JP2007283334A - Method and apparatus for press work - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for press work, which method can be suitably applied to the work besides deep drawing work and can simply prevent the generation of wrinkles and thin thickness portions, and an apparatus therefor. <P>SOLUTION: The apparatus 10 for press working carries out the press work for a steel plate 12 by approaching an upper die 38 to a lower die 52 by the operation of a servomotor 24 while gripping the edge portions of the steel plate 12 by means of a holder 40 and a blank holder 54. In the press work, when the blank holder 54 has arrived at a grip releasing position after the start of the press work for the steel plate 12 and before the arrival to the bottom dead point at which both dies most approach, the gripping of the steel plate 12 by means of the blank holder 54 and the holder 40 is released. By this operation, the steel plate 12 is not excessively pulled, and the generation of the wrinkles and the thin thickness portions can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a press processing method and a press processing apparatus for processing a press molded product by servo press molding.

  In a conventional mechanical press, a slider connected to a crankshaft is driven up and down by a crankshaft rotating motor to perform press working. In such a mechanical press, since the mold is continuously moved up and down, it is difficult to change the speed according to the processing conditions or to temporarily stop the mold.

  From such a background, recently, a servo press capable of flexibly controlling the operation of a mold using a servo motor has been used (for example, see Patent Document 1 and Patent Document 2). In such a servo press, the die can be stopped at a predetermined position during one stroke in which the die moves up and down.

  Further, in the press working, the wrinkles can be prevented from occurring if the processing is performed while the periphery of the pressed portion is held by a predetermined holder. Patent Document 3 describes a method of performing processing while sandwiching a steel plate with a holder.

  By the way, when the steel plate is held by the holder during the press working, an excessive tension is applied to the steel plate depending on the shape of the molded product, and on the other hand, wrinkles are generated or an excessively thin portion may be generated.

  In the method described in Patent Document 3, the steel plate is lightly pressed by a blank corresponding to a holder, and is drawn into the back side of the die while sliding during processing. That is, since it is not always pressed with a blank, it is thought that generation | occurrence | production of a wrinkle and generation | occurrence | production of a thin part can be prevented to some extent.

JP 2001-150200 A Japanese Patent No. 3537287 JP 2005-199318 A

  However, the method described in Patent Document 3 is a so-called deep drawing process, and cannot be efficiently applied to mass production parts as it is.

  In the method described in Patent Document 3, since it is assumed that almost all of the steel sheet is drawn into the back side of the die while sliding during processing, the shape of the molded product, the material of the steel sheet, the surface roughness The pressing force by the blank must be finely adjusted in accordance with the above, and sufficient experience is required for proper selection of the lubricant.

  The present invention has been made in consideration of such problems, and can be suitably applied to processes other than deep drawing, and a press working method and a press that can easily prevent generation of wrinkles and thin portions An object is to provide a processing apparatus.

  The press working method according to the present invention is a press working method in which a press-molded product is formed by a servo press. The first mold is fixed to the second mold while the plate material is sandwiched between the first holder and the second holder. And pressing the plate material close to each other, and during the press molding step, after the pressing of the plate material is started and before reaching the bottom dead center where both molds are close to each other, the first holder and the first And a clamping release step of releasing the clamping of the plate material by two holders.

  In this way, by releasing the clamping between the first holder and the second holder before reaching the bottom dead center where both molds are close to each other, the plate material can be moved to prevent generation of wrinkles and thin parts due to excessive pulling. can do. Here, “before reaching the bottom dead center” means including the time when the bottom dead center is reached.

  In this case, if the operation timing of the control in the clamping release step is set by a control unit that controls the first die to be close to the second die, the clamping release is accurately performed for the press work. Synchronize with

  The press working apparatus according to the present invention is a press working apparatus that performs servo press control, wherein a first mold and a second mold for press-molding a plate material, and a first holder provided in the first mold, A second holder that is provided at a position facing the first holder and sandwiches the plate together with the first holder; and a control means for moving the second holder forward and backward. The control means includes the first holder In the press molding process of pressing the plate material by pressing the plate material while the plate material is sandwiched between the first holder and the second mold, both the molds are Before reaching the close bottom dead center, the holding of the plate material by the first holder and the second holder is released.

  In this way, by releasing the clamping between the first holder and the second holder before reaching the bottom dead center where both molds are close to each other, the plate material can be moved to prevent generation of wrinkles and thin parts due to excessive pulling. can do. Here, “before reaching the bottom dead center” means including the time when the bottom dead center is reached.

  In this case, when the control unit further controls the first die to be close to the second die, the clamping release is accurately synchronized with the press work.

  According to the press processing method and the press processing apparatus according to the present invention, the plate material can be moved by releasing the holding of the plate material by the first holder and the second holder before reaching the bottom dead center where both molds are close to each other. Thus, generation of wrinkles and thin portions due to excessive pulling can be prevented.

  In addition, since the plate material is securely held between the first holder and the second holder at least at the start of pressing, the plate material can be accurately positioned and the generation of wrinkles at the initial stage of machining can be prevented. Further, the holding and releasing of the plate material by the first holder and the second holder may be performed by on / off control, and it is not necessary to consider sliding on the plate material. Therefore, there is no need to adjust the pressing force, and there is no special need for the lubricant, which can be performed easily. Further, it can be suitably applied to press work other than deep drawing.

  Hereinafter, the press working method and the press working apparatus according to the present invention will be described with reference to FIGS. The press working apparatus 10 according to the present embodiment performs press working of a steel plate (plate material) 12 that is a workpiece.

  As shown in FIG. 1, the press working apparatus 10 includes an apparatus main body 14 that performs processing, and a control unit 16 that controls the apparatus main body 14.

  The apparatus main body 14 includes an upper mold mechanism 18 and a lower mold mechanism 20. The upper mold mechanism 18 includes a servo motor 24 as a drive source, a reduction gear 26 that is rotationally driven by the servo motor 24, a rotary plate 28 that is rotationally driven by the reduction gear 26 with a large torque, and the rotary plate 28. The connecting rod 30 is pivotally supported on the side surface thereof so that the upper end portion thereof is swingable. The servo motor 24 is, for example, an AC type, and has high responsiveness and small torque unevenness. The shaft rotation position of the servo motor 24 is detected by the encoder 24 a and supplied to the control unit 16.

  The upper die mechanism 18 further detects the position of the slider 32 supported by the lower end of the connecting rod 30, a plurality of (for example, four) rails 34 for guiding the slider 32 in the vertical direction, and the position of the slider 32. The first linear sensor 36 to be supplied to the control unit 16 and an upper mold (first mold) 38 provided on the lower surface of the slider 32.

  The upper mold 38 is pressed by pressing the steel plate 12 together with the lower mold (second mold) 52, and a mold surface 38 a for contacting the upper surface of the steel plate 12 is provided on the lower surface. In addition, an annular holder (first holder) 40 is slightly protruded around the upper die 38 so as to prevent wrinkles and displacement when the steel plate 12 is pressed. Therefore, the holder 40 comes into contact with the steel plate 12 ahead of the mold surface 38a. The lower surface of the holder 40 has a shape corresponding to the molding shape, and is set to a horizontal plane, for example.

  The lower mold mechanism 20 includes a fixed base 50 serving as a base, a lower mold 52 provided on the upper part of the fixed base 50, an annular blank holder (second holder) 54 that supports the periphery of the steel plate 12, and the And a die cushion mechanism 56 for raising and lowering the blank holder 54. The blank holder 54 is provided at a position facing the holder 40, and the holder 40 is for holding the end of the steel plate 12 together.

  The lower mold 52 is pressed by pressing the steel plate 12 together with the upper mold 38, and a mold surface 52a for contacting the lower surface of the steel plate 12 is provided on the upper surface. The mold surface 52a is formed in a shape corresponding to the mold surface (press molding surface) 38a.

  The die cushion mechanism 56 connects, from below, a plurality of pins 60 that pass through the fixing base 50 and the attachment portion 52b of the lower mold 52 and are fixed to the lower portion of the blank holder 54, and the lower ends of these pins 60. A plate 62, a plurality of cylinders 64 for moving the plate 62 up and down, and a second linear sensor 66 that detects the position of the plate 62 and supplies it to the control unit 16.

  The die cushion mechanism 56 further includes a hydraulic motor 68 that supplies / recovers pressure oil to / from the cylinder 64 and a servo motor 70 that rotates the hydraulic motor 68. The rotation of the servo motor 70 is transmitted to the hydraulic motor 68 via a transmission unit 72 including a coupling, a speed reducer, and the like. The hydraulic motor 68 rotates in both forward and reverse directions under the action of the servo motor 70, and can selectively supply pressure oil to the rod side and the cap side of the cylinder 64. Thus, the wrinkle pressing can be performed by appropriately pressing the peripheral portion of the steel plate 12 with the holder 40 and the blank holder 54 while performing the predetermined pressure control.

  The control unit 16 performs servo control while referring to a signal supplied from the second linear sensor 66 and a press drive unit 16a that controls the drive of the servo motor 24 while referring to signals supplied from the encoder 24a and the first linear sensor 36. And a die cushion drive unit 16b for moving the blank holder 54 up and down by driving the motor 70. The press drive unit 16a and the die cushion drive unit 16b are connected to each other and can be operated synchronously. The die cushion drive unit 16b can change the elevation speed of the blank holder 54 at a predetermined timing while synchronizing with the press drive unit 16a.

  As shown in FIG. 2, the press driving unit 16 a uses a servo power unit 104 that is supplied after the power obtained from the power source 100 is boosted by the transformer 102, and servo power using the power adjusted by the servo power unit 104. And a servo amplifier 106 for driving the motor 24. In the servo amplifier 106, the drive amount of the servo amplifier 106 is set under the action of the software function unit 108. A large-capacitance capacitor 110 is provided between the servo power supply unit 104 and the servo amplifier 106.

  The die cushion drive unit 16 b includes a servo power supply unit 112 to which power from the power supply 100 is supplied, and a servo amplifier 114 that drives the servomotor 70 using the power adjusted by the servo power supply unit 112. In the servo amplifier 114, the drive amount of the servo motor 70 is set under the action of the software function unit 116.

  The servo power supply unit 112 and the servo amplifier 114 can energize both in the forward and reverse directions. When the servo motor 70 is rotated by a load to generate power, the current obtained by power generation is supplied to the press drive unit 16a. A regenerative operation is possible. The regenerative power is stored in the large-capacity capacitor 110 and used for driving the servo motor 24, so that the capacity of the power supply facility can be suppressed.

  Next, a method for processing the steel plate 12 as a workpiece using the press working apparatus 10 configured as described above will be described with reference to FIG.

  First, initial setting is performed in step S1 of FIG. That is, the blank holder 54 is raised to a predetermined position, and the blank steel plate 12 is supported by the blank holder 54. The upper die 38 is raised to the top dead center.

  In step S2, the servo motor 24 is rotationally driven to lower the slider 32 under the action of the press drive unit 16a.

  When lowered to some extent, the holder 40 comes into contact with the upper surface of the steel plate 12, and the steel plate 12 is held between the holder 40 and the blank holder 54. From this point (see displacement x3 in FIG. 7A), the blank holder 54 is lowered under the action of the die cushion drive unit 16b (step S3). The die cushion drive unit 16b performs pressure control so that the blank holder 54 moves downward while generating an appropriate force so that the lower surface of the steel plate 12 is pressed and holds the steel plate 12 securely. That is, the blank holder 54 is pressed through the steel plate 12 by the holder 40 and is pressed down while applying an appropriate pressure to the steel plate 12.

  As a result, the steel plate 12 is lowered while the peripheral portion is held by the holder 40 and the blank holder 54, and is gradually pressed into a product shape by the upper die 38 and the lower die 52.

  Further, when the blank holder 54 is lowered, the servo motor 70 may generate electric power and perform the above regenerative operation.

  In step S <b> 4, the press driving unit 16 a refers to the signal of the first linear sensor 36 and confirms whether or not the positions of the holder 40 and the blank holder 54 have reached a predetermined clamping release position. When the holder 40 and the blank holder 54 reach the nipping release position, the process proceeds to step S5, and when not reached, the descent continues. This nipping release position is set in advance to an appropriate position based on the press shape, and is generally the bottom dead center where the steel plate 12 is pressed by the mold surface 38a and the mold surface 52a (that is, while the upper mold 38 makes one stroke). It is set at a position slightly higher than the lowest point. The clamping release position is adjusted according to the degree of deformation by pressing, and in the case of only bending bending with little plastic flow, the distance xp from the bottom dead center to the clamping release position (see FIG. 7B) is extremely high. The distance xp is set large when it is set small and the degree of plastic flow and throttling is large.

  Further, when the product shape is a gentle shape in which almost no press line is recognized, the nipping release position may coincide with the bottom dead center (that is, xp = 0). In other words, the nipping release position may be set to a position before reaching the bottom dead center after the time when the pressing of the steel plate 12 is started (see displacement x3 in FIG. 7A) according to the product shape. .

  As shown in FIG. 4, in this clamping release position, pressing of the steel plate 12 by the upper die 38 and the lower die 52 is started, but since the bottom dead center is not reached, the pressing is not finished.

  In step S <b> 5, the blank holder 54 is separated from the holder 40 and the steel plate 12 by increasing the lowering speed of the blank holder 54 than the lowering speed of the holder 40 under the action of the die cushion driving unit 16 b. Thereby, the holding | maintenance of the steel plate 12 is cancelled | released, the steel plate 12 becomes freely movable, and a part of the hold | maintained part plastically flows. At this point, since the press work is almost finished, the product shape of the steel plate 12 is almost formed, and the product shape does not collapse even if there is no positioning reference by clamping.

  At this time, since the blank holder 54 does not have to apply a pressing force to the steel plate 12, the distance away from the holder 40 may be small, and as shown by the phantom line in FIG. May be in contact with the blank holder 54. Further, the pressure applied by the cylinder 64 may be sufficiently reduced by a predetermined depressurization mechanism.

  In step S <b> 6, the press driving unit 16 a refers to the signal of the first linear sensor 36 and confirms whether or not the position of the slider 32 has reached the bottom dead center. When the slider 32 reaches the bottom dead center, the process proceeds to step S7, and when it does not reach, the descent continues.

  In step S7, the descent of the slider 32 and the descent of the blank holder 54 are stopped. At this time, as shown in FIG. 5, the steel plate 12 is sandwiched between the mold surface 38 a of the upper mold 38 and the mold surface 52 a of the lower mold 52, and the press work is finished. Further, since the blank holder 54 is separated from the holder 40, the clamping of the steel plate 12 is released. On the other hand, in the press working, the degree of reduction in the plate thickness is the greatest at the bottom dead center where both dies re-approach. At this point, the clamping of the steel plate 12 is released, so that wrinkles due to excessive pulling. Occurrence of occurrence and generation of a thin portion can be effectively prevented.

  In step S8, it is confirmed whether or not a predetermined stop time has elapsed. If the stop time has elapsed, the process proceeds to step S9. Thus, by stopping the slider 32 at the bottom dead center for a predetermined time, it becomes possible to impart distortion in the thickness direction, and the product shape of the steel plate 12 can be further stabilized.

  In step S9, the servo motor 24 is rotationally driven to raise the slider 32 under the action of the press drive unit 16a. At this time, the blank holder 54 is kept stopped.

  In step S10, it is confirmed whether or not the position of the slider 32 has reached the panel transport position. If it has reached, the process proceeds to step S11, and if not reached, the slider 32 continues to rise.

  In step S11, the blank holder 54 is raised under the action of the die cushion drive unit 16b. As a result, the blank holder 54 rises slightly later than the slider 32, comes into contact with the end of the steel plate 12 again, and raises the steel plate 12.

  In step S12, the die cushion drive unit 16b confirms whether or not the position of the blank holder 54 has reached the panel transport position. When the blank holder 54 reaches the panel transport position, the process proceeds to step S13, and when it has not reached, the ascending is continued.

  In step S13, as shown in FIG. 6, the raising of the blank holder 54 is temporarily stopped, and the pressed steel plate 12 is transported to a next process (for example, welding process) station by a predetermined transport means.

  In step S14, the die cushion drive unit 16b raises the blank holder 54 again.

  In step S15, the die cushion drive unit 16b checks whether or not the position of the blank holder 54 has reached the processing standby position. When the blank holder 54 reaches the processing standby position, the process proceeds to step S16.

  In step S16, the raising of the blank holder 54 is stopped, and the unprocessed steel plate 12 is arranged at a predetermined position. During this time, the slider 32 continues to rise.

  In step S <b> 17, the press driving unit 16 a refers to the signal of the first linear sensor 36 and confirms whether or not the position of the slider 32 has reached the top dead center. When the slider 32 has not reached the top dead center, the ascent is continued. When the slider 32 has reached the top dead center, the current process shown in FIG. When the slider 32 reaches the top dead center, the slider 32 may be stopped once in view of the cycle time with other processes. In particular, when there is no influence of other processes, the slider 32 is not stopped and is stopped as it is. Processing of the next steel plate 12 may be continued.

  Although the above processing is shown in one flowchart, for example, the drive units of the press drive unit 16a and the die cushion drive unit 16b may operate independently while performing mutual synchronization confirmation.

  The above-described series of processing cycles is represented by time charts as shown in FIGS. 7A and 7B. In these FIG. 7A and FIG. 7B, the step number in the above processing is attached to the corresponding position on the horizontal axis of time.

  As shown in FIG. 7A, the displacement x of the slider 32 reciprocates between the top dead center x1 and the bottom dead center x2, and stops at the bottom dead center x2 for a predetermined time (between steps S5 and S8). . Further, at the time corresponding to step S <b> 3, the holder 40 has reached the displacement x <b> 3 in contact with the upper surface of the steel plate 12. The displacement x4 at the time of step S11 is a panel transport position, which is a position corresponding to the displacement y3 of the blank holder 54.

  As shown in FIG. 7B, the displacement y of the blank holder 54 is stopped at the processing standby position y1 during the period corresponding to steps S1 to S3 and the period after step S15. Further, the blank holder 54 is also stopped at the position of the displacement y2 during steps S7 to S11 where the slider 32 is stopped at the bottom dead center x2. The blank holder 54 descends at substantially the same speed as the slider 32 during steps S3 to S4, and descends slightly faster than the slider 32 during steps S4 to S5 after exceeding the nipping release position y4. In the period from step S13 to step S14, the blank holder 54 is stopped at the panel transport position y3.

  As described above, according to the press processing method and the press processing apparatus 10 according to the present embodiment, the holding of the steel plate 12 by the holder 40 and the blank holder 54 is released before reaching the bottom dead center where both molds are close to each other. Thus, the steel plate 12 can move, and generation of wrinkles and thin portions due to excessive pulling can be prevented.

  Moreover, since the steel plate 12 is securely held between the holder 40 and the blank holder 54 at least at the start of press working, the steel plate 12 can be accurately positioned and the generation of wrinkles can be prevented.

  Furthermore, since the steel plate 12 is basically unnecessary to be slid by the holding portion between the holder 40 and the blank holder 54, the pressing force of the steel plate 12 does not need to be finely adjusted. On-off control of switching the lowering speed of the blank holder 54 is sufficient for clamping and releasing. Further, it is not necessary to apply the lubricant to the steel plate 12 in the clamping portion between the holder 40 and the blank holder 54. Therefore, the press processing method and the press processing apparatus 10 according to the present embodiment can be suitably applied to press processing other than deep drawing, and is suitable for mass production.

  Furthermore, in the case of machining a workpiece whose shape, size, etc. are approximate, the greater the degree of plastic flow and drawing, the more the press-worked portion of the steel plate 12 is pulled from the sandwiched portion between the end holder 40 and the blank holder 54. Since the degree increases, the distance xp from the bottom dead center to the nipping release position may be set large according to the degree of plastic flow and squeezing.

  Since the control unit 16 integrally performs control for bringing the upper die 38 close to the lower die 52 and release of the clamping, the clamping release is accurately synchronized with the press work.

  In the above description, the example in which the holding of the steel sheet 12 is released by increasing the lowering speed of the blank holder 54 at the holding release position has been described. However, the holder 40 is separated from the mold surface 38a by a predetermined mechanism to reduce the lowering speed. Then, the clamping may be released.

  The press working method and the press working apparatus according to the present invention are not limited to the above-described embodiments, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention.

It is a schematic diagram which shows the structure of the press work apparatus which concerns on this Embodiment. It is a block block diagram of a press drive part and a die cushion drive part. It is a flowchart which shows the procedure of the press work method which concerns on this Embodiment. It is a partial cross-section enlarged view of an upper mold, a lower mold, a holder, and a blank holder when the blank holder reaches a clamping release position. It is a partial cross section enlarged view of an upper model, a lower model, a holder, and a blank holder when a slider reaches bottom dead center. It is a schematic diagram of the press processing apparatus of the state which suspended the raise of the blank holder at the panel conveyance position. FIG. 7A is a graph showing the displacement of the slider in one cycle, and FIG. 7B is a graph showing the displacement of the blank holder in one cycle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Press processing apparatus 12 ... Steel plate 16 ... Control part 24, 70 ... Servo motor 24a ... Encoder 32 ... Slider 38 ... Upper die 38a, 52a ... Mold surface 40 ... Holder (1st holder) 52 ... Lower die 54 ... Blank holder (Second holder) 56 ... Die cushion mechanism x1 ... Top dead center x2 ... Bottom dead center xp ... Distance from bottom dead center to nipping release position

Claims (4)

In the press processing method that forms press-formed products with a servo press,
A press molding step of pressing the plate material by bringing the first mold close to the second mold while sandwiching the plate material by the first holder and the second holder;
In the press molding step, after the pressing of the plate material is started and before reaching the bottom dead center where both molds are close to each other, the clamping release step of releasing the clamping of the plate material by the first holder and the second holder When,
A press working method characterized by comprising: The press working method according to claim 1,
The press working method according to claim 1, wherein the operation timing of the control in the nipping release step is set by a control means for controlling the first die to approach the second die. In press processing equipment that performs servo press control,
A first mold and a second mold for press-molding a plate material;
A first holder provided in the first mold;
A second holder provided at a position facing the first holder and sandwiching the plate material together with the first holder;
Control means for advancing and retracting the second holder;
Have
In the press molding step of pressing the plate material by bringing the first die close to the second die, the control means starts pressing the plate material while holding the plate material between the first holder and the second holder. After that, before reaching the bottom dead center where both dies are close to each other, the pressing of the plate material by the first holder and the second holder is released. The press working apparatus according to claim 3,
The said control means is further controlled to make the said 1st type | mold close to the said 2nd type | mold, The press work apparatus characterized by the above-mentioned.

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