JP3028643B2 - Metal foil punching method and die using piezoelectric actuator applied press - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of punching a metal foil by a press using a piezoelectric actuator as a driving source of a punch, and a die structure used for carrying out the method.

[0002]

2. Description of the Related Art Accuracy and quality of precision parts manufactured by shearing have been remarkably improved in recent years due to advances in processing technology, mold manufacturing technology, and performance of press machines. In the field of processing precision components that are required, an attempt has been made to switch an electronic component such as a lead frame, which has conventionally been manufactured by an etching method, to a manufacturing method by shearing.

On the other hand, as a press in which an extremely thin metal foil having a thickness of 100 μm or less is machined by precision punching, position control on the order of microns is possible, and the force required for shearing can be obtained. A press for using a piezoelectric actuator as a driving source for a punch to punch a work material up and down is already known in Japanese Patent Application Laid-Open No. 2-127997.

FIG. 5 shows a vertical punching press using the above-described piezoelectric actuator. In the figure, an upper die 2, a lower die 3, a movable stripper 4, an upper die 5, a lower die 6 are provided on a frame 1. , An upper punch 7, a lower punch 8, and a piezoelectric actuator 9 for opening and closing the stripper 4, and a piezoelectric actuator 10 for driving the upper punch 7 and the lower punch 8 are provided at the upper and lower ends of the frame 1, respectively. , 11 are movable pieces (rod members for transmitting the displacement of the piezoelectric actuator to the punch) 12a,
12b, together with the preload springs 13a and 13b, the case 1a,
1b. In addition, 14 is a mold 2, 3
Are fixed to the inside of the frame 1, 15 is a biasing spring of the movable stripper 4, and 16 is a return spring of the punches 7, 8.

In order to punch a work material by a press having such a configuration, first, the piezoelectric actuator 9 is operated to push up the movable stripper 4 to open the mold, and in this state, the work material (band-shaped metal) is externally opened. The foil 17 is fed between the upper die 5 and the lower die 6, and then the piezoelectric actuator 9 is returned to clamp the work material 17 between the upper die 5 and the lower die 6. Next, a voltage is applied to the piezoelectric actuators 10 and 11, and the upper punch 7 and the lower punch 8 are driven so as to alternately protrude from the retracted position, and the processing material 17 is punched by a so-called vertical punching method. After the processing, the movable stripper 4 is opened again by driving the piezoelectric actuator 9, and the clamp of the processing material 17 is released. In this state, the processing material 17 is fed at a pitch.

Next, steps of the above-described vertical blanking method will be described with reference to FIG. First, FIG. 7A shows a state of an initial step in which the work material 17 is clamped between the upper die 5 and the lower die 6, and in this initial state, the upper punch 7 and the lower punch 8 are located inside the dies 5 and 6. Retreats and waits. Here, when a voltage is applied to the piezoelectric actuator 10 (see FIG. 5) of the upper punch 5, the upper punch 5 protrudes from above as shown in FIG. Half-punched. Subsequently, the upper punch 7 is retracted, and a voltage is applied to the piezoelectric actuator 11 (see FIG. 5) of the lower punch 8 to protrude the lower punch 8 from below as shown in FIG. Then, the shear deformation portion formed on the work material 17 is pushed back so as to push back to apply a shear deformation from the lower surface side. As a result, the punched portion 17a breaks and separates from the work material 17 along the shear plane. In the last step, the punched portion 17a projecting into the upper die 7 is pushed back by operating the upper punch 5 as shown in FIG.

FIG. 7 is an electron micrograph showing a cut section obtained by shearing a copper alloy foil having a thickness of 80 μm as a test material by the above-mentioned vertical cutting method. It is observed that the sheared surface is caused by the shearing and the fractured surface is formed at the center. The mold used in this experiment had a clearance of 2% for the punch on the half punch side,
The clearance of the punch on the reverse side is 4%.

[0008]

According to the knowledge obtained by the inventors through various punching experiments, a metal foil having a thickness of 100 μm or less, particularly a thin metal foil having a thickness of 50 μm or less, is formed by a vertical punching method. In the case of shearing, it became clear that the clearance of the mold had a great effect on the processing accuracy in addition to the accuracy of the punch position control. That is, in the above-described vertical punching method, generally a good shear surface can be obtained if the clearance of the mold is 10% or less of the plate thickness of the processing material. However, if the metal foil, which is a processing material, has a plate thickness of several tens of μm and its punching contour is complicated, it is extremely difficult to make the mold to have an appropriate clearance of 10% or less by ordinary die processing technology. In particular, when a hard material such as a stainless steel material is punched, burrs are generated without a sufficient drooping surface being formed at the shear cut.

FIG. 8 is an electron micrograph showing a cross section of the sample of the punched part shown in FIG. 7 immediately after the reverse punching, and a sharp burr is formed at the lower end of the right side member. The appearance of occurrence is observed.
As described above, in the conventional vertical punching method, burrs are generated particularly when the thickness of the metal foil is reduced, resulting in poor shearing.

The present invention has been made in view of the above points, and an object of the present invention is to precisely punch a metal foil having a thickness of several tens μm or less using a press applied to a piezoelectric actuator as described above without burrs. It is an object of the present invention to provide a new punching method that can be performed and a punching die used for implementing the punching method.

[0011]

In order to solve the above-mentioned problems, in the punching method of the present invention, a processing material is clamped between dies, and both surfaces of the processing material are kept under pressure by a punch. In this state, each punch is driven up and down so as to alternately repeat the half-punching and reverse-punching steps, thereby punching the work material.

Here, half punching in the punching method,
The stroke amount of the punch in the reverse punching process shall be set to a ratio of 10 to 40% with respect to the plate thickness of the work material. The punch can be driven to vibrate up and down by alternately applying a positive voltage. In addition, in order to reliably press and restrain the processing material in the process of the vibration drive, it is preferable to apply a negative voltage to the piezoelectric actuator on the opposite side with a slight time difference from the piezoelectric actuator for applying the positive voltage. .

Further, in the present invention, as a mold structure for suppressing the generation of burrs when the clearance of the mold is larger than the plate thickness of the work material, in the present invention, one of two sets of dies and punches is used. One of the cutting edges is chamfered.

[0014]

With the work material clamped between the dies as described above pressed and sandwiched by the upper punch and the lower punch from both sides, the stroke amount of the punch (the amount of punch biting into the work material) can be increased and decreased by the conventional method. When the stroke is set to a smaller stroke amount (10 to 40%) than in the punching method, and each punch is vibrated by a piezoelectric actuator so as to alternately repeat half punching and reverse punching in this state, punches from above and below are applied to the processing material. In addition to the shearing due to the slight bite, the area along the shear plane is broken by low cycle fatigue, and the work material is finally punched without generating burrs.

In this case, the piezoelectric actuator of the upper punch and the piezoelectric actuator of the lower punch are alternately applied with a positive voltage to drive up and down, and the piezoelectric actuator on the opposite side to the piezoelectric actuator applying the positive voltage is applied to the piezoelectric actuator. By applying a negative voltage with a slight time lag, the punching half of the work material is restrained and held in a pressurized state by skillfully utilizing the spring characteristics inherent to the piezoelectric actuator and the hysteresis characteristics of the displacement with respect to the applied voltage. You can do a reverse pull,
Moreover, during the punching process, by pressing both surfaces of the processing material under pressure with a punch, it is possible to reliably prevent the processing material from being warped during the punching process.

In particular, when the clearance of the mold is as large as 50 to 100% with respect to the thickness of the work material, stress concentration occurs on both sides of the clearance due to the repetition of the half-punching and reverse-punching steps, so that a so-called two-dimensional process is performed. There is a risk of heavy shear and burr, but this point, two sets of upper and lower dies,
By performing chamfering (R processing or C-chamfering) on one of the cutting edges of the punch, stress concentration applied to the work material is reduced on the chamfered side. A good shear cut surface can be obtained by suppressing shearing and the accompanying burr generation.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a process chart of the punching process according to the present invention. The press used here is the same as the stamping press applied to the piezoelectric actuator described in FIG. 5, and the same members corresponding to FIG. The same reference numerals are given. The upper half of the figure shows the stroke operation of the upper punch 7 and the lower punch 8 corresponding to the punching steps 1 to 5 and the state of the shear deformation of the work material 17 accompanying this, and the lower half of the upper punch and the lower punch. This represents the applied voltage of each piezoelectric actuator. The piezoelectric actuators (indicated by reference numerals 10 and 11 in FIG. 5) for driving the upper and lower punches 7 and 8 are:
The punches 7 and 8 are protruded and driven toward the work material 17 by the generated force induced when a positive voltage is applied, and conversely, the punches 7 and 8 are operated to be displaced backward along the hysteresis characteristic line when a negative voltage is applied. In the figure, the applied voltage (+) indicates a positive voltage application, and the (-) indicates a negative voltage application state.

First, step 1 is an initial state in which the work material 17 is clamped between the upper die 5 and the lower die 6.
Both the upper and lower punches 7, 8 are waiting at the initial position.
In the subsequent half-punching step represented by the step 2, a positive voltage is applied to the piezoelectric actuator 10 (see FIG. 5) of the upper punch 7 at time t1, and the upper punch 7 is directed toward the work material 17 by elongation displacement at that time. Protrude and drive. As a result, the work material 17 is sheared by the upper punch 7 biting as shown in the drawing while the work material 17 is kept under pressure between the upper punch 7 and the lower punch 8. In this case, the piezoelectric actuator 11 of the lower punch 8 (see FIG. 5) contracts with the spring constant inherent to the piezoelectric actuator following the movement of the upper punch 7, but at a time t2 slightly delayed from the time t1. By applying a negative voltage to the piezoelectric actuator 11 and displacing it slightly in the negative direction, the lower punch 8 is further retracted. (10 of plate thickness of processing material 17)
(About 40%). Then, in the second half of the process 2, at time t3, the piezoelectric actuator 1
The application of the negative voltage to 1 is stopped and a slightly delayed time t
At 4, the application of the positive voltage to the piezoelectric actuator 10 of the upper punch 7 is stopped.

In the reverse punching step represented by the following step 3, a positive voltage is applied to the piezoelectric actuator 11 of the lower punch 8 and the work material 17 is applied by the upper and lower punches 7, 8 in a manner opposite to the half punching step. The lower punch 8 is protruded from below and driven while the pressure is restrained. As a result, the shear deformation portion generated in step 2 is pushed in the opposite direction. In this step, the control of the voltage application pattern for the piezoelectric actuators 10 and 11 is performed in the same manner as in Step 2. In the subsequent step 4, the operations of the above steps 2 and 3 are alternately and continuously repeated a plurality of times. As a result, the punched portion 17a of the work material 17 is finally sheared as shown in step 5. Here, at the shear cut of the punched portion 17a, A,
B indicates a shear surface generated by the punch biting from above and below, and C indicates a fracture surface generated between the shear surfaces A and B due to low cycle fatigue. In addition, the said punching part 17
In the case a, the work material 17 is pushed into the work material 17 by a push-back operation in the same manner as the conventional vertical punching method, and then the mold is opened to feed the work material 17 to the next punching position.

FIGS. 9 and 10 are electron micrographs showing shear cuts of a sample punched by the above method using a stainless metal foil having a thickness of 13 μm as a test sample. However, in this punching experiment, the clearance of the mold was set to approximately 40% (5 μm) of the plate thickness, each stroke amount of half punching and reverse punching was set to 30% of the plate thickness, and the number of times of half punching and reverse punching was repeated. Performed 10 times. Here, FIG.
Is a photograph of the sample taken from the side, the white background portion of the photograph represents the contour after punching, the left and right contour lines are the foil surface, and the bottom contour line is the shear cut. FIG.
Reference numeral 0 denotes a photograph of the shear cut surface shown in FIG. 9 taken from the front, and a portion extending to the left and right at the center of the photograph represents the shear cut. As can be seen from these photographs, no burrs are formed on the cut surface, and it is observed that a smooth "shape" is formed at the upper and lower edges of the cut surface. In addition, the white background portions seen above and below the shear cut are halation generated at the time of photographing and have nothing to do with the shear cut.

Next, a punching die used for performing the punching method will be described. First, FIG. 2 schematically shows each process state in the case where the clearance of the mold is increased to 50 to 100% of the plate thickness of the work material 17 and punching is performed by using a normal mold. That is, FIG. 2A shows an initial state in which the work material 17 is clamped to a mold, FIG. 2B shows a state of a half-punching step, and FIG. 2C shows a state of a reverse-punching step. By repeating the process alternately several times, the work material 17 is finally sheared as shown in FIG. When the clearance of the mold is large with respect to the plate thickness, plastic deformation (a plastic deformation region is indicated by P) occurs at two locations on both sides of the clearance in the work material 17 due to repetition of half punching and reverse punching. In some cases, a deep crack Q with a notch generated in the plastic deformation region on the side that is not sheared (the side clamped between the dies 5 and 6) remains as it is, resulting in poor shearing. The generation of such a deep crack Q is caused by excessive stress concentration being applied to a portion of the processing material sandwiched between the dies during the punching process.

Therefore, in the present invention, as shown in FIG. 3A, the upper die 7 and the lower die 8 for clamping the work material 17 are preliminarily chamfered (R processing or C chamfering) on the cutting edges. By doing so, the concentration of stress applied to the portion during the punching process is reduced. As a result, as shown in FIG. 3 (b), only a slightly dented trace is left in the plastic deformation region on the side not sheared, and a deep crack Q as shown in FIG. 2 (d) is almost generated. Disappears. The same effect can be obtained even if the edge of the cutting edge is chamfered on the punch side, contrary to the illustrated example. In this case, the portion sandwiched by the die is broken and separated.

FIG. 4 is a table showing the relationship between the punch bite amount (stroke amount of the punch) and the number of punch vibrations (the number of repetitions of the half-punching and reverse-punching steps) until the work material is sheared by the vibration punching method. The tendency is that the processing material is sheared with a smaller number of vibrations as the punch bite amount is larger, whereas a larger number of vibrations is required with a smaller punch bite amount. Further, the appropriate amount of punch penetration depends on the material of the processing material, and it is preferable that the punching amount is large for a soft material and small for a hard material.

[0024]

As described above, according to the metal foil punching method of the present invention, a piezoelectric actuator capable of controlling the position on the order of microns is used as a punch driving source.
Each punch was driven to vibrate by a piezoelectric actuator so that the half-punching and reverse-punching steps were alternately repeated while maintaining the state in which both surfaces of the work material clamped between the dies were pressed and constrained by the punch. Due to the difficulty of shearing without burrs with the conventional vertical punching method, a plate thickness of several tens μm
Even a thin metal foil can be punched accurately without generating burrs.

According to the punching method of the present invention, punching can be performed without burrs even if the clearance of the mold is 10% or more of the plate thickness. If the clearance is provided, even if the clearance of the mold is as large as 50 to 100% of the thickness of the processing material, unnecessary stress concentration applied to the processing material is reduced, and cracks and burrs due to double shearing are generated. Can be satisfactorily prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a punching process showing an applied voltage of a piezoelectric actuator and a corresponding movement of an upper and lower punch in an embodiment of the punching method of the present invention.

FIGS. 2A and 2B are schematic diagrams showing a state in which punching is performed by a mold having a large clearance, wherein FIG. 2A is an initial step of clamping a processing material, FIG. 2B is a half-punching step, and FIG. (D) is a state diagram of a cross-section of the cut material after punching.

3A and 3B are diagrams illustrating a punching die of an embodiment of the present invention and a cross section of a cut surface of a processing material punched by the die, wherein FIG. 3A illustrates a clamped state of the processing material, and FIG. Cross section

FIG. 4 is a diagram showing the relationship between the amount of punch punching and the number of punch vibrations until the processing material is sheared.

FIG. 5 is a configuration diagram of a piezoelectric actuator applied press used in the punching method of the present invention.

FIG. 6 is a process chart showing a conventional vertical blanking method, and FIG.
Is an initial step of clamping a work material, (b) is a half-punching step, (c) is a reverse-punching step, and (d) is a state diagram of a push-back step.

FIG. 7 is an electron micrograph of a cut face of a sample punched by a conventional vertical punching method taken from the front.

8 is an electron micrograph of a cross section of the cut surface shown in FIG.

FIG. 9 is an electron micrograph showing a cross section of a cut surface of a sample punched by the punching method of the present invention.

10 is an electron micrograph of the cut surface shown in FIG. 9 taken from the front.

[Explanation of symbols]

 Reference Signs List 5 upper die 6 lower die 7 upper punch 8 lower punch 10 piezoelectric actuator 11 piezoelectric actuator 17 processing material (metal foil)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tokatsu Matsumoto 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Fumita Niino, Tanabe Nitta, Kawasaki-ku, Kawasaki-ku, Kanagawa Prefecture No. 1 Fuji Electric Co., Ltd. (56) References JP-A-63-162195 (JP, A) JP-A-57-102310 (JP, A) JP-A-63-278617 (JP, A) 4-57699 (JP, A) Japanese Utility Model 1-80218 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B26F 1/00 B21D 28/16 B26D 5/08

Claims (5)

(57) [Claims] 1. A method for punching a metal foil by a press using a piezoelectric actuator as a driving source of a punch, wherein the press sandwiches a metal foil processing material and vertically sets two dies, a punch and a piezoelectric for driving the punch. Equipped with an actuator, clamp the work material between the dies, and maintain the state that both surfaces of the work material are pressed and constrained by two sets of punches. In the method of punching a working material by vibration driving, a positive voltage is alternately applied to two sets of piezoelectric actuators corresponding to each of the half-punching and the reverse punching, and the piezoelectric actuator on the side to which the positive voltage is applied. A piezoelectric actuator press characterized by applying a negative voltage to the opposite side of the piezoelectric actuator with a slight time difference to drive the punch up and down Metal foil stamping method by. 2. The punching method according to claim 1, wherein the stroke amount of the punch in each of half-punching and reverse-punching is set to a ratio of 10 to 40% with respect to the thickness of the work material. A metal foil punching method using a piezoelectric actuator application press. 3. The punching method according to claim 1, wherein the punch is vibrated up and down by alternately applying a positive voltage to two sets of piezoelectric actuators corresponding to each of half-punching and reverse-punching. A method of punching metal foil using a piezoelectric actuator application press. 4. A stamping method according to claim 3, wherein a negative voltage is applied to a piezoelectric actuator on the opposite side with a slight time difference from a piezoelectric actuator for applying a positive voltage. Metal foil punching method. 5. A die for use in a punching method according to claim 1, wherein one of the upper and lower dies and punches is chamfered.