Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DESCRIPTION
PUNCH HOLE FORMING METHOD AND PUNCH HOLE FORMING
DEVICE
Technical Field
[00011 The present invention relates to a punch hole forming method of
punching a substrate, and a punch hole forming device.
Background Art
[00021 In general, when a hole is provided in a workpiece material, which is
an object to be punched, a workpiece is placed on a die, and a punch is used
to
provide a hole in the workpiece material. Patent Document 1 discloses a hot
forging technique in which a workpiece is punched after the workpiece is
heated to reduce the deformation resistance of the workpiece material, namely
to increase the deformability thereof. In the case where a workpiece is heated
as described above, abrasion, thermal damage, and the like occur in the punch
due to the temperature of the heated workpiece itself, friction during
punching,
and the like, and thus the lifetime of the punch is reduced. Therefore, in the
technique disclosed in Patent Document 1, a coolant always flows inside the
punch, and the leading end of the punch is cooled by intensively spraying the
coolant onto the leading end of the punch.
Prior Art Documents
Patent Document
[00031 Patent Document 1: JP H8-309473A
Disclosure of the Invention
Problem to be Solved by the Invention
[00041 In a case of a relatively thin workpiece, when the workpiece is placed
on a die and is then punched, the temperature of the workpiece decreases due
to the die and the punch, and thereby the deformability thereof is reduced,
thus
making it difficult to punch the workpiece. As mentioned above, in the
technique disclosed in Patent Document 1, the punch is cooled in order to
prevent the punch from being heated and thermally damaged due to the very
hot workpiece. That is, Patent Document 1 does not disclose a technique in
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which a workpiece is punched in a state in which the heat of the workpiece is
prevented from being transferred to a die, a punch, and the like.
[00051 Accordingly, the present invention was made in view of the
aforementioned problem, and an object thereof is to provide a punch hole
forming method and a punch hole forming device that can suppress a decrease
in the temperature of a workpiece due to a machining tool when a hole is
formed by punching the workpiece using the machining tool.
Means for Solving Problem
[00061 In a characteristic configuration of a punch hole forming method
according to the present invention, the punch hole forming method is a method
of placing a workpiece that is a plate-like member having a thickness of 0.01
mm or more and 1 mm or less on a die, and forming a hole by punching the
workpiece in a thickness direction using a punch, and includes keeping the
workpiece at a temperature TO at which the workpiece can be punched at least
during formation of the hole.
[00071 When a relatively thin workpiece having a thickness of 0.01 mm or
more and 1 mm or less is placed on a die, the temperature of the workpiece
may decrease due to contact with the die. On the other hand, since the
workpiece is a relatively thin plate, when the workpiece is excessively
heated,
there is a possibility that the plate shape of the workpiece cannot be kept,
and
the workpiece undergoes deformation such as warping.
[00081 With this characteristic configuration, while taking these points into
account, the workpiece, which is a relatively thin plate, is kept at the
.. temperature TO at which the workpiece can be punched, in a state in which
the workpiece is placed on the die. Accordingly, a decrease in the temperature
of the workpiece can be suppressed, and the deformation resistance (tensile
strength) can be kept small. That is, in the state in which the deformation
resistance of the workpiece is kept small and thereby the deformability is
increased, a hole can be formed by easily punching the workpiece using a
punch.
In addition, the resistance is small while a hole is being formed, thus making
it possible to suppress deformation of the workpiece itself, which is a
relatively
thin plate, and to accurately form a hole having a desired diameter. Also, for
the reason that the temperature TO is not a temperature at which the shape
of the workpiece itself is changed but a temperature at which the workpiece
can be punched, a change in the shape of the workpiece itself can be
suppressed.
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Moreover, since the deformation resistance of the workpiece is small,
the possibility of the punch buckling can also be avoided.
[00091 In another characteristic configuration of the punch hole forming
method according to the present invention, a load applied by the punch to the
workpiece while the workpiece at the temperature TO is being punched using
the punch is smaller than or equal to a predetermined value.
[00101 With this characteristic configuration, the deformation resistance of
the workpiece is reduced by keeping the workpiece at the temperature TO at
which the workpiece can be punched. Due to the reduction in the deformation
resistance of the workpiece, a load (compressive stress applied to the
punching
blade of the punch) is smaller than or equal to a predetermined value while
the
workpiece is being punched using the punch. If a workpiece is punched with
a large load, a portion of the workpiece located at a position at which a hole
is
formed and a portion therearound may be pulled in the punching direction,
leading to deformation of the workpiece. While a hole is being formed, a load
(compressive stress) can be set to be smaller than or equal to a predetermined
value by keeping the workpiece at the temperature TO, thus making it possible
to suppress the deformation of the workpiece itself, which is a relatively
thin
plate, and to accurately form a hole having a desired diameter.
[00111 A load applied by the punch to the workpiece kept at the temperature
TO while a hole is formed in the workpiece using the punch is 10% or more and
30% or less of a load required to form a hole in the workpiece at room
temperature using the punch.
[00121 With this characteristic configuration, a load required to form a hole
in
a workpiece that is kept at the temperature TO can be sufficiently reduced
compared with a load required to form a hole in the workpiece at room
temperature. Accordingly, it is possible to suppress the deformation of the
workpiece itself, which is a relatively thin plate, and to accurately form a
hole
having a desired diameter.
[00131 In another characteristic configuration of the punch hole forming
method according to the present invention, the temperature TO is 300 C or
higher and 950 C or lower.
[00141 With this characteristic configuration, keeping the temperature TO of
the workpiece at a temperature of 300 C or higher and 950 C or lower makes
it possible to suppress the deformation of the workpiece itself, which is a
thin
plate, and to accurately form a hole having a desired diameter.
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[00151 In another characteristic configuration of the punch hole forming
method according to the present invention, the workpiece is kept at the
temperature TO by placing the workpiece on the die heated to a temperature
TD.
[00161 Conventionally, there has been a problem in that thermal damage and
the like occur in a die and a punch due to heating, leading to a reduction in
the
lifetimes thereof. Therefore, an idea of punching a workpiece after heating a
die and the like has been ignored. With this characteristic configuration, the
workpiece is relatively thin, and thus the temperature of the workpiece
decreases immediately after the workpiece is placed on a die that is not
preheated. Based on this fact, a technique is employed in which the die is
heated to the temperature TD, which is completely different from conventional
techniques. By placing the workpiece on the heated die, the workpiece is kept
at the temperature TO due to heat transfer caused by heat conduction, heat
radiation, and the like from the heated die.
[00171 In another characteristic configuration of the punch hole forming
method according to the present invention, the workpiece is kept at the
temperature TO by punching the workpiece using the punch heated to a
temperature TP.
[00181 Conventionally, a punch has not been heated in consideration of the
lifetime of the punch. However, with this characteristic configuration, the
punch is heated to the temperature TP based on the fact that the workpiece is
relatively thin. The workpiece placed on the die is punched using this heated
punch. The workpiece is kept at the temperature TO due to not only heat
transfer from the die but also heat transfer caused by heat conduction, heat
radiation, and the like from the heated punch with which the workpiece is in
contact while holes are being formed through punching.
[00191 In another characteristic configuration of the punch hole forming
method according to the present invention, an aspect ratio defined as a ratio
of
the thickness of the workpiece to the diameter of a hole (thickness/diameter)
is
set to be larger than a threshold value in a conventional punch hole forming
method. The increased aspect ratio is advantageous because the strength of
the workpiece is increased and thus the workpiece can be used in a wider range
of applications when being used as a filter, for example. Therefore, the
aspect
ratio is preferably 2 or more, more preferably 3 or more, and even more
preferably 5 or more. It should be noted that an excessively large aspect
ratio
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causes problems in the strength and the durability of the punch and the die,
and therefore, the aspect ratio is preferably 30 or less, more preferably 20
or
less, and even more preferably 15 or less.
[00201 When being punched, the workpiece, which is a relatively thin plate, is
kept at the temperature TO at which the workpiece can be easily punched
using a punch, and the deformation resistance thereof is kept small.
Accordingly, in the state in which the deformation resistance of the workpiece
is kept small and thereby the deformability is increased, and a change in the
shape of the workpiece itself is suppressed, the workpiece can be easily
punched using a punch. Therefore, as in this characteristic configuration, a
hole having an aspect ratio of 2 or more and 30 or less can be formed by
punching the workpiece, which is a relatively thin plate. The lower limit of
the range of the thickness of the thin plate is preferably 0.01 mm or more,
more
preferably 0.05 mm or more, and even more preferably 0.1 mm or more, from
the viewpoint of the processing cost. It should be noted that the upper limit
thereof is preferably 1 mm or less, more preferably 0.75 mm or less, and even
more preferably 0.5 mm or less.
[00211 In another characteristic configuration of the punch hole forming
method according to the present invention, the upper limit of the range of the
diameter of the hole is 1 mm or less, which is difficult to achieve by a
conventional punch hole forming method. It should be noted that the lower
limit thereof is preferably 0.005 mm or more, more preferably 0.01 mm or more,
and even more preferably 0.02 mm or more, from the viewpoint of the degree
of difficulty and the cost of manufacturing of a punch and a die.
[00221 In another characteristic configuration of the punch hole forming
method according to the present invention, a plurality of the holes are formed
in the workpiece. In the case where the workpiece is used as a filter or the
like for the purpose of filtration, for example, it is advantageous to provide
a
larger number of holes because pressure loss of the filter is further reduced.
On the other hand, the hole is formed in the workpiece based on the principle
that a punch hole is formed through the application of shearing force by a
punch. Therefore, if an interval between adjacent holes is too small, defects
such as significant deformation and breakage may occur between holes of the
workpiece. From this viewpoint, the interval between adjacent holes is
preferably two or more times, more preferably three or more times, and even
more preferably four or more times as large as the diameter of the punch
holes.
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[00231 In another characteristic configuration of the punch hole forming
method according to the present invention, the workpiece is made of a heat-
resistant metal material selected from ferrite-based stainless steel,
austenite-
based stainless steel, and martensite-based stainless steel, and on the other
hand, a material to be processed into the punch and the die is a material that
is ten or more times as strong as the material of the workpiece at a
processing
temperature.
[00241 Using the material as described in this characteristic configuration to
form the workpiece makes it easy to form a desired hole in the workpiece in
which at least one of heat resistance, oxidation resistance, and cost
reduction
is achieved. Accordingly, such a workpiece can be favorably applied to a
substrate on which various electrodes and electrolytes for a cell for a fuel
cell
are to be stacked, a filter provided with a plurality of pores, and the like.
[00251 In another characteristic configuration of the punch hole forming
method according to the present invention, at least one of the punch and the
die is made of a superhard material containing at least one of ceramic and
tungsten.
[00261 With this characteristic configuration, at least one of the punch and
the
die is made of a predetermined material having a relatively high hardness.
Accordingly, even if the punch and the die are heated when a hole is formed by
punching the workpiece, the punch and the die do not undergo deformation due
to heating, and do not undergo deformation due to a load during punching,
either. Therefore, such a material is preferable.
[00271 In another characteristic configuration of the punch hole forming
method according to the present invention, a coolant gas is blasted onto the
punch after the workpiece has been punched using the punch.
[00281 When the workpiece is punched using the punch, the temperature of
the punch rises due to friction. With this characteristic configuration, an
excessive rise in the temperature of the punch is suppressed by blasting a
coolant gas onto the punch. This suppress a reduction in the lifetime of the
punch due to thermal damage and oxidation.
[00291 In another characteristic configuration of the punch hole forming
method according to the present invention, the coolant gas is at least one of
oxygen-free carbonic acid gas, nitrogen, and argon.
[00301 With this characteristic configuration, the coolant gas is at least one
of
carbonic acid gas, nitrogen, and argon, thus making it possible to suppress
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corrosion of the punch.
[00311 In another characteristic configuration of the punch hole forming
method according to the present invention, the punch includes:
a punch main body having a plate shape with a predetermined
thickness:
a punching blade that protrudes and extends from an opposed face of
the punch main body opposed to the workpiece and that is used to form a hole
in the workpiece; and
a stripper member including a base portion that is located on a face
facing in a direction opposite to a protruding direction of the punching blade
out of two opposite faces of the punch main body, and a stripper pin that
extends from the base portion, passes through the punch main body in the
protruding direction of the punching blade, and has a length larger than a
thickness of the punch main body,
wherein the stripper pin is retracted so as not to protrude from the
opposed face while the workpiece is being punched using the punch, and
after the workpiece has been punched using the punch, a leading end
of the stripper pin protrudes from the opposed face and presses the workpiece,
and the punching blade is removed from the workpiece together with the punch
main body.
[00321 With this characteristic configuration, when the workpiece, which is a
thin plate, is punched, the punching blade can be easily removed from the
workpiece due to the stripper pin pressing the workpiece.
[00331 In a characteristic configuration of a punch hole forming device
according to the present invention,
the punch hole forming device forms a hole in the workpiece using the
punch hole forming method described above, and includes:
a die on which the workpiece is to be placed;
a punch for forming a hole by punching the workpiece placed on the die
in a thickness direction; and
a control unit that performs control to keep the workpiece at a
temperature TO at which the workpiece can be punched while the hole is being
formed.
[00341 With this characteristic configuration, the workpiece, which is a
relatively thin plate, is kept at the temperature TO at which the workpiece
can
be punched, in a state in which the workpiece is placed on the die.
Accordingly,
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a decrease in the temperature of the workpiece can be suppressed, and the
deformation resistance (tensile strength) can be kept small. That is, in the
state in which the deformation resistance of the workpiece is kept small and
thereby the deformability is increased, a hole can be formed by easily
punching
the workpiece using a punch. In addition, the resistance is small while a hole
is being formed, thus making it possible to suppress deformation of the
workpiece itself, which is a relatively thin plate, and to accurately form a
hole
having a desired diameter. Also, for the reason that the temperature TO is
not a temperature at which the shape of the workpiece itself is changed but a
temperature at which the workpiece can be punched, a change in the shape of
the workpiece itself can be suppressed.
Moreover, since the deformation resistance of the workpiece is small,
the possibility of the punch buckling can also be prevented.
Brief Description of the Drawings
[00351 FIG. 1 is a perspective view showing the overall configuration of a
punch hole forming device.
FIG. 2 is a schematic diagram showing a state in which a punch is used
for a workpiece placed on a die.
FIG. 3 is a partially enlarged schematic diagram showing a state in
which holes are formed in a workpiece using the punch hole forming device.
Modes Of Embodying The Invention
[00361 Embodiments
Hereinafter, a punch hole forming device and a punch hole forming
method according to this embodiment will be described with reference to FIGS.
1 to 3.
(1) Punch Hole Forming Device
First, a punch hole forming device 100 will be described below.
The punch hole forming device 100 includes a die 10 on which a
workpiece 0 to be provided with holes is to be placed, a punch 20 for forming
holes by punching the workpiece 0 placed on the die 10, a stripper member 50
for facilitating removal of punching blades 23 from the workpiece 0, a cooling
device 60 for cooling the punching blades 23 of the punch 20, and a control
unit
30 that performs various types of control when holes are formed by punching
the workpiece 0.
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[00371 The workpiece 0 of this embodiment is a relatively thin plate-like
member having a thickness of 0.01 mm or more and about 1 mm or less. As
shown in FIG. 2, the workpiece 0 is set in the punch hole forming device 100
and punched, and thereby a plurality of holes passing through the workpiece
0 are formed simultaneously. In this embodiment, these holes have a large
aspect ratio of 2 or more.
It should be noted that the aspect ratio refers to a ratio of the thickness
of the workpiece 0 to the diameter of each hole (thickness/diameter). In this
embodiment, each hole has a diameter of 0.005 mm or more and 0.5 mm or less,
for example, and the pitch of the holes is four or more times as large as the
diameter of each punch hole.
[00381 For example, the workpiece 0 is made of a heat-resistant metal
material selected from ferrite-based stainless steel, austenite-based
stainless
steel, and martensite-based stainless steel, but the material is not limited
thereto. Using such a material to form the workpiece 0 makes it possible to
form desired holes in the workpiece 0 in which at least one of heat
resistance,
oxidation resistance, and cost reduction is achieved. Accordingly, such a
workpiece 0 can be favorably applied to a substrate on which various
electrodes and electrolytes for a cell for a fuel cell are to be stacked, a
filter
provided with a plurality of pores, and the like.
[00391 In this embodiment, in order to simultaneously form a plurality of
holes having a large aspect ratio of 2 or more in the workpiece 0 as described
above, the control unit 30 performs control to form holes by punching the
workpiece 0 placed on the die 10 using the punch 20 in the state in which the
workpiece 0 is kept at a temperature TO. In this case, the control unit 30
performs control to keep the workpiece 0 at the temperature TO by heating
the die 10 and the punch 20.
[00401 It should be noted that the die 10 is fixed at a predetermined
position,
and the movable punch 20 is moved down toward the workpiece 0 placed on
the die 10 and holes are formed in the workpiece 0 on the die 10 using the
punch 20.
[00411 The punch 20 includes a punch main body 21 having a substantially
plate shape, and a plurality of punching blades 23 protruding from the punch
main body 21. The punch main body 21 includes a punch bottom face
(opposed face) 21a that is a flat face and is opposed to the die 10, and a
punch
top face 21b on the other side. The plurality of punching blades 23 are formed
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protruding downward from the punch bottom face 21a toward the die 10.
[00421 As shown in FIG. 3, each of the punching blades 23 includes a main
portion 23a having a cylindrical shape, and a tip portion 23b that tapers from
the main portion 23a toward the tip. The diameter of the main portion 23a of
the punching blade 23 corresponds to the diameter of each hole to be formed in
the workpiece 0, which is 0.005 mm or more and 0.5 mm or less, and is
substantially the same as the diameter of each hole. The pitch of the
plurality
of punching blades 23 provided on the punch main body 21 is four or more times
as large as the diameter of the punch holes, which is a pitch of the hole. The
plurality of punching blades 23 that each have such a diameter and are aligned
at such a pitch are arranged at positions corresponding to lattice points of a
square lattice along a row and a column, for example.
[00431 When the punch 20 is moved close to the die 10, the plurality of
punching blades 23 are inserted into insertion holes 13 provided in the die 10
as shown in FIGS. 2 and 3.
[00441 The punch 20 further includes a punch heater 25 for heating the punch
main body 21 to a predetermined temperature TP. The punch heater 25 is
provided inside the punch main body 21, for example, and heats the punch
main body 21 and the punching blades 23 to the temperature TP. In this case,
the punch heater 25 may heat the punch bottom face 21a and the punching
blades 23 to be brought into contact with the workpiece 0. Alternatively, the
punch heater 25 may heat, to the temperature TP, at least the punching blades
23 that come into contact with the workpiece 0 while the workpiece 0 is being
punched.
In the description below, heating only the entire punch main body 21,
only the punch bottom face 21a of the punch main body 21, only the punching
blades 23, or any combination thereof in the punch 20 is referred to as
"heating
of the punch 20".
[00451 The die 10 includes a die main body 11 having a substantially plate
shape on which the workpiece 0 is to be placed. The die main body 11 includes
a die top face 11a that is a flat face and is opposed to the punch 20, and a
die
bottom face 11b on the other side. The die main body 11 is provided with a
plurality of insertion holes 13 that pass through the die main body 11 from
the
die top face 11a to the die bottom face 11b. The plurality of insertion hole
13
are formed at positions corresponding to the plurality of punching blades 23,
and the plurality of punching blades 23 are to be inserted into the plurality
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insertion holes 13.
[00461 The die 10 further includes a die heater 15 for heating the die main
body 11 to a predetermined temperature TD. The die heater 15 is provided
inside the die main body 11, for example, and heats the die main body 11 to
the
temperature TD. In this case, the inner surfaces located inside the insertion
holes 13 are also heated to the temperature TD due to heating of the die main
body 11. Alternatively, the die heater 15 may heat only the die top face ha
on which the workpiece 0 is to be placed, only the inner surfaces of the
insertion holes 13, or both the die top face 11a and the inner surfaces of the
insertion holes 13.
In the description below, heating only the entire die main body 11, only
the die top face 11a of the die main body 11, only the inner surfaces of the
insertion holes 13, or any combination thereof in the die 10 is referred to as
"heating of the die 10".
[00471 Small protrusions 17 (FIG. 3) are formed on the die top face 11a. The
small protrusions 17 are formed protruding upward from the die top face 11a.
The small protrusions 17 protrude to such a height that the workpiece 0 placed
on the die top face ha is prevented from being shifted from a predetermined
position and is not damaged. It is preferable that the small protrusions 17
have a shape that causes no damage to the workpiece 0. As shown in FIG. 1
and the like, the small protrusions 17 are formed at portions located adjacent
to the insertion holes 13, for example. It is sufficient that the small
protrusions 17 are formed to an extent that the workpiece 0 is not shifted
from
a predetermined position on the die top face 11a, and are not necessarily
formed corresponding to all the insertion holes 13.
[00481 At least one of the die 10 and the punch 20 is made of a superhard
material containing at least one of ceramic and tungsten, but the material is
not limited thereto. At least one of the punch 20 and the die 10 is made of a
material having a relatively high hardness. Accordingly, even if the punch 20
and the die 10 are heated when holes are formed by punching the workpiece 0,
the punch 20 and the die 10 do not undergo deformation due to heating, and
do not undergo deformation due to a load during punching, either. Therefore,
such a material is preferable.
Even when a heat-resistant metal material such as ferrite-based
stainless steel, austenite-based stainless steel, or martensite-based
stainless
steel is selected as the material of the workpiece 0, the die 10 and the punch
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20 made of the above-described material are strong enough to apply an
appropriate load to punch the workpiece 0.
[00491 The control unit 30 performs control to keep the workpiece 0 at the
temperature TO at which holes having an aspect ratio of 2 or more and 30 or
less can be formed through punching. More specifically, when holes are
formed by punching the workpiece 0 in the thickness direction of the plate-
like
member using the punch 20, the control unit 30 performs control to keep the
workpiece 0 at the temperature TO during at least while the holes are being
formed.
In this case, the control unit 30 turns on the die heater 15 to heat the
die 10 to the temperature TD before punching the workpiece 0. The
temperature TD is a temperature that allows the workpiece 0 placed on the
die 10 to be kept at the temperature TO. When the temperature TO is lower
than the temperature TD, the workpiece can be easily kept at the temperature
TO due to the die 10 at a higher temperature, and thus such a temperature
relationship is preferable.
[00501 In addition, the control unit 30 turns on the punch heater 25 to heat
the punch 20 to the temperature TP before punching the workpiece 0. The
temperature TP is a temperature that allows the workpiece 0 placed on the
die 10 to be kept at the temperature TO while the workpiece 0 is being punched
using the punch 20. When the temperature TO is lower than the temperature
TP, the workpiece 0 can be easily kept at the temperature TO due to the punch
20 at a higher temperature, and thus such a temperature relationship is
preferable.
[00511 It should be noted that each of the temperature TD of the die 10, the
temperature TP of the punch 20, and the temperature TO of the workpiece 0
may indicate a certain point of temperature or a certain range of temperature.
Depending on the materials, the temperature TD, the temperature TP, and the
temperature TO are within a range of 300 C or higher and 950 C or lower when
the workpiece 0 is a substrate used to form a fuel cell, for example. Setting
these temperatures to be within this range makes it possible to suppress
deformation of the workpiece 0 itself, which is a thin plate, and to
accurately
form holes having a desired diameter.
[00521 As described above, the workpiece 0 is kept at the temperature TO by
heating the die 10 and the punch 20. Accordingly, when the workpiece 0 is
punched using the punch 20, a load applied by the punch 20 to the workpiece
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0 at the temperature TO is smaller than or equal to a predetermined value.
A load required to punch the workpiece 0 at the temperature TO using the
punch 20 is 10% or more and 30% or less of a load required to punch the
workpiece 0 at room temperature using the punch 20, for example.
[00531 After holes are formed by punching the workpiece 0 placed on the die
using the punching blades 23, and then the punching blades 23 are removed
from the workpiece 0, the cooling device 60 blasts a coolant gas onto the
punching blades 23. Examples of the coolant gas include, but are not limited
to, carbonic acid gas, nitrogen, and argon.
10 [00541 As shown in FIG. 3, the stripper member 50 includes a base
portion 51
that is located on the punch top face 21b side of the punch main body 21, and
stripper pins 53 that extend from the base portion 51 in the direction in
which
the punching blades 23 protrude, pass through the punch main body 21, and
have a length larger than the thickness of the punch main body 21. It is
preferable that the length of each stripper pin 53 is substantially the same
as
the sum of the thickness of the punch main body 21 and the length of each
punching blade 23 in the protruding direction. The stripper pins 53 includes
stripper pins 53a and stripper pins 53h, and are arranged such that a punching
blade 23 is located substantially at the center between a pair of stripper
pins
53a and 53b. The stripper pins 53 can be slid inside the punch main body 21
in the extending direction of the stripper pins 53. An example of the use of
the stripper member 50 will be described later.
[00551 (2) Punch Hole Forming Method
Next, a punch hole forming method in which the above-mentioned
punch hole forming device 100 is used will be described mainly with reference
to FIG. 3.
First, a workpiece 0 that is a relatively thin plate-like member having
a thickness of 0.01 mm or more and 1 mm or less is prepared. Holes to be
formed in the workpiece 0 have a diameter of 0.005 mm or more and 0.5 mm
or less, and the pitch of the holes is four or more times as large as the
diameter
of each punch hole. The holes have an aspect ratio of 2 or more and 30 or
less.
[00561 (2-1) FIG. 3(0
When the holes are formed by punching the workpiece 0, the control
unit 30 turns on the die heater 15 to heat the die 10 to the temperature TD
and
turns on the punch heater 25 to heat the punch 20 to the temperature TP before
punching the workpiece 0.
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[00571 For example, the control unit 30 may start the step of heating the die
and the punch 20 after receiving an instruction to start the punching of the
workpiece 0 from an operator and a separate device.
[00581 After the temperatures of the die 10 and the punch 20 reach
5 predetermined temperatures, the control unit 30 plays a sound or shows an
image, for example, and thereby notifies the operator that the workpiece 0 may
be placed on the die 10. After receiving the notification, the operator places
the workpiece 0 on the die 10.
Alternatively, after the temperatures of the die 10 and the punch 20
10 reach predetermined temperatures, the control unit 30 may control a
robot arm
or the like to place the workpiece 0, which is prepared at a predetermined
position, on the die 10.
[00591 In FIG. 3(i), the workpiece 0 is placed in accordance with
predetermined hole forming positions on the die top face 11a of the die 10
fixed
at a predetermined position. The punch 20 is arranged such that the punch
bottom face 21a is opposed to the workpiece 0 placed on the die top face 11a.
In this case, the punch 20 is arranged such that the punching blades 23
protruding from the punch bottom face 21a are opposed to the insertion holes
13 of the die 10.
[00601 In FIG. 3(i) showing a state before the workpiece 0 is punched using
the punch 20 and subsequent FIG. 3(ii) showing a state in which the workpiece
0 is being punched using the punch 20, the stripper member 50 is located at a
retracted position. That is, regarding the stripper member 50, when the
workpiece 0 is punched using the punch 20, the base portion 51 is pulled up
and located above the punch top face 21b, and thereby the pairs of the
stripper
pins 53a and 53b are retracted in the punch main body 21 so as not to protrude
from the punch bottom face 21a. Accordingly, only the punching blades 23
protrude from the punch bottom face 21a.
[00611 (2-2) FIG. 3(i) to FIG. 3(ii)
In the state shown in FIG. 3(i), the punch 20 is moved close to the
workpiece 0 placed on the die 10 located at a fixed position, and then holes
are
formed by punching the workpiece 0 using the punching blades 23 as shown
in FIG. 3(ii). As shown in FIGS. 1 and 2, a plurality of holes are
simultaneously formed in the workpiece 0 using the plurality of punching
blades 23. Punch chips Oa produced through punching are pushed out by the
punch 20 and separated from the workpiece 0.
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[00621 From the start of the punching of the workpiece 0 to the end of the
punching, the die 10 and the punch 20 are heated to the temperature TD and
the temperature TP, respectively, and thus the workpiece 0 is kept at the
temperature TO. It should be noted that the temperature TO is a
temperature at which the workpiece 0 can be punched or is easily punched.
[00631 When a relatively thin workpiece 0 having a thickness of 0.01 mm or
more and 1 mm or less is placed on the die 10, the temperature of the
workpiece
0 may decrease due to contact with the die 10. On the other hand, since the
workpiece 0 is a relatively thin plate, when the workpiece 0 is excessively
heated, there is a possibility that the plate shape of the workpiece 0 cannot
be
kept, and the workpiece 0 undergoes deformation such as warping.
[00641 While taking these points into account, the workpiece 0, which is a
relatively thin plate, is kept at the temperature TO at which the workpiece 0
can be punched, in a state in which the workpiece 0 is placed on the die 10.
Accordingly, a decrease in the temperature of the workpiece 0 can be
suppressed, and the deformation resistance (tensile strength) can be kept
small.
That is, in the state in which the deformation resistance of the workpiece 0
is
kept small and thereby the deformability is increased, holes can be formed by
easily punching the workpiece 0 using the punch 20. In addition, the
resistance is small while holes are being formed, thus making it possible to
suppress deformation of the workpiece 0 itself, which is a relatively thin
plate,
and to accurately form holes having a desired diameter. Also, for the reason
that the temperature TO is not a temperature at which the shape of the
workpiece 0 itself is changed but a temperature at which the workpiece 0 can
be punched, a change in the shape of the workpiece 0 itself can be suppressed.
Moreover, since the deformation resistance of the workpiece 0 is small,
the possibility of the punch 20 buckling can also be prevented.
[00651 Conventionally, there has been a problem in that thermal damage and
the like occur in a die 10 and a punch 20 due to heating, leading to a
reduction
in the lifetimes thereof. Therefore, an idea of punching a workpiece 0 after
heating a die 10 and the like has been ignored. With the configuration
described above, the workpiece 0 is relatively thin, and thus the temperature
of the workpiece 0 decreases immediately after the workpiece 0 is placed on
the die 10 that is not preheated. Based on this fact, a technique is employed
in which the die 10 is heated to the temperature TD, which is completely
different from conventional techniques. By placing the workpiece 0 on the
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heated die 10, the workpiece 0 is kept at the temperature TO due to heat
transfer caused by heat conduction, heat radiation, and the like from the
heated die 10.
[00661 As described above, conventionally, a punch 20 has not been heated in
consideration of the lifetime of the punch 20. However, with the configuration
described above, the punch 20 is heated to the temperature TP based on the
fact that the workpiece 0 is relatively thin. The workpiece 0 placed on the
die 10 is punched using this heated punch 20. The workpiece 0 is kept at the
temperature TO due to not only heat transfer from the die 10 but also heat
transfer caused by heat conduction, heat radiation, and the like from the
heated punch 20 with which the workpiece 0 is in contact while holes are being
formed through punching.
[00671 In the methods in which holes are formed in the workpiece 0 using a
boring technique in which a rotary blade such as a drill is used, melting
penetration by laser irradiation, and the like, holes are formed one by one.
Therefore, when a plurality of holes are formed, it takes a long time to
perform
processing, which has a harmful influence on mass production. However,
with the configuration described above, the workpiece 0 is kept at the
temperature TO at which the workpiece can be punched, that is, a state in
which the substantially entire workpiece 0 can be easily punched is
maintained, and therefore, a plurality of holes can be simultaneously formed
in a processing region located in a predetermined range of the workpiece 0.
Accordingly, a plurality of holes can be formed in the workpiece 0 in a short
time. For example, a plurality of holes can be formed in the workpiece 0
placed on the die 10 by punching the workpiece 0 using a plurality of punches
20. Accordingly, a large number of workpieces 0 provided with a plurality of
holes can be produced in a short time, and thus the workpieces 0 can be
processed at low cost.
[00681 It should be noted that, in the methods in which holes are formed in
the workpiece 0 using melting penetration by laser irradiation and the like, a
portion of the workpiece 0 needs to be melted. Therefore, problems arise in
that dross such as oxides produced through melting attaches to the inside of
the holes and blocks the holes, and in that another processing for removing
the
attached dross needs to be performed. However, with the configuration
described above, holes are formed by punching the workpiece 0 using the
punch 20, and therefore, punch chips Oa produced through punching are
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pushed out by the punch 20 and separated from the workpiece 0. Accordingly,
the problem in that holes are blocked is less likely to arise unlike the case
where laser irradiation and the like are performed.
[00691 It should be noted that, since the workpiece 0 is kept at the
temperature TO, a load (compressive stress applied to the punching blades 23
of the punch 20) required to punch the workpiece 0 at the temperature TO
using the punch 20 is 10% or more and 30% or less of a load required to punch
the workpiece 0 at room temperature using the punch 20, for example.
If the workpiece 0 is punched with a large load, portions of the
workpiece 0 located at positions at which holes are formed and portions
therearound may be pulled in the punching direction while the workpiece 0 is
being punched, leading to deformation of the workpiece 0. While holes are
being formed, a load can be set to be smaller than or equal to a predetermined
value by keeping the workpiece 0 at the temperature TO, thus making it
possible to suppress the deformation of the workpiece 0 itself, which is a
relatively thin plate, and to accurately form holes having a desired diameter.
[00701 Holes formed by punching the workpiece 0 have an aspect ratio of 2 or
more and 30 or less. As described above, when being punched, the workpiece
0 is kept at the temperature TO at which the workpiece 0 can be easily
punched using the punch 20, and the deformation resistance (tensile strength)
thereof is kept small. Accordingly, in the state in which the deformation
resistance of the workpiece 0 is kept small and thereby the deformability is
increased, and a change in the shape of the workpiece 0 itself is suppressed,
the workpiece 0 can be easily punched using the punch 20. Therefore, holes
having an aspect ratio of 2 or more and 30 or less can be formed by punching
the workpiece 0, which is a relatively thin plate. For the same reason, holes
having a large aspect ratio of 2 or more and 30 or less and a diameter of
0.005
mm or more and 0.5 mm or less can be formed by punching the workpiece 0,
which is a relatively thin plate, with a pitch that is four or more as large
as the
diameter of the punch holes.
[00711 When holes having an aspect ratio of 2 or more are formed in the
workpiece 0 using the punch 20 through cold forging, which is performed at
room temperature or the like without heating the workpiece 0, a load
(compressive stress applied to the punching blades 23 of the punch 20) applied
to the punch 20 during punching is large. Moreover, in the case where the
relatively thin workpiece 0 is punched, even if the workpiece 0 is placed on
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the die 10 after the workpiece 0 has been heated, the workpiece 0 is cooled
due to its small thickness. As a result, compressive stress applied to the
punch 20 is large when holes having an aspect ratio of 2 or more are formed in
the workpiece 0 using the punch 20. In this case, compressive stress and
buckling stress applied to the punch 20 excess the threshold values, and thus
it is difficult to form holes having an aspect ratio of 2 or more.
However, with the configuration described above, by heating the die 10
and the punch 20, the workpiece 0 is kept at the temperature TO at which the
workpiece 0 can be punched. Accordingly, compressive stress applied to the
punch 20 is reduced to a relatively small value, and thus holes having an
aspect
ratio of 2 or more can be easily formed.
[00721 (2-3) FIG. 3(ii) to FIG. 3(iii)
After holes are formed by punching the workpiece 0 using the
punching blades 23 as shown in FIG. 3(ii), the punching blades 23 are removed
from the workpiece 0 as shown in FIG. 3(iii).
When the punching blades 23 are removed, the stripper member 50 is
pressed and moved toward the workpiece 0, and the punch 20 is moved upward
away from the die 10. Thus, the leading ends of the pairs of the stripper pins
53a and 53b protrude from the punch bottom face 21a and press the top face of
the workpiece 0. Accordingly, the punching blades 23 are easily removed
from the workpiece 0 together with the punch main body 21.
[00731 It should be noted that the stripper member 50 may also be manually
moved by an operator. Alternatively, the control unit 30 may perform control
such that the stripper member 50 is placed at the retracted position until the
punching of the workpiece 0 performed using the punching blade 23 is
completed, and the punching blade 23 are removed by moving the stripper
member 50 toward the workpiece 0 and press it against the workpiece 0 after
the punching is completed.
[00741 After the punching blades 23 are removed from the workpiece 0, an
operator performs a manual operation or the control unit 30 performs control
such that a coolant gas is blasted from the cooling device 60 onto the
punching
blades 23. When the workpiece 0 is punched using the punch 20, the
temperatures of the punching blades 23 rise due to friction. By blasting the
coolant gas onto the punching blades 23 as described above, a rise in
temperatures of the punching blades 23 is suppressed. Thus, a reduction in
lifetime of the punch 20 due to thermal damage is suppressed.
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Using at least one of carbonic acid gas and argon as the coolant gas
makes it possible to suppress corrosion of the punch 20. It should be noted
that the coolant gas is not limited to these types of gas as long as corrosion
of
the punch 20 can be suppressed.
[00751 (3) Simulation of Formation of Holes in Workpiece
As described above, when holes are formed in the workpiece 0, the
control unit 30 performs control to heat the die 10 to the temperature TD and
the punch 20 to the temperature TP. Thus, the workpiece 0 to be punched
that is placed on the die 10 is kept at the temperature TO at which the
.. workpiece 0 can be punched.
The following is a description of a simulation performed to confirm
whether or not holes having an aspect ratio of 2 or more and 30 or less can be
formed when such a punch hole forming method is used to form holes.
[00761 A plate-like member that is made of 5U5430 (ferrite-based stainless
steel) and has a thickness of 0.3 mm is used as the workpiece 0. Holes formed
through punching have a diameter of 0.025 mm and an aspect ratio of 12. The
punch and the die are kept at 700 C. The punch 20 are provided with
cylindrical punching blades 23.
[00771 The tensile strength G700 of 5U5430 at 700 C is about a fifth of the
tensile strength o20 at room temperature 20 C, and is about 100 MPa (10.2
kgf/mm2). It should be noted these values are obtained with reference to the
thesis "High-Temperature Characteristics of Stainless Steel" by KIKUCHI
Masao.
[00781 Next, punching force P (kgf) required to perform punching using the
punch 20 is calculated based on Formula (1) below.
P=LHxtxSxk ... (1)
In this formula, LH is the entire circumferential length (mm) of each
hole formed in the workpiece 0 using the punch 20. t is the thickness (mm)
of the workpiece 0, S is the shearing stress (kgf/mm2), and kis the safety
factor.
It should be noted that S is commonly 0.8 times as large as the tensile
strength, and therefore, S is determined by multiplying the tensile strength
0700 by 0.8.
k is commonly 1.2, but in this description, k is set to 1.0 in order to
calculate a collapse safety factor K, which will be described later, for
improved
safety.
[00791 The following values are substituted into Formula (1): 0.025 mm x
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3.142 for LH, 0.3 mm for t, 0.8 x 10.2 kgf/mm2 for S, and 1.0 for k. Thereby,
a
value 0.1923 (kgf) below is obtained.
P=(0.025x3.14)x(0.3)x(0.8x10.2)x(1.0)
=0.1923 (kg0=1.886 (N)
Accordingly, the punching force P required to form a single hole
through punching is 0.1923 (kgf), namely 1.886 (N).
[00801 When each cylindrical punching blade 23 of the punch 20 for forming a
single hole through punching has a cross-sectional area of A (mm2),
compressive stress o-p applied to each cylindrical punching blade 23 is
determined based on Formula (2) below.
o-p=P/A ... (2)
If the diameter of the cylindrical punching blade 23 is the same as the
diameter of the hole, the cross-sectional area A is determined as follows.
A=(0.025/2)x (0.025/2)x 3.142
Accordingly, the compressive stress o-p is determined as follows by
applying this formula to Formula (2).
op =(0. 1923)/((0.025/2)x (O. 025/2)x 3. 142)
=391.7 (kgf/mm2)
[00811 The punch 20 is made of M78 (manufactured by NJS Co., Ltd.). M78
has a compressive strength on of 8.120 MPa (828.0 kgf/mm2) at 700 C.
Accordingly, the collapse safety factor K for compression failure of the
cylindrical punching blade 23 is determined as follows: K=on/op=2.1. It is
clear
from this value that the punching blade 23 does not undergo compression
fracture at 700 C.
[00821 It should be noted that since the holes have a large aspect ratio of
12,
buckling of the punching blades 23 also needs to be tested. Each punching
blade 23 is formed to have a length LP of 0.35 mm, which is longer than the
thickness of the workpiece 0 of 0.3 mm, and a diameter of 0.025 mm, which is
the same as the diameter of the hole.
In this case, each punching blade 23 has a slenderness ratio of 14.0
(0.35 mm/0.025 mm).
Commonly, buckling needs to be taken into
consideration when the slenderness ratio is 15 or more, and therefore, the
punching force P is compared with the Euler's buckling load Pcr (N). The
Euler's buckling load Pcr (N) is determined based on Formula (3) below.
Buckling load Pcr (N)=mx((3.142)2xExI)/LP2 ... (3)
In this formula, m is 0.25 under the condition that one end is fixed, and
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LP is 0.35 mm.
E is the Young's modulus (Pa), and I is the cross-sectional secondary
moment (mm4). ExI is the bending moment and commonly corresponds to
deflective strength in die machining. The nominal value of the deflective
strength of M78 is 1500 (MPa) (1500 (N/mm2)).
Accordingly, the buckling load Pcr (N) is determined as follows by
substituting the values into Formula (3).
Buckling load Pcr=0.25x (3.142)2x 1500/(0.35)2
=3.022x104 (N)
[00831 The punching force P (kgf) is 1.886 (N), and is smaller than the
buckling load Pcr of 3.022x104 (N) (Pcr>>P). It is thus clear that the
punching
force P is sufficiently smaller than the buckling load Pcr, and the punch 20
does
not buckle even when the punching force P is applied to the punch 20 in order
to punch the workpiece 0.
[00841 For example, the entire load PP required to simultaneously form a
million holes in a single punching step is determined based on Formula (4)
below.
Entire load PP=punching force P x number of holes ... (4)
Accordingly, the entire load PP is determined as follows: 0.1973
(kg0x1000000 (holes)=197300 (kg0=198 (ton). In the case of performing
punching using a conventional method, a five-fold larger load applying ability
is needed, and therefore, a large-sized pressing machine of a 1000-ton class
is
needed. However, it is clear that, with the present invention, a small-sized
pressing machine of a 200-ton class can be used to perform punching.
.. [00851 Other Embodiments
The configuration disclosed in the embodiment described above
(including the other embodiments; the same applies to the following) can be
applied in combination with configurations disclosed in the other embodiments
as long as no contradiction arises. Also, the embodiments disclosed in this
specification are illustrative, embodiments of the present invention are not
limited to the disclosed embodiments, and appropriate modifications can be
made without departing from the object of the present invention.
[00861 (1) In the embodiment described above, a plurality of holes having a
large aspect ratio of 2 or more are formed in the workpiece 0. Therefore, the
control unit 30 performs control to heat the die 10 to the temperature TD and
the punch 20 to the temperature TP, and thus the workpiece 0 is kept at the
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temperature TO at which the workpiece 0 can be punched.
However, the control to heat the die 10 and the punch 20 in order to
keep the workpiece 0 at the temperature TO at which the workpiece 0 can be
punched as described in the embodiment above can be applied to a case where
a plurality of holes having a small aspect ratio of less than 2 are formed in
the
workpiece 0.
As in the embodiment above, even when a plurality of holes having a
small aspect ratio of less than 2 are formed, keeping the workpiece 0 at the
temperature TO makes it possible to form holes by easily punching the
workpiece using a punch in the state in which the deformation resistance of
the workpiece is kept small and thereby the deformability is increased. In
addition, the resistance is small while holes are being formed, thus making it
possible to suppress deformation of the workpiece itself, which is a
relatively
thin plate, and to accurately form holes having a desired diameter.
[00871 (2) In the embodiment described above, after holes are formed by
punching the workpiece 0 using the punch 20, the punching blades 23 are
removed from the workpiece 0 using the stripper member 50. However, the
stripper member 50 may be omitted.
[00881 (3) In the embodiment described above, the workpiece 0 is kept at the
temperature TO while holes are being formed by punching the workpiece 0.
In order to keep the workpiece 0 at the temperature TO, the die 10 is heated
using the die heater 15 and the punch 20 is heated using the punch heater 25.
However, a configuration may also be employed in which only the die 10 is
heated using the die heater 15 without heating the punch 20 in order to keep
the workpiece 0 at the temperature TO.
Also, the workpiece 0 may be heated in advance and then placed on
the heated die 10.
The method for keeping the workpiece 0 at the temperature TO while
holes are being formed by punching the workpiece 0 is not limited to the
method described in the embodiment above. For example, the workpiece 0
can be kept at the temperature TO by keeping the atmosphere in which the
workpiece 0 is punched at the temperature TO. Also, the workpiece 0 can be
kept at the temperature TO by applying a voltage to the workpiece 0, for
example.
[00891 (4) In the embodiment described above, each of the punching blades 23
of the punch 20 includes the cylindrical main portion 23a and the tapering tip
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portion 23b. In consideration of load pressure applied to the punch 20, the
tapering shape of the tip portion can be changed as appropriate. Also, a
configuration may be employed in which each of the punching blades 23 does
not include the tip portion 23b and is constituted by the main portion 23a.
[00901 (5) In the embodiment described above, after the workpiece 0 is
punched using the punch 20, the coolant gas is blasted from the cooling device
60 onto the punching blades 23 of the punch 20 in order to cool the punching
blades 23. However, the coolant gas is not necessarily blasted onto the
punching blades 23, and the cooling device 60 may be omitted.
[00911 (6) In the embodiment described above, as shown in FIG. 2 and the like,
the workpiece 0 is placed on the die top face 11a of the die 10 from above the
die 10. However, the workpiece 0 may be slid along a groove-like guide (not
shown) provided on the die 10 and placed on the die top face 11a.
Alternatively, the punch hole forming device 100 may be provided with a
pressing member (not shown) for pressing the workpiece 0 placed on the die
top face 11a from above.
[00921 (7) In the embodiment described above, the die 10 is fixed at a
predetermined position, and the punch 20 is moved toward the die 10.
However, a configuration may also be employed in which the punch 20 is fixed
at a predetermined position, and the die 10 is moved toward the punch 20.
[00931 (8) In the embodiment described above, the small protrusions 17 are
formed in order to prevent the positional shift of the workpiece 0 placed on
the
die 10. However, the small protrusions 17 may be omitted.
Description of Reference Signs
[00941 10: Die
20: Punch
23: Punching blade
0: Workpiece
23
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