counting means.
In accordance with another aspect of the present
invention, there is provided a method of automatically
adjusting a holding force to be applied to blanks during a
pressing job on a pressing machine which has a die set
including a lower and an upper die and a pressure ring , and
a fluid-actuated cylinder to produce the holding force. The
method comprises the steps of determining a temperature of a
blank holding portion of the die set; and adjusting the
fluid pressure so that the fluid pressure which determines
the holding force decreases with an increase in the
determined temperature of the blank holding portion.
In accordance with another aspect of the present
invention, there is also provided an apparatus for
automatically adjusting a holding force to be applied to
blanks during a pressing job on a pressing machine which has
a die set including a lower and an upper die and a pressure
ring, and a fluid-actuated cylinder to produce the holding
force. The apparatus comprises temperature determining
means for determining a temperature of a blank holding
portion of the die set; adjusting means for adjusting the
fluid pressure which determines the holding force; and
control means for controlling the adjusting means so that
the fluid pressure which determines the holding force and
which is adjusted by the adjusting means decreases with an
increase in the temperature of the blank holding portion
determined by the temperature determining means.
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BRIEF DESCRIPTION OF THE DRAWINGS
The above and optional objects, features and advantages
of this invention will become more apparent by reading the
following detailed description of presently preferred
embodiments of the invention, when considered in connection
with the accompanying drawings, in which:
Fig. 1 is a schematic elevational view partly in cross
section of an example of a single-action press whose
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operating conditions may be automatically adjusted by an
apparatus according to the principle of the present
invention;
Fig. 2 is a schematic view showing a die-height
adjusting mechanism, a counterbalancing pneumatic cylinder,
and the related components of the press of Fig. 1;
Fig. 3 is a block diagram indicating a control
system for the press of Fig. 1, which is used according to a
first embodiment of the present invention;
Fig. 4 is a block diagram for explaining the
functions of a controller of the control system of Fig. 3;
Fig. 5 is a block diagram for explaining the
functions of an ID card attached to a punch 12 installed on
the press of Fig. 1;
Fig. 6 is a schematic view of the press of Fig. 1
as equipped with an apparatus for measuring the holding
force expected to act on the pressure ring, which holding
force is used to obtain information on the press;
Fig. 7 is a graph showing an example of a waveform
of the load detected by strain gages 116 used in the
measuring apparatus of Fig. 6;
Fig. 8 is a graph indicating a relationship
between the holding force Fsi detected by the measuring
apparatus of Fig. 6 and a pneumatic pressure Pa;
Fig. 9 is a graph indicating a pressing force Fpi
of the press and a distance h as indicated in Fig. 2;
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Fig. 10 is a flow chart illustrating details of
the functional block 146 of Fig. 4 for adjusting the
distance h;
Fig. 11 is a flow chart illustrating an operation
performed in step R2 of the flow chart of Fig. 10;
Fig. 12 is an elevational view showing an example
of a double-action press whose operation conditions are
automatically adjusted according to a second embodiment of
this invention;
Fig. 13 is a schematic view showing a die-height
adjusting mechanism, a counterbalancing pneumatic cylinder
and the related components associated with an outer slide of
the press of Fig. 12;
Fig. 14 is a schematic view showing a die-height
adjusting mechanism, a counterbalancing pneumatic cylinder
and the related components associated with an inner slide of
the press of Fig. 12;
Figs. 15A and 15B are block diagrams illustrating
a control system for the press of Fig. 12 according to the
second embodiment of the invention;
Fig. 16 is a block diagram for explaining the
functions of a controller of the control system of Fig. 15A;
Fig. 17 is a block diagram for explaining Lne
functions of an exclusive controller of the control system
of Fig. 15B;
Fig. 18 is a front elevational view of a control
console provided in the control system of Figs. 15A and 15B;
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Fig. 19 is a left-hand side elevational view of
the control console of Fig. 18;
Fig. 20 is graph indicating a relationship between
the holding force Fsi and the distance ha on the press of
Fig. 12;
Fig. 21 is a graph for explaining a manner of
determining the distance hax on the basis of the
relationship of Fig. 20;
Fig. 22 is an elevational view in cross section
showing the measuring apparatus of Fig. 6 as incorporated in
the double-action press of Fig. 12;
Figs. 23A and 23B are views showing an operator's
control panel used in a third embodiment of this invention;
Fig. 24 is a flow chart illustrating an operation
to adjust the hydraulic pressure Ps on the press equipped
with the operator's control panel of Figs. 23A and 23B;
Figs. 25A and 25B are flow charts illustrating an
operation performed in step S4 of the flow chart of Fig. 24;
Fig. 26 is a graph for explaining the position of
the main slide of the press at which the generated hydraulic
pressure PXn read in step S4-7 of the flow chart of Fig. 25
is detected;
Fig. 27 is a graph indicating an example of the
generated hydraulic pressure PXn detected for adjusting the
optimum initial pressure PO according to the flow charts of
Figs. 25A and 25B, in relation to the provisional initial
hydraulic pressure Pn;
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Fig. 28 is a flow chart illustrating an operation
to write and read data on or from the ID card, using the
display panel of Figs. 23A and 23B;
Figs. 29-31 are views showing an operator's
control panel used in a fourth embodiment of this invention;
Figs. 32-35 are flow charts illustrating an
operation for effecting adjustment of the distance h on the
press equipped with the operator's control panel of Figs.
29-31;
Fig. 36 is a graph for explaining a relationship
between the travel of the cushion pins and the pressing
force Fp, when the distance h is adjusted according to the
flow charts of Figs. 32-35;
Figs. 37 and 38 are flow charts illustrating an
operation to re-establish the distance h on the press
equipped with the operator's control panel of Figs. 29-31;
Fig. 39 is a block diagram corresponding to that
of Fig. 3 of the first embodiment, showing a control system
according to a fifth embodiment of the invention;
Fig. 40 is an illustration showing an arrangement
of a manual adjusting device used in the fifth embodiment;
Fig. 41 is a block diagram corresponding to that
of Fig. 4, showing functions of a controller used in the
fifth embodiment;
Figs. 42A, 42B, 43, 44 and 45 are views
corresponding to those of Figs. 15, 16, 18 and 21 of the
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second embodiment, showing a sixth embodiment of the present
invention;
Fig. 46 is a block diagram corresponding to that
of Fig. 3 of the first embodiment, showing a control system
according to a seventh embodiment of the invention;
Fig. 47 is a block diagram corresponding to that
of Fig. 4, showing functions of a controller used in the
seventh embodiment;
Fig. 48 is a flow chart illustrating an operation
performed by functional block 466 of the controller of Fig.
47;
Fig. 49 is a graph indicating an example of an a-T
relationship received as one item of the die set
information;
Fig. 50 is an elevational view showing a radiation
thermometer used according to an eighth embodiment of the
invention, to detect the temperature of a product produced
on a press similar to that of Fig. 1;
Fig. 51 is a graph indicating an example of an
Fso-T relationship received as one item of the die set
information;
Fig. 52 is a block diagram corresponding to that
of Fig. 4, showing functions of a controller used in the
eighth embodiment; and
Figs. 53A, 53B and 54 are block diagrams
corresponding to those of Figs. 15A, 15B and 16, showing a
control system used in a ninth embodiment of this invention.
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DETAILED DESCRIPTION OF THE PREFERRF~D EI~ODIMENTS
Referring first to Fig. 1, one example of a
single-action press is shown generally at 10. The press 10
is capable of effecting a drawing operation to produce a
formed outer panel used for a motor vehicle. The press 10
has a bolster 14 disposed on a press bed 16, which in turn
rests on a base of the press. The bolster 14 supports a
lower die in the form of a punch 12 disposed thereon. The
press 10 further has a movable main slide 20 which carries
an upper die 18 fixed thereto. The main slide 20 is moved in
the vertical direction by four plungers 22. The bolster 14
has a multiplicity of through-holes 26 through which
respective cushion pins 24 extend. Located below the bolster
14 is a cushion pad 28 for supporting the cushion pins 24.
The cushion pins 24 also extend through the punch 12, to
support at their upper ends a pressure member in the form of
a pressure ring 30 disposed around a working portion of the
punch 12. The number n and positions of the cushion pins 24
are suitably determined depending upon the size and shape of
the pressure ring 30, for example.
The punch 12, upper die 18 and pressure ring 30
constitute a die set which is removably installed on the
press 10. In operation of the press, a blank or workpiece is
drawn by the punch 12 and the upper die 18, while the blank
is held at its peripheral portion under a suitably adjusted
holding pressure applied through the die 18 and pressure
ring 30.
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The cushion pad 28 incorporates a multiplicity of
hydraulic cylinders 32 corresponding to the cushion pins 24
which extend through the respective through-holes 26 formed
through the bolster 14. The lower ends of the cushion pins
24 are held in abutting contact with the pistons of the
respective hydraulic cylinders 32. The pressure chambers of
these cylinders 32 communicate with each other and are
supplied with a pressurized working fluid delivered from an
electrically operated hydraulic pump 34. Hydraulic pressure
Ps within the pressure chambers of the cylinders 32 is
regulated by opening and closing a solenoid-operated
shut-off valve 36. The hydraulic pressure Ps is detected by
a hydraulic pressure sensor 38, and adjusted so as to apply
a holding force Fs to the pressure ring 30, with the force
Fs substantially evenly distributed to the individual
cushion pins 24. The cushion pins 24, cushion pad 28 and
hydraulic cylinders 32 constitute a cushioning device 51 for
even distribution of the holding force Fs on the pressure
ring 30.
The cushion pad 28 is guided by a guide 40 to be
moved up and down in the longitudinal direction of the
cushion pins 24. The cushion pad 28 is biased in the upward
direction by a fluid-actuated cylinder in the form of a
pneumatic cylinder 42, whose pressure chamber communicates
with an air tank 44. The pressure chamber is partly defined
by a piston 43 which is connected to the underside of the
cushion pad 28. The air tank 44 is connected to an air
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source 48 (provided in a plant in which the press 10 is
installed), via a solenoid-operated pressure control valve
46. Pneumatic pressure Pa within the air tank 44 and the
fluid chamber of the pneumatic cylinder 42 is suitably
adjusted by controlling the pressure control valve 46. The
pneumatic pressure Pa is detected by a pneumatic pressure
sensor 50. This pneumatic pressure Pa is one of the
operating conditions of the press 10, which is adjusted
depending upon the required holding force Fs to be applied
to the pressure ring 30.
The pneumatic cylinder 42 and air tank 44
cooperate with the cushion pins 24 and the cushion pad 28 to
constitute a fore applying device 53 for applying the
holding force Fs to the pressure ring 30, while the press is
in a drawing operation on the blank in the form of a metal
strip or sheet. Described more particularly, a force acting
on the blank under drawing is applied to the cushion pad 28
via the pressure ring 30 and the cushion pins 24, whereby
the cushion pad 28 is lowered, forcing down the piston 43 of
the pneumatic cylinder 42. As a result, the holding force Fs
corresponding to the pneumatic pressure Pa in the cylinder
42 is applied to the pressure ring 30 through the cushion
pad 28 and the cushion pins 24. Although only one pneumatic
cylinder 42 is shown in Fig. 1, two or more pneumatic
cylinders 42 may be used as needed. In this case, all the
pneumatic cylinders are connected to the common air tank 44.
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As shown in Fig. 2, each of the four plungers 22
is connected to the main slide 20 via a die-height adjusting
mechanism indicated generally at 52 in the figure. The
die-height adjusting mechanism 52 engages a threaded shaft
54 formed integrally with the corresponding plunger 22. The
mechanism 52 includes a nut 56 engaging the threaded shaft
54, a worm wheel 58 fixed to the nut 56, and a servomotor 60
for rotating a worm which meshes with the worm wheel 58. The
servomotor 60 is bidirectionally operated to rotate the worm
wheel 58 and the nut 56 clockwise or counterclockwise, for
thereby adjusting the height or the vertical position of the
die-height adjusting mechanism 52 relative to the threaded
shaft 54, that is, a distance h between the plunger 22 and
the main slide 20, more precisely, between the lower end of
the plunger 22 and the upper end of the mechanism 52. The
distance h is detected by a rotary encoder 59 (Fig. 3)
attached to the servomotor 60.
It will be understood that the main slide 20 is
lowered away from the plunger 20 as the distance h
increases, and that the position of the main slide 20 when
the press 10 is at rest, namely, the upper stroke end of the
main slide 20 is shifted toward the punch 12. Accordingly, a
pressing force Fp which acts on the blank when the plunger
22 is at its lower stroke end can be adjusted by changing
the distance h. In other words, the distance h is adjusted
for each of the four plungers 22, depending upon the desired
pressing force Fp, by suitably operating the servomotor 60.
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The distance h is also one of the operating conditions of
the press 10, which is adjusted depending upon the desired
pressing force Fp. As shown in Figs. 2 and 3, each plunger
22 is provided with a strain gage 61. This gage 61 is
adapted to detect a load Foi (i - 1, 2, 3, 4) which acts on
the corresponding plunger 22. In practice, the load Foi
represented by the output of the strain gage 61 is converted
into a load value which is expected to act on a portion of
the main slide 20 at which the appropriate plunger 22 is
connected. This load value can be calculated, for example,
according to a predetermined relationship between the output
(load Foi) of the strain gage 61 and the pressing force Fp
measured by a load measuring apparatus 100 shown in Fig. 6.
The predetermined relationship is represented by a data map
stored in a controller 90 (Fig. 3), which will be described.
The main slide 20 incorporates an
overload-protective hydraulic cylinder 62 which has a piston
64 connected to the die-height adjusting mechanism 52, and a
housing fixed to the main slide 20. The pressure chamber of
the hydraulic cylinder 62 is filled with a working fluid and
communicates with an oil chamber 68 of a cylinder 66. The
cylinder 66 also has an air chamber 70 which communicates
with an air tank 72 connected to the above-indicated air
source 48 through another solenoid-operated pressure control
valve 74. Pneumatic pressure Pc within the air chamber 70
and air tank 72 is adjusted by means of the pressure control
valve 74. The pneumatic pressure Pc is detected by a
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pneumatic pressure sensor 76, and is adjusted depending upon
the pressing capacity of the press 10. That is, the
pneumatic pressure Pc is determined so that when an
excessive load acts on the overload-protective hydraulic
cylinder 62, the piston of the cylinder 66 is moved towards
the air chamber 70, so as to permit movements of the
adjusting mechanism 52 and the main slide 20 towards each
other, for thereby protecting the press 10 and the dies 12,
18 against damage due to an overload. The hydraulic cylinder
62, cylinder 66, air tank 72 and the related components are
provided for each of the four plungers 22 associated with
the respective mechanisms 52, and the pneumatic pressure Pc
in each of the four air tanks 72 is suitably controlled.
The main slide 20 is also connected to four
counterbalancing pneumatic cylinders 80 attached to a frame
78 (indicated at the top of Fig. 1) of the press 10. Each
pneumatic cylinder 80 has a pressure chamber communicating
with an air tank 82, which is also connected to the air
source 48 via a solenoid-operated pressure control valve 84.
By controlling the valve 84, pneumatic pressure Pb within
the pressure chamber of the cylinder 80 and the air tank 82
can be regulated. The pressure Pb is detected by a pneumatic
pressure sensor 86, and is one of the operating conditions
of the press 10, which is adjusted so that the total weight
of the main slide 20 and the upper die 18 does not influence
the pressing force Fp, that is, so that the force
corresponding to the pressure Pb in the four cylinders 80
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counterbalances the total weight of the main slide 20 and
upper die 18. The pressure chambers of the four
counterbalancing pneumatic cylinders 80 communicate with the
common air tank 82.
The press 10 uses a controller 90 as shown in Fig.
3. The controller 90 is adapted to receive output signals of
the pneumatic pressure sensors 50, 86, 76, hydraulic
pressure sensor 38, rotary encoder 59 and strain gages 61,
which are indicative of the pneumatic pressures Pa, Pb, Pc,
hydraulic pressure Ps, distance h and pressing force Foi,
respectively. The controller 90 is constituted by a
microcomputer, which incorporates a central processing unit
(CPU), a random-access memory (RAM), a read-only memory
(ROM), an input/output interface circuit, and an
analog-digital (A/D) converter. The CPU operates to process
various signals according to control programs stored in the
ROM, while utilizing a temporary data storage function of
the RAM, so as to control the pressure control valves 46,
84, 74 and shut-off valve 36, and apply drive signals to the
pump 34 and servomotor 60. Although Fig. 3 shows only one
piece or unit, for the servomotor 60, strain gage 61,
pressure control valve 74 and pneumatic pressure sensor 76,
the controller 90 is operated to control all of the four
pieces provided on the press 10, as described above with
respect to the above-indicated four components. The
controller 90 is also adapted to receive data from a data
input device 92 in the form of a keyboard or personal
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computer, for example, and is connected to a
transmitter/receiver (transceiver) 94. The data received
from the data input device include information ("machine
information") indicative of the specifications of the press
10. The controller 90 also receive from the
transmitter/receiver 94 data indicative of the
specifications of the die set 12, 18, 30. To this end, each
punch 12 carries data storage medium in the form of an ID
card 96 attached thereto, as shown in Fig. 1. The ID card 96
stores the information ("die set information") indicative of
the specifications of the die set 12, 18, 30 and has a
built-in battery and a data transmitting function. The
transmitter/receiver 94 is disposed so as to face the ID
card 96, as also shown in Fig. 1, and transmits a signal to
the ID card 96, to request transmission of the appropriate
information on the die set. The transmitter/receiver 94
which receives the information from the ID card 96 transmits
the information to the controller 90.
As shown in the functional block diagram of Fig.
5, the ID card 96 includes a die set data memory 125 which
stores the die set information, a control CPU 126, a
transceiver 127, and a press operation data memory 128 which
stores data indicative of the operating conditions of the
press 10. The control CPU 126 is adapted to receive the
information from the data memories 125, 128 and transmit the
received information to the transmitter/receiver 94, via the
transceiver 127. The control CPU is also adapted to receive
CA 02251503 1999-08-06
- 24 -
information from the transceiver/transmitter 94 via the
transceiver 127 and store the received information in the
data memory 128. The transmitter/receiver 94 and the ID card
96 function as data input means for receiving the
appropriate die set information.
The data indicative of the specifications of the
press 10 and the die set 12, 18, 30 are necessary to
determine the pneumatic pressure values Pa, Pb, hydraulic
pressure Ps, and distance h, which are optimum for effecting
0 a drawing operation under the best conditions. The data
received by _the controller 90 include the following
information, for example. It is noted that the information
on the die set also includes data indicative of the specific
die set used, which differs depending on the product to be
obtained, a model of a car for which a part produced by the
press is used, a type of press on which the die set is used,
and a process in which the product is obtained from the
blank.
[MACHINE INFORMATION]
o Weight Wa of the cushion pad 28
o Average weight Wp of the cushion pins 24
o Weight Ws of main slide
o Pressure-receiving area Aa of the pneumatic cylinder 42
o Total pressure-receiving area Ab of the four pneumatic
cylinders 80
o Average pressure-receiving area As of the hydraulic
CA 02251503 1999-08-06
;.:.a
- 25 -
cylinders 32
o Modulus K of elasticity of volume of the working fluid
used for the hydraulic cylinder 32
o Mean travel Xav of the pistons of the hydraulic cylinders
32
o Total volume V of the fluid in the hydraulic circuit of
the hydraulic cylinders 32
o Provisional h-Fpi characteristic relationship (Fpi = a~h)
[DIE SET INFORMATION}
o Weight Wr of the pressure ring 30
o Weight Wu of the upper die 18
o Optimum holding force Fso
o Optimum pressing force Fpoi of each cushion pin 24
o Number n of the cushion pins 24
The weight Wa of the cushion pad 28 is the actual
weight of the pad 28 minus the sliding resistance applied to
the pad 28. This weight value Wa can be obtained by a load
measuring apparatus 100 installed on the press 10, as shown
in Fig. 6. Described in detail, the weight value Wa is
obtained from a Fs-Pa relationship, which is obtained by
measuring the holding force Fs while the pneumatic pressure
Pa is changed.
As shown in Fig. 6, the load measuring apparatus
100 is installed on the press 10, without the punch 12,
upper die 18 and pressure ring 30 installed on the press 10.
CA 02251503 1999-08-06
- 26 -
The apparatus 100 has a positioning member 102 of
rectangular box construction fixed on the bolster 14, and a
measuring member 106 accommodated within the positioning
member 102. The measuring member 106 is movable in the
vertical direction, and has a plurality of sensing pins 104
protruding from the underside thereof . The sensing pins 104
correspond to the cushion pins 24. The positioning member
102 has a plurality of apertures 108 through which the
respective cushion pins 24 extend. The measuring member 106
rests on the cushion pins 24 extending through the
through-holes 26 and the apertures 108, such that the
sensing pins 104 are held in abutting contact with the
corresponding upper ends of the cushion pins 24. The
positioning member 102 also has four sensing posts 110
projecting upwards at the four corners of the rectangular
box. On the other hand, the measuring member 106 has four
sensing elements 112 projecting upwards from the upper
surface, near the four corner portions of an area in which a
drawing operation is effected. The four sensing posts 110
and the four sensing elements 112 are provided with
respective sets of strain gages 114, 116. Suitably selected
ones of the sensing pins 104 indicated above are provided
with respective sets of strain gages 118. The strain gages
114, 116, 118 are connected to a dynamic strain detector
120, which is connected to an electromagnetic oscilloscope
122, so that waveforms of loads detected by the strain gages
114, 116, 118 are recorded on a photosensitive recording
CA 02251503 1999-08-06
~:,w i
- 27 -
medium by the oscilloscope 122. The dynamic strain detector
120 has a function of an amplifier, and is capable of
adjusting a zero point thereof. The oscilloscope 122 is
capable of recording, with high response, the load values
which vary as the main slide 20 is moved up and down. The
positioning member 102 and the measuring member 106 are
designed to have higher rigidity than the punch 12 and upper
die 18 which are used for an actual drawing operation.
The strain gages 114, 116, 118 function as means
for detecting the holding force and pressing force which are
. expected to act on the pressure ring 30 and the blank,
respectively. Each set of strain gages 114, 116, 118
consists of four strain gages attached to each sensing post
110, sensing element 112 or sensing pin 104, at respective
four side surface portions of the latter. The four strain
gages of each set are connected to each other so as to form
a bridge circuit. The strain gages 114 are provided for
measuring the holding force associated with the outer slide
of a double-action press. The strain gages 116 are provided
for measuring the pressing force associated with the inner
slide of the double-action press, and the pressing and
holding forces on the single-action press 10. The strain
gages 118 are provided for measuring the load values which
act on the individual cushion pins 24 of the cushioning
device 51.
To measure the holding force and the pressing
force which are expected to be generated on the
CA 02251503 1999-08-06
- 28 -
single-action press 10, the positioning member 102 and the
measuring member 106 are installed on the press 10, without
the punch 12, pressure ring 30 and upper die 18 installed on
the press 10. For the measurement, the main slide 20 is
lowered to its lower stroke end. During this downward
movement of the main slide 20, the lower surface of the main
slide 20 is brought into contact with the sensing elements
112 on the measuring member 106, whereby the measuring
member 106 is lowered against the biasing force of the
pneumatic cylinder 42. The loads acting on the four sensing
elements 112 during this downward movement of the measuring
member 106 are detected by the strain gages 116. Before the
main slide 20 has reached its lower stroke end, the
measuring member 106 comes into abutting contact with the
positioning member 102. At this time, the loads detected by
the strain gages 116 suddenly rise, due to rigidity of the
structure of the press 10. The heights of the sensing
elements 112 from the upper surface of the measuring member
106 are determined or adjusted so that the measuring member
106 abuts on the positioning member 102 shortly before the
main slide 20 has reached the lower stroke end.
The graph of Fig. 7 indicates a variation in the
load detected by the strain gages 116 provided on one of the
four sensing elements 112. In the graph, a load value Fsi
corresponds to the holding force expected to be applied to
the pressure ring 30, and a load value Fpi corresponds to
the pressing force expected to be applied to the punch and
CA 02251503 1999-08-06
r
.,~,s:
- 29 -
die 12, 18 (blank). The load value Fpi includes the load
value Fsi.
The graph of Fig. 8 indicates a relationship
between the pneumatic pressure Pa of the pneumatic cylinder
42 and the load value Fsi (corresponding to the holding
pressure), which was obtained by measuring the load value
Fsi while the pneumatic pressure Pa was continuously
changed. The weight Wa of the cushion pad 28 is calculated
on the basis of a load value Fxi which can be obtained from
the Pa-Fsi relationship. Described more specifically, the
_weight Wa is calculated by subtracting the total weight of
the measuring member 106 (including the weight of the
sensing pins 104 and elements 112) and the cushion pins 24,
from a total load value Fx of the load values Fxi (i = 1, 2,
3, 4) of the four sensing elements 112. Alternatively, the
weight Wa can be obtained from a relationship between the
pneumatic pressure Pa and a total load value Fs of the
detected load values Fsi of the four sensing elements 112.
The thus obtained weight Wa is different from and smaller
than the actual weight of the cushion pad 28, by an amount
which is determined by various parameters such as the
sliding resistance values of the guide 40 and piston 43, a
degree of the air leakage of the pneumatic cylinder 42 and a
detecting error of the pneumatic pressure sensor 50.
Accordingly, the obtained weight Wa is specific to the
particular condition of the press 10 on which the measuring
apparatus 100 was operated. As indicated above, the weight
CA 02251503 1999-08-06
s
- 30 -
Wa is used as one item of the machine specifications. The
weight Wa may be replaced by an actual weight of the cushion
pad 28, and a sliding resistance value which can be obtained
on the basis of a difference ~Fsi between the load values
Fsi and Fpi shown in the graph of Fig. 7.
The weight Wp is an average value of the weights
of the multiple cushion pins 24 used on the press 10. The
weight Ws is equal to the actual weight of the main slide 20
minus a sliding resistance value of the slide 20 with
respect to a guide therefor. To obtain the weight Ws, the
load values Foi are detected by the respective strain gages
61 during the downward movement of the main slide 20. The
total load value Fo of the four load values Foi of the four
plungers 22 is detected while the pneumatic pressure Pb of
the pneumatic cylinder 80 is continuously changed. Like the
weight Wa of the cushion pad 28, the weight Ws of the main
slide 20 can be obtained from the obtained characteristic
relationship between the total load Fo and the pneumatic
pressure Pb. The weight Ws may be replaced by the actual
weight of the main slide 20, and the related sliding
resistance value.
The pressure-receiving area Aa of the pneumatic
cylinder 42 is a value which reflects an influence of the
air leakage of the cylinder 42. For instance, the area Aa
corresponds to a gradient of a line which represents the
relationship between the holding force Fs (total load value
Fsi) and the pneumatic pressure Pa. When a plurality of
CA 02251503 1999-08-06
r
- 31 -
pneumatic cylinders 42 are provided, the area As is a total
pressure-receiving area of all the cylinders 42. Like the
pressure-receiving area As, the total pressure-receiving
area Ab of the four pneumatic cylinders 80 can be obtained
from the Fo-Pb characteristic relationship. The average
pressure-receiving area As of the hydraulic cylinders 32 can
be obtained from a characteristic relationship between the
holding force Fs, and the hydraulic pressure Ps which is
detected by the hydraulic pressure sensor 38 when the Fsi-Pa
characteristic relationship of Fig. 8 is obtained, for
example.
The modulus K of elasticity of volume of the
working fluid is determined depending upon the specific
property of the oil used. The mean travel Xav of the pistons
of the hydraulic cylinders 32 is an average value of travel
distances of the pistons of the cylinders 32 from the upper
stroke ends, when the main slide 20 has reached its lower
stroke end. The travel distances are determined so as to
apply the holding force to the pressure ring 30 evenly
through all of the cushion pins 24 in abutting contact with
the ring 30. Described more particularly, the travel
distances are determined so that all of the pistons of the
cylinders 32 are lowered from their upper stroke ends by the
respective cushion pins 24 while none of the pistons are
bottomed or lowered to their lower stroke ends by the
cushion pins 24, upon reaching of the main slide 20 to its
lower stroke end, even in the presence of a variation in the
CA 02251503 1999-08-06
- 32 -
length of the cushion pins 24 and an inclination of the
cushion pad 28. The travel distances can be obtained by an
experiment, or on the basis of the measured length variation
of the cushion pins 24 and maximum strokes of the pistons of
the cylinders 32. The volume V is a total volume of the
working fluid existing in a portion of the hydraulic circuit
associated with the hydraulic cylinders 32, which portion
includes the pressure chambers of the cylinders 32 and is
bounded by a check valve 39 (Fig. 1). The volume V is a
value when the pistons of the cylinders 32 are at their
upper stroke ends.
The provisional h-Fpi characteristic relationship
( i = 1, 2 , 3 , 4 ) is a relationship ( Fpi - a ~ h ) between the
distance h and the pressing force Fpi when the plungers 22
have reached the lower stroke ends. This relationship is
obtained by measuring the pressing force values Fpi (when
the plungers 22 have reached the lower stroke ends), with
different values of the distance h. Since the value Fpi
differs depending upon the rigidity of the punch and upper
die 12, 18, suitable members having considerably higher
rigidity than the die set are used for the measurement of
the value Fpi. The obtained provisional h-Fpi relationship
reflects the rigidity of the press 10 ( except for the punch
and upper die). It is noted that the measurement is effected
after the pneumatic pressure Pb of the pneumatic cylinders
80 is adjusted so that the lifting force produced by the
CA 02251503 1999-08-06
- 33 -
cylinders 80 counterbalances the total weight of the main
slide 20 and the upper die 18.
An example of the provisional h-Fpi characteristic
relationship is indicted by one-dot chain line in the graph
of Fig. 9, wherein the maximum value h0 of the distance h
when the pressing force Fpi is zero is used as a reference.
This h-Fpi characteristic relationship is obtained for each
of the four plungers 22 (four die-height adjusting
mechanisms 52). The overall pressing force Fp is a sum of
the pressing forces Fpi of the individual plungers 22. The
provisional h-Fpi characteristic relationship may be
obtained from the load values Fpi shown in Fig. 7, by using
the load measuring apparatus 100.
There will next be described the individual items
of the information on the die set 12, 18, 30.
The weight Wr of the pressure ring 30 and the
weight Wu of the upper die 18 are the values actually
measured of the ring 30 and die 18 as manufactured. The
holding pressure Fso and the pressing force Fpoi (i = 1, 2,
3, 4) are obtained by a trial-and-error procedure, in which
the optimum forces Fso and Fpoi suitable for performing a
desired drawing operation are determined by test operations
on a trial or test press on which the pressure ring 20,
upper die 18 and punch 12 are installed. The holding
pressure Fso and pressing force Fpoi do not include
components due to the influences by the weights of the punch
and die 12, 18 and the sliding resistance values of the
CA 02251503 1999-08-06
! ,~,..,r
- 34 -
associated components. In the case where the trial press is
similar to that shown in Figs. 1 and 2, for example, the
pneumatic pressure Pb is adjusted so that the main slide 20
is lowered by the plungers 22 while the total weight of the
slide 20 and the upper die 18 is counterbalanced by the
lifting force produced by the cylinders 80. The load values
Foi are detected by the strain gages 61 during a trial
drawing operation effected with the adjusted pneumatic
pressure Pb. The holding force Fso and pressing force Fpoi
can be obtained on the basis of the detected load values
Foi. While the holding force Fso is a total force applied to
the pressure ring 30 through the cushion pins 24, the
pressing force Fpoi is a force produced by each of the four
plungers 22, and the total pressing force Fp is a sum of the
forces Fpoi of the four plungers 22. The number n of the
cushion pins 24 is determined depending upon the size and
shape of the pressure ring 30, so as to draw a blank into a
desired product.
The press operation data memory 128 of the ID card
96 stores data indicative of optimum distances h* associated
with the four plungers 22 of the specific press 10, and data
representative of the serial numbers of individual machines
of the press 10 on which the punch 12 with the ID card 96
attached thereto is used. The data are written in the data
memory 128, through the transmitter/receiver 94 and the
transceiver 127, and sent to the controller 90 through the
transmitter/receiver 94 and transceiver 127. Each optimum
CA 02251503 1999-08-06
- 35 -
a
a .":. N
distance h* stored in the data memory 128 is the distance h
as adjusted by the die-height adjusting mechanism 52 so that
the drawing operation is effected on the press 10, with the
pressing forces Fpoi stored in the die set data memory 125.
Since the punch 12 may be used for different machines of the
press 10, the optimum distances h* specific to the
individual machines are stored in the data memory 128 of the
ID card 96 attached to the punch 12 used. When a drawing
operation is effected on the specific pressing machine 10,
the distances h associated with the four plungers 22 on that
machine 10 is adjusted to the optimum value h* corresponding
to the appropriate serial number of the machine. If a single
servomotor 60 is used to adjust the distance h associated
with the four plungers 22, only one optimum distance h* is
stored in the data memory 125, for each pressing machine 10.
Referring back to Fig. 3, the controller 90 is
adapted to achieve various functions as illustrated in the
block diagram of Fig. 4, according to the control programs
stored in its ROM. The controller 90 includes a machine data
memory 130 for storing data including the machine
information entered through the data input device 92. The
controller 90 further includes a die data memory 132 for
storing the data including the die set information which is
read and transmitted by the transmitter/receiver 94, from
the ID card 96 on the punch 12 installed on the press 10. As
indicated above, the die set information stored in the die
set data memory 125 of the ID card 96 includes the data
CA 02251503 1999-08-06
- 36 -
indicative of the optimum distances h* of the press 10 in
question.
The block diagram of Fig. 4 shows various
functional blocks which correspond to respective means for
performing the corresponding functions. A Pax calculating
block 134 is for calculating an optimum pneumatic pressure
Pax for producing the holding force Fso, according to the
following equation (1), on the basis of the machine
information stored in the machine data memory 130 and the
die set information stored in the die data memory 132. The
holding force Fso to be produced is represented by the die
set information:
Pax = (Fso + Wa + Wr + n~Wp)/Aa ............. (1)
A Pa adjusting block 136 is for controlling the
solenoid-operated pressure control valve 46 so that the
pneumatic pressure Pa in the air tank 44 detected by the
pneumatic pressure sensor 50 coincides with the optimum
pneumatic pressure Pax calculated by the Pax calculating
block 134. With the pneumatic pressure Pa thus adjusted, the
holding force Fso specified by the die information is
applied to the pressure ring 30. The pneumatic pressure Pax
may be calculated, with suitable compensation for a change
in the volume of the pressure chamber of the pneumatic
cylinder 42 due to a downward movement of the cushion pad
28. In this respect, however, since the capacity of the air
tank 44 is sufficiently large, the amount of change in the
pneumatic pressure Pa due to the change in the volume of the
CA 02251503 1999-08-06
r
s,~,,,
- 37 -
pressure chamber of the cylinder 42 is so small and
negligible. Thus, the block 134 corresponds to means for
calculating the optimum pneumatic pressure Pax, while the
block 136 cooperates with the pressure control valve 46 and
the pressure sensor 50, to constitute means for adjusting
the pneumatic pressure Pa as one of the operating conditions
of the press 10.
A P0, P1 calculating block 138 is for calculating
an optimum initial hydraulic pressure PO and an optimum
final hydraulic pressure P1 according to the following
equations (2) and (3), respectively, on the basis of the
machine information in the machine data memory 130 and the
die set information in the die data memory 132.
Xav = (Fso - n~As~PO)V/n2~Asz~K ........ (2)
Fso + Wr + n~Wp = n~As~P1 .............. (3)
The optimum initial hydraulic pressure PO is a
pressure for applying the holding force Fso to the pressure
ring 30 substantially equally through the cushion pins 24,
when the upper die 18 is not in contact with the pressure
ring 30. On the other hand, the optimum final hydraulic
pressure P1 is a similar pressure when the upper die 18 is
in pressing contact with the pressure ring 30.
A Ps adjusting block 140 is for controlling the
pump 34 and shut-off valve 36, so that the initial value of
the hydraulic pressure Ps detected by the hydraulic pressure
sensor 38 is equal to the calculated optimum initial
hydraulic pressure PO indicated above. With the hydraulic
CA 02251503 1999-08-06
- 38 -
pressure Ps thus adjusted to the optimum initial value P0,
it is theoretically possible to lower the pistons of all the
hydraulic cylinders 32 by the average travel distance Xav,
in a drawing operation with the pressure ring 30 in pressing
contact with the upper die 18, and to apply the holding
force Fso to the pressure ring 30 substantially equally
through the cushion pins 24. However, the optimum initial
hydraulic pressure PO is not necessarily accurate enough due
to a possibility of existence of air in the hydraulic
circuit including the cylinders 32, which causes a variation
in the modulus K of elasticity of volume of the working
fluid. In view of this drawback, the Ps adjusting block 140
is adapted to read the hydraulic pressure Ps in a test
operation, and adjust the pressure Ps once adjusted to the
optimum initial value P0, so that the pressure Ps is made
substantially equal to the optimum final pressure P1 also
calculated according to the P0, P1 block 138. If the
actually detected hydraulic pressure Ps during the test
operation is higher than the optimum final value P1, some of
the cushion pins 24 are not in abutting contact with the
pressure ring 30, and the holding force Fso is applied to
the pressure ring 30 through the other cushion pins 24 only.
In this case, the initial hydraulic pressure PO is lowered
to move the cushion pins 24 upwards so that all the cushion
pins 24 may contact the pressure ring 30. If the actual
hydraulic pressure Ps is lower than the optimum final value
P1, on the other hand, the pistons of some of the hydraulic
CA 02251503 1999-08-06
- 39 -
f
cylinders 32 are bottomed, and a portion of the holding
force Fso acts on the pressure ring 30 directly through the
cushion pad 28 and the cushion pins 24 corresponding to the
bottomed pistons. In this case, the initial hydraulic
pressure PO is raised to avoid the bottoming of the pistons
of any cylinders 32. The test operation indicated above is
conducted after the pneumatic pressure Pa is adjusted to
obtain the holding force Fso. The block 138 corresponds to
means for calculating the optimum initial and final pressure
values PO and P1, while the block 140 cooperates with the
pump 34, pressure control valve 36 and pressure sensor 38 to
constitute means for adjusting the hydraulic pressure Ps, as
one of the operating conditions of the press 10.
A Pbx calculating block 142 is for calculating an
optimum pneumatic pressure Pbx of the pneumatic cylinders 80
to produce a lifting force for counterbalancing the total
weight of the main slide 20 and the upper die 18, according
to the following equation ( 4 ) , on the basis of the machine
information and die set information.
Pbx = (Wu + Ws)/Ab ................ (4)
A Pb adjusting block 144 is for controlling the
solenoid-operated pressure control valve 84 so that the
pneumatic pressure Pb in the air tank 82 detected by the
pneumatic pressure sensor 86 coincides with the optimum
pressure Pbx calculated according to the Pbx calculating
block 142. With the pressure Pb thus adjusted, the pressing
force Fpoi as specified by the die set information can be
CA 02251503 1999-08-06
,;_ J,
- 40 -
applied to the die set 12, 18, in a drawing operation,
without an influence of the weights of the slide 20 and
upper die 18. The optimum pneumatic pressure Pbx may be
calculated, with suitable compensation for a change in the
volume of the pressure chamber of each pneumatic cylinder 80
due to a downward movement of the main slide 20. In this
respect, however, since the capacity of the air tank 82 is
sufficiently large, the amount of change in the pneumatic
pressure Pb due to the change in the volume of the pressure
chamber of the cylinder 80 is so small and negligible. The
block 142 corresponds to means for calculating the optimum
pneumatic pressure Pbx, while the block 144 cooperates with
the pressure control valve 84 and the pressure sensor 86 to
constitute means for adjusting the pneumatic pressure Pb as
one of the operating conditions of the press 10.
An h adjusting block 146 is for adjusting the
distances h associated with the four die-height adjusting
mechanisms 52, independently of each other, according to a
control routine as illustrated in the flow chart of Fig. 10.
The control routine is started with step R1 to determine
whether data representative of the optimum distances h* for
the press 10 in question are stored in the die data memory
132, or not. If the data representative of the optimum
distances h* are stored in the memory 132, step R7 is
implemented. If the data are not stored in the memory 132,
namely, if the die set 12, 18, 30 (including the punch 12
CA 02251503 1999-08-06
~..;,G: :v
- 41 -
carrying the ID card 96) is used for the first time on the
appropriate press 12, the control flow goes to step R2.
The details of a sub-routine in step R2 of Fig. 10
are shown in the flow chart of Fig. 11. This sub-routine is
started with step R2-1 in which the provisional h-Fpi
relationship and the optimum pressing force Fpoi are read
from the machine data memory 130 and the die data memory
132, respectively. Step R2-1 is followed by step R2-2 in
which the reference value h0 which is the maximum value of
the distance h when the pressing force Fpi of each plunger
. 22 is zero is determined from the corresponding load value
Foi detected by the strain gages 61 on the corresponding
plunger 22. To this end, test operations are conducted with
different values of the distance h for each plunger 22,
which increase in steps by a predetermined amount, and the
actual distance h is detected when the pressing force Foi
exceeds a predetermined threshold. Alternatively, the main
slide 20 is lowered down to its lower stroke end with the
distance h set at its minimum value, and the distance h is
increased by operating the appropriate servomotor 60 until
the pressing force Foi exceeds a predetermined threshold. In
either case, the actual distance h when the pressing force
Foi exceeds the threshold is used as the reference value h0.
The reference value may also be determined by visual
inspection by the operator of the abutting condition of the
punch and die 12, 18.
CA 02251503 1999-08-06
- 42 -
C
t:~~
Step R2-2 is followed by step R2-3 in which a
distance hl for obtaining the pressing force Fpoi is
obtained from the provisional h-Fpi characteristic
relationship (Fpi - a~h) as indicated by one-dot chain line
in the graph of Fig. 9, and the distance h is then adjusted
to the obtained value hl, with respect to the reference
value h0, by operating the servomotor 60. The control flow
then goes to step R2-4 to perform a test operation (one
reciprocation of the main slide 20) on the press 10. Step
R2-4 is followed by step R2-5 in which the pressing force
Fpl is determined on_ the basis of the load value Foi
represented by the output signals of the strain gages 61
when the main slide 20 is at its lower stroke end. Since the
predetermined provisional h-Fpi characteristic relationship
is based on higher rigidity of the die set than the rigidity
of the actually used die set 12, 14, 30, the pressing force
Fpl is generally smaller than the load value Fpoi. Then, the
control flow goes to step R2-6 to calculate a distance h2
which is smaller than hl by a predetermined amount oh, and
to adjust the distance h to h2. Step R2-6 is followed by
steps R2-7 and R2-8 similar to steps R2-4 and R2-5, to
measure the pressing force Fp2 in the same manner as
described above with respect to the value Fpl. Step R2-9 is
then implemented to obtain a final h-Fpi characteristic
relationship (Fpi - b~h) as indicated by solid line in Fig.
9, based on the thus obtained values Fpi, Fp2, and a
difference 0h between the distances hl and h2. Finally, step
CA 02251503 1999-08-06
;...,.r
- 43 -
R2-10 is implemented to determine an optimum distance hx
(corresponding to the optimum distance h* indicated above)
for obtaining the pressing force Fpoi, according to the
obtained final h-Fpi relationship, and activate the
servomotor 60 for adjusting the distance h to the determined
optimum distance hx. The determination of the distance hx
and the adjustment of the distance h to the determined
distance hx by the servomotor 60 are effected for each of
the four mechanisms 52 (four plungers 22). The sub-routine
of Fig. 11 corresponds to means for calculating the optimum
. distance hx (h*). The above step R2-10 of Fig. 11 cooperates
with step R8 of Fig. 10 (which will be described) to provide
means for adjusting the distance h as one of the operating
conditions of the press 10.
Referring back to the flow chart of Fig. 10, step
R2 is followed by step R3 in which a desired drawing
operation is effected on the blank, with the distances h
associated with all the plungers 22 adjusted to the optimum
distances hx determined in step R2. This step R3 is also
effected following step R8 (which will be described). In
this case, the drawing operation in step R3 is effected with
the distances h adjusted to the optimum distances h* stored
in the die data memory 132. Step R3 is followed by step R4
to determine whether an absolute value ~Foi - Fpoi~, a
difference between the load value Foi represented by the
output signals of the strain gages 61 and the pressing force
Fpoi when the main slide 20 is at its lower stroke end is
CA 02251503 1999-08-06
- 44 -
r
r...~.>
smaller than a predetermined value a, or not. The
predetermined value a is determined depending upon the
detecting error and control accuracy associated with the
values Foi and Fpoi. If the difference is equal to or larger
than the predetermined value a, step R6 is implemented to
change the distances h by a predetermined amount. Step R6 is
repeatedly implemented until the difference becomes smaller
than the predetermined value a. With this adjustment of the
distances h, it is possible to perform a drawing operation
with the optimum pressing force Fpoi as specified by the die
set information stored in the data memory 132, irrespective
of a variation in the rigidity from one pressing machine to
another. When the difference becomes is smaller than the
threshold value a, step R4 is followed by step R5 in which
the data representative of the distances h as represented by
the output signals of the rotary encoders 59 associated with
the four plungers 22 are sent from the transmitter/receiver
94 to the ID card 96 and stored in the press operation data
memory 128, as the optimum distances h*, together with the
data indicative of the serial number .of the pressing machine
10 in question. If the corresponding data are already stored
in the data memory 128, the already stored data are replaced
by the data sent from the transmitter/receiver 94.
If an affirmative decision (YES) is obtained in
step R1, that is, if the data representative of the optimum
distances h* of the press 10 in question are already stored
in the die data memory 132 because a drawing operation using
CA 02251503 1999-08-06
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the same punch 12 (die set 12, 18, 30) has ever been
performed on the press 10, the control flow goes to step R7
in which the data representative of the optimum distances h*
and the load force Fpoi are read from the die data memory
132. Step R8 is then implemented to activate the servomotors
60 to adjust the distances h to the optimum values h*. Step
R8 is followed by steps R3-R6 to adjust the distances h as
needed until the load values Foi as detected by the strain
gages 61 are made substantially equal to the pressing force
Fpoi, and send the data representative of the adjusted
distances h, to the ID card 96 as the data representative of
the optimum distances h*.
The controller 90 is also adapted to regulate the
pneumatic pressure Pc in the air chamber 70 of the cylinder
66, so that the load value Foi detected by the strain gages
61 on each plunger 22 does not exceed a predetermined upper
limit Foli (i = 1, 2, 3, 4). That is, the solenoid-operated
pressure control valve 74 is controlled to adjust the
pneumatic pressure Pc to a predetermined optimum value Pcx.
This optimum value Pcx is determined on the basis of the
pressure-receiving area of the cylinder 62 and the
pressure-receiving areas of the oil and air chambers 68, 70
of the cylinder 66, so that if a load exceeding the upper
limit Foli acts on the overload-protective hydraulic
cylinder 62, due to increased sliding resistance of the main
slide 20, for example, the piston of the cylinder 66 may be
moved towards the air chamber 70, thereby permitting the
CA 02251503 1999-08-06
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working oil to flow from the hydraulic cylinder 62 into the
oil chamber 68 of the cylinder 66, and allowing the
corresponding plunger 22 to be moved towards and relative to
the main slide 20. This adjustment of the pneumatic pressure
Pc is effected for all of the four cylinders 66 provided for
the respective four plungers 22, so that the pressure values
Pci of the four cylinders 66 are adjusted independently of
each other. Thus, the overload-protective cylinder 62
protects the press 10 and the die set against damage due to
an overload. Since the optimum pneumatic pressure Pc is not
influenced by the die set, the adjustment may be effected
manually, i.e., by manipulation of the pressure control
valve 74 by the operator of the press 10.
It will be understood from the above explanation
that the press 10 is capable of automatically calculating
optimum values of the operating conditions of the press,
such optimum pneumatic pressures Pax, Pbx, initial hydraulic
pressure PO and-optimum distances hx, so as to establish the
optimum holding pressure Fso and optimum pressing force Fpoi
as determined in a trial or test operation on a test machine
and stored in the die data memory 132, irrespective of
variations or differences in the rigidity and sliding
resistances of the press from one machine to another. The
automatic calculation of the optimum operating parameters is
effected by the controller 90, according to the machine
information stored in the machine data memory 130 and the
die set information stored in the die data memory 132
CA 02251503 1999-08-06
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'=,F:.-....r
(received from the ID card 96 via the transmitter/receiver
94). The controller 90 is further adapted to automatically
adjust the operating conditions such as the pneumatic
pressures Pa, Pb, hydraulic pressure Ps and distances h to
the calculated optimum values Pax, Pbx, PO and hx. Thus, the
press 10 eliminates or minimizes the conventional cumbersome
manual adjustment of the operating conditions of the press
by the trial-and-error procedure, and reduces the operator's
work load during a setup procedure of press, while assuring
high stability in the quality of formed products obtained.
As described above, when a given die set (12, 18,
30) is used for the first time to perform a drawing
operation on the press 10, the optimum distances hx are
determined according to the provisional h-Fpi relationship
and the pressing force Fpoi, during test pressing operations
(in step R2 of Fig. 10), and the distances h are adjusted to
the determined optimum distances hx, as explained above in
detail by reference to the flow chart of Fig. 11. The thus
adjusted distances h are stored in the ID card 96 as the
optimum distances h* (step R5 of Fig. 10), so that when a
pressing operation is effected again using the same die set
on the press 10, the distances h are adjusted according to
the stored optimum distances h*, without the sub-routine of
Fig. 11 being executed. Therefore, the time necessary for
the adjustment of the distances h is shortened, and the
production efficiency of the press 10 is accordingly
improved.
CA 02251503 1999-08-06
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In the present embodiment, steps R2, R3, R4 and R6
of Fig. 10 are considered as a step for determining the
optimum values hx (h*) and adjusting the distances h to the
optimum values hx (h*), when a certain drawing operation is
effected for the first time using a given die set on the
press 10. Further ,step R5 is considered a step for storing
the data representative of the adjusted distances h (optimum
distances h*) in the press operation data memory 128 of the
ID card 96. Steps R7 and R8 are considered as a step for
utilizing the data stored in the memory 128 to establish or
reproduce the optimum distances hx (h*) for the subsequent
drawing operations using the same die set. It is also noted
that a portion of the controller 90 assigned to implement
steps R2-R4 and R6 constitutes means for determining the
optimum distances hx (h*) and adjusting the distances h to
the optimum values hx, when a given die set is used for the
first time on the press 10. A a portion of the controller 90
assigned to implement steps S7 and R8 constitutes
reproducing means for utilizing the press operation data
stored in the data memory 128 to reproduce the optimum'
distances h* for the subsequent drawing operations using the
same die set. Further, the transmitter/receiver 94 and the
ID card 96 constitute data input means for receiving the
pressing force Fpoi as die set information and storing the
die set information into the die data memory 132 of the
controller 90, while the press operation data memory 128 of
CA 02251503 1999-08-06
:,."~..
- 49 -
the ID card 96 serves as memory means for storing the data
representative of the optimum distances h*.
It is appreciated that data representative of the
hydraulic pressure Ps as adjusted for the first time
according to the optimum initial and final values P0, P1 are
also stored in the ID card 96, as data representative of
optimum hydraulic pressure Ps*, together with the data
representative of the serial number of the specific pressing
machine 10 used, so that when the same die set is
subsequently used on the machine, the hydraulic pressure Ps
is adjusted to Ps* without the prior determination of the
optimum values P0, P1 and adjustment according to P0, P1.
The pneumatic pressures Pa and Pb may be comparatively
readily adjusted according to the above equations (1) and
(4). However, data representative of optimum pneumatic
pressures Pa* and Pb* may also be stored the ID card 96,
depending upon the requirements.
It is not absolutely necessary to adjust the
operating conditions Pa, Pb, Ps and h exactly to the optimum
values Pax, Pbx, PO and hx as calculated. In this respect,
it is possible to provide certain ranges of tolerances for
those operating conditions, within which the quality of the
products produced by the press 10 satisfies appropriate
requirements.
While the automatic adjustments of the parameters
Pa, Pb, Ps and h under the control of the controller 90 have
been described above, these parameters may be manually
CA 02251503 1999-08-06
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adjusted in a manual mode established by a suitable selector
switch provided in the controller 90, for example. The
selector switch has respective positions for establishing
the automatic and manual modes.
Although the pressure sensors 50, 86 and the
pressure control valves 46, 84 are provided on the press 10,
they may be provided on a stand-alone control console
separate from the press, as in a second embodiment of the
invention described below.
Referring next to Fig. 12, there is shown an
example of a double-action press 150 also adapted ~o perform
a drawing operation on a blank in the form of a metal strip
or sheet. The double-action press 150 is controlled by a
control system as shown in Figs. 15A and 15B, which is
constructed according to the second embodiment of this
invention.
The press 150 has: a bolster 154 on which a lower
die 152 is fixed; an outer slide 160 which carries a
pressure ring 156 through a blank holder plate 158 secured
thereto; and an inner slide 164 to which is fixed an upper
die in the form of a punch 162. The outer slide 160 and the
inner slide 164 are vertically reciprocated by four outer
plungers 166 and four inner plungers 168, respectively. As
shown in Fig. 13, the lower die 152 includes a pressure
portion 170, which cooperates with the pressure ring 156 to
hold a peripheral portion of the blank 171 therebetween
while the blank 171 is drawn by the punch 162 and the lower
CA 02251503 1999-08-06
f
- 51 -
die 152. The lower die 152, pressure ring 156 and punch 162
constitute a die set removably installed on the press 150.
As is apparent from Fig. 13, each of the four
outer plungers 166 is connected to the outer slide 160, via
a die-height adjusting mechanism 172 similar to the
mechanism 52 described above with respect to the
single-action press 10. The mechanism 172 is operated by a
servomotor 174 to adjust a distance ha. The adjusted
distance ha is detected by a rotary encoder 176 (Fig. 15B)
provided on the servomotor 174. The outer slide 166 is
lowered with respect to the outer plunger 166 as the
distance ha increases. Accordingly, the holding force Fs
applied to the pressure ring 156 when the outer plunger 166
is at its lower stroke end is changed with the distance ha.
Thus, the distance ha is one of the operating conditions of
the press 150, which is adjusted depending upon the desired
holding force Fs. The die-height adjusting mechanism 172 is
provided for each of the four outer plungers 166, so that
the distances ha associated with all the plungers 166 can be
adjusted. The outer plungers 166 are provided with
respective sets of strain gages 178 to detect the load
values Fai (i = 1, 2, 3, 4) acting thereon.
Each die-height adjusting mechanism 172 is
integrally connected to a piston 182 of a hydraulic cylinder
180, which is provided for adjusting the holding pressure.
The housing of the hydraulic cylinder 180 is built in the
outer slide 160. The pressure chamber of the hydraulic
CA 02251503 1999-08-06
- 52 -
cylinder 180 is filled with a working oil and communicates
with an oil chamber 186 of a cylinder 184. The cylinder 184
also has an air chamber 188 communicating with an air tank
190, which is connected to connectors 198, 200 disposed on a
frame 196, through respective conduits 192, 194,
respectively. The connectors 198, 200 are connected to
respective pressure-tight connector hoses 208a, 210a, which
are connected to respective connectors 204a, 206a provided
on a control console 202 (Fig. 15A), at their ends remote
from the connectors 198, 200. Pneumatic pressure Pe within
the air tank 190 is detected by a pneumatic pressure sensor
212a provided in the control console 202, and is adjusted by
a solenoid-operated pressure control valve 214a also
provided on the control console 202. The cylinder 180,
cylinder 184 and air tank 190 are provided for each of the
four outer plungers 166 (four die-height adjusting
mechanisms 172 provided on the outer slide 160). The other
three air tanks 190 are connected through respective pairs
of conduits to respective pairs of connectors on the machine
frame 196, which are connected to~ respective connectors
204a-204d through respective pressure-tight connector hoses
208b-208d, and also to respective connectors 206b-206d
through respective pressure-tight connector hoses 210b-210d.
Pneumatic pressures Pe within those three other tanks 190
are detected by respective pneumatic pressure sensors
212b-212d, and adjusted by respective solenoid-operated
pressure control valves 214b-214d. The pneumatic pressure Pe
CA 02251503 1999-08-06
- 53 -
~:r
in each air tank 190 is also one of the operating conditions
of the press 150, which is adjusted depending upon the
holding force Fs. The connectors 198, 200, 204a-204d,
206a-206d, and hoses 208a-208d and 210a-210d are differently
colored for facilitating their connection.
The cylinder 180 of each die-height adjusting
mechanism 172 and the corresponding cylinder 184 and air
tank 190 constitute a force applying device 191 for
producing the holding force Fs to the blank 171 through the
pressure ring 156.
The outer slide 160 is connected to four
counterbalancing pneumatic cylinders 216 attached to the
machine frame 196 of the press 150. The pressure chamber of
each pneumatic cylinder 216 communicates with an air tank
218, which in turn is connected to connectors 224, 226
disposed on the machine frame 196, through respective
conduits 220, 222. The connectors 224, 226 are connected to
respective pressure-tight connector hoses 232, 234, which
are connected to respective connectors 228, 230 provided on
the control console 202, at their' ends remote from the
connectors 224, 226. Pneumatic pressure Pd within the air
tank 218 is detected by a pneumatic pressure sensor 236
provided in the control console 202, and is adjusted by a
solenoid-operated pressure control valve 238 also provided
on the control console 202. The pneumatic pressure Pd is one
of the operating conditions of the press 150, which is
adjusted such that the holding force Fs is not influenced by
CA 02251503 1999-08-06
i
v
- 54 -
the weights of the outer slide 160 and the pressure ring
156. The four counterbalancing pneumatic cylinders 216 are
connected to the common air tank 218.
As shown in Fig. 14, each of the four inner
plungers 168 is connected to the inner slide 164 through a
die-height adjusting mechanism 240 similar to the mechanism
172, so that a distance hb as indicated in the figure is
adjustable by a servomotor 242. The distance hb is detected
by a rotary encoder 244 (Fig. 15B) provided on the
servomotor 242. The inner slide 164 is lowered with respect
to the inner plunger 168 as the distance hb increases.
Accordingly, the pressing force Fp applied to the blank 171
when the inner plunger 168 is at its lower stroke end is
changed with the distance hb. Thus, the distance hb is one
of the operating conditions of the press 150, which is
adjusted depending upon the desired pressing force Fp. The
die-height adjusting mechanism 240 is provided for each of
the four inner plungers 168, so that the distances hb
associated with all the plungers. 168 can be adjusted. The
inner plungers 168 are provided with respective sets of
strain gages 246 to detect the load values Fbi (i = 1, 2, 3,
4) acting thereon.
Each die-height adjusting mechanism 240 is
integrally connected to a piston 250 of an
overload-protective hydraulic cylinder 248. The housing of
the hydraulic cylinder 248 is built in the inner slide 164.
The pressure chamber of the hydraulic cylinder 248 is filled
CA 02251503 1999-08-06
r
- 55 -
with a working oil and communicates with an oil chamber 254
of a cylinder 252. The cylinder 252 also has an air chamber
256 communicating with an air tank 258, which is connected
to an air source 262 through a solenoid-operated pressure
control valve 260. Pneumatic pressure Pg within the air
chamber 256 and air tank 258 is adjusted by the pressure
control valve 260. The pneumatic pressure Pg is detected by
a pneumatic pressure sensor 264, and adjusted depending upon
the pressing capacity of the press 150, so that when an
overload acts on the hydraulic cylinder 248, the piston of
the cylinder 252 is moved toward the air chamber 256 to
permit the adjusting mechanism 240 and the inner slide 164
to move towards each other, for protecting the press 150 and
the die set against damage. The hydraulic cylinder 248,
cylinder 252 and air tank 258 are provided for each of the
four inner plungers 168 (for each of the four die-height
adjusting mechanisms 240 of the inner slide 168), and the
pneumatic pressure Pg in each of the four cylinders 252 is
adjusted as described above.
The inner slide 164 is connected to four
counterbalancing pneumatic cylinders 266 attached to the
machine frame 196 of the press 150. The pressure chamber of
each pneumatic cylinder 266 communicates with an air tank
268, which in turn is connected to the air source 262
through a solenoid-operated pressure control valve 270.
Pneumatic pressure Pf within the pressure chamber of the
cylinder 266 and the air tank 268 is adjusted by the
CA 02251503 1999-08-06
- 56 -
pressure control valve 270. The pneumatic pressure Pf is
detected by a pneumatic pressure sensor 272, and is one of
the operating conditions of the press 150, which is adjusted
such that the pressing force Fp is not influenced by the
weights of the inner slide 164 and the punch 162. The
pressure chambers of the four pneumatic cylinders 266 are
connected to the common air tank 268.
As shown in Figs. 18 and 19, the control console
202 is mounted on a trolley 284 provided with four wheels
280 for easy movement with a handle 282 gripped by the user.
The control console 202 is used selectively for two or more
pressing machines 150, as needed. As described above, the
control console 202 has the connectors 204a-204d, 206a-206d,
228, 230, and the solenoid-operated pressure control valves
2141-214d, 238. The control console 202 also has a connector
286 connected to the pressure control valves 214a-214d and
238. This connector 286 is connected to a pressure-tight
connector hose 288 which in turn is connected to the
above-indicated air source 262, as shown in Fig. 15A. The w
control console 202 is equipped with~various pressure gages
290 for analog indication of the pneumatic pressures Pe, Pd
as detected by the pressure sensors 212a-212d, 236, and a
display panel 292 for digital indication of various
parameters such as the holding force Fsi ( i - 1, 2 , 3 , 4 , )
and the counterbalancing force which are obtained by the
pneumatic pressures Pe, Pd. The control console 202 is also
provided with adjusting switches 293 for manually adjusting
CA 02251503 1999-08-06
- 57 -
the holding force Fsi and the counterbalancing force. The
pressure-tight connector hoses 288, 208a-208d, 210a-210d,
232 and 234 can be accommodated within a storage box 294
provided on the control console 202.
As indicated in Fig. 15A, the control console 202
incorporates a controller 296, which receives output signals
of the pneumatic pressure sensors 212a-212d, 236 which
represent the pneumatic pressures Pe, Pd. The controller 296
is a microcomputer including a central processing unit
(CPU), a random-access memory (RAM), a read-only memory
(ROM), and an input-output interface circuit, as well known
in the art. The CPU processes the signals, to control the
pressure control valves 214a-214d and 238, according to
control programs stored in the ROM, while utilizing a
temporary data storage function of the RAM. The control
console 202 is connected to a power source in a factory,
through a plug 298, and to an exclusive controller 302
through a connector 300, as also indicated in Fig. 15A. The
controller 296 of the control console 202 and the exclusive
controller 302 effect interactive communication so that the
exclusive controller 302 controls the servomotors 176, 242
and the pressure control valves 260, 270.
The exclusive controller 302 may be a personal
computer including a CPU, a RAM, a ROM, an input-output
interface circuit, and an A/D converter. The CPU operates
according to control programs stored in the ROM, while
utilizing a temporary data storage function of the RAM. The
CA 02251503 1999-08-06
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exclusive controller 302 receives the output signals of the
pneumatic pressure sensors 264, 272 representative of the
pneumatic pressures Pg, Pf, the output signals of the rotary
encoders 176, 244 representative of the distances ha, hb,
and the output signals of the strain gages 178, 246
representative of the load values Fai, Fbi. The controller
302 controls the servomotors 174, 242 and the pressure
control valves 260, 270, based on the received signals.
Although Fig. 15B shows only one piece or unit, for the
servomotors 174, 242, strain gages 178, 246, pressure
control valve 260, and pressure sensor 264, four pieces are
in fact provided for each of these elements, as described
above, and the exclusive controller 302 controls all of the
four pieces.
The exclusive controller 302 is adapted to store
machine information on the specifications of the machine
150, and die set information on the die set 152, 156, 162
used on the press 150. The machine information is received
from a suitable input device such as a keyboard, while the
die set information is received from~an ID card 306 through
a transmitter/receiver 304. The ID card 306 is attached to
the lower die 152 as indicated in Fig. 12, and the
transmitter/receiver 304 is disposed on the machine frame
196 such that the transmitter/receiver 304 faces the ID card
306, as also shown in Fig. 12. Like the ID card 96 used in
the first embodiment, the ID card 306 has a data
transmitting function and incorporates a battery. Upon
CA 02251503 1999-08-06
cue",.
- 59 -
reception from the transmitter/receiver 304 of a signal
requesting transmission of the die set information, the ID
card 96 transmits the die set information to the
transmitter/receiver 304, which in turn transmits the
received information to the exclusive controller 302. The
transmitter/receiver 304 and the ID card 306 function as
data input means for receiving the appropriate die set
information. The die set information received by the
transmitter/receiver 304 is sent to the controller 296
through the exclusive controller 302.
The information indicative of the specifications
of the press 150 and the die set 152, 156, 162 is necessary
to determine the pneumatic pressure values Pd, Pe, Pf, and
distances ha and hb, which are optimum for effecting a
drawing operation under the best conditions. The information
received by the controller 302 include the following items,
for example. It is noted that the information on the die set
also includes data indicative of the specific die set used,
which differs depending upon a model of a car for which a
part produced by the press is used, a~type of press on which
the die set is used, and a process in which the product is
obtained from the blank.
[MACHINE INFORMATION]
o Travel Y of the piston of the cylinder 184
o Pressure-receiving area Ax of the hydraulic cylinder 180
o Pressure-receiving area Ay of the oil chamber 186 of the
CA 02251503 1999-08-06
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cylinder 184
o Pressure-receiving area Az of the air chamber 188 of the
cylinder 184
o Volume Ve of the air tank 190
o Total weight Wos of the outer slide 160 and the blank
holder plate 158
o Weight Wis of the inner slide 164
o Total pressure-receiving area Ad of the four pneumatic
cylinders 216
o Total pressure-receiving area Af of the four pneumatic
cylinders 266
o Provisional ha-Fsi relationship (Fsi = c~ha + d)
o Provisional hb-Fpi relationship (Fsi = e~hb)
[DIE SET INFORMATION}
o Weight Wr of the pressure ring 156
o Weight Wq of the punch 162
o Holding force Fsoi
o Pressing force Fpoi
The travel Y, pressure-receiving areas Ax, Ay, Az
and volume Ve are obtained for each of the four outer
plungers 166 connected to the outer slide 160. The travel Y
is a travel distance of the piston of the cylinder 184 from
its lower stroke end toward the air chamber 188. The travel
Y is determined by an experiment, for example, so as to
apply a suitable holding force to the pressure ring 156
based on the pneumatic pressure Pe. The pressure-receiving
CA 02251503 1999-08-06
r
- 61 -
areas Ax, Ay and Az are effective areas which are determined
according to the operating characteristics of the cylinders
180, 184 and which reflect influences of the sliding
resistance and the fluid leakage. The volume Ve includes the
volume of the air chamber 188 of the cylinder 184, and can
be obtained on the basis of a change in the pressure Pe in
relation to the travel distance of the piston of the
cylinder 184.
The total weight Wos of the outer slide 160 and
the blank holder plate 158 is the actual total weight minus
the sliding resistance of the outer slide 160. Like the
weight Ws of the slide plate 20 in the first embodiment,
this weight value Wos can be obtained from a Fa-Pd
relationship, which is obtained from the total load Fa
measured upon lowering of the outer slide 160 while the
pneumatic pressure Pd in the cylinder 216 is changed. The
total load Fa is a sum of the four load values Fai detected
by the strain gages 178. The weight Wos may be replaced by
the actual total weight of the outer slide 160 and the blank
holder plate 158, and the sliding resistance value of the
outer slide 160. The weight Wis of the inner slide 164 can
be obtained from the Fb-Pf relationship.
The total pressure-receiving area Ad of the four
pneumatic cylinders 216 ref lects the influences of the air
leakage of the individual cylinders 216. A gradient of the
line representing the Fa-Pd relationship corresponds to the
total pressure-receiving area Ad. The total
CA 02251503 1999-08-06
- 62 -
~.~~:
pressure-receiving area Af of the four pneumatic cylinders
266 reflects the influences of the air leakage of the
individual cylinders 266. A gradient of the line
representing the Fa-Pf relationship corresponds to the total
pressure-receiving area Af.
The provisional ha-Fsi relationship (i = 1, 2, 3,
4) is a relationship (Fsi - c~ha + d) between the distance
ha and the holding force Fsi when the outer plungers 166
have reached the lower stroke ends. This relationship is
obtained from the load values Fsi detected by the strain
gages 178 (when the plungers 166 have reached the lower
stroke ends), with different values of the distance ha.
Since the value Fsi differs depending upon the rigidity of
the die set 152, 156, 162, suitable members having
considerably higher rigidity than the die set are used for
the measurement of the value Fsi. The obtained provisional
ha-Fsi relationship reflects the rigidity of the press 150
(except for the die set). It is noted that the measurement
is effected after the pneumatic pressure Pd of the pneumatic
cylinders 216 is adjusted so that the lifting force produced
by the cylinders 216 counterbalances the total weight of the
outer slide 160 and the blank holder plate 158. Since the
load value Fsi (holding force Fs) changes with the pneumatic
pressure Pe, the Fsi-ha relationship is set in relation to
the pneumatic pressure Pe, as indicated in the graph of Fig.
20. To obtain the ha-Fsi relationship, the maximum value ha0
of the distance ha when the load value Fsi is zero is used
CA 02251503 1999-08-06
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as a reference. The provisional ha-Fsi relationship is
obtained for each of the four outer plungers 166 (four
die-height adjusting mechanisms 172). The overall holding
force Fs is a sum of the load values Fsi of the individual
plungers 166. The provisional ha-Fsi relationship may be
obtained from the load values Fsi measured by the load
measuring apparatus 100 as shown in Fig. 22. In this case,
spacer blocks 119 are placed on the sensing posts 110 of the
positioning member 102, as shown in Fig. 22, and the load
values Fsi upon abutting contact of the outer slide 160 with
the spacer block 119 are detected by the strain gages 114 on
the sensing posts 110.
The provisional hb-Fpi relationship (i = 1, 2, 3,
4) is a relationship (Fpi - e~hb) between the distance hb
and the pressing force Fpi when the inner plungers 168 have
reached the lower stroke ends. This relationship is obtained
in the same manner as the relationship h-Fpi (Fpi = a~h) in
the first embodiment. That is, the load values Fpi are
detected by the strain gages 246 when the plungers 168 have
reached the lower stroke ends, with different values of the
distance hb. Since the value Fpi differs depending upon the
rigidity of the die set 152, 156, 162, suitable members
having considerably higher rigidity than the die set are
used for the measurement of the load value Fpi. The obtained
provisional hb-Fpi relationship reflects the rigidity of the
press 150. The measurement is effected after the pneumatic
pressure Pf of the pneumatic cylinders 266 is adjusted so
CA 02251503 1999-08-06
a
4 ,
- 64 -
that the lifting force produced by the cylinders 266
counterbalances the weight of the inner slide 164. The
provisional hb-Fpi relationship is obtained for each of the
four inner plungers 168 (four die-height adjusting
mechanisms 240). The overall pressing force Fs is a sum of
the load values Fpi of the individual plungers 168. The
provisional hb-Fpi relationship may be obtained from the
load values Fpi measured by the strain gages 116 of the load
measuring apparatus 100 as shown in Fig. 22.
There will next be described the individual items
of the die set information.
The weight Wr of the pressure ring 156 and the
weight Wq of the punch 162 are the values actually measured
of the ring 156 and punch 162 as manufactured. The holding
force Fsoi (i = l, 2, 3, 4) and the pressing force Fpoi (i =
1, 2, 3, 4) are obtained by a try-and-error procedure, in
which the optimum forces Fsoi and Fpoi suitable for
performing a desired drawing operation are determined by
test operations on a trial or test press on which the
pressure ring 156, lower die 152 and punch 162 are
installed. The holding force Fsoi and pressing force Fpoi do
not include components due to the influences by the weights
of the die set 156, 152, 162 and the sliding resistance
values of the associated components. In the case where the
trial press is similar to that shown in Fig. 12, for
example, the pneumatic pressure Pd is adjusted so that the
outer slide 160 is lowered by the outer plungers 166 while
CA 02251503 1999-08-06
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the total weight of the outer slide 160, blank holder plate
158 and pressure ring 156 is counterbalanced by the lifting
force produced by the cylinders 216. The load values Fai are
detected by the strain gages 178 during a trial drawing
operation effected with the thus adjusted pneumatic pressure
Pd. The load values Fsoi are obtained on the basis of the
detected load values Fai. Further, the pneumatic pressure Pf
is adjusted so that the inner slide 164 is lowered while the
total weight of the inner slide 164 and the punch 162 is
counterbalanced by the lifting force produced by the
pneumatic cylinders 266. The load values Fbi are detected by
the strain gages 246 during a trial drawing operation
effected with the thus adjusted pneumatic pressure Pf. The
load values Fpoi are obtained on the basis of the detected
load values Fbi. Thus, the four load values Fsoi associated
with the four outer plungers 166, and the four load values
Fpoi associated with the four inner plungers 168 are
obtained. The total holding force Fso is a sum of the four
load values Fsoi, while the total pressing force Fpo is a
sum of the four load values Fpoi.
Referring back to Fig. 15A, the controller 296 is
adapted to achieve various functions as illustrated in the
block diagram of Fig. 16, according to the control programs
stored in its ROM. The controller 296 includes a machine
data memory 310 for storing the machine information entered
and stored in the exclusive controller 302. The controller
296 further includes a die data memory 312 for storing the
CA 02251503 1999-08-06
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die set information received from the ID card 306, through
the transmitter/receiver 304. The ID card 306 is attached to
the lower die 152 installed on the press 150.
The block diagram of Fig. 16 shows various
functional blocks which correspond to respective means for
performing the corresponding functions. A Pdx calculating
block 314 is for calculating an optimum pneumatic pressure
Pdx for producing the lifting force which counterbalances
the total weight of the outer slide 160, blank holder plate
158 and pressure ring 156. This calculation is effected
according to the following equation (5), on the basis of the
machine information stored in the machine data memory 310
and the die set information stored in the die data memory
312.
Pdx = (Wr + Wos)/Ad ............. (5)
A Pd adjusting block 316 is for controlling the
solenoid-operated pressure control valve 238 so that the
pneumatic pressure Pd in the air tank 218 detected by the
pneumatic pressure sensor 236 coincides with the optimum
pneumatic pressure Pdx calculated by the Pdx calculating
block 314. With the pneumatic pressure Pd thus adjusted; the
holding force Fsoi specified by the die information is
applied to the pressure ring 156. The pneumatic pressure Pdx
may be calculated, with suitable compensation for a change
in the volume of the pressure chamber of the pneumatic four
cylinders 216 due to a downward movement of the outer slide
160. In this respect, however, since the capacity of the air
CA 02251503 1999-08-06
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tank 218 is sufficiently large, the amount of change in the
pneumatic pressure Pd due to the change in the volume of the
pressure chamber of the cylinders 216 is so small and
negligible. Thus, the block 314 corresponds to means for
calculating the optimum pneumatic pressure Pdx, while the
block 316 cooperates with the pressure control valve 238 and
the pressure sensor 236, to constitute means for adjusting
the pneumatic pressure Pd as one of the operating conditions
of the press 150.
A Pex calculating block 318a is for calculating an
optimum pneumatic pressure Pex for producing the holding
force Fsoi, according to the following equation (6), on the
basis of the machine information in the machine data memory
310 and the die set information in the die data memory 312.
Fsoi = (Ax~Az/Ay){(Pex + Pt)[Ve/(Ve - Az~Y)] - Pt}
............. (6)
where, Pt: atmospheric pressure
A Pe adjusting block 320a is for controlling the
pressure control valve 214a so that the pneumatic pressure
Pe in the air tank 190 detected by the pressure sensor 212a
coincides with the optimum pneumatic pressure Pex calculated
by the Pex calculating block 318a. The optimum pneumatic
pressure Pex is calculated for all of the four air tanks 190
on the basis of the stored machine and die set information,
and the pressure control valves 214b-214d are similarly
controlled to adjust the pneumatic pressures Pe in the other
three air tanks 190, which are detected by the corresponding
CA 02251503 1999-08-06
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-. J
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pressure sensors 212b-212d. To this end, Pex calculating
blocks 318b-318d and Pe adjusting blocks 320b-320d are
provided in the controller 296. In Fig. 16, the blocks 318a,
318b and 320a, 320b are indicated by way of example. The
pneumatic pressures Pe in the four air tanks 190 thus
adjusted assure the optimum holding forces Fsoi at the
positions of the individual four outer plungers 166, as
specified by the die set information, irrespective of the
difference in the pressure-receiving areas of the four
cylinders 180, 184. The blocks 318a-318d correspond to means
for calculating the optimum pneumatic pressures Pex of the
four cylinders 184, and the blocks 320a-320d cooperate with
the pressure control valves 214a-214d and the pressure
sensors 212a-212d to provide means for adjusting the
pneumatic pressures Pe as one of the operating conditions of
the press 150.
The exclusive controller 302 is adapted to achieve
various functions as illustrated in the block diagram of
Fig. 17, according to the control programs stored in its
ROM. The controller 302 includes a.machine data memory 322
for storing the machine information entered through a
keyboard, for example, and a die data memory 324 for storing
the die set information received from the ID card 306
through the transmitter/receiver 304, when the lower die 152
is installed on the press 150.
The block diagram of Fig. 17 shows various
functional blocks which correspond to respective means for
CA 02251503 1999-08-06
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performing the corresponding functions. A Pfx calculating
block 326 is for calculating an optimum pneumatic pressure
Pfx for producing the lifting force which counterbalances
the total weight of the inner slide 164 and the punch 162.
This calculation is effected according to the following
equation (7), on the basis of the machine information stored
in the machine data memory 322 and the die set information
stored in the die data memory 324.
Pfx = (Wq + Wis)/Af ............. (7)
A Pf adjusting block 328 is for controlling the
solenoid-operated pressure control valve 270 so that the
pneumatic pressure Pf in the air tank 268 detected by the
pneumatic pressure sensor 272 coincides with the optimum
pneumatic pressure Pfx calculated by the Pfx calculating
block 326. With the pneumatic pressure Pf thus adjusted, the
pressing force Fpoi as specified by the die information is
applied to the blank 171, without an influence of the
weights of the inner slide 164 and the punch 162. The
pneumatic pressure Pfx may be calculated, with suitable
compensation for a change in the volume of the pressure
chamber of the pneumatic cylinders 266 due to a downward
movement of the inner slide 164. In this respect, however,
since the capacity of the air tank 268 is sufficiently
large, the amount of change in the pneumatic pressure Pf due
to the change in the volume of the pressure chamber of the
cylinders 266 is so small and negligible. It will be
understood that the block 326 corresponds to means for
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calculating the optimum pneumatic pressure Pfx, while the
block 328 cooperates with the pressure control valve 270 and
the pressure sensor 272, to constitute means for adjusting
the pneumatic pressure Pf as one of the operating conditions
of the press 150.
An ha adjusting block 330 is for adjusting the
distances ha associated with the four die-height adjusting
mechanisms 172, independently of each other, so as to
provide the holding force values Fsoi, on the basis of the
machine information and die set information stored in the
memories 322, 324. Initially, a reference value ha0 which is
a maximum value of the distance ha when the holding force
Fsi is zero is determined on the basis of the load value Fai
detected by the strain gages 178. Then, the provisional
ha-Fsi relationship (Fsi = c~ha + d) (as shown in the graph
of Fig. 20) which corresponds to the optimum pneumatic
pressure Pex calculated by the appropriate one of the
calculating blocks 319a-318d is selected and read out from
the machine data memory 322. On the basis of the selected
provisional ha-Fsi relationship, a distance hat for
obtaining the holding force value Fsoi is obtained as
indicated in the graph of Fig. 21, and the distance ha is
adjusted to the obtained value hal, with respect to the
reference value ha0, by operating the servomotor 174. In
this condition, a test operation is conducted on the press
150, with the outer slide 160 moved between their stroke
ends. The holding force value Fsl is measured on the basis
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....,r
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of the load value Fai represented by the output signals of
the strain gages 178 when the outer slide 160 is at its
lower stroke end. Since the predetermined provisional ha-Fsi
relationship is based on higher rigidity of the die set than
the rigidity of the actually used die set 152, 156, 162, the
holding force value Fsl is generally smaller than the
holding force value Foi. Based on a difference between the
values Fsl and Fsoi, a final ha-Fsi relationship (Fsi = c~ha
+ f) is obtained as also indicated in the graph of Fig. 21.
Then the optimum distance hax for obtaining the holding
force value Fsoi is determined by the obtained final ha-Fsi
relationship. The servomotor 174 is operated to adjust the
distance has to the distance hax. The determination of the
distance hax and the adjustment of the distance ha to hax
are effected for each of the four die-height adjusting
mechanisms 172, in the same manner as described above. The
adjustment of the distances ha according to the functional
block 330 assures the holding force values Fsoi as specified
by the die set information, irrespective of a variation in
the rigidity of the press 150 from, one machine to another.
The block 330 corresponds to means for calculating the
optimum distance hax, and cooperates with the servomotor 174
and the strain gages 178 to provide means for adjusting the
distances ha as one of the operating conditions of the press
150.
An hb adjusting block 332 is for adjusting the
distances hb associated with the four die-height adjusting
CA 02251503 1999-08-06
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a.a~,,.
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mechanisms 240, independently of each other, so as to
provide the pressing force values Fpoi, on the basis of the
machine information and die set information stored in the
memories 322, 324, in a manner similar to that used to
adjust the distances ha described above. The block 332
corresponds to means for calculating the optimum distances
hax, and cooperates with the servomotor 242 and the strain
gages 246 to provide means for adjusting the distances hb as
one of the operating conditions of the press 150.
The exclusive controller 302 also functions to
adjust the pneumatic pressure Pg of each cylinder 252, in
the same manner as used for the pneumatic pressure Pc, so
that the load values Fbi detected by the strain gages 246 do
not exceed the respective upper limit values Foli (i = 1, 2,
3, 4). Since the pneumatic pressure Pg can be adjusted
irrespective of the die set used, it may be manually
adjusted by the operator of the machine 150.
It will be understood from the above explanation
of the second embodiment of the invention, that the press
150 is capable of automatically calculating optimum values
of the operating conditions of the press, such as the
optimum pneumatic pressures Pdx, Pex, Pfx, and optimum
distances hax, hbx, so as to establish the optimum holding
pressure Fsoi and optimum pressing force Fpoi as determined
in a trial or test operation on a test machine, irrespective
of variations or differences in the rigidity and sliding
resistances of the press from one machine to another. The
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r
~." ,
automatic calculation of the optimum operating parameters is
effected by the controllers 296, 302, according to the
machine information stored in the machine data memories 310,
322 and the die set information stored in the die data
memories 312, 324 (received from the ID card 306 via the
transmitter/receiver 304). The controllers 296, 302 are
further adapted to automatically adjust the operating
conditions such as the pneumatic pressures Pd, Pe, Pf and
distances ha, hb to the calculated optimum values Pdx, Pex,
Pfx, and hax, hbx. Thus, the press 150 eliminates or
minimizes the conventional cumbersome manual adjustment of
the operating conditions of the press by the trial-and-error
procedure, and reduces the operator's work load upon setting
up the press, while assuring high stability in the quality
of formed products obtained.
In the present second embodiment, the pneumatic
pressure sensors 212a-212d, 236 and the pressure control
valves 214a-214d, 238 necessary for automatic adjustment of
the pneumatic pressures Pd and Pe are provided on the
control console 202, which is easily movable to the location
of the desired one of the pressing machines 150 of the same
type as shown in Fig. 12. Therefore, the automatic
adjustment of the pressures Pd, Pe according to the present
invention may be accomplished even if the machine in
question is not equipped with such pressure sensors and
control valves. The control console 202 may be carried to a
desired factory to demonstrate its functions and the
CA 02251503 1999-08-06
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advantages of the automatic adjustment of the pressure Pd,
Pe for improved quality of formed articles produced by the
adjusted press. The control console 202 is also convenient
where a certain pressing operation is effected on selected
ones of the machines in a pressing line. Further, the
control console 202 permits manual adjustment of the holding
force values Fsi and the counterbalancing force values at
the positions of the four adjusting mechanisms 172, 240, and
provides analog indication of the pressures Pd, Pe on the
pressure gages 290, which is helpful in diagnosing the press
150.
As described above with respect to the first
embodiment, it is not absolutely necessary to adjust the
operating conditions Pd, Pe, Pf, ha and hb exactly to the
optimum values Pdx, Pex, Pfx, hax and hbx as calculated by
the controllers 296, 302. That is, certain ranges of
tolerances may be provided for those operating conditions,
provided the tolerance ranges satisfy appropriate
requirements in terms of the quality of the products
produced.
While the operating parameters Pd, Pe, Pf, ha and
hb are automatically controlled under the control of the
controllers 296, 302 according to the second. embodiment,
suitable mode selector switches may be provided on the
controller 296 and/or the controller 302, so that those
parameters are automatically adjusted when the appropriate
selectors switches are set in the automatic mode position,
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and may be manually adjusted when the switches are set in
the manual mode position.
In the second embodiment, only the pressure
sensors 212a-212d and 236 and the pressure control valves
214a-214d and 238 for the pressures Pd and Pe are provided
on the stand-alone control console 202 separate from the
press 150, the pressure sensor 272 and the pressure control
valve 270 for the pressure Pf may also be provided on the
control console 202. Conversely, the sensors 212a-212d, 236,
and valves 214a-214d, 238 may be provided on the press 150.
Referring to Figs. 23-28, there will be described
a third embodiment of this invention.
The third embodiment is identical with the first
embodiment of Figs. 1-11, except for the functions of the
controller 90, and the use of an operator's control panel
368 as shown in Figs. 23A and 23B. The control panel 368 is
connected to the controller 90 for interactive communication
therebetween, to perform various functions such as the
adjustment of the hydraulic pressure Ps of the cushioning
device 51. In the present embodiment, the controller 90 is
adapted to receive, from the press 10, a TEST RUN signal
indicating that a TEST RUN switch for performing a test
operation on the press 10 is in the ON position, and a LOWER
END signal indicating that the main slide 20 is at the lower
stroke end or at a position slightly above the lower stroke
end. In the present embodiment, the press operation data
memory 128 of the ID card 96 stores data indicative of the
CA 02251503 1999-08-06
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optimum initial values of the hydraulic pressure Ps*,
together with data indicative of the serial' numbers of
different machines of the press 10.' The adjustment of the
hydraulic pressure Ps is effected according to a control
routine as illustrated in the flow chart of Fig. 24, which
is stored in the ROM of the controller 90.
The control routine of Fig. 24 is started with
step Sl to determine whether a selector switch 372 on the
operator's control panel 368 is set in AUTO position for
automatic adjustment of the hydraulic pressure Ps, or not.
If the selector switch 372 is placed in the AUTO position,
step S2 is implemented to determine whether a SETUP
pushbutton 374 on the panel 368 has been depressed, or not.
If the pushbutton 374 has not been depressed, step 53 is
implemented to determine whether data indicative of the
optimum initial hydraulic pressure Ps* are stored in the die
data memory 132, or not. If the data indicative of the
optimum initial hydraulic pressure Ps* are stored in the
memory 132, step S3 is followed by step S5 which will be
described. If the data are not stored in the memory 132,
that is, the die set 12, 18, 30 is used for the first time
on the press 10 in question, the control flow goes back to
step S1. Steps S1-S3 are repeatedly implemented until the
SETUP pushbutton 374 is depressed.
When the pushbutton 374 is depressed, an
affirmative decision (YES) is obtained in step S2, and the
control flow goes to step S4 to adjust the initial hydraulic
CA 02251503 1999-08-06
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r
pressure Ps, namely, to establish the optimum initial
hydraulic pressure P0, according to a control routine as
illustrated in the flow chart of Figs. 25A and 25B.
Initially step S4-1 is implemented to adjust the pneumatic
pressure Pa so as to obtain the optimum holding force Fso.
This adjustment is made because the pneumatic pressure Pa
influences the optimum initial hydraulic pressure Ps that
assures uniform or even distribution of the holding force
Fso on the pressure ring 30. That is, the adjustment of the
pneumatic pressure Pa so as to obtain the optimum holding
force Fso is a prerequisite for adjusting the hydraulic
pressure Ps prior to a pressing operation. Although the
pneumatic pressure Pa may be adjusted to the optimum value
Pax according to the above equation (1), the pneumatic
pressure Pa may be adjusted so that the holding pressure Fs
detected by the strain gages 61 when the press 10 is
operated substantially coincides with the optimum holding
pressure Fso as specified by the die set information. To
this end, the pneumatic pressure Pa is changed until the
detected holding force Fs substantially coincides with the
specified optimum holding pressure Fso.
Step S4-1 is followed by step S4-2 in which
provisional initial hydraulic pressure Pn (n = 1 through 10)
is set or changed. In the first execution of the routine of
Figs. 25A and 25B, the provisional value P1 is set at
200kgf/cm2 in the RAM of the controller 90. As the routine
of Figs. 25A and 25B is repeated, the provisional value Pn
CA 02251503 1999-08-06
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is lowered in decrements of 20kgf/cm2, down to 20kgf/cm2
which corresponds to P10. It is noted that lkgf/cmz is equal
to about 9.8 x 10''Pa (Pascal).
Step S4-2 is followed by step S4-3 in which the
pump 34 and the pressure control valve 36 are operated so
that the initial hydraulic pressure Ps prior to a pressing
operation is adjusted to the currently set provisional value
Pn (e.g., 200kgf/cm2 in the first cycle of execution of the
routine of Figs. 25A and 25B). When the actual hydraulic
pressure Ps detected by the pressure sensor 38 becomes
substantially equal to the provisional value Pn, step S4-4
is implemented to activate an appropriate buzzer, which
indicates that the pressure Ps has been adjusted to the
currently selected provisional value Pn. Step S4-4 is
followed by step 54-5 to determine whether the TEST RUN
switch for initiating a test operation on the press 10 is
turned ON or not. When the TEST RUN switch is turned ON by
the operator who has recognized the activation of the buzzer
RUN switch, step S4-6 is implemented to turn off the buzzer,
and the control flow goes to step S4-7 in which the press 10
is operated to perform a test operation with a reciprocation
of the main slide 20, and the hydraulic pressure Ps at this
time is stored as pressure PXn in the RAM and indicated on
the indicator 376 on the panel 368. The pressure Ps during
the pressing operation vibrates as shown in the graph of
Fig. 26. The pressure Ps stored as the pressure PXn is a
pressure when the vibration has settled, that is, a pressure
CA 02251503 1999-08-06
_ 79 _
detected by the sensor 38 when the LOWER END signal
indicative of the lower stroke end of the main slide 20 is
received by the controller 90. Thus, the pressure PXn is the
pressure Ps when the main slide 20 has been lowered to its
lower stroke end SL (Fig. 26), or a position slight above
the lower stroke end SL. However, the pressure PXn may be
the maximum, minimum or average pressure detected during a
downward movement of the main slide 20 to its lower stroke
end SL. The hydraulic pressure Ps is always displayed on an
indicator 370 on the operator's control panel 368,
irrespective of whether the press 10 is in a pressing
operation or not.
Then, step S4-8 is implemented to calculate an
amount of change OPX - ~PXn - PXn-1~ of the currently
obtained pressure PXn with respect to the preceding value
PXn-1. Step S4-8 is followed by step S4-9 to determine
whether the amount of change SPX is equal to or smaller than
a predetermined value S, or not. The predetermined value
is for determining whether the pressure PXn remains
substantially constant in spite of a change in the
provisional initial hydraulic pressure Pn. This value ~ is
determined depending upon the expected fluctuation and
detecting error of the pressure PXn, and is usually in the
neighborhood of 5kgf/cmz. If an affirmative decision (YES)
is obtained in step S4-9, step S4-10 is implemented to set a
flag F to "1", and step S4-11 is implemented to activate one
of ten indicator lights 378 on the panel 368. More
CA 02251503 1999-08-06
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specifically, the ten indicator lights 378 correspond to the
ten provisional values Pn set in step S4-2, and the light
378 corresponding to the preceding value Pn-1 is activated.
If the amount of change SPX is larger than the
predetermined value ~, step S4-9 is followed by step S4-12
to determine whether the flag F is equal to "1" or not. If
an affirmative decision (YES) is obtained in step S4-12,
step S4-13 is implemented~to reset the flag F to "0", and
step S4-11 is then implemented. The control flow goes to
step S4-14 if a negative decision (NO) is obtained in step
S4-12, or after step S4-11 has been implemented. Step S4-14
is provided to determine whether the currently set
provisional value Pn is 20kgf/cm2 or not, that is, whether
the pressures PXn corresponding to all the ten provisional
values Pn have been detected and stored. If not, the control
flow goes back to step S4-2. Steps S4-2S4-14 are repeatedly
implemented with the provisional value Pn decremented down
to 20kgf/cm2. In the first control cycle in which the
provisional value Pn is 200kgf/cm2, steps S4-8 through S4-13
are skipped, and step S4-7~is followed by step S4~-14.
The graph of Fig. 27 shows an example of the
hydraulic pressure PXn obtained for the 10 provisional
pressure values Pn (n = 1 through 10), by repeated execution
of steps S4-2 through S4-14 of Figs. 25A and 25B. In this
specific example, the pressure PX4 when the provisional
value P4 is 140kgf/cmz is 200kgf/cmz, and the pressure PX5
CA 02251503 1999-08-06
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when the provisional value P5 is 120kgf/cmz is 198kgf/cmz.
Accordingly, the amount of change SPX =
~PX5 - PX4) of the pressure PX5 with respect to the pressure
PX4 is 2kgf/cmz, which is smaller than the predetermined
value ~ of 5kgf/cm2, for example. Therefore, an affirmative
decision (YES) is obtained in step S4-9, whereby the
indicator light 378 corresponding to the provisional value
P4 (140kgf/cm2) is activated. Similarly, the affirmative
decision (YES) is obtained in step S4-9 for the provisional
values P6 (100kgf/cm2) and P7 (80kgf/cmz), and the indicator
lights 378 corresponding to the provisional values P5
(120kgf/cm2) and P6 (100kgf/cm2) are activated. When the
provisional value PS is 60kgf/cmz, the amount of change SPX '
- ~PX8 - PX7~ is larger than the predetermined value (3, and a
negative decision (NO) is obtained in step S4-9. Since the
flag F has been set to "1", an affirmative decision (YES) is
obtained in step S4-12, step S4-13 is implemented to reset
the flag F to "0", and step S4-11 is implemented to activate
the indicator light 378 corresponding to -the preceding
provisional value P7 (80kgf/cmz)..Hatched circles in the
bottom row of the indicator lights 178 in Fig. 23B indicate
the activated lights 178.
An optimum range of the initial pressure Ps
indicated by the activated indicator lights 378 corresponds
to a range C of Fig. 27 in which the amount of change oPX of
the pressure PXn is smaller than the predetermined value
in spite of the change in the provisional initial pressure
CA 02251503 1999-08-06
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Pn. While the initial hydraulic pressure Ps of each
hydraulic cylinder 32 is held within this optimum range, the
pistons of the cylinders 32 connected to the respective
cushion pins 24 are located between their upper and lower
travel or stroke ends, without bottoming thereof, during a
pressing operation with the main slide 20 lowered down to
its lower stroke end. The range of the provisional initial
pressure values Pn and the decrementing amount used in step
S4-2 to detect the optimum range of the initial hydraulic
pressure Ps are suitably determined for individual pressing
operations effected with different holding forces and
different numbers of the cushion pins 24, depending upon the
number of the cylinders 32, pressure-receiving area and
travel distance of the pistons of the cylinders 32, and
optimum range of the holding force, so that the optimum
range of the initial hydraulic pressure Ps can be detected
for each specific pressing job.
An excessive variation in the length of the
cushion pins 24 or in the travel distance of the pistons of
the hydraulic cylinders 32 may cause bottoming of the
pistons of some of the cylinders 32. In the event of such
abnormality of the cushioning device 51, the optimum range
of the initial hydraulic pressure Ps cannot be found out
according to the routine of Figs. 25A and 25B. In this case,
the abnormality can be detected by the operating states of
the indicator lights 378. For instance, none of the lights
CA 02251503 1999-08-06
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378 are activated or none of the successive lights 378 are
activated.
If the selector switch 372 is set to "MANUAL"
position, the provisional initial hydraulic pressure Pn can
be set as desired by using Pn setting dials 380 on the panel
368. In this manual adjustment, too, the hydraulic pressure
PXn is indicated on the indicator 376, facilitating the
manual adjustment of the initial hydraulic pressure Ps by
changing the provisional value Pn by a desired incremental
or decremental amount.
When the provisional value Pn is relatively low,
the amount of change SPX in response to a change in the
provisional value Pn may be small due to the introduction of
air in the hydraulic cylinders 32. In this case, an
affirmative decision (YES) may be obtained in step S4-9. To
avoid this drawback, the control routine of Figs. 25A and
25B may be modified so that the activation of the indicator
lights 378 to indicate the optimum range of the initial
hydraulic pressure Ps is controlled on the basis of the
pressure PXn detected when the first affirmative decision
(YES) is obtained in step S4-9, or so that step S4-9 is
followed by step S4-15 and the following steps, when the
negative decision (NO) is obtained in step S4-9 for the
first time after the first affirmative decision (YES) in
step S4-9.
When an affirmative decision (YES) is obtained in
step S4-14, step S4-15 is implemented to determine whether
CA 02251503 1999-08-06
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'a°~p~,;
- 84 -
the flag F is set at "1" or not. If so, step S4-16 is
implemented to activate the indicator light 378
corresponding to the provisional value P10 (20kgf/cmz).
Then, the control flow goes to step S4-17 to reset the flag
F to "0", and to step S4-18. If a negative decision (NO) is
obtained in step S4-15, the control flow goes to step S4-18,
skipping steps S4-16 and S4-17. Steps S4-15 through S4-17
are provided to activate the indicator light 378
corresponding to the provisional value P10, if the amount of
change SPX of the pressure PX10 (with the provisional value
P10 is 20kgf/cm2) from the pressure PX9 (with the
provisional value P9 is 40kgf/cm2) is equal to or smaller
than the predetermined value S.
Step S4-18 is provided to calculate an optimum
hydraulic pressure P0, which is an average of the
provisional values Pn whose indicator lights 378 are
activated. In the specific example as shown in Fig. 23B, the
optimum initial value PO of the hydraulic pressure Ps is
equal to 110kgf/cm2 - (80kgf/cmz + 100kgf/cm2 + 120kgf/cm2 +
140kgf/cm2)/4. Then, the pump 34 and pressure control valve
36 are controlled so that the hydraulic pressure Ps prior to
a pressing operation is adjusted to the calculated optimum
initial value P0. As a result, the pressing operation can be
achieved with even distribution of the optimum holding force
on the pressure ring 30, with the pistons of all the
cylinders 32 located between their upper and lower travel
ends. As described below, the optimum initial value PO thus
CA 02251503 1999-08-06
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calculated is used as data indicative of the optimum initial
hydraulic pressure Ps* stored in the die data memory 132.
Referring back to the flow chart of Fig. 24, step
S5 is implemented if the data indicative of the optimum
initial hydraulic pressure Ps* are stored in the memory 132,
that is, if the die set in question has ever been used on
the present press 150. In step S5, the optimum initial
hydraulic pressure Ps* is read from the die data memory 132.
Then, step S6 is implemented to control the pump 34 and the
pressure control valve 36 so that the hydraulic pressure Ps
coincides with the optimum pressure Ps*.
As indicated in Fig. 23B, the operator's control
panel has a selector switch 382 for writing and reading data
on and from the ID card 96, according to a control routine
illustrated in the flow chart of Fig. 28. This routine is
initiated with step SS1 to determine whether the selector
switch 382 is set in WRITE position or not. When the switch
382 is placed in the WRITE position, step SS2 is implemented
so that the data provided on the operator's control panel
368 are sent to the ID card 96 through the
transmitter/receiver 94. The data sent to the ID card 96
include the optimum initial hydraulic pressure PO as
displayed on the indicator 370, and the number of the
cushion pins 24 as manually entered through setting dials
386. The optimum initial hydraulic pressure PO which is the
pressure Ps prior to a pressing operation is stored as the
optimum initial hydraulic pressure Ps* in the press
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operation data memory 128 of the ID card 96, together with
the serial number of the press 10. When the number of the
cushion pins 24 as manually entered through the setting
dials 386 is different from that stored the die set data
memory 125 of the ID card 96, the number stored in the
memory 125 is updated to the actual number entered through
the setting dials 386. In this respect, it is noted that the
optimum initial hydraulic pressure PO obtained according to
the routine of Figs. 25A and 25B differs with the number of
the cushion pins 24 actually used on the press 10, and
therefore the number n of the pins 24 stored in the ID card
96 must be updated to the actual number n. Since the number
n stored in the ID card 96 is thus updated with the switch
382 set in the WRITE position, the number displayed on the
indicator 184 is accordingly changed.
If a negative decision (NO) is obtained in step
SS1, that is, if the switch 382 is not placed in the WRITE
position, step SS3 is implemented to determine whether the
switch 382 is placed in READ position or not. If so, the
control flow goes to step SS4 to read out the data from the
ID card 96 and transmit the data to the die data memory 132
of the controller 90 through the transmitter/receiver 94. As
described above, the data stored in the ID card 96 include
the number n of the cushion pins 24, and may include the
optimum initial hydraulic pressure Ps* for the press 10 in
question. The number n is displayed on the indicator 384
according to the data stored in the die data memory 132. If
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the optimum initial hydraulic pressure Ps* is transmitted to
the memory 132, the hydraulic pressure Ps is adjusted to the
optimum value Ps* in step S6 of the routine of Fig. 24.
In the present third embodiment, the optimum
initial hydraulic pressure PO is obtained according to the
control routine of Figs. 25A and 25B if the die set in
question is used for the first time on the press 10 in
question. The pressure PO thus obtained is stored as the
optimum initial hydraulic pressure Ps* in the ID card 96, so
that the hydraulic pressure Ps of the hydraulic cylinders 32
is adjusted to the optimum value Ps* when the same die set
is subsequently used on the same press 10. The utilization
of the optimum pressure Ps* eliminates redundant execution
of the routine of Figs. 25A and 25B each time a pressing
operation using the same die set is performed on the press
10, whereby the overall time required to establish the
optimum initial hydraulic pressure Ps prior to a production
run is considerably reduced, and the production efficiency
of the press 10 is accordingly improved. In the present
embodiment, the routine of Figs. 25A and 25B requires the
operator to activate the TEST RUN switch (step S4-5) to
establish the optimum initial hydraulic pressure PO (Ps*).
Hence, the elimination of the routine of Figs. 25A and 25B
for the subsequent pressing job using the same die set on
the press 10 significantly reduces the operator's load.
Although the control routine of Figs. 25A and 25B
is adapted such that the operator is required to depress the
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TEST RUN switch to perform a test operation to measure the
pressure PXn for finding out the optimum initial hydraulic
pressure PO (Ps*), the press 10 may be automatically started
to perform the test operation, if a safety fence is provided
around the press 10 to safeguard the operator.
In the present third embodiment, step S4 of Fig.
24 (steps of the routine of Figs. 25A and 25B) is a step for
determining the optimum value Ps* and adjusting the initial
hydraulic pressure Ps of the hydraulic cylinders 32 to the
optimum value Ps*, as one of the operating conditions of the
press 10. Further, steps SS1 and SS2 correspond to a step
for storing the optimum initial value Ps* of the hydraulic
pressure Ps, and steps S5 and S6 of Fig. 24 correspond to a
step of reproducing the stored optimum initial value Ps* on
the press 10. It is also noted that a portion of the
controller 90 assigned to implemented step S4 of Fig. 24
functions as adjusting means for adjusting the initial
hydraulic pressure Ps to the determined optimum value Ps*,
while a portion of the controller 90 assigned to implement
steps S5 and S6 of Fig. 24 functions as reproducing means
for establishing the optimum value Ps* on the press 10.
Further, the transmitter/receiver 94, ID card 96 and
selector switch 382 constitute means for receiving the
optimum holding force Fso as die set information necessary
to adjust the pneumatic pressure Pa of the pneumatic
cylinder 42, which is necessary for the adjustment of the
hydraulic pressure Ps. The press operation data memory 128
CA 02251503 1999-08-06
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of the ID card 96 serves as memory means for storing the
optimum initial value Ps* of the hydraulic pressure Ps.
While the first, third and fourth embodiments of
Figs. 1-11 and 23-38 utilize the stored die set information
such as the optimum pressing and holding forces Fpo, Fso to
determine the optimum values h*, Ps* of the operating
conditions, these optimum values h* and Ps* need not be
obtained on the basis of the stored die set information, but
may be determined by a trial-and-error procedure, by
observing the quality of the products obtained in test
operations. In this case, too, storing the determined
optimum values h* and Ps* in the ID card 96 for the
subsequent use is effective to improve the production
efficiency of the press.
Referring to Figs. 29-31, there is shown an
operator's control panel 390 used in a fourth embodiment of
this invention. The control panel 390 is connected to the
controller 90 of Fig. 4 for interactive communication
therebetween. In the present embodiment, a suitable sensor
is provided to detect the vertical position H of the main
slide 20 of the press 10. This sensor may be a sensor for
directly detecting the position H of the slide 20, or a
rotary encoder for detecting the rotating angle of a
crankshaft for reciprocating the slide 20. The output of the
sensor is applied to the controller 90. Further, the die set
data memory 125 of the ID card 96 stores data indicative of
the thickness t of the blank (metal strip) to be drawn on
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the press 10, while the press operation data memory 128
stores data indicative of the optimum distances h* of the
die-height adjusting mechanisms 52, for the individual
machines of the press 10, whose serial numbers are also
stored in the memory 128. The distance h of the mechanisms
52 is adjusted in a procedure illustrated in the flow charts
of Figs. 32-35 and 37-38, which show the manual operations
by the operator, as well as the operations performed by the
controller 90. In the present fourth embodiment, the
distances h associated with the four die-height adjusting
mechanisms 52 are adjusted by the single servomotor 60, and
the bolster 14 is a moving bolster which is movable for
facilitating the installation of the die set (12, 18, 30) on
the press 10.
The procedure for adjusting the distance h will be
explained. Initially in step Q1, the bolster 14 on which the
die set (12, 18, 30) are placed is moved inward of the press
10, by suitable switches. In the next step Q2, the bolster
14 is automatically positioned in place. At this time, the
piston of the pneumatic cylinder 42 is held at its lower
stroke end by a hydraulic brake. In step Q3, a selector
switch 392 on~the operator's control panel 390 is turned to
"MANUAL" position. Then, in step Q4, a selector switch 394
is turned to "SETUP" position, whereby a SETUP light 396 is
activated. Step Q4 is followed by step S5 in which a SETUP
pushbutton 398 is depressed. In the next step S6, the TEST
RUN switch is turned ON, and the press 10 is operated in an
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inching mode. Step Q6 is followed by step Q7 to determine
whether a pressing force Fp detected by the strain gages 61
has reached a predetermined value F0, or not. When the force
Fp has become equal to the value F0, the downward movement
of the main slide 20 is automatically stopped. The
predetermined value FO ranges from several tons to several
tens of tons, for example, and is determined so as to
prevent an overload of the driving system of the press 10.
This value FO is stored as one item of the machine
information in the machine data memory 130. The automatic
stopping of the downward movement of the main slide 20 in
step Q8 is effected since the selector switch 394 is placed
in the SETUP position.
In the next step Q9, the upper die 18 is fixed to
the main slide 20, by automatic activation of a clamping
device on the slide 20. However, the die 18 may be manually
installed on the main slide 20 by the operator, using bolts
or other fastening means. Step Q9 is followed by step Q10 in
which the vertical position H of the main slide 20 is
detected and stored in the RAM of. the controller 90. Step
Q11 (Fig. 33) is then implemented to move the main slide 20
upwards, using a suitable switch. In the next step Q12, the
upper stroke end of the main slide 20 is detected, and the
main slide 20 is stopped at the upper stroke end, whereby an
UPPER END light 400 is activated.
In the next step Q13, the selector switch 394 is
turned to "TEST" position, and'a TEST light 402 is
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activated. Step Q13 is followed by step Q14 in which an
adjusting amount ~h of the distance h is calculated
according to the following equation (8), on the basis of a
dimension DH, the thickness t of the blank stored as the die
set information), and a predetermined pressing distance x0.
The servomotor 60 is operated to adjust the distance h of
the die-height adjusting mechanisms 52 by the calculated
adjusting amount ~h. The dimension 0H is calculated from the
vertical position H of the main slide 20, and the
subtraction of this dimension DH in the equation (8) to
calculate the adjusting amount ~h assures the pressing force
Fp equal to the predetermined value F0, when the main slide
is at its lower stroke end. The subtraction of the
thickness t assures the pressing force Fp - FO in a
15 production run with the blank loaded on the
press 10. Thus,
by adjusting the distance h of the die-height adjusting
mechanisms 52 by the calculated amount ~h, the blank is
pressed with the effective pressing distance x0 at the end
of the downward movement of the main slide 20. The pressing
20 distance x0 is in the neighborhood of l.Omm, for instance.
oh = -off - t + x0 ...............:. (8)
In step Q15, the blank is loaded onto the press
10. In the next step Q16, the TEST RUN switch is depressed
to effect a test pressing operation with one reciprocation
of the main slide 20. Step Q16 is followed by step Q17 in
which the pressing force Fp is detected by the strain gages
61 at the end of the downward movement of main slide to its
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lower stroke end, and the detected force Fp is stored as F1.
In the next step Q18, a ratio Da is calculated according to
the following equation (9), on the basis of the values FO
and F1 and the pressing distance x0.
~a = (F1 - FO)/x0 .................
(9)
The graph of Fig. 36 indicates a relationship
between the pressing forces FO and F1 and the pressing
distance x0. The ratio ~a corresponds to the gradient of a
line representing the relationship. The graph of Fig. 36
corresponds to the h-Fpi relationship of Fig. 9~of the first
embodiment. The relationship of Fig. 36 is specific to each
individual machine of the press 10.
In the next steps Q19 and Q20, an ID CARD
COMMUNICATION selector switch 404 is turned to ON position,
and an ID CARD READ pushbutton 406 is depressed, whereby the
die set information are read out from the ID card 96 and
stored in the die data memory 132, in step Q21 (Fig. 34).
The die set information stored in the memory 132 are
displayed on a display section 408 of the control panel 390.
The display section 408 includes: an indicator 410 for
indicating the total pressing force Fpo (sum of the load
valuss Fpoi associated with the four plungers 22); an
indicator 412 for indicating the holding force Fso; an
indicator 414 for indicating the weight Wr of the pressure
ring 30; an indicator 416 for indicating the weight Wu of
the upper die 18; and an indicator 418 for indicating the
number n of the cushion pins 24.
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In step Q22, a difference Ffo - (Fpo - Fso)
between the pressing and holding forces Fpo and Fso is
calculated. Step Q22 22 is followed by step Q23 to calculate
an adjusting amount xl of the distance h according to the
following equation (10). The servomotor 60 is operated to
adjust the distance h by the calculated amount xl. With the
distance h adjusted by the amount xl, the pressing force Fp
at the lower stroke end of the main slide 20 is
substantially equal to the calculated value Ff0 when the
piston of the pneumatic cylinder 42 is at the lower stroke
end at which the holding force Fs is zero, as is apparent
from the graph of Fig. 36.
xl = (Ff0 - fl)/~a ..................... (10)
In the next step Q24, the TEST RUN switch is
turned on to perform a test operation with one reciprocation
of the main slide 20. Step Q25 is then implemented to detect
the pressing force Fp (at the lower stroke end of the main
slide 20) on the basis of the output of the strain gages 61,
calculate a difference ~Fp - FfO~, and determine whether the
difference ~Fp - FfO~ is smaller than a predetermined
tolerance value yl. If a negative decision (NO) is obtained
in step Q25, step Q26 is implemented to incrementally or
decrementally change the distance h. Steps Q24-Q26 are
repeatedly implemented until the difference ~Fp - FfO~
becomes smaller than the tolerance yl. The determination in
step Q25 and the adjustment in step Q26 may be automatically
effected under the control of the controller 90, or may be
CA 02251503 1999-08-06
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manually conducted by the operator. In the latter case, the
operator makes the determination in step Q25 by observing
the pressing force Fp indicated on the indicator 410, and
operates the servomotor 60 by using an appropriate switch.
The indicator 420 in the display section 408 indicates the
distance h as detected by the encoder 59.
After the difference ~Fp - FfO~ has become smaller
than the tolerance Y1, the main slide 20 is lowered in step
Q27, and stopped at its lower end in step Q28, by using the
appropriate switch. Then, in step Q29, the pneumatic
cylinder 42 is unlocked and the cushion pad 28 is moved
upwards. In the next step Q30 (Fig. 35), the pneumatic
pressure Pa of the pneumatic cylinder 42 is adjusted so as
to obtain the holding force Fso, according to the equation
(1), for example. In this respect, it is noted that the
weight Wr of the pressure ring 30 used for producing an
outer panel of a motor vehicle is generally 10 tons and is
considerably smaller than those of the other components
whose weights are used in the equation (1). Therefore, the
weight Wr may be ignored in adjusting the pneumatic pressure
Pa. This may also apply to the first embodiment.
With the pneumatic pressure Pa adjusted in step
Q30, the pressing force Fp detected by the strain gages 61
is increased by the amount equal to the holding force Fso.
Step Q30 is followed by step Q31 to determine whether a
difference ~Fp - Fpo~ is smaller than a predetermined
tolerance Y2. If a negative decision (NO) is obtained in
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step Q31, step Q30 is again implemented. Steps Q30 and Q31
are repeatedly implemented until the difference ~Fp - Fpo~
becomes smaller than the tolerance y2. If an affirmative
decision ( YES ) is obtained in step Q31, a NORMAL light 424
is activated in step Q32. The activation of the light 424
indicates that the pressing force Fp is adequate.
Subsequently, the ID CARD COMMUNICATION switch 404 is turned
to the ON position in step Q33, and an ID CARD WRITE
pushbutton 426 is depressed in step Q34. As a result, the
distance h indicated on the indicator 420 in the display
section 420 and the pressing force Fp indicated on the
indicator 410 are written as optimum distance h~ and optimum
pressing force Fp in the press operation data memory 128 of
the ID card 96, together with the serial number of the press
10 in question. Other data such as the number n of the
cushion pins 24 indicated on the indicator 418 and the
optimum hydraulic pressure Ps indicated on an indicator 428
are also transmitted and written in the ID card 96, as in
the third embodiment of Figs. 23-28. The present fourth
embodiment has the same function as~the third embodiment, in
connection with the hydraulic pressure Ps.
Referring to the flow charts of Figs. 37 and 38,
there will be described a procedure for adjusting the
distance h when the die set once used on the press 10 and
removed therefrom is again used on the press 10.
Steps W1-W3 are the same as steps Q1-Q3 of Fig.
32. In the next step W4, the selector switch 394 is turned
CA 02251503 1999-08-06
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~c a;
to the TEST position. In step W5, the selector switch 404 is
turned to the ON position. Then, the ID CARD COI~iUNICATION
pushbutton 406 is depressed in step W6. Consequently, the
die set information, and the press operation data
corresponding to the press 10 in question are read out from
the ID card 96, and displayed on the display section 408. In
the next step W8, the servomotor 60 is operated to adjust
the distance h to the optimum value h*. This adjustment of
the distance h may be achieved automatically under the
control of the controller 90, or may be done by the
operator, using the appropriate switch while observing the
optimum value h* indicated on the indicator 420. Thus, the
distance h is adjusted, and the same pressing conditions as
established by the procedure of Figs. 32-35 are reproduced.
In the next step W9 (Fig. 38), the main slide 20
is lowered in an inching mode by using the appropriate
switch. In step W10, the downward movement of the slide 20
is stopped at its lower stroke end, by the same switch.
Suppose the thickness t of the blank is about 0.6-0.7mm, the
main slide 20 comes into abutting contact with the upper die
18 placed on the pressure ring 30, before the blank is
loaded on the press 10. However, there is not a risk that
the motor to drive the main slide 20 is overloaded. The
position at which the main slide 20 is stopped need not be
the lower stroke end. In step W11, the upper die 18 is fixed
to the main slide 20. In step W12, the pneumatic cylinder 42
is unlocked, and the cushion pad 28 is moved upwards.
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Further, the pneumatic pressure Pa is adjusted so as to
obtain the optimum holding force Fso. These steps W11 and
W12 are similar to steps the Q9, Q29 and Q30 described
above. Then, step W13 is implemented to move the main slide
20 to its upper stroke end. The blank is loaded onto the
press 10, in step W14, and the press 10 is operated in step
W15, with one reciprocation of the main slide 20 as in a
production pressing cycle. Step W16 is then implemented to
confirm the pressing force Fp and holding force Fs indicated
on the respective indicators 410, 412, and visually check
the product manufactured, for reconsidering the pressing
conditions for further adjustment.
In the present fourth embodiment, too, the
distance h must be adjusted according to the procedure
i l lustrated in the f low charts of Figs . 3 2-3 5 , when the die
set is used for the first time on the press 10. The adjusted
optimum distance h* for this specific pressing machine is
stored in the ID card 96, so that the optimum distance h*
can be utilized when the same die set is used again on the
press 10. Thus, the adjustment of the distance h may be done
using the stored optimum value h* and can be completed in a
reduced time, whereby the production efficiency of the press
10 is improved and the operator's work load is considerably
reduced.
Although the fourth embodiment also requires the
operator's manipulation of the press 10 using the
appropriate switches to perform various operations necessary
CA 02251503 1999-08-06
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,: .
r.w..r
to adjust the distance h, the adjustment of the distance h
may be fully automated under the control of the controller
90. In this case, the automatic adjustment may be started by
simply operating a suitable switch.
It will be understood that steps Q6-Q26 correspond
to a step of adjusting the distance h as one of the
operating conditions of the press 10, and steps Q33-Q35
correspond to a step of storing the optimum distance value
h* in the ID card 96. Further, steps W5-W8 correspond to a
step of reproducing or establishing the optimum distance
value h* on the press 10 when the same die set is again used
on the same press 10. The press operation data memory 128 of
the ID card 96 functions as memory means for storing the
optimum distance value h*.
Referring next to Figs. 39-41, there will be
described a fifth embodiment of the present invention, which
is identical with the first embodiment of Figs. 1-11, except
for the use of a controller 430 as shown in Figs. 39 and 41,
and a manual adjusting device 440 as shown in Fig. 40. The
controller 430 has a Pax calculating block 434 and a Pa
adjusting block 436 which correspond to the respective
blocks 134 and 136 of the controller 90 of the first
embodiment. The Pax calculating block 434 receives an output
signal of the manual adjusting device 440, which represents
a desired adjusting amount ~Fs for the holding force Fs.
Accordingly, the Pax calculating block 334 and the Pa
adjusting block 336 of the controller 430 have additional
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functions not achieved by the corresponding blocks 134, 136
of the controller 90.
As shown in detail in Fig. 40, the manual
adjusting device 440 has two keys 442 for changing the
second digit (more significant digit) of a two-digit
numerical value for the adjusting amount ~Fs, and two keys
446 for changing the first digit of the numerical value. The
device 440 also has two digit indicators 444 and 448 on
which are indicated the second and first digits of the
numerical value, respectively. The device 440 further has a
. selector switch 450 located to the left of the indicators
444, 448. The selector switch 450 can be turned to one of
five positions, with a key inserted in the switch. The
adjusting amount ~Fs by which the holding force Fs is
adjusted is determined by the numerical value set by the
keys 442, 446, and a multiplication coefficient which
corresponds to the selected one of the five positions of the
selector switch 450. Thus, the adjusting amount ~Fs is
variable in five steps, for the same numerical value
indicated on the indicators 444, 448. If the two-digit
numerical value indicated on the indicators 444, 448 is
"05", and the switch 450 is set at the uppermost position
"+2X", the adjusting amount ~Fs is equal to (+2 x 5) -
+10(tf). If the switch 450 is set at the second position
"+1X", the adjusting amount ~Fs is equal to (+1 x 5) -
+5(tf). If the switch 450 is set at the intermediate
position "~OX", the adjusting amount ~Fs is zero. If the
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switch 450 is set at the fourth position "-1X", the
adjusting amount oFs is equal to (-1 x 5) - -5(tf). If the
switch 450 is set at the lowermost position "-2X", the
adjusting amount ~Fs is equal to (-2 x 5) - -10(tf).
The press 10 has a suitable operator-controlled
ON-OFF switch for enabling and disabling the manual
adjusting device 440. When the pneumatic pressure Pax is
adjusted for the first time for a given pressing job, the
ON-OFF switch is placed in the OFF position in which the
manual setting device 440 is not effective. In this
condition, therefore, the calculation of the optimum
pneumatic pressure Pax according to the Pax calculating
block 434 and the adjustment of the pressure Pa according to
the Pa adjusting block 436 are effected irrespective of the
adjusting amount oFs manually entered through the manual
adjusting device 440.
If the operator finds cracking and/or wrinkling of
the product obtained after the pneumatic pressure Pa is
initially adjusted on the basis of the machine information
and the die set information, with the ON-OFF switch set at
OFF, the ON-OFF switch is turned ON, and the press 10 is
test-operated with different values of the adjusting amount
OFs entered through the manual adjusting device 440, until
the pressing operation can be performed with the optimum
holding force Fs, without cracking and/or wrinkling of the
product which might arise from the variation in the physical
properties of the blanks. Explained more particularly, when
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the adjusting amount ~Fs entered through the device 440 is
made effective with the ON-OFF switch turned ON, the Pax
calculating block 434 calculates the optimum pneumatic
pressure Pax according to the following equation (11), and
the Pa adjusting block 436 controls the pressure control
valve 46, on the basis of the optimum pressure Pax
calculated according to the equation (11).
Pax = (Fso + nFs + wa + wr + n~wp)/Aa ....... (11)
The above equation (11) uses the parameter (Fso +
~Fs), in place of the parameter Fso used in the above
equation (1) used for the initial adjustment of the pressure
Pa (for the initial adjustment of the actual holding force
Fs), where Fso is the optimum holding force as specified by
the die set information. As a result, the actual holding
force Fs is changed by the manually entered adjusting amount
~Fs. Since the adjusting amount ~Fs can be changed by the
keys 442, 446 and/or the selector switch 450, the holding
force Fs, that is, the pneumatic pressure Pa can be adjusted
to an optimum value. The optimum value can be confirmed by a
test operation on the press 10, which is repeated with
different adjusting amounts ~Fs until the blank is drawn or
pressed without cracking or wrinkling. The Pax calculating
block 434 of the controller 430 functions as calculating
means for calculating the optimum pneumatic pressure Pax,
according to the equation (11) which includes the adjusting
amount ~Fs entered through the manual adjusting device 440.
The equation (11) represents a predetermined relationship
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between the holding force Fs produced by the force applying
device 53, and the pneumatic pressure Pa of the
fluid-actuated cylinder 42 of the device 53. Further, the
adjusting block 436 of the controller 430 cooperates with
the pressure control valve 46 and the sensor 50 to
constitute pressure adjusting means for adjusting the
pneumatic pressure Pa so that the holding force Fs is
changed by the entered adjusting amount oFs.
In the present fifth embodiment, the optimum
holding force Fso itself is changed by means of the manual
adjusting device_ 440, to adjust the optimum pneumatic
pressure Pax so that the pressure Pax permits the adjustment
of the actual holding force Fs to the changed optimum
holding force (Fso + ~Fs~. Namely, the fifth embodiment is
not adapted to directly change the optimum pneumatic
pressure Pax, but to, determine the optimum adjusting amount
~Fs of the optimum holding force Fso, while observing the
quality of the products in terms of the cracking and
wrinkling. The present arrangement permits fast and accurate
adjustment of the pneumatic pressure Pa, without influences
by a variation in the pressure-receiving area and fluid
leakage of the pneumatic cylinder 42, sliding resistance
values of the various components and other characteristics
of the individual pressing machines. Although the amount of
adjustment of the pneumatic pressure Pa required to
eliminate a given degree of cracking or wrinkling of the
product differs from one machine to another, the required
CA 02251503 1999-08-06
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>~,r
adjusting amount (~Fs) of the holding force Fs is
substantially the same for the different machines of the
press 10. Therefore, the present arrangement assures
relatively easy and fast adjustment of the holding force Fs
(pressure Pa) by the operator's determination of the
adjusting amount ~Fs based on the experience and knowledge
associated with the adjusting amount oFs in relation to the
amount of reduction in the degree of cracking and wrinkling.
Referring next to Figs. 42-45, there will
. described a sixth embodiment of this invention as applied to
the double-action press 150 of Figs. 12-14 of the second
embodiment of Figs. 12-22. The sixth embodiment uses the
control system as illustrated in the block diagrams of Figs.
42A, 42B and 43, which includes a controller 452 in place of
the controller 296 of the second embodiment. The controller
452 has four Pex calculating blocks 456a-456d (only 456a and
456b being indicated in Fig. 43 by way of example) and four
Pe adjusting blocks 458a-458d (only 458a and 458b being
indicated in Fig. 43 by way of example), which correspond to
the respective four fluid-actuated cylinders 184 associated
with the four outer plungers 166 (die-height adjusting
mechanisms 172) as shown in Fig. 13. As described above with
respect to the second embodiment, the cylinder 180 of each
mechanism 172 and the corresponding cylinder 184 and air
tank 190 constitute the force applying device as generally
indicated in Fig. 13, which functions to produce the holding
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force Fs to be applied to the blank 171 through the pressure
ring 156.
As in the second embodiment, the controller 452 is
provided in the control console 202 as shown in Fig. 44.
ilnlike the controller 296 of the second embodiment, the
controller 452 is adapted to receive an output signal of a
manual adjusting device 454 similar to the device 440 of the
fifth embodiment of Figs. 39-41. The manual adjusting device
454 is provided as one of the adjusting switches 293 on the
control panel of the control console 202, as shown in Fig.
44. As indicated in Fig. 43, the output signal of the manual
adjusting device 454 representative of the adjusting amount
~Fs is applied to the Pex calculating blocks 456a-456d. With
an appropriate ON-OFF switch turned ON, the adjusting amount
~Fs manually entered through the manual adjusting device 454
is made effective, and the Pex calculating blocks 456a-456d
calculate the optimum pneumatic pressures Pex of the
cylinders 184, according to the following equation (12),
which includes a parameter equal to a quarter of the
adjusting amount ~Fs.
Fsoi + ~Fs/4 = (Ax~Az/Ay){(Pex + Pt)[Ve/(Ve - Az~Y)] - Pt}
............. (12)
The Pe adjusting blocks 4587a-458d control the
respective pressure control valves 214a-214d, according to
the optimum pneumatic pressures Pex calculated by the blocks
456. As a result, the total holding force Fs (sum of the
four components Fsi associated with the four cylinders 184)
CA 02251503 1999-08-06
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is changed by the amount aFs. Thus, the present arrangement
is not adapted to adjust the individual load values Fsi by
changing the distances ha, but to directly chance the
components Fsi as produced by the pneumatic pressures Pe, as
indicated by arrows Q in the graph of Fig. 45. The optimum
holding force Fs, that is, the optimum adjusting amount ~Fs
manually entered through the device 454 can be found out by
observing the degree of cracking and wrinkling of the
products obtained in test operations with different
adjusting amounts OFs, as explained above with respect to
._ the fifth embodiment of Figs. 39-41.
The present sixth embodiment also permits easy,
fast and accurate adjustment of the holding force Fs by
means of the pneumatic pressure values Pe of the four
fluid-actuated cylinders 184 of the force applying device
191, by using the manual adjusting device 454.
Further, the pneumatic pressures Px of the four
cylinders 184 are simultaneously adjusted by entering the
adjusting amount ~Fs for the total holding force Fs (optimum
total holding force Fso). In this respect, too, the required
adjusting time for the individual cylinders 184 is
considerably shortened. Although the pressure Pe of each
cylinder 184 can be adjusted by observing the load value Fsi
detected by the strain gages 178 (which corresponds to each
of the four components of the total holding force Fs), this
procedure takes a relatively long time, that is, four times
CA 02251503 1999-08-06
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that required in the present sixth embodiment in which the
adjusting amount ~Fs is used for all the four cylinders 184.
While the fifth and sixth embodiments are adapted
to add the manually entered adjusting amount ~Fs to the
predetermined optimum holding force Fso (as specified by the
die set information stored in the ID card 306) fir
calculating the optimum pressure Pax or optimum pressures
Pex, it is possible to suitably modify the manner of
adjusting the pneumatic pressure Pa or pressures Pex in
relation to the adjusting amount ~Fs. For example, the fifth
embodiment may be modified such_that an amount of change ~Pa
of the pressure Pa is calculated according to the following
equation ( 13 ) , on the basis of the adjusting amount ~Fs. In
this case, the Pa adjusting block 436 controls the pressure
control valve 46 so that the pressure Pa is changed by the
calculated amount aPa. This modification also applies to the
sixth embodiment.
~Pa = ~Fs/As ...................... (13)
In the fifth and sixth embodiments, the pneumatic
pressures Pa and Pe are initially adjusted automatically
under the control of the controller 430, 452. However, the
principle of adjustment of the holding force Fs (pneumatic
pressure Pa, Pe) according to the fifth and sixth
embodiments is applicable to the initial adjustment of the
pressures Pa, Pe by a trial-and-error procedure. The
initially adjusted value Fs, Fsi need not be known before a
production run of the press is started. In the case of
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initial adjustment of the pneumatic pressure Pa, for
example, an amount of change ~Fs in the holding force Fs is
determined by a test operation, a suitable amount of change
~Pa in the pneumatic pressure Pa is calculated according to
the above equation (13), and the actual pneumatic pressure
Pa is changed by the calculated amount ~Pa.
Although the manual adjusting device 440 is
constructed as shown in Fig. 40 and the device 454 is
similarly constructed, these devices 440, 454 may be
replaced by other devices, for example, a device having ten
- keys corresponding to the ten digits for entering the
adjusting amount ~Fs.
Referring next to Figs. 46-49, there will be
described a seventh embodiment of the present invention,
which is identical with the first embodiment of Figs. 1-11,
except for the use of a controller 460 as shown in Figs. 46
and 47, and a limit switch 462 and a START switch 464
connected to the controller 460. The controller 460 and the
switches 463, 464 will described. In the present seventh
embodiment, the die set data memory 125 of the ID card 96
provided on each punch 12 available on the press 10 as shown
in Fig. 1 stores data indicative of a Fso-N relationship,
and data indicative of an a-T relationship.
The Fso-N relationship is a relationship between
the optimum holding pressure Fso, and the number N which
indicates a range of the number of successive pressing
cycles which have been performed on the press 10 during each
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pressing job. Like the optimum pressing force Fpoi whose
data are also stored in the die set data memory 125, the
optimum holding force Fso is determined by a test operation
on a test or trial press, so as to assure an adequate
pressing operation without cracking of the product formed
from the blank, such that the determined optimum holding
force Fso does not include components due to the influences
of the weight of the die set and the sliding resistances of
the components of the press. In the present embodiment, the
optimum holding force Fso is thus determined for each of
different ranges of the number of the pressing cycles
performed on the successively loaded blanks. The Fso-N
relationship is used because the optimum holding force Fso
changes, more precisely, decreases with an increase in the
cumulative number of the pressing cycles performed, since
the temperature of the die set (12, 18, 30) increases as the
pressing job continues on the successive blanks. More
specifically, the temperature of the blank holding portion
of the die set gradually increases with heat generated
during a continuous pressing job due to the sliding
resistance a of the blanks with respect to the upper die 18
and the pressure ring 30. A rise in the temperature of the
die set causes changes in the property of the lubricating
oil deposited on the blank and in the friction
characteristics of the die set and blank, and leads to
increased volatility of the lubricating oil and consequent
increase in the sliding resistance u, whereby the tensile
CA 02251503 1999-08-06
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force Te acting on the blank under drawing is increased. The
Fso-N relationship is obtained by a test pressing operation
performed under the same conditions as an actual production
run on successive blanks, particularly in terms of the
lubricating condition. The Fso-N relationship is determined
by observing the change in the temperature of the die set
and the degree of cracking of the test specimens.
An example of the Fso-N relationship is indicated
in TABLE 1 below, in which the number N is incremented with
an increase in the number of the pressing cycles in
increments of a predetermined value Co, for example, about
100. Suppose the predetermined value Co is 100, the number N
is equal to "1" when the cumulative number of the pressing
cycles is 50, and equal to "2" when the number of the cycles
is 160, for instance. The optimum holding force Fso is
determined for each incremental value of the number N. That
is, the optimum holding force Fso decreases with an increase
in the number N (the number of the pressing cycles). The
value Fso is the total holding force, which is the sum (Fo)
of the load values Foi detected by the strain gages 61
described above with respect to the first embodiment.
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T A B L E 1
N Number ofPressing Cycles Optimum Holding Force Fso
1 0 ~ Co 100tf
2 Co + 1 ~. 2Co 98tf
3 2Co + 1 ~ 3Co 96tf
4 3Co + 1 ~ 4Co 89tf
4Co + 1 ~ 5Co ~ 86tf
The a-T relationship is a relationship between a
decreasing value a used to determine the effective number N
used by an N determining block 466 (which will be described)
of the controller 460, and a non-operation time T of the
5 press 10 during which the operation of the press 10 is
interrupted or' temporarily stopped during a continuous
pressing job on successive blanks. The decreasing value a
determined by this a-T relationship is subtracted from the
number N as determined by the actual number of the pressing
cycles. The a-T relationship is formulated such that the
decreasing value a increases with the non-operation time T,
as indicated in the graph of Fig. 49 by way of example.
Namely, the optimum holding force Fso increases with an
increase in the non-operation time T, even with the same
number of the pressing cycles.
The rationale of the a-T relationship is such that
the temperature of the upper die 18 and pressure ring 30
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rises during a continuous pressing job, up to a level at
which the amount of heat Qs generated due to the sliding
resistance is counterbalanced by the amount of heat
radiation, while the temperature drops due to the heat
radiation during interruption of the pressing job, depending
upon the amount of heat radiated during the interruption.
Thus, the change in the temperature of the die set due to
the interruption of the pressing job influences the
lubricating condition and the sliding resistance a of the
blank. If the pressing job is resumed with the same holding
force, the tensile force acting on the blank decreases with
a decrease in the sliding resistance u, whereby the product
formed by the pressing tends to suffer from wrinkling. On
the other hand, if the pressing job is resumed with the
initial holding force, i.e., the holding force Fso
corresponding to the initial number N = 1, the tensile force
Te acting on the blank tends to be excessively large,
causing the product to crack. In view of the above
phenomenon, the a-T relationship is used to determine the
effective number N (which determines the optimum holding
force Fso), depending upon the non-operation time T
(interruption time of the pressing job). In the graph of
Fig. 49, "Nmax" appearing in (Nmax - 1) corresponds to the
maximum value of the number N, at which the heat generation
amount Qs is almost counterbalanced by the heat radiation
amount, and at which the optimum holding force Fso is the
smallest. Generally, the temperature of the die set falls
CA 02251503 1999-08-06
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,.~;r
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down to the ambient or room temperature in about one hour of
interruption of the pressing job, and the decreasing value a
is fixed at its maximum (Nmax - 1) after the interruption or
interruption time T exceeds about one hour.
Referring back to Fig. 46, the limit switch 462 is
turned ON when the main slide 20 is lowered to its lower
stroke end, and thus applies a signal SP to the controller
460 each time one pressing cycle is performed on the press
10, that is, each time one blank is drawn into a desired
product. The START switch 464 is turned ON to start a
pressing job or resume the interrupted job, and turned OFF
to interrupt or terminate the pressing job. A signal SS
generated by this switch 464 applied to the controller 460
indicates the operating and non-operating states of the
press 10.
The functions of the controller 460 are indicated
in the block diagram of Fig. 47. The controller 460 is
identical in function with the controller 90 of the first
embodiment, except for the addition of the N determining
block 466 indicated above, and a Pax calculating block 463
and a Pa adjusting block 465. For initial adjustment of the
pneumatic pressure Pa of the pneumatic cylinder 42 (initial
adjustment of the holding force Fso), the Pax calculating
block 463 and the Pa adjusting block 465 operate in the same
manner as explained with respect to the first embodiment,
i.e., adjust the initial pneumatic pressure Pa according to
the optimum pneumatic pressure Pax calculated according to
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r
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the equation (1) indicated above. That is, the N determining
block 466 selects "1" as the effective number N, so that the
holding force Fs is initially adjusted to the optimum value
(e. g., 100tf in this specific embodiment) Fso corresponding
to the number N = 1.
The functions of the other functional blocks 138,
140, 142, 144 and 146 are the same as described above with
respect to the first embodiment.
After the pneumatic pressures Pa, Pb, hydraulic
pressure Ps and distance h have been initially adjusted
under the control of the controller 460 on the basis of the
machine and die set information (stored in the memories 130,
132), the production run of the press 10 is initiated. In
this case, the pneumatic pressure Pa is adjusted depending
upon the number of the pressing cycles in progress and the
non-operation time T. Described in detail, the N determining
block 466 determines the effective number N on the basis of
the signals SP and SS received from the limit switch 462 and
the START switch 464, that is, on the basis of the number of
the pressing cycles) and the non-operation time T
(decreasing value a), and the Pax calculating block 463 uses
the optimum holding force Fso determined by the determined
effective number N, to calculate the optimum pneumatic
pressure Pax.
The details of the function of the N determining
block 466 are illustrated in the flow chart of Fig. 48. The
control routine of this flow chart is executed at a suitable
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cycle time. Initially step 5101 is implemented to determine
whether the signal SS is ON or not. If a negative decision
(NO) is obtained in step 5101, a flag F is set to "0" in
step 5102. When the signal SS is turned ON, step S101 is
followed by step 5103 to determine whether the flag F is set
at "1" or not. Since the flag F is set at "0" immediately
after a pressing job is started, a negative decision (NO) is
obtained in step S103, and the control flow goes to step
5104 to determine the effective number N on the basis of the
number N determined by the current content of a counter C,
and the decreasing number a determined by the current
content of a timer TI. As described below, the counter C is
incremented each time the signal SP is turned ON, while the
timer TI is reset each time the START switch 464 is turned
ON. The content of the timer TI upon implementation of step
S104 represents the non-operation time T between the moment
when the START switch 464 was turned OFF and the moment when
the same switch 464 is turned ON to resume the .interrupted
pressing job. The decreasing value a is determined according
to the a-T relationship of Fig. 49, and on the basis of the
non-operation time T, and the determined decreasing value a
is subtracted from the number N determined by the current
content of the counter C. Thus, the effective number N is
determined or updated. The updated effective number N is
applied to the Pax calculating block 463, which in turn
determines the optimum holding force Fso according to the
Fso-N relationship of TABLE 1, and on the basis of the
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effective number N. The Pax calculating block 463 calculates
the optimum pneumatic pressure Pax according to the equation
(1) and on the basis of the optimum he .ing force Fso
determined. The Pa adjusting block 465 adjusts the pneumatic
pressure Pa according to the thus calculated optimum
pneumatic pressure Pax. In the present embodiment,
therefore, the actual holding force Fs can be suitably
adjusted depending upon the number of the pressing cycles
performed and the non-operation time T. The present
arrangement permits pressing operations without cracking or
wrinkling of the products, even in a period immediately
after the interruption of the pressing job, namely, even
after the pressing conditions such as the lubricating
condition and the sliding resistance a of the blank have
changed due to a temperature drop of the die set (12, 18,
30) during the interruption.
It is noted that if the decreasing value a
determined by the non-operation time T is equal to or larger
than the number N as determined by the number of the
pressing cycles, the effective number N is set at "1". The
a-T relationship as indicated in the graph of Fig. 49 is the
relationship when the number N is at a maximum (Nmax), i.e.,
when the temperature of the die set is substantially
constant at a highest level. Since the temperature drop
characteristic of the die set varies depending upon the
temperature when the pressing job is interrupted, the a-T
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relationship may be desirably provided for each value of the
number N as determined by the number of the pressing cycles.
Step 5104 is followed by step S105 to set the flag
F to "1". In the next cycle of execution of the control
routine, an affirmative decision (YES) is obtained in step
5103, and step 5106 is implemented to reset the timer TI.
Then, step 5107 is implemented to determine whether the
signal SP is ON or not. If the signal SP is ON, namely, each
time a pressing cycle is performed with the main slide 20
lowered to its lower stroke end, the counter C is
incremented in step 5108. Then, the control flow goes to
step 5109 to determine whether the content of the counter c
has become equal to the predetermined value Co or not. If an
affirmative decision (YES) is obtained in step S109, step
S111 is implemented to determine whether the effective
number N is equal to Nmax or not. If an affirmative decision
(YES) is obtained in step S110, step 5112 is implemented to
clear the counter C, and the control flow returns to step
5101. If a negative decision (NO) is obtained in step S110,
- step 5111 is implemented to add "1" to the effective number
N to update the effective number N. It will therefore be
understood that the effective number N is incremented each
time the pressing cycles are performed the predetermined
number of times Co. The thus determined effective number N
is sent to the Pax calculating block 463, so that the Pax
calculating block 463 determines the optimum holding force
Fso, according to the Fso-N relationship of TABLE 1 stored
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in the die data memory 132, and calculates the optimum
pneumatic pressure Pax according to the above equation (1)
and on the basis of the determined effective number N. The
Pa adjusting block 465 controls the pressure control valve
46 to adjust the pneumatic pressure Pa to the calculated
optimum value Pax. Thus, the holding force Fs is adjusted
depending upon the number of the pressing cycles performed,
namely, depending upon the temperature of the die set, which
increases as the number of the pressing cycles increases.
Accordingly, the present arrangement assures a pressing job
without cracking of the products formed from the blanks,
even if the sliding resistance a of the blanks is increased
due to the change in the lubricating characteristic as a
result of the temperature rise of the die set. The
predetermined value Co and maximum value Nmax are suitably
determined so as to optimize the Fso-N relationship.
According to the present seventh embodiment, the
optimum holding force Fso is reduced with an increase in the
number of the pressing cycles performed, according to the
Fso-N relationship of TABLE 1,. whereby the pneumatic
pressure Pa and the actual holding force Fs are accordingly
decreased as the pressing job continues. Further, the
optimum holding force Fso is increased with an increase in
the non-operation time T, according to the a-T relationship
of Fig. 49, whereby the pneumatic pressure Pa and the actual
holding force Fs are accordingly increased. Hence, the
actual holding force Fs is controlled to an optimum level,
CA 02251503 1999-08-06
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to assure adequate pressing operations without cracking of
the products, irrespective of the variation in the
temperature of the die set and the variation in the sliding
resistance a of the blanks. Moreover, since the pneumatic
pressure Pa and the holding force Fs are reduced with the
increase in the number of the pressing cycles, the die set
is protected against early wearing due to the excessive
tensile force Te on the blanks. Further, the amount of heat
Qs generated is reduced, and the temperature of the die set
at which the generated heat amount Qs is counterbalanced
with the radiated heat amount, whereby the influences of the
generated are reduced throughout the pressing job.
It will be understood from the above description
of the seventh embodiment of the invention that the Pa
adjusting block 465 of the controller 460 cooperates with
the pressure control valve 46 and sensor 50 to constitute
adjusting means for adjusting the actual holding force Fs.
It will also be understood that the N determining block 466
(steps S107 and 5108) and the limit switch 462 constitute
counting means for counting thenumber of the pressing
cycles performed, while the N determining block 466 (steps
S101, 5102 and S106) cooperates with the START switch 464
and the timer TI to constitute time measuring means for
measuring the non-operation time T. Further, the N
determining block 466 and the Pax calculating block 463 of
the controller 460 constitute control means for controlling
the adjusting means (465, 46, 50) so that the holding force
CA 02251503 1999-08-06
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Fs decreases with an increase in the number of the pressing
cycles, and increases with an increase in the non-operation
time T.
Reference is now made to Figs. 50-52, which show
an eighth embodiment of the present invention, which is
identical with the first and seventh embodiments, except for
the use of a controller 474 as shown in Fig. 52, and a
radiation thermometer 468 mounted on a bracket 470 fixed to
the machine frame 78 as shown in Fig. 50. The radiation
thermometer 468 is provided to detect the temperature a of
the product 472 formed from a blank as a result of a drawing
operation. The thermometer 468 is a non-contact type
temperature sensor capable of detecting the temperature
based on an energy of radiated heat. In operation of the
thermometer 468, a visible radiation is emitted to irradiate
the area of the product 472 whose temperature is to be
measured. The irradiated measuring area can be visually
confirmed by the operator of the machine. The bracket 352
permits orientation of the radiation thermometer 468 as
needed depending upon the shape of the product 472 and other
factors. The thermometer 468 is oriented so as to irradiate
the area in which the temperature of the product 472 is the
highest, namely, to measure the temperature a of the portion
of the product 472 whose thickness has been increased to the
largest extent by a drawing action on the blank and in which
the temperature is most likely to rise due to the sliding
resistance a of the blank with respect to the upper die 18
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and pressure ring 30. For improved accuracy of measurement
of the temperature of the product 472, two more more
thermometers 468 are preferably used to detect the
temperatures in different areas of the product 472,
depending upon the shape of the product.
In the present embodiment, the die set data memory
125 of the ID card 96 stores data indicative of a Fso-a
relationship in place of the Fso-N and a-T relationships
used in the preceding seventh embodiment of Figs. 46-49. The
Fso-a relationship is a relationship between the optimum
holding force Fso and the temperature a of the product 472
as detected by the radiation thermometer 468. The optimum
holding force Fso within the same meaning as described above
with respect to the Fso-N relationship is determined by a
test operation on a test or trial press, in relation to the
temperature a of the product 472. As described above, the
optimum holding force Fso decreases with an increase in the
temperature of the die set, i.e., in the temperature A of
the product 472. An example of the Fso-8 is indicated by the
graph of Fig. 51. The Fso-8 relationship is used for the
same reasons as described above on the Fso-N relationship.
That is, the optimum holding force Fso varies with an
increase in the temperature of the die set (12, 18, 30)
during a continuous pressing job, due to the sliding
resistance u, and the temperature rise changes the property
of the lubricating oil on the blank and the friction
characteristics of the die set and blank, leading to
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increased volatility of the oil and consequent increase in
the sliding resistance a and the tensile force Te. Like the
Fso-N relationship, the Fso-8 relationship is obtained by a
test pressing operation performed under the same conditions
as an actual production run.
As shown in Fig. 52, the controller 474 includes
an Fso determining block 476 in place of the N determining
block 466 used in the seventh embodiment of Fig. 47. The Fso
determining block 476 receives an output of the radiation
thermometer 468 indicative of the temperature B of the
product 472, and also receive from the die data memory 132
the data indicative of the Fso-a relationship. In operation,
the block 476 determines the optimum holding force Fso
according to the Fso-a relationship and on the basis of the
temperature e, so that the optimum holding force Fso used by
a Pax calculating block 477 is updated depending upon the
varying temperature e. The thus updated optimum holding
force Fso, which assures an adequate pressing operation at
the temperature A without cracking of the product 472, is
applied to the Pax calculating block 477, to calculate the
optimum pneumatic pressure Pax according to the equation (1)
and on the basis of the optimum holding force Fso. Based on
the calculated optimum pneumatic pressure Pa, a Pa adjusting
block 478 operates to adjust the actual pressure Pa to the
calculated optimum value Pa.
According to the present arrangement, the optimum
holding force Fso is reduced to lower the pneumatic pressure
CA 02251503 1999-08-06
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Pa with an increase in the temperature 8 and the sliding
resistance u, while on the other hand the optimum holding
force Fso is increased to increase the pressure Pa with a
decrease in the temperature 8 and the sliding resistance u.
Accordingly, the tensile force Te acting on the blanks is
maintained at an optimum level irrespective of the varying
temperature a and sliding resistance u, whereby the product
472 is protected from cracking or wrinkling, and the die set
is protected against early wearing due to the excessive
tensile force Te. Further, the holding force Fs thus
controlled to decrease with the rise of the temperature a
contributes to lowering the amount of heat Qs generated,
thereby lowering the temperature a at which the generated
heat amount Qs is counterbalanced by the radiated heat
amount, whereby the influences of the generated heat are
reduced throughout a pressing job.
Lt will be understood that the Pa adjusting block
478, control valve 46 and pressure sensor 50 constitute
adjusting means for adjusting the actual holding force Fs,
while the Fso determining block 476. and the Pax calculating
block 477 constitute control means for controlling the
adjusting means to change the holding force Fs in relation
to the temperature 8 of the product 472.
Referring next to Figs. 53A, 53B and 54, there
will be described a ninth embodiment of this invention,
which is identical with the second embodiment of Figs.
12-22, except for the use of an exclusive controller 480, a
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limit switch 482, a START switch 484 and a controller 486.
The limit switch 482 and the START switch 484 are connected
to the exclusive controller 480, and are identical in
function with the switches 462, 464 used in the seventh
embodiment of Figs. 46-49. As in the second embodiment, the
controller 486 is incorporated within the stand-alone
control console 202 as illustrated in Figs. 18 and 19. The
controller 486 includes an N determining block 488, four Pex
calculating blocks 490a-490d (only 490a and 490b indicated
in Fig. 54 by way of example) corresponding to the four
die-height adjusting mechanisms 172, and four Pe adjusting
blocks 492a-492d (only 492a and 494b indicated in Fig. 54).
The signals SP and SS of the limit switch 482 and
the START switch 484 are sent to the N determining block 488
of the controller 486. Further, the die data memory 312 is
adapted to receive from the ID card 306 data indicative of a
Fsoi-N relationship and data indicative of an a-T
relationship similar to that of Fig. 49 used in the seventh
embodiment.
The Fsoi-N relationship is determined for each of
the four die-height adjusting mechanisms 172 (each of the
four cylinders 184) corresponding to the four outer plungers
166 of the outer slide 160 of the double-action press 150.
Each of these Fsoi-N relationships may be determined by a
test operation in the same manner and is used for the same
reasons as described above with respect to the Fso-N
relationship used in the seventh embodiment. It is noted,
CA 02251503 1999-08-06
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- 125 -
however, the value Fsoi is an optimum value of the component
of the optimum holding force Fso associated with the
corresponding mechanism 172 (outer plunger 166). In the test
operation, the load value Fai detected by the strain gages
178 is used to determine the corresponding component Fsoi in
relation to the number N (number of the pressing cycles). An
example of the Fsoi-N relationship is indicated in TABLE 2
below.
T A B L E 2
N Number of Pressing Cycles Optimum
Holding
Force
Component
Fsoi
(tf)
1 0 ~. Co 25 25 25 25
2 Co + 1 ~ 2Co 23 25 25 25
3 2Co + 1 ~ 3Co 23 23 25 25
4 3Co + 1 ~ 4Co 20 23 23 23
5 4Co + 1 ~. 5Co I 20 I 20 23 23
I I
For initial adjustment of the holding force Fs,
the Pex calculating blocks 490a-490d determine the optimum
holding force components Fsoi which correspond to the
effective number N - 1, and calculate the corresponding
optimum pneumatic pressure levels Pex. The corresponding
pneumatic pressure levels Pe are adjusted by the Pe
adjusting blocks 492a-492d based on the calculated optimum
values Pex. Thus, the total holding force Fs is initially
adjusted.
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In a production run of the press 150, the four
components Fsi of the actual holding force Fs are adjusted
independently of each other, depending upon the number of
the pressing cycles (effective number N) and the
non-operation time T (decreasing value a), in a manner
similar to that shown in the flow chart of Fig. 48. Briefly,
the effective number N is determined by the N determining
block 488, on the basis of the signals SP and SS, namely,
the number of the pressing cycles and the non-operation time
T. The optimum component Fsoi for each of the four
mechanisms 172 is determined by the appropriate Pex
calculating block 490, according to the corresponding Fsoi-N
relationship stored in the die data memory 312 and on the
basis of the determined effective number N. The Pex
calculating block 490 calculates the optimum pressure Pex
for each of the four cylinders 194. Finally, the appropriate
Pe adjusting block 492 controls the corresponding pressure
control valve 214 to adjust the pneumatic pressure Pe of the
corresponding cylinder 184 according to the calculated
optimum pressure Pex. Thus, each component Fsi of the
holding force Fs is adjusted as indicated by arrows Q in~the
graph of Fig. 45.
In the present ninth embodiment, each of the four
components Fsoi of the optimum holding force Fso are
decreased with in increase in the number of the
pressing
cycles, according to the Fsoi-N relationships, whereby the
corresponding pressure levels Pe are lowered as the
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operation time of the press 150 increases. On the other
hand, the components Fsoi are increased with an increase in
the non-operation or interruption time T of the press.
Therefore, if the pressing job is interrupted, the pressure
levels Pe are increased with the non-operation time.
In the ninth embodiment, the Pe adjusting blocks
492a-492d, pressure control valves 214a-d and pressure
sensors 212a-d constitute adjusting means for adjusting the
holding force Fs, while the N determining block 488 and the
limit switch 482 constitute counting means for counting the
number of the pressing cycles. The N determining block 488
and the START switch 484 (and the timer TI) constitute time
measuring means for measuring the non-operation time T.
Further, the N determining block 488 and the Pex calculating
blocks 490a-d constitute control means for controlling the
adjusting means to adjust the holding force Fs (components
Fsi) depending upon the number of the pressing cycles
performed and the non-operation time T.
Although the seventh and ninth embodiments are
adapted such that the optimum holding force Fso or component
Fsoi is changed each time the number of the pressing cycles
increases by the predetermined value Co (e. g., about 100),
the relationship between the value Fso (Fsoi) and the number
of the pressing cycles may be suitably modified. For
instance, if a pressing job causes a comparatively fast rise
of the temperature of the die set, the value Fso, Fsoi may
be changed more frequently or at a higher rate in an initial
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period of the pressing job, than in the following period.
That is, the comparatively small values Co are used in the
initial period.
In the seventh and ninth embodiments, the limit
switches 462, 482 are used to detect the lower stroke end of
the slide 20, 160 (plungers 22, 166), other means may be
used to count the number of the pressing cycles. For
example, the number of the pressing cycles may be counted
based on the number of rotation or rotating angle of the
crankshaft of the press 10, 150.
While the eighth embodiment is adapted to detect
the temperature a of the upper surface of the product 474,
the portion whose temperature is measured may be suitably
selected, depending upon the specific construction of the
press and the configuration of the die set (including the
surface condition of the die set, e.g., plated or non-plated
surface). For instance, suitable temperature detecting means
is provided to measure the temperature of the lower surface
of the product 472, or the surface of the upper die 18 or
pressure ring 30 which contacts the blank.
While the radiation thermometer 468 used in the
eight embodiment is attached to the machine frame 78, it may
be attached to the bolster 14, main slide 20, punch 12 or
upper die 18.
It will be understood that the principle of the
eighth embodiment using the thermometer 468 is applicable to
the double-action press 150. In this case, the suitable
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temperature detecting means may be provided for each of the
four portions corresponding to the four outer plungers 166
(four components or load values Fsi which can be adjusted
independently of each other).
In the seventh, eighth and ninth embodiments, the
pneumatic pressures Pa and Pe are initially adjusted
automatically under the control of the controller 460, 474,
486. However, the principle of adjustment of the holding
force Fs (pneumatic pressure Pa, Pe) according to the
seventh, eighth and ninth embodiments is applicable to the
initial adjustment of the pressures Pa, Pe by a
trial-and-error procedure. In the case of initial adjustment
of the pneumatic pressure Pa, for example, an amount of
change OFa in the holding force Fs is determined by a test
operation, in which the degree of cracking or wrinkling of
the products is observed in relation to a change in the
number of pressing cycles and a change in the die set
temperature during the test pressing operation. Then, a
suitable amount of change oPa in the pneumatic pressure Pa
is calculated according to the above equation (13), and the
actual pneumatic pressure Pa is changed by the calculated
amount ~Pa. The initially adjusted value Fs, Fsi need not be
known before a production run of the press is started.
Although the ninth embodiment is adapted to adjust
the pneumatic pressures Pe to adjust the components Fsi of
the holding force Fs, the distances ha of the die-height
adjusting mechanisms 172 may be adjusted according to the
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Fsi-ha relationship (Fsi - c~ha + f) of Fig. 45, to adjust
the pneumatic pressures Pe depending upon the number of the
pressing cycle and the non-operation time.
While the present invention has been described in
detail in its preferred embodiments, it is to be understood
that the invention may be otherwise embodied.
For instance, the presses 10, 150 adapted to
perform a drawing operation may be modified to perform other
pressing operations such as a bending operation. Although
the pneumatic pressures Pa, Pe, hydraulic pressure Ps and
the distances h, ha, hb are controlled as the operating
conditions of the press, for example, the other operating
conditions or parameters may be controlled according to the
principles of the present invention as described above. In
this respect, the machine information and the die set
information used to control the machine operating conditions
are not limited to those items described herein and may be
suitably selected.
In the presses 10 , 150 of Figs . 1 and 12 , the die
set information stored in the ID card 96, 306 is sent to the
controller 90, 296, 430, 452, 460, 474 by means of the
transmitter/receiver 94, 304. However, the ID card 96, 306
may be replaced by a bar code , a magnetic tape or a f loppy
disk. In this case, the die set information in the form of
the bar code or stored in the tape or disk is read by a
suitable reader connected to the controller. Further, the
die set information may be manually entered into the
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controller through a keyboard, for exat'~ple. Where the number
of the die sets used for a press is relatively small, the
die set information for each die set may be stored in a
random-access-memory provided in the controller 90 of the
press, or in a memory device separate from the machine and
the die sets. In the latter case, the die set information
for each combination of a die set and a pressing machine is
stored. In this case, too, a floppy disc or a magnetic tape
may be used.
Although the press 10, 150 uses the common air
tank 82, 218, 268 for the four counterbalancing pneumatic
cylinders 80, 216, 266, the counterbalancing cylinders may
be provided with respective air tanks, so that the pressures
of the cylinders may be adjusted independently of each
other. The present invention is applicable to the press 10,
150 as otherwise modified.
While the press 10, 150 is adapted to determine
the pressing conditions such as the pneumatic pressure Pa
according to the equations (1) through (13), other equations
or data maps may be used to obtain the pressing conditions.
In the illustrated embodiments, the operating
conditions are automatically adjusted or controlled
according to the corresponding optimum values (e. g., Pax)
calculated by the controller. However, the operating
conditions may be manually adjusted by the operator of the
machine, with the calculated optimum values displayed or
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otherwise indicated by suitable means such as digital
indicators.
While the single-action press 10 is equipped with
the cushioning device 51, the present invention is
applicable to a single-action press without the cushioning
pneumatic cylinders 32. Further, the pneumatic cylinder 42
may be replaced by a hydraulic cylinder whose pressure is
released so as to apply the holding force to the blank.
It is to be understood that the present invention
may be embodied with various other changes, modifications,
and improvements, which may occur to those skilled in the
art, without departing from the spirit and scope of the
invention defined in the accompanying drawings.
