Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE 1NV~N~ION
-- TWO-SPINDLE OPPOSED TYPE CNC LATHE
BACXGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a machine tool for
working a workpiece principally in the shape of a rotary
body, and relates to a CNC (computer numerical control)
lathe provided with two spindle stocks and two tool
rests opposed on a single base.
2. Description of the Prior Art
It has been heretofore carried out to add a
milling working means to a single-spindle CNC lathe. A
spindle stock in the single-stock CNC lathe of this kind
is secured to a base, the spindle being provided with a
spindle motor for machining and working, a spindle index
driving device capable of being connected and
disengaged, a spindle orientation mechanism using a
locating cam, a locating pin and the like for stopping
the spindle at an angle of an original point and the
like so that when the spindle is stopped at an angle of
an original point, the spindle index driving device can
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be connected to the spindle. The tool rest is of the
turret type, which can be moved and located in a
direction of the spindle (hereinafter referred to as the
direction of axis Z) and in a direction perpendicular to
the direction of axis Z (hereinafter referred to as the
direction of axis X) and which indexes the turret having
a plurality of tools, such as machining tools, milling
tools and drilling tools arranged in the periphery
thereof to work the workpiece. The milling tool and the
drilling tool are driven by a driving motor for rotating
the tools.
Thereafter, there has been proposed a machine
which is provided with a sub-spindle improved over a
conventional tail stock for the purpose of attaining a
composite working in order to meet the demand of
industrial fields with the desire of obtaining a
finished product by a single machine in which the
workpiece held by the chuck of the spindle is subjected
to machining and milling after which it is subjected to
the back working by the same machine.
In the single-spindle type CNC lathe of this
kind, a subspindle unit is arranged at a position of the
conventional tail stock. This subspindle can be moved
and located in the direction of axis Z by a hydraulic
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cylinder or an NC servo. In the back working, the
subspindle is moved toward the spindle, the end of the
workpiece is gripped by the chuck, the workpiece is
received from the spindle, the subspindle is moved away
from the spindle, the subspindle in which the workpiece
is held by the chuck is rotated and driven by the
subspindle motor, and the tool mounted on the turret on
one and the same tool rest is used to work the back of
the workpiece.
In summary, the subspindle in the
aforementioned single-spindle type CNC lathe is
approximately one in place of the tail stock, in which
case, for working materials which are small and flange
materials which require large chucks, power is often
short, and the sizes of workpiece that may be worked are
limited so that only the chamfering of the back and
finishing thereof may be performed. Above all, the
spindle remains rest during the back working, efficiency
of which is not so good.
On the other hand, various improvements have
been progressed in order to meet the earnest desire of
the industrial field of increasing the number of
composite working by the machine and apparatus of this
kind to obtain various efficient and more complete
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finished products by a single machine. As the result,
there has been developed a two-spindle opposed type CNC
lathe comprising a first working unit wherein a
conventional spindle is used as a first spindle, a
spindle stock is used as a first spindle stock and a
conventional tool rest is used as a first tool rest and
a second working unit wherein a subspindle is made to be
powerful to the same extent as that of the first spindle
to use it as a second spindle, a spindle stock is used
as a second spindle stock, and a turret type tool rest
equal to the first tool rest is provided to use it as a
second tool rest, whereby the synchronous orientation
operation of the first and second spindles and powerful
composite working are rendered possible, and in
addition, the continuous operation can be made while
simultaneously executing the front and back working of
the workpiece as well as the automatic delivery of the
workpiece between both the spindles, such lathe being
put to a practical use.
The two-spindle opposed type CNC lathe of this
kind, in view of the mode of installation and
arrangement of the spindle stocks and tool rests on the
base, roughly includes the following three different
types:
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Wherein as disclosed in the specification of
European patent publication No. 289,333, both the first
and second spindle stocks and both the first and second
tool rests are installed on the base so that they can be
moved and located in the direction of axis Z and in the
direction of axis X, respectively, both the tool rests
being arranged deep in the base from both the spindle
stocks;
wherein the first spindle stock is secured to
the base, the second spindle stock can be moved and
located in the direction of axis Z, and the first and
second tool rests can be moved and located in the
direction of axes Z and X, the second tool rest being
arranged on the base so as to be positioned this side of
the second spindle stock; and
wherein both the first and second spindle
stocks can be moved and located in the direction of axis
z and both the first and second tool rests can be moved
and located in the directions of axes Z and X, both the
tool rests being arranged on the back of the base from
both the spindle stocks.
However, among these three different types,
the first type described in the European patent
publication No. 289,333 and the third type are rational
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in construction in that the shape to be worked is
determined by the synthetic operation of the movement of
the first and second spindle stocks in the direction of
axis Z and the movement of the first and second tool
rests in the direction of axis X and have the merit in
that they have a simple construction which is
symmetrical to left and right. However, there gives
rise to a problem in the short of rigidity in the first
spindle stock and a problem in workability when a bar
material is automatically supplied and worked resulting
from the structure in which the first spindle stock is
moved.
That is, normally, the workpiece or blank is
first mounted on the first spindle, and therefore the
weight of workpiece and the amount of unbalance are
greatest during the entire processing step, and the
first step often results in heavy cutting. Accordingly,
a great rigidity is required particularly in the first
spindle. However, in the construction in which the
first spindle stock is moved, the problem in the short
of rigidity tends to occur in the first spindle stock.
In case where a method for automatically supplying the
bar material through a hollow hole in the first spindle
is employed, when the first spindle stock moves, an
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unworked blank extending through the first spindle also
moves axially, posing a problem in that most of bar
feeders so far used cannot be used.
In the aforementioned second type in which the
first or second tool rest is provided on this side from
the firæt or second spindle, there involves a problem in
that accessibility of the operator or robot arm to the
spindle is bad, mounting and removing operation for
workpiece are not only inconvenient but a danger is
accompanied.
Furthermore, two tool rests are arranged to
close to each other because it is necessary to make the
machine small-size. However, in the construction in
which both the tool rests may be moved only in the
direction of axis X, it has no moving ability to move
both the tool rests in a direction of moving away from
each other, and therefore there involves a difficulty in
that the workability is bad in mounting and removing the
tool from the turret and in maintenance and repair of
the tool rests.
Moreover, the base of the conventional machine
of this kind is mostly of the flat shape, of which
central portion has a chip receiving box mounted thereon
so as to make the machine compact. With this, there
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gives rise to problems in that a leak of cutting liquid
caused by the inconvenience of filtration of the cutting
liquid, the inconvenience in maintenance work after the
tip conveyor has been mounted, and the like in view of
limitation of space.
SUMMARY OF THE INVENTION
This invention has been provided in an attempt
of improving various problems as noted above.
It is a primary object of this invention to
provide a two-spindle opposed type CNC lathe in which a
base is of a slant type inclined forwardly, and both two-
tool rests are arranged in deep of both opposed spindles
with the result that the accessibility to both the
spindles is good, the workability during mounting and
removing the workpiece is good, no danger involves in
operation, monitoring of the working state can be easily
made and chips and cutting liquid may be quickly
discharged into the chip receiving box disposed at this
side of the base, which can minimize a thermal
deformation particularly of the base. It is a second
object of this invention to provide a two-spindle
opposed type CNC lathe in which the first spindle stock
is secured to the base, whereby the sufficient rigidity
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is given to the first spindle stock, no problem occurs
in which a blank on the bar feeder moves in an axial
direction during working of the bar material, and the
bar feeder so far used can be used without modification.
It is a third object of this invention to
provide a two-spindle opposed type CNC lathe in which
connection of spindle indexing and driving devices
disposed on the opposed two spindles, respectively, and
adjustment of phase of two spindles can be quickly
accomplished, the work effficiency in the composite
continuous working including the back working and
indexing can be considerably enhanced and the respective
spindles can be indexed and located or rotated at low
speeds by the spindle indexing and driving devices with
the result that the reverse resistance of the spindles
during the aforesaid working can be increased, and the
lathe has a powerful working ability as well as the
aforementioned increase in rigidity of the first
spindle.
It is a fourth object of this invention to
provide a two-spindle opposed type CNC lathe in which
since a difference in phase or speed between the first
spindle and the second spindle can be detected in a very
short period of time without delay to continuously
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correct a speed command given to a spindle motor, the
phase and speed of the two spindles can be accurately
synchronized during rapid acceleration and deceleration
as well as during the constant-speed operation, and in
addition, since the control construction is simple,
working can be simply done, and a synchronous control
device is provided in which the set value is set by the
CNC device adjusting to the size of workpiece and the
working situation to thereby positively avoid hunting
and a torsional stress acting on the workpiece.
It is a fifth object of this invention to
provide a two-spindle opposed type CNC lathe in which
the same NC program can be used in continuous working of
the same workpiece by the first and second working units
to reduce the trouble in preparation of programs; and if
the moving directions of the first tool rest and the
second spindle stock in the direction of axis Z are the
same (for example, rightward movement), the relative
moving relation between the tool and the workpiece is
also the same (for example, the tool is in the direction
away from the spindle), and therefore, erroneous
operation can be avoided during manual operation and
collision or the like between the workpieces resulting
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from the erroneous operation can be positively prevented.
Other features and advantages of the invention
will be apparent from the following description taken in
connection with the accompanying drawings.
For achieving the aforesaid objects, this
invention provides a two-spindle opposed type CNC lathe
comprising two opposed spindle stocks consisting of a first
spindle stock and a second spindle stock, each spindle
stock supporting a spindle for rotation about parallel
spindle axes, two tool rests consisting of a first turret
type tool rest forming a first working unit together with
said first spindle stock and a second turret type tool rest
forming a second working unit together with said second
spindle stock, said two spindle stocks and said two tool
rests being mounted on a common base, said lathe being
provided with a CNC device for working a workpiece
principally in the shape of a rotary body, characterized in
that
a. the base is of the slant type inclined at a
down gradient;
b. the first spindle stock is secured to the
base;
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c. the second spindle stock is mounted on the
base through a slide capable of being moved and located in
the direction of the axis of its respective spindle; and
d. the first tool rest is mounted on the base
through a slide capable of being moved and located in the
direction of the axis of its respective spindle, and in the
direction perpendicular thereto, and the second tool rest
is mounted on the base through a slide adapted to be moved
and located only in the direction perpendicular to the
axial direction of its respective spindle, said mounting
position being offset from both the spindle stocks.
DESCRIPTION OF THE DRAWINGS
The drawings show e_bodiments of the two-spindle
opposed type CNC lathe according to the invention of this
patent application. However, in the illustration of the
~mhodiments, there is employed the way of illustration to
a degree that may be easily understood by those having an
ordinary knowledge in the technical field to which belongs
the two-spindle opposed type CNC lathe according to the
invention of this patent application, and the illustration
of constituent parts that may not be greatly affected in
underst~n~;ng the---------------------------------------_
A
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two-spindle opposed type CNC lathe according to the
invention of this patent application is made as simple
as possible or omitted.
FIG. 1 is a view of arrangement of various
machines and devices installed on the base, that is,
principal members which constitute a two-spindle opposed
type CNC lathe according to the invention of this patent
application;
FIG. 2 iS a schematic sectional view of
apparatus;
FIG. 3 iS a perspective view showing a chip
discharge system;
FIGS. 4 and 5 are explanatory views showing
the relationship with the control program;
FIG. 6 is a developed view for explaining the
spindle stock;
FIG. 7 iS a detailed view of a brake device;
FIG. 8 iS a block diagram showing the control
system of the brake device;
FIG. 9 iS a perspective view of a spindle
indexing and driving device;
FIG. lO is a block diagram showing the control
system of an indexing and driving motor;
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FIG. 11 is a block diagram showing the
connection control system between the spindle and the
spindle indexing and driving device;
FIG. 12 i8 a block diagram showing the control
system of spindle motors;
FIG. 13 is a view showing an example of a
slow/fast discriminating circuit partly omitted;
FIG. 14 is a view for explaining a spindle
encoder; and
FIG. 15 i8 a view showing an example of pulses
generated from the slow/fast discriminating circuit.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Also in the description of this embodiment,
the spindle direction is referred to as the Z-axis
direction, and the direction perpendicular to the Z-axis
is referred to as the X-axis direction.
In FIGS. 1 to 3, reference numeral 1
designates a base, 2a a first spindle stock, 2b a second
spindle ~tock, 3a a first turret type tool rest, 3b a
second turret type tool rest, 4 a chip receiving box,
and 5 a chip discharging conveyor.
The base 1 is of a slant type with an upper
surface inclined at 45 degrees to the horizontal. The first
,A''
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spindle stock 2a is secured to the base 1, and supports a
spindle lla for rotation about an axis ext~n~;ng in the Z-
direction. The second spindle stock 2b is arranged in
opposition to the first spindle stock 2a and is slidable
only in the Z-axis direction through a slide 6. Spindle
stock 2b supports a spindle llb for rotation about an axis
exten~;ng in the Z-direction. The tool rests 3a and 3b are
offset with respect to the first spindle stock 2a and the
second spindle stock 2b, respectively. The first spindle
stock 2a and the first tool rest 3b form a first working
unit 17a, and the tools on the first tool rest 3a work a
workpiece mounted on the first spindle stock 2a. The
second spindle stock 2b and the second tool rest 3b form a
second working unit 17b, and the tools on the second tool
rest 3b work a workpiece mounted on the second spindle
stock 2b.
The first tool rest 3a is mounted slidably in the
z-axis direction (the spindle direction) and in the X-axis
direction (the direction perpendicular to the spindle
direction) by a slide 7 composed of a slides 71 and 7~, and
the second tool rest 3b i~ mounted slidably only in the X-
axis direction by a slide 8.
The slides 6, 7 and 8 are each provided with a feed
device composed of feed motors 12b, 12a, 13a and 13b, feed
screws 14b, 14a, 15a, 15b and ball nuts not shown. The
rotation of the feed motors 12b, 12a, 13a and 13b is
controlled by a program of a CNC device 26 to
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determine the feed speed of and position movement of the
second spindle stock 2b, the first tool rest 3a and the
second tool rest 3b.
The tool rests 3a and 3b are respectively
provided with turrets 9a and 9b having a plurality of
tools including rotary tools such as milling cutters,
drills or the like, the turrets 9a and 9b being indexed
and driven by index motors lOa and lOb so as to ~elect
the desired tool. Motors 39a and 39b for milling are
disposed for rotating the selected tool if the latter i~
a rotary tool.
The po~itions of the first turret 9a, the
second turret 9b and the second spindle llb shown by the
phantom lines in FIGS. 4 and 5 are position~ of original
points. At this position of the oriqinal point, the
positional relation between the turrets 9a and 9b and
the spindles lla and llb is symmetrical to left and
right.
The reason why the base l of the ~lant type
inclined at 45 degrees is employed is that the
chip~ described later are quickly discharged, that the
workability of replacement of the tool on the turret is
taken into consideration, that a loader or an unloader
can be arranged at a ~uitable po~ition upwardly or
16
A
2!~09g93
frontwardly of the machine, and that an excessively
large eccentric load i8 prevented from being exerted on the
slide surfaces of the spindle stocks 2b and the tool
rests 3a, 3b. In the actual construction, three
slideways are integrally cut in the upper surface of the
base 1 to increase the rigidity and are formed in build-
block system to thereby reduce an increase in cost.
The upper surface of the base 1 in the working
area formed between both the spindle stocks 2a and 2b is
covered by an expansible cover 18 mounted between the
slide 6 of the second spindle stock 2b and the first
spindle stock 2a.
(Chip receiving box)
The chip receiving box 4 is removably arranged
on the front edge of the base 1, and a conveyor 5 for
discharging the chips sideward is arranged on the bottom
surface of the chip receiving box 4. Accordingly, the
chip~ generated in the working area slip down on the
cover 18, fa}l onto the chip receiving box 4 and are
promptly discharged sideward by the conveyor 5.
In the turning working, a tool capable of
heavy cutting is used in order to complete rough cutting
as soon as possible, and the workpiece 16 is rotated at
a high speed and the tool is fed at a high speed to
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effect rough cutting. Because of this, a high working
heat is generated. It is therefore an important
requirement for preventing thermal deformation of the
machine and the workpiece 16 to maintain a high working
precision to apply a cutting liquid to cool the chips
and promptly remove the latter from the working area.
Accordingly, one of most important problems in the
machine of this kind is to process the chips. The lathe
according to this invention employs the aforementioned
construction described in connection with the embodiment
to solve the problem. The chip conveyor 5 can be of the
construction in which the chips are discharged
rearwardly of the machine, which type however has the
construction in which the chips are gathered in the
center of the chip receiving box, in which case the
conveyor 5 passes along the center of the base 1 and
therefore, the maintenance operation is not convenient.
Generally, a number of controllers are arranged at the
rear of the machine, and therefore, the aforesaid type
is not preferable in terms of maintenance of the
controllers.
(Spindle stock)
As shown in FIGS. 1 to 6, the spindles lla and
llb are rotatably mounted on the first and second
18
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. .
spindle stocks 2a and 2b, respectively, the spindles lla
and llb having chucks l9a and l9b secured to first ends
thereof, and having chuck cylinders 20a and 20b for
opening and closing chucks mounted on the other ends
thereof, respectively. The spindles lla and llb are
rotated by the spindle motors 21a and 21b through V-
belt~ 28a and 28b, respectively, and the angle of
rotation thereof i5 detected by spindle encoders 27a and
27b through timing belts 29a and 29b. The spindle
motors 21a and 21b are provided to independently drive
the spindles during the high speed working such as the
turning.
On the first and second spindle stocks 2a and
2b are mounted brake devices 22a and 22b later described
in detail, spindle indexing and driving devices 23a and
23b, ~hift gears 24a and 24b for engaging and
disengaging the spindle indexing and driving devices 23a
and 23b and the spindles lla and llb, gears 25a and 25b,
indexing encoders 26a and 26b and spindle encoders 27a
and 27b.
(Brake devices)
The brake devices 22a and 22b mounted on the
spindles lla and llb have the function to freely and
automatically control the braking force such that in
19
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case where the position of the spindles lla and llb need
be stopped at the de~ired position, the rotation of the
spindles lla and llb i9 positively braked at the desired
position, and in case of milling for contouring, the
rotation thereof is braked by the force half of the
former. The rotational speed and the angle of rotation
of the spindles lla and llb can be controlled by the
pro~ram of the CNC device 46 accurately without any
vibration.
As shown in PIGS. 7 and 8, the brake devices
22a and 22b in this embodiment comprise brake disks 31a
and 31b secured to the spindles lla and llb, brake shoes
32a and 32b held from both sides and movable to and from
the brake disks, and brake cylinders 33a and 33b for
applying a holding force thereto, and are secured to the
spindle stocks 2a and 2b through brackets 34a and 34b.
In the present embodiment, the braking force of the
brake devices 22a and 22b can be automatically
controlled by controlling the hydraulic pressure of the
brake cylinders 33a and 33b. However, other
constructions of brake devices can be employed as
long as they have a construction in which the braking
force can be automatically controlled.
993
The operation of the braking devices 22a and
22b will be described in detail with reference to FIG.
8. For example, where the milling for contouring is
discontinuously operated, vibrations sometimes occur in
the spindles lla and llb. The brake devices 22a and 22b
are to damp the vibrations of this kind by applying a
brake to the spindles lla and llb to vary the braking
force according to the magnitude of the working
reaction.
In the present invention, servo drivers 47a
and 47b for controlling the index motors 40a and 40b of
the spindle indexing and driving devices 23a and 23b
have measuring units 36a and 36b for measuring the
driving force thereof mounted thereon, and output
signals therefrom are guided to brake control devices
37a and 37b. Signals outputted from the brake control
devices 37a and 37b are inputted into pressure control
servo valves 38a and 38b thereby regulating the oil
pressures of the brake cylinders 33a and 33b.
- In this embodiment, output of the index motors
40a and 40b when the spindles lla and llb are rotated at
low speeds for milling work only with braking load is
set to a predetermined value (when no brake is applied,
a very small output is present), therefore the brake
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hydraulic pressure is regulated in advance so as to
balance with the output. When the load of the index
motors 40a and 40b exceeds the aforesaid level, the
brake hydraulic pressure is automatically regulated by
the brake control devices 37a and 37b in a direction of
relieving the brake through that amount. In doing so,
the braking force reduces as the load increases after
commencement of milling work, and the index motors 40a
and 40b continue their running while maintaining an
output in a fixed range. Even if the load of the
milling work is varied, the torque variation in the
spindle indexing and driving devices 23a and 23b will
not occur, and the vibrations of the spindles lla and
llb are effectively suppressed so that the working can
be effected in a stable manner.
(Spindle indexing and driving devices)
As shown in FIGS. 6, 9 and 10, the spindle
indexing and driving devices 23a and 23b are
disengageably connected to the spindles lla and llb
through disengageable mechanisms 23'a and 23'b of the
devices 23a and 23b. The spindle indexing and driving
devices 23a and 23b are provided to rotate the spindles
lla and llb during working at low speed rotation such as
indexing, milling work for contouring, etc. and comprise
22
20~993
index motors 40a and 40b, worms 41a and 41b secured to
the output shafts thereof, worm wheels 42a and 42b
meshed therewith, worm wheel shafts 43a and
43b secured thereto, and disengageable mechanisms 23'a
and 23'b. The disengageable mechanisms 23'a and 23'b
comprise shift gears 24a and 24b axially movably mounted
on the worm wheel shafts 43a and 43b with precise
spline, gears 25a and 25b secured to the spindles lla
and llb, shift forks 44a and 44b for engaging the shift
gears 24a and 24b with the gears 25a and 25b, and shift
cylinders 45a and 45b.
The shift gears 24a and 24b and the gears 25a
and 25b are precise gears having the same number of
teeth. In turning, the shift gears 24a and 24b are
moved rightward in FIG. 9 by the shift cylinders 45a and
45b to release the engagment with the gears 25a and 25b,
and the spindles lla and llb are rotated at high speeds
by the spindle motors 21a and 21b. In milling or
drilling, the shift gears 24a and 24b are returned to
the state shown in FIG. 9 into engagement with the gears
25a and 25b, and the rotation of the index motors 40a
and 40b is reduced by the worms 41a, 41b and worm wheels
42a, 42b to rotate the spindles lla and llb through the
gears 24a, 24b and gears 25a, 25b whereby working can
23
take place while effecting locating at a predetermined
angle or rotation at a low speed.
A harmonic drive type reduction gear or a
differential reduction gear can be also employed in
place of the aforementioned worms 41a, 41b and worm
wheels 42a, 42b. A large reduction ratio is used
whereby an accurate angle positioning of the spindles
lla and llb can be accomplished. Also, which respect to
the disengageable mechanisms 23'a and 23'b of the
spindle indexing and driving devices 23a and 23b, an
engaging type mechanical clutch or the like can be used
in place of a shift type gear, of which driving may be
of air pressure type or electric type. In short, such
spindle indexing and driving devices 23a and 23b are
independently respectively provided on the two spindles
lla and llb of the two-spindle opposed type CNC lathe.
The spindle indexing and driving devices 23a
and 23b employ the construction in which the motor
output is transmitted to the spindles lla and llb
through a high reduction-ratio mechanism composed of the
worms 41a, 41b and worm wheels 42a, 42b having a high
reverse resistance to increase the reverse drive
resistance of the spindles lla and llb, thus rendering
possible heavy cutting milling.
24
2(~ 95~3
(Disengageable mechanism for the spindle indexing
and driving devices)
As shown in FIG. 6, the index motors 40a and
40b in the spindle indexing and driving devices 23a and
23b are provided with the indexing encoders 26a and 26b,
whereby the phase and rotational speed of the shift
gears 24a and 24b secured to the worm wheel shafts 43a
and 43b can be detected, which are used for connection
between the spindle indexing and driving devices 23a and
23b and the spindles lla and llb. That is, a control
system is employed in which there is provided means for
computing a position of engagement of the spindles lla
and llb with the shift gears 24a, 24b and gears 25a, 25b
from each four of data comprising phases of a reference
position and a present position of the spindles detected
by the spindle encoders 27a, 27b and phases of a
reference position and a present position detected by
the indexing encoders 26a and 26b so that when the
spindle indexing and driving devices 23a and 23b are
connected to the spindles lla and llb by the
disengageable mechanisms 23'a and 23'b, the spindle
indexing and driving devices 23a and 23b are rotated to
the engaging position determined by said computation
means on the basis of the command of the CNC device 46
to effect engagement of the shift gears 24a, 24b and the
gears 25a, 25b.
As the control system, as shown in FIG. 11,
the spindle encoders 27a and 27b and the indexing
encoders 26a and 26b are provided with pitch counters
49a, 49b, 48a and 48b, respectively. These pitch
counters 49a, 49b, 48a and 48b are counters whose
maximum count number comprises the number of pulses
issued by the spindle encoders 27a and 27b or indexing
encoders 26a and 26b when the spindles or worm wheel
shafts are rotated through an angle corresponding to a
circumferential pitch of the shift gears 24a, 24b, and
gears 25a, 25b, indicating phases from the engaging
points of the shift gears 24a, 24b and gears 25a, 25b.
The pitch counters 49a, 49b, 48a and 48b are
reset by their count up pulses and reference angle
pulses of the encoders 27a, 27b, 26a and 26b (pulses
outputted when the spindles and worm wheel shafts 43a
and 43b assume reference phases). Accordingly, the
pitch counters 49a, 49b and 48a, 48b start counting when
the spindles lla and llb and the shift gears 24a and 24b
assume the reference phases and are reset every time the
shift gears 24a, 24b and gears 25a, 25b rotate through
one circumferential pitch or one pitch portion of the
26
2009~3
gear to newly start counting. Therefore, if the
counting number of the pitch counters 49a and 49b is
equal to that of the pitch counters 48a and 48b, the
phases of the spindles lla and llb are adjusted to those
of the shift gears 24a and 24b and the engagement
between the shift gears 24a, 24b and the gears 25a, 25b
can be made at a given position. Dividers 50a and 50b
are provided to roughen the divided number of the
indexing encoders 26a and 26b to the divided number of
the spindle encoders 27a and 27b. For example, if the
divided number of the spindle encoders 27a and 27b is
3600 and that of the indexing encoders 26a and 26b is
360000, the divided number of the dividers 50a and 50b
is 100. When the spindle indexing and driving devices
23a and 23b are connected to the spindles lla and llb,
the CNC device 46 issues a rotation command to the index
motors 40a and 40b through a difference in value between
the pitch counters 49a and 48a, 49b and 48b detected by
comparators 51a and 51b to engage the gears 24a, 24b and
gears 25a, 25b.
Thereby, the orientation operation of the
spindles lla and llb at the low speed at the time of
connection to the spindle indexing and driving devices
23a and 23b is eliminated, and the spindles lla and llb
27
2003993
are rapidly reduced in speed to stop as it is. The
stopped phase is detected by the pitch counters 49a and
49b of the spindle encoders 27a and 27b. The shift
gears 24a and 24b are rapidly located so as to meet the
phase to render possible the operation of connecting the
spindle indexing and driving devices 23a and 23b to the
spindles lla and llb. Since the index motors 40a and
40b comprise servomotors, even if they are rapidly
stopped, no deviation occurs in position, and the
connecting operation can be terminated in a short period
of time.
It is necessary for employment of the
aforesaid construction to sufficiently increase the
pitch accuracy of the shift gears 24a, 24b and gears
25a, 25b. When the high pitch accuracy of the shift
gears 24a, 24b and gears 25a, 25b cannot be expected,
the pitch counters 49a, 49b and 48a, 48b in FIG. 11 are
increased in amount so that counting is made by the
pitch counters 49a, 49b and 48a, 48b of the angle of
rotation of gears 25a, 25b and shift gears 24a, 24b from
the reference phase and the the shift gears 24a and 24b
of the spindle indexing and driving devices 23a and 23b
may be rotated through the count difference detected by
the comparators 51a and 51b. In this case, since the
28
~0~)99~3
engagement of the gears 25a, 25b and shift gears 24a,
24b is always at a constant position, the accuracy may
be easily maintained.
According to the above-described construction,
the connecting operation with idle time considerably
reduced is rendered possible, and thereby the
orientation mechanism herefore required becomes
unnecessary to render possible a great reduction in cost
in terms of construction of machine.
While the control system shown in FIG. 11 is
shown by the circuit block diagram, it is to be noted
that similar operation can be carried out by the program
of the CNC device. Such a device controlled by the
program can be employed as the connecting mechanism of
the spindle indexing and driving devices. This is also
true for the following phase adjusting mechanism of
spindles.
(Control mechanism for the spindle indexing and
driving devices)
The index motors 40a and 40b are controlled by
the servo drivers 47a and 47b upon receipt of a command
from the CNC device 46, as shown in FIG. 10.
Outputs of the indexing encoders 26a and 26b
are inputted as speed signals into the servo drivers 47a
29
:
2(~t)9993
and 47b to feedback control the speeds of the index
motors 40a and 40b, and on the other hand, inputted as
phase signals into the CNC device 46, so that when the
phase signals assume a predetermined value, that is,
when the spindles lla and llb are located at a
predetermined angle, the CNC device issues a stop
command to the servo drivers 47a and 47b.
The indexing operation is carried out at high
speeds by rotating the index motors 40a and 40b at high
speeds, whereas at the indexing position, the brake
devices 22a and 22b are powerfully actuated to stop them
at a predetermined position. In case of milling for
contouring, the CNC device 46 issues a feed speed to the
servo drivers 47a and 47b, which in turn cause the
spindles lla and llb to be rotated at a speed instructed
by the feedback control.
When the spindle indexing and driving devices
23a and 23b are used to rotate the spindles lla and llb,
powerful continuous milling work can be accomplished.
At that time, the spindles lla and llb are applied with
half brake by the brake devices 22a and 22b when
necessary to prevent vibrations of the spindles lla and
llb due to the variation in load.
2~99~3
Moreover, since the phase of the spindles lla
and llb during the transfer of the workpiece can be set
by the program of the CNC device 46, a variety of
transfers and workings of workpiece can be executed,
making it possible to provide an effective composite
machine coupled with an increase in rigidity of the
first spindle stock 2a aæ previously mentioned.
(Phase-adjusting device for both spindles)
The phase adjustment of the spindles lla and
llb when the workpiece is transferred is carried out, as
shown in FIG. 11, in the procedure such that a value (a
difference in indicated value between a reference phase
and a present phase) of the counters 60a and 60b of the
indexing encoders 26a and 26b and a rotation command is
given to either index motor 40a or 40b so that both are
the coincided or set phase difference, or rotation
commands in both normal and reverse directions are given
to both the index motors 40a and 40b so that both are
the coincided or set phase difference. Further, a
preferable construction is that a control device is
provided so that the second spindle llb and the first
spindle lla are rotated in the opposite direction to
each other toward the target phase.
31
Z~0~993
Servo motors are used as the index motors 40a
and 40b whereby the phase adjustment of the spindles lla
and llb each other can be made in a very short period of
time.
A specific description will be made
hereinafter.
Assume that both the gears 25a and 25b of the
spindles lla and llb and the shift gears 24a and 24b
have the same number of teeth, the number of teeth being
z, and n = 360/z, then, the number of meshing points of
the gears is z every n.
It is assumed that the reference positional
phase of the gear 25a on the first spindle side is
normally 0, the present positional phase (stop
positional phase) of the gear 25a on the first spindle
side is al, the reference positional phase of the shift
gear 24a on the first spindle side is 0, and the
present positional phase (stop positional phase) of the
shift gear 24a on the first spindle side is ~1.
It is assumed that the reference positional
phase of the gear 25b on the second spindle side is
normally 0, the present positional phase (stop
positional phase) of the gear 25b on the second spindle
side is a2, the reference positional phase of the gear
Z 0~9~3
24b on the second spindle side is normally 0, and
present positional phase (stop positional phase) of the
shift gear 24b on the second spindle side is ~2.
In the foregoing, phase data are two sets
amounting to four.
The shift gear 24a is meshed with the gear 25a
of the spindle lla, and 81 is obtained from the formula
below:
al - a2 = m x n + ~1
where m is an integer including 0. If the gear 24a is
rotated through 81, it reaches the meshing position.
The value of 81 is normally smaller than n. That is,
for example, if z is 36, 81 is less than 10. The time
required for indexing is very short.
Also in case of the second spindle, similar
operation is able to carry out.
The phase at the meshing position between the
gears 25a and 25b and the shift gears 24a and 24b is
+ 81 in the first spindle, and ~2 ~ 82 in the second
spindle.
In adjusting phases of the spindles lla and
llb for transfer of a workpiece, an angular phase at
which workpiece is transferred is set to r.
2~0~39~3
In case of r = o, that is, in case where
transfer is effected with a workpiece is stopped at an
original phase, the spindles are indexed and rotated by
+ 81 in the first spindle, and ~2 + 82 in the second
spindle.
Since r may not be O unless an interference of
fixtures or machinery is present, if r is not O and the
transfer is effected if phases of the first and second
spindles are coincided, the spindles are indexed and
rotated by 1/2 of a phase difference between the first
and second spindles, and a transfer phase is
automatically obtained by calculation and both the
spindles are indexed to that position~then
Q = [ (~1 + 81) ~ 2 + ~i2) ] / 2
If indexing is made through an angle of Q, a transfer
point is obtained. In this manner, an angular phase of
milling executed by the first spindle is succeeded as an
accurate phase angle even after a workpiece has been
moved to the second spindle.
In case of a shape such that an interference
occurs in a chuck jaws when a workpiece is transferred,
an offset angle free from interference is predetermined,
and there may be set an angle obtained by adding a
34
20~)~`993
required offset angle to a phase at which the first and
second spindles are coincided at the time of transfer.
Let r be the offset angle, the following
formula holds in place of the above-described formula.
Q + r/2 = [(~1 + ~ 2 + ~2) + r] / 2
That is, if the spindles are mutually rotated
in derections of (+) and (-) through an angle of Q +
r/2, the transfer of a workpiece may be made.
(Spindle motor control mechanism)
FIG. 12 shows the control system for the
spindle motors 21a and 21b. When the spindle motors 21a
and 21b are individually operated, the speeds thereof
are individually controlled by motor control portions
52a and 52b which receive the individual speed commands
from the CNC device 46. When the spindle motors 21a and
21b are synchronously operated, they are controlled by a
synchronous control device 53 through switching of a
switch 57.
In FIG. 12, the synchronous control device 53
encircled by the dash-dotted contour lines comprises a
slow/fast discriminating circuit 54 for comparing
magnitude of signals issued by both the spindle encoders
27a and 27b, a correction value setting unit 55 for
setting a correction value of one unit, a correction
2~9993
command circuit 56 for causing said correction value of
one unit to input as an addition or subtraction signal
into speed command correction circuits 58a and 58b on
the basis of the output of said slow/fast discriminating
circuit 54, a switch 57, and speed command correction
circuits 58a and 58b for correcting the speed command
applied to the motor control portions 52a and 52b of the
spindle motors 21a and 21b from the CNC device 46. The
slow/fast discriminating circuit 54 counts and compares
output pulses of the spindle encoders 27a and 27b in a
fine time of millisecond unit to monitor whether or not
a phase difference or a speed difference between the
first and second spindles lla and llb occurs according
to the magnitude of the output pulses.
FIG. 13 is an example showing a circuit partly
omitting on the side of the second spindle llb in the
aforesaid slow/fast discriminating circuit 54. A
circuit similar to that on the side of first spindle lla
with an affix "a" applied thereto is also provided on
the side of the second spindle llb, in which circuit,
output pulses of the spindle encoders 27a and 27b are
provided in predetermined width to count them by the
counters 63a and 63b, and a difference therebetween is
discriminated by a comparator 64. The spindle encoders
36
2Q~999;~
27a and 27b have phase detecting slits 65, ... for
generating output pulse every predetermined angle and
reference angle pulse generating slits 65' for
generating reference angle pulse every predetermined
angle as shown FIG. 14, the latter output pulse being
inputted into AND gates 69a and 69b for providing count
pulses through one shot circuits 66a, 66b, AND gates
67a, 67b and OR gates 68a and 68b.
On the other hand, acceleration signal and
deceleration signal to the spindle motors 21a and 21b
are formed into a common signal (acceleration and
deceleration signal) P by OR gates 70a and 70b, which is
fed to the AND gates 67a and 67b, and also fed to the OR
gates 68a and 68b via inverters 71a and 71b. The
acceleration signal and deceleration signal may be
outputted, for example, when the count value before last
is compared with the previous count value of the
counters 63a and 63b and the resultant value is larger
or smaller than an allowable value.
A one shot circuit 72 for defining the width
of count pulse is provided, which is triggered by a
timing pulses TP applied at regular time intervals
(sampling time intervals), outputs of which serve as
input signals of AND gates 69a and 69b.
20~993
With the above-described arrangement, when the
spindle lla and llb are operated at constant speed, the
acceleration and deceleration signal P is at LOW level
and when the inverters 71a and 71b are inverted, outputs
of OR gates 68a and 68b are maintained at HIGH level,
and therefore, the count pulses in pulse width of the
one shot circuit 72 are provided as shown in FIG. 15(a).
If a speed difference is present between the spindles
lla and llb, a difference in count value between the
first counter 63a and the second counter 63b occurs, the
magnitude of which is discriminated by the comparator
64. When the spindles lla and llb are being accelerated
and decelerated, the timing pulse TP of the one shot
circuit 72 rises, and thereafter the pulses of the one
shot circuits 66a and 66b triggered by the reference
angle pulse rise, after which output pulses of the
spindle encoders 27a and 27b are counted. Therefore,
the count start time on the side in which the phase is
early becomes fast, and even if the speeds are the same,
the count value on the side in which the phase is early
becomes large. Accordingly, the phase difference can be
discriminated by comparing the count values of the first
and second counters 63a and 63b similarly to the case of
20~9993
the constant speed rotation. Thereby, hunting during
the constant speed rotation can be prevented.
A speed correction value to be given every
unit time interval to the correction command circuit 56
is set to the correction value setting unit 55. This
correction value can be given by the NC program as
previously mentioned. The correction command circuit 56
receives the output of the slow/fast discriminating
circuit 54 to supply the correction value set to the
correction value setting unit 55 as a subtraction
command or an addition command to the speed command
correction circuits 58a and 58b. Of course, correction
values are supplied as a subtraction command and an
addition command to the side in which phase and speed
are gained and to the side in which they are delayed,
respectively. The speed command correction circuits 58a
and 58b adds or subtracts the correction value from the
speed command supplied ~rom the CNC device 46 to supply
the speed command to the motor control portions 52a and
52b.
When the first spindle lla and the second
spindle llb are desired to be synchronously driven, the
speed command for the first spindle lla is supplied to
both the motor control portions 52a and 52b by the
39
20~)99~3
switch 57, and the switch 57 is switched so that the
correction signal may be supplied to the speed command
correction circuits 58a and 58b so that the correction
value is subtracted and inputted into the side in which
the phase is gained and conversely the correction value
is added and inputted into the side in which the phase
is delayed. This series of control cycles are
repeatedly carried out at short time intervals whereby
the first spindle lla and the second spindle llb can be
synchronized.
While in the above-described embodiment, the
synchronous control device 53 is formed from a hard
structure for better understanding, it is to be noted
that it may be formed from a soft ware of a computer.
Actually, the soft ware structure is preferable because
it has a high flexibility.
(Procedure for working the workpiece)
Working of the workpiece 16 by the two-spindle
opposed type CNC lathe according to this invention is
carried out in the following procedure.
First, the chuck opening and closing cylinder
20a of the first spindle lla forming the first working
unit 17a is operated so that the workpiece 16 is held by
the chuck l9a to effect turning operation in cooperation
2 ~ ~ ~ 3
with the first tool rest 3a. At this time, the shape of
the workpiece 16 to be worked is determined according to
the degree of movement of the first tool rest 3a in the
Z-axis direction and in the X-axis direction. Upon
termination of the turning operation, the first spindle
lla is rapidly reduced in speed to be stopped without
locating to a predetermined reference phase.
When milling or drilling is required in the
working by the first working unit 17a, phases of
connecting portions between the spindle lla and the
spindle indexing and driving device 23a are adjusted,
and the first spindle lla and the spindle indexing and
driving device 23a are connected by the disengageable
mechanism 23'a to effect indexing and milling operation
of contouring.
When the first spindle lla and the spindle
indexing and driving device 23a are connected by the
disengageable mechanism 23'a, the index motor 40a is
rotated to the engaging position between the shift gear
24a and the gear 25a on the basis of the count value
from the spindle encoder 27a showing the phase of the
spindle lla and the count value from the indexing
encoder 26a, and the shift gear 24a is moved by the
shift cylinder 45 and the shift fork 44 to engage the
2(~0~3993
shift gear 24a with the gear 25a. The thereafter
indexing is carried out by rotating the index motor 40a
on the basis of the count value from the indexing
encoder 26a. If the servo motor normally used is used
as the index motor 40, high speed locating of the
spindle indexing and driving device 23a can be easily
accomplished, and the connection between the first
spindle lla and the spindle indexing and driving device
23a can be carried out in a few seconds.
Upon termination of the working by the first
working unit 17a, the phase of the first spindle lla is
made in coincidence with that of the second spindle llb,
the second spindle stock 2b is moved toward the first
spindle stock 2a, and the workpiece 16 is transferred
from the chuck l9a to the chuck l9b by the operation of
the chuck cylinders 20a and 20b.
In case where the workpiece 16 is a bar, there
includes the step in which the end of the bar is held by
the chuck l9b of the second spindle llb, and thereafter,
the first spindle lla and the second spindle llb are
synchronously rotated by the synchronous control device
53a and the workpiece 16 is cut off from the end of the
bar by cutting-off operation.
42
ZO~)99g3
The adjustment of phases between the first
spindle lla and the second spindle llb when the
workpiece is to be delivered is carried out by
connecting the spindle indexing and driving device 23b
with the second spindle llb through the connecting
mechanism, then reading the count value from the index-
ing encoder 26a of the first spindle stock 2a when the
indexing has been terminated, and rotating the index
motor 40b till said value coincides with that of the
second spindle stock 2b or assumes the designated angle
difference to adjust the phases to effect the delivery
of the workpiece 16. In case where the servo motor is
used as the index motor 40b, the adjustment of phases at
the time of delivery of the workpiece 16 can be done in
a very short period of time. At this time, the
adjustment of phases between the first spindle lla and
the second spindle llb can be carried out by reversely
rotating both the spindle indexing and driving devices
23a and 23b in an approaching direction.
In case where the workpiece 16 is a flange,
the lengthwise dimension of the workpiece 16 is often
relatively small, and therefore, in this case, when the
workpiece 16 is approached for the transfer from the
first spindle lla to the second spindle llb, there is a
43
2~ 33
fear that the chucks l9a and l9b collide with each
other. To avoid this, it is necessary to deviate the
phase of the second spindle llb from the phase of the
first spindle lla through 60 degrees (in case where the
chucks l9a and l9b are of three jaws). However, in the
present invention, when the workpiece 16 is transferred,
the amount of rotation of the first spindle lla or the
second spindle llb may be corrected through a deviation
portion. This phase difference will suffice to be input
in the NC program.
Furthermore, rising of rotation in the state
where both ends of the work are held at the time of
working a bar is promptly and smoothly carried out by
the synchronous control device 53. Therefore, in this
respect, the working cycle can be shortened, the second
spindle stock 2b is given sufficient rigidity and an
excessively large torsional load is not exerted on the
workpiece 16. Moreover, by the addition of the
synchronous control device 53, the workpiece 16 may be
transferred while synchronously rotating the first
spindle lla and the second spindle llb. In case where
the final working on the side of the first spindle lla
is turning, such operations are carried out whereby the
44
2009993
idle time required to once stop and again accelerate the
first spindle lla can be reduced.
The synchronous control device 53 compares
signals from the spindle encoders 27a and 27b so that a
speed command is offset and inputted to the spindle of
which speed is high or the spindle of which phase is
gained in a direction of delaying it whereas a speed
command is offset and inputted to the spindle of which
speed is low or the spindle of which phase is delayed in
a direction of advancing it to thereby make a control so
as to make zero the speed difference or phase difference
between both the spindles lla and llb covering the
rotational characteristics and inertia characteristics.
In the system for correcting and inputting as a common
command the speed command supplied from the CNC device
46 to the spindle motor control portions 52a and 52b to
modify the speed difference or phase difference as
described above, controlling to follow each other is
effected to follow an average value between both the
spindles toward the target unlike the conventional
following system heretofore often used, that is, the
system to cause one to follow with the other being a
principal.
2009393
With this, the amount of correction per each
spindle when the phase difference or speed difference is
corrected will suffice to be half of the one-side
following system. The prompt following operation can be
effected during high speed rotation or during rapid
acceleration or deceleration while suppressing servo
hunting.
In the conventional controling,for the
detection of the speed difference or phase difference,
an amount of deviation is detected to obtain a command
value corresponding to a differential thereof by
computation. This requires a time for computation
process and a repeated unit of period for correction
cannot be shortened. Therefore, for those machines such
as the lathe which rotates at high speed and is short in
acceleration and deceleration time, the speed difference
or phase difference between both the spindles lla and
llb becomes already varied when the correction value is
calculated, resulting in a rough control with time lag
to fail to maintain a good synchronous accuracy. On the
other hand, in the present invention, since the repeated
unit of control period is shortened and therefore all
the computation to obtain the correction command value
from the phase difference or speed difference can be
46
~o~
omitted, and the slow/fast is merely discriminated to
ignore the amount thereof. The set correction values
are simply added or subtracted so as to obtain the
command value. The correction values of one unit to be
set are individually set in advance in consideration of
the characteristics of individual motors, and the
individual working programs are set in consideration of
the mass or the like of workpiece. Thereby, the
repeated period for the correcting operation is a
millisecond unit. Correction can be made almost
continuously. Furthermore, by setting an adequate unit
correction value, prompt synchronous control can be
effected without occurrence of hunting.
In the sampling of the encoder signal, the
phase difference between both the spindles lla and llb
is discriminated during the acceleration or deceleration
to effect acceleration control, whereas the speed
difference is discriminated during constant speed
operation to effect speed control. In doing so, it is
possible to positively prevent a large torsional torque
which involves a danger acting on the workpiece during
acceleration or deceleration and to effectively prevent
hunting during constant speed operation.
47
2009993
In case where in inputting a predetermined
correction value, the speed difference or phase
difference is below a fixed value, an insensitive zone
is provided so as not to produce a correction signal
from the synchronous control device, thus preventing
control hunting to stabilize the operation. In case
where both the spindles lla and llb are operated at
independent rotational speeds, the synchronous control
device 53 is disengaged by the switch 57 whereby
sufficiently coping with the independent operation of
each of the spindles lla and llb.
After the workpiece 16 has been delivered to
the chuck l9b of the second spindle llb, the second
spindle llb is moved in the direction of moving away
from the first spindle lla to work the back of the
workpiece 16 in cooperation with the second tool rest
3b. At this time, the shape of the workpiece 16 to be
worked is determined by the movement of the second
spindle stock 2b in the Z-axis direction and the
movement of the second tool rest 3b in the X-axis
direction. During that period, the next workpiece 16 is
supplied to the chuck l9a of the first spindle lla, and
the previous workpiece 16 and the next workpiece 16 are
simultaneously worked. After the working by the second
48
2(~ 993
working unit 17b has been terminated, the previous
workpiece 16 is discharged outside the machine, and the
chuck l9b of the second spindle stock 2b moves to grip
the workpiece 16 which has been worked in the first
spindle stock 2a. The workpieces 16 are successively
worked in a similar procedure.
Cutting liquid is sprinkled over the workpiece
16 being worked, and the chips ruptured by the tools on
the tool rests 3a and 3b flow down on the cover 18
together with the cutting liquid and thence fall into
the chip receiving box 4 at the front edge of the base
1. The chips gathered in the chip receiving box 4 are
delivered into a bucket provided laterally of the
machine by means of the chip conveyor 5, the cutting
liquid being filtered and circulated for use.
In the working accompanied by the transfer of
the work between the first working unit 17a and the
second working unit 17b, as shown in FIG. 4, a command
is given to the first working unit 17a with a first
working program A with a work transfer program JA added
to the end thereof whereas a command is given to the
second working unit 17b with a work transfer program JB
added to the head thereof.
49
20~3~3;3
In case where for example, the program A
portion of the working for the workpiece 16 as shown in
FIG. 4 is simultaneously carried out by the first
working unit 17a and the second working unit 17b, using
the two-spindle opposed type CNC lathe according to this
invention, a command is given with the same working
program A to both the working units 17a and 17b, as
shown in FIG. 5. At this time, the rightward movement
of the first tool rest 3a and the rightward movement of
the second spindle stock 2b are the movements of the
tools in the direction of moving away from the spindles
lla and llb, and the relative moving relation between
the workpiece 16 and the tool is the same in the irst
working unit 17a as well as in the second working unit
17b. Accordingly, if a command of movement in the X-
axis direction given to the first tool rest 3a is given
to the second tool rest 3b as it is, exactly the same
working as that to be done in the first working unit 17a
can be effected even in the second working unit by the
same program. Exactly the same working program A may be
given to both units.
According to this invention, since the spindle
indexing and driving devices 23a and 23b having a large
reverse resistance are mounted on the first spindle lla
2~0~9~3
and the second spindle llb, powerful contouring millings
can be simultaneously carried out with the coincided
phase of the back working, and naturally, the same
rotary tool for milling as that of the first tool rest
is mounted on the second tool rest 3b. In this
construction, the slant type base 1 is employed to
facilitate the maintenance operation of the tool, and
the chip receiving box 4 is arranged frontwardly of the
machine to promote quick discharge of chips and quick
radiation of cutting heat.
According to the construction of the two-
spindle opposed type CNC lathe of this invention, since
two tools are positioned in deep of the spindles, good
accessability to the spindles is obtained, good
workability during mounting and removal of the work is
obtained, and no danger involves in operation. These
effects are further promoted by the use of the slant
type base.
Furthermore, since there is employed a
construction in which the first spindle stock is fixed,
sufficient rigidity can be applied to the first spindle
stock. During working of a bar no problem occurs that a
workpiece on the bar feeder is axially moved.
51
2~
A conventional bar feeder can be used without
modification. If the first tool rest is moved in the Z-
axis direction, mounting and removal of the tool to the
turret and maintenance and repair of the tool rests can
be easily carried out.
Moreover, since the discharge of the chips or
cutting liquid into the chip receiving box installed
frontwardly of the base can be quickly done, it is
possible to minimize the thermal deformation of the
machine body. Various types of workpiece loaders and
unloaders may be utilized without modification.
In addition, connection of the spindle
indexing and driving device to the spindle and
adjustment of phases of the first and second æpindles
can be very quickly accomplished to considerably enhance
the working efficiency in the composite one continuous
operation of the workpiece including the back working
and indexing. Since the index locating and low speed
rotation feed can be given to the spindle by the
independent spindle indexing and driving device, the
reverse resistance can be increased during the working.
It is possible to provide a two-spindle opposed type CNC
lathe provided with a powerful working ability as well
52
200~9~
as an increase in rigidity of the first spindle stock as
mentioned above.
Moreover, according to the æynchronous control
device of this invention, the phase difference or speed
difference between the first and ~second spindles can be
detected at extremely short time intervals to correct
the speed command continuously given to the spindle
motor, and therefore the phases or speeds of two
spindleæ can be accurately synchronized during the rapid
acceleration or deceleration as well as constant speed
operation. Since the control construction is simple,
the machine can be operated in a simple manner. If the
set value is set by the CNC device while adjusting to
the size of workpiece and working situation, hunting and
torsional stress acting on the workpiece can be
positively avoided.
Furthermore, in the lathe of this invention,
when the same workpiece is worked by the first and
second working units, the same NC program can be used to
thereby relieve the trouble in preparation of program.
In addition, if the moving direction of the first tool
rest in the Z-axis direction is the same (for example,
rightward movement) as that of the second spindle stock,
the relative moving relation between the tool and the
2~)0~9~3
workpiece is also the same (for example, the direction
in which the tool moves away ~rom the spindle), and
therefore, erroneous operation during manual operation
can be avoided, and collision or the like between the
workpieces resulting from the erroneous operation can be
positively prevented.
54
