Mold position adjustment device

Abstract

This invention provides a mold position adjustment device that can accurately determine the timing for adjusting the mold position using parameters directly related to the finished dimensions of the workpiece, with a simpler configuration than conventional technologies. [Solution] A die position adjustment device (7) is provided on a machine tool (1) that plastically deforms a workpiece (W1) using a fixed die (23) and a movable die (26), and adjusts the position of the fixed die or the movable die, comprising: an adjustment mechanism (4) capable of automatically adjusting the position; a detection unit (3) that repeatedly detects waveforms (V1, V2) showing the temporal change of at least one of the processing forces generated in the fixed die and the movable die, respectively, when the machine tool repeatedly performs plastic deformation processing; a determination unit (84) that determines whether or not it is time to adjust the position based on the change in the feature quantities, and a control unit (85) that controls the adjustment mechanism to adjust the position when it is determined that it is time to adjust the position.

Description

Technical Field

[0001] The present invention relates to a die position adjusting device provided in a machine tool that performs plastic deformation processing and adjusts the position of a fixed die or a movable die.

Background Art

[0002] In a machine tool such as a forging press that performs plastic deformation processing, a fixed die and a movable die arranged opposite to each other are paired to plastically deform a workpiece to produce a product. When the machine tool continuously produces a product for a long time, the finished dimensions of the product gradually change due to the influence of thermal expansion of the die and the like caused by processing heat. If the machine tool continues production as it is, there is a risk that the finished dimensions will exceed the allowable error and become defective products. To avoid this risk, in the prior art, the extraction inspection of the product was performed at any time to check the finished dimensions. Furthermore, in order to return the changed finished dimensions to their original state, the machine tool was stopped as necessary to adjust the position of the die.

[0003] In this prior art, it was necessary to frequently stop the machine tool to adjust the position of the die, which caused a decrease in operating efficiency. In addition, the adjustment method for optimizing the position of the die based on the change amount of the finished dimensions of the product has not advanced in terms of formalization and quantification, depends on the skill (intuition, know-how) of the operator, and requires trial and error. Therefore, problems such as an increase in the adjustment work time (the stop time of the machine tool) and an increase in scrap (defective products) due to repeated inefficient adjustments often occurred.

[0004] One example of a technology aimed at automating the positioning of a die is disclosed in Patent Document 1. The forging machine in Patent Document 1 comprises a die (fixed die), a punch (movable die), a drive unit that drives the reciprocating motion of the punch, a determination unit that monitors or detects changes in the dimensions of the workpiece and determines whether or not an adjustment operation is necessary to adjust the dimensions of the workpiece, and an automatic adjustment unit that automatically performs an adjustment operation to cancel the amount of change in the dimensions of the workpiece during operation based on the determination result of the determination unit. Since the determination unit cannot directly detect the dimensions of the workpiece, it detects the temperature of each part inside the machine and calculates the amount of thermal expansion to make a determination. According to this, the forging machine can automatically perform adjustment operations during operation and suppress a decrease in the dimensional accuracy of the workpiece. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-129116 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, the technical example in Patent Document 1 is desirable because it allows for automatic adjustment operations during operation, thereby suppressing a decrease in operational efficiency. However, thermal expansion due to processing heat occurs in many parts other than the mold, affecting the finished dimensions of the workpiece (product), thus requiring numerous temperature sensors and a large amount of computational processing. Furthermore, since temperature itself is not a parameter directly related to the finished dimensions of the workpiece, there was a risk of mistiming adjustments, and depending on the shape of the workpiece, the correlation between the calculated thermal expansion and the finished dimensions may be low. In addition, to confirm that the adjustment operation was performed correctly, it was necessary to check the finished dimensions by sampling the product, as in the conventional technology.

[0007] This invention has been made in view of the aforementioned background technology, and aims to solve the problem of providing a mold position adjustment device that can accurately determine the timing of mold position adjustment using parameters directly related to the finished dimensions of the workpiece, with a simpler configuration than the conventional technology. [Means for solving the problem]

[0008] The mold position adjustment device of the present invention is provided on a machine tool that performs plastic deformation processing on a workpiece, having a fixed mold for holding a workpiece and a movable mold that reciprocates toward the fixed mold, and is a mold position adjustment device for adjusting the position of the fixed mold or the movable mold, comprising: an adjustment mechanism capable of automatically adjusting the position; a detection unit that repeatedly detects waveforms showing the temporal change of at least one of the processing forces generated in the fixed mold and the movable mold, respectively, when the machine tool repeats the plastic deformation processing; a determination unit that determines whether or not it is time to adjust the position based on the changes in the plurality of feature quantities that are repeatedly detected and determines whether or not it is time to adjust the position; and a control unit that controls the adjustment mechanism to adjust the position when the determination unit determines that it is time to adjust the position.

[0009] Furthermore, the mold position adjustment device is provided in a machine tool that performs plastic deformation processing on a workpiece, having a fixed mold for holding a workpiece and a movable mold that reciprocates toward the fixed mold, and is a mold position adjustment device for adjusting the position of the fixed mold or the movable mold, and may include: an adjustment mechanism that allows the position to be adjusted manually; a detection unit that repeatedly detects waveforms showing the temporal change of at least one of the processing forces generated in the fixed mold and the movable mold when the machine tool repeats the plastic deformation processing; a determination unit that determines whether or not it is time to adjust the position based on the changes in the multiple waveforms that have been repeatedly detected and feature quantities included in each of the multiple feature quantities; and a notification unit that notifies the determination result of the determination unit. [Effects of the Invention]

[0010] In the mold position adjustment device of the present invention, the detection unit can repeatedly detect at least one waveform of the processing force generated by the fixed mold and the movable mold as a parameter directly related to the finished dimensions of the workpiece. Here, the number of sensors for detecting the processing force can be less than or equal to the number of molds, so the number of sensors can be reduced compared to conventional technology for detecting the temperature of each part inside the machine, resulting in a simpler configuration. Furthermore, the determination unit can grasp the progress of how the characteristic quantities obtained from multiple waveforms change gradually due to the influence of thermal expansion of the mold, etc., so it can accurately determine the timing for adjusting the mold position. In addition, in a configuration equipped with an adjustment mechanism that can automatically adjust the mold position, the control unit can control the adjustment mechanism to automatically adjust the mold position. On the other hand, in a configuration equipped with an adjustment mechanism that can manually adjust the mold position, the operator can manually operate the adjustment mechanism to adjust the mold position in a timely manner based on the determination result of the determination unit notified by the notification unit. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic plan view showing the overall configuration of a forging machine, which is an example of a machine tool equipped with the mold position adjustment device of the embodiment. [Figure 2] This is a schematic side cross-sectional view of the forging process, showing the load cell (detection unit) and cotter adjustment mechanism of the mold position adjustment device. [Figure 3] This is a schematic plan view illustrating the cotter adjustment mechanism. [Figure 4] This is a block diagram showing the functional configuration of a mold position adjustment device. [Figure 5] This figure shows the waveform indicating the temporal change in processing force detected by the load cell (detection unit), and the feature quantities determined by the judgment unit. [Figure 6] Figure 5 is a side view showing the shape of the workpiece before processing during the cold forging process, where the waveform was detected. [Figure 7] Figure 5 is a side view showing the shape of a flanged hex socket head bolt produced in the cold forging process where the waveform was detected. [Figure 8]Figure 5 is a side cross-sectional view showing the shape of the die and punch used in the forging process in which the waveform was detected, as well as the processing status. [Figure 9] This figure illustrates the waveform of the machining force detected during thermal expansion of the die and punch. [Figure 10] This diagram illustrates examples of the good range, adjustment range, and abnormal range set by the judgment unit. [Figure 11] This is a diagram illustrating the operation flow of the mold position adjustment device according to the embodiment. [Figure 12] This diagram illustrates a variation of the integral value, one of the features sought by the classification unit. [Figure 13] This diagram illustrates variations in the maximum and minimum values ​​of the differential, which are one of the features sought by the determination unit. [Modes for carrying out the invention]

[0012] 1. Overall configuration of the forging machine 1 First, the overall configuration of the forging machine 1, which is an example of a machine tool equipped with the die position adjustment device 7 of the embodiment, will be explained with reference to Figure 1. The forging machine 1 is a horizontal multi-stage forging machine that repeatedly performs forging, which corresponds to plastic deformation. The forging machine 1 consists of a frame 21, a ram 24, five sets of dies 23 and punches 26, a transfer device 27, a wire supply device 28, a control device 8, and a drive unit 9, etc. The dies 23 correspond to fixed dies, and the punches 26 correspond to movable dies.

[0013] The forging machine 1 has five pairs of opposing dies 23 and punches 26 forming the first to fifth forging processes. In Figure 1, the left-right direction of the paper represents the front-to-back direction of the forging machine 1, and the up-down direction of the paper represents the width direction of the forging machine 1. In Figure 1, the first to fifth forging processes are arranged from the top to the bottom of the paper in the width direction. The axis passing through the centers of the dies 23 and punches 26 extends in the left-right direction of Figure 1, and the punches 26 reciprocate along this axis. Note that the number of processes in the forging machine 1 is not limited to five, but is generally between one and eight.

[0014] The frame 21 is a housing for arranging each part. Five die holders 22 are provided side by side in the width direction at a position closer to the front of the frame 21. Each of the five dies 23 is detachably attached to the rear part of each die holder 22. A predetermined processing die is formed on the rear side of each die 23 facing left in the drawing. The die 23 holds the workpiece inside the processing die.

[0015] The ram 24 is generally rectangular in plan view and is disposed at approximately the center of the frame 21. The ram 24 reciprocates in the front-rear direction. Five punch holders 25 are provided side by side in the width direction at a position closer to the front of the ram 24. Each of the five punches 26 is detachably attached to the front part of each punch holder 25. A predetermined processing die is formed on the front side of each punch 26 facing right in the drawing. Each punch 26 reciprocates together with the ram 24. In each forging process, the punch 26 reciprocates in the front-rear direction (axial direction) while facing the die 23, and repeats the forging process of the workpiece in combination with the die 23.

[0016] The transfer device 27 is disposed from above the die holder 22 to the rear of the die 23. The transfer device 27 has six pairs of finger pairs (not shown in the figure) for gripping the workpiece. The first finger pair at the most upstream grips the workpiece supplied from the wire supply device 28 and conveys it to the first forging process. The second to fifth finger pairs grip the workpiece in the upstream forging process and convey it to the downstream forging process. The sixth finger pair at the most downstream grips the workpiece in the fifth forging process and conveys it to the carry-out part (not shown in the figure).

[0017] The wire supply device 28 is positioned at the front of the frame 21, from next to the first forging process, to the front. The wire supply device 28 cuts long wires supplied from the front to produce workpieces and supplies them to the first forging process. The wire supply device 28 consists of a fixed gripping section 281, a movable gripping section 282, and a cutter and pusher (not shown). The fixed gripping section 281 grips and releases the wire supplied from the front. The movable gripping section 282 grips the wire released by the fixed gripping section 281 and feeds it to the cutter. The cutter cuts the tip of the fed wire to produce a workpiece. The pusher pushes the cut workpiece out of the cutter and hands it over to the transfer device 27. After this, the fixed gripping section 281 grips the wire, and the movable gripping section 282 releases the wire and returns to its original position. Typically, the wire has a circular cross-section, and the workpiece has a cylindrical initial shape. Examples of materials for the wire and workpiece include iron, aluminum, and various alloys.

[0018] A drive unit 9 is provided to drive the reciprocating motion of the punch 26. The drive unit 9 also drives the transfer device 27 and the wire supply device 28. The drive unit 9 consists of a drive source 91 and various transmission mechanisms and cam mechanisms. The drive source 91 can be, for example, an induction motor or a synchronous motor that operates on a three-phase AC power supply. The driving force of the drive source 91 is input to the crankshaft 96 via a flywheel 92, a clutch mechanism 93, a disc brake 94, and a reduction mechanism 95.

[0019] A connecting rod 29 is positioned between the crankshaft 96 and the ram 24. One end of the connecting rod 29 is connected to the crankshaft 96, and the other end is connected to the ram 24. When the crankshaft 96 is rotated by the drive source 91, one end of the connecting rod 29 rotates along a circular orbit, and the other end of the connecting rod 29 reciprocates in the forward and backward direction. As a result, the ram 24 reciprocates in the forward and backward direction, and the five punches 26 on the ram 24 also reciprocate in the forward and backward direction.

[0020] Five kick-out cams 98 are provided on the upper part of the connecting rod 29. The kick-out cams 98 are arranged at equal intervals in the width direction and correspond to the positions of the first to fifth forging processes, respectively. The kick-out cams 98 drive the center punch 265 (see Figure 8), which is part of the punch 26, in the front-rear direction. The kick-out cams 98 may not be used depending on the shape of the workpiece.

[0021] Furthermore, the driving force is branched and transmitted from the crankshaft 96 to the side shaft 99 via a branch gear pair 97. The side shaft 99 branches and transmits the driving force upward. The upwardly branched driving force rotates the transfer cam 9A. The transfer cam 9A drives the reciprocating movement of the transfer device 27 between the forging processes. Also, six open-close cams 9C are connected to the side shaft 99 via the transfer drive 9B so as to be rotationally driven. The open-close cams 9C are arranged at equal intervals in the width direction. The open-close cams 9C drive each pair of fingerings of the transfer device 27 to open and close.

[0022] Furthermore, a cutter cam 9D is provided on the side shaft 99, and a pusher cam 9E, a feed cam 9F, and five kickout cams 9H are connected to it. The cutter cam 9D drives the cutter of the wire feeding device 28. The pusher cam 9E drives the pusher of the wire feeding device 28. The feed cam 9F drives the reciprocating motion of the movable gripping part 282 of the wire feeding device 28. The kickout cams 9H are arranged at equal intervals in the width direction and correspond to the positions of the first to fifth forging processes, respectively. The kickout cams 9H drive a kickout pin (not shown) in the front-rear direction to eject the workpiece after forging from the die 23 and transfer it to the transfer device 27.

[0023] The control device 8 is configured using a computer and its location is not limited. As shown in Figure 4, the control device 8 controls the drive source 91. The control device 8 also receives a detection signal of the rotation angle of the crankshaft 96 from the angle detection sensor 81 to check the operating status of the drive source 91. The control device 8 can switch between multiple operating modes, for example, between adjustment mode and operation mode. In adjustment mode, the control device 8 can drive the drive source 91 at a low speed or intermittently. In operation mode, the control device 8 drives the drive source 91 at high speed continuously.

[0024] 2. Configuration of the mold position adjustment device 7 in the embodiment Next, the configuration of the mold position adjustment device 7 of the embodiment will be described with reference to Figures 2-10. The mold position adjustment device 7 consists of load cells 3 individually provided for each of the five punches 26, a cotter adjustment mechanism 4 commonly provided for the five punches 26, and three functional units provided in the control device 8, namely a memory unit 83, a determination unit 84, and a control unit 85.

[0025] As shown in Figure 2, the punch 26 is mounted approximately in the center of the punch holder 25. Two pressure-receiving members (261, 262) are arranged in series behind the punch 26. A load cell 3 is provided so as to be in close contact with the rear surface of the rear pressure-receiving member 262. The rear surface of the load cell 3 is a driven slope 31, with the lower side protruding forward and the upper side recessed backward. The area from the punch 26 to the load cell 3 is normally biased backward by a biasing member (not shown).

[0026] The load cell 3 is a type of detection unit that repeatedly detects waveforms showing the temporal changes in the processing force generated by the punch 26 when the forging machine 1 repeatedly performs forging. The load cell 3 is composed of four strain gauges embedded inside a block-shaped body and connected in a bridge configuration. The load cell 3 detects the processing force generated by the punch 26 during forging (plastic deformation) that is parallel to the axis. The processing force generated by the punch 26 can also be described as the reaction force acting from the workpiece to the punch 26.

[0027] The load cell 3 detects a single waveform of the processing force each time the forging process is repeated. Therefore, the load cell 3 can sequentially detect a large number of processing force waveforms that gradually change due to the thermal expansion of the punch 26 accompanying the repeated forging process. The load cell 3 transmits the detected waveforms to the control device 8. Waveform amplification or digital conversion may be performed along the transmission path. In addition, sensors with detection methods other than the load cell 3, such as pressure sensors, may be used in the processing force detection unit.

[0028] The cotter adjustment mechanism 4 is a mechanism that can automatically adjust the position of the punch 26. The cotter adjustment mechanism 4 is provided in common to the five punches 26 on the ram 24 and automatically adjusts the axial position of the selected punch 26. The cotter adjustment mechanism 4 consists of a cotter member 41 and a cotter operating part 42 provided individually for each punch 26, as well as a common operating part 44 provided in common to all of them.

[0029] As shown in Figure 2, the cotter member 41 is positioned on the rear side of the load cell 3. The cotter member 41 has an inclined adjustment slope 411 on the front side and a vertical surface 412 on the rear side. The adjustment slope 411 has its lower side protruding forward and its upper side recessed backward, allowing it to slide vertically while in close contact with the driven slope 31 of the load cell 3. The vertical surface 412 is movable vertically while sliding against the vertical surface 243 on the ram 24 side. As a result, the cotter member 41 is supported by the ram 24 so that it can move vertically but cannot move in the front-rear direction. An operating shaft 413 extending vertically is fixed to the upper part of the cotter member 41. The operating shaft 413 has a male thread formed on its outer circumference.

[0030] The cotter operating section 42 consists of a nut member 421 and a gear mechanism 422, among other components. The nut member 421 is formed in a bottomed cylindrical shape with an opening at the bottom and is supported so as to be rotatable around a central axis but unable to move up and down. The nut member 421 has a female thread formed on its inner surface that screws onto the male thread of the operating shaft 413, and is positioned on the upper side of the operating shaft 413 in a screwed state. The nut member 421 and the operating shaft 413 constitute a screw feed mechanism that allows relative movement in the vertical direction. The gear mechanism 422 rotates the nut member 421 and allows for switching of the direction of rotation.

[0031] Furthermore, the cotter operation unit 42 is equipped with a clutch mechanism (not shown) and a lock mechanism (not shown) that operate automatically under control from the control device 8. The clutch mechanism switches between an engaged state, in which it transmits rotational force transmitted from the common operation unit 44 (described later) to the gear mechanism 422, and a disengaged state, in which it does not transmit force. The lock mechanism switches between a locked state, in which it restricts the operation of the gear mechanism 422, and an unlocked state, in which it does not restrict it. Under normal circumstances, the clutch mechanism is in the disengaged state and the lock mechanism is in the locked state. The clutch mechanism and the lock mechanism can be formed as a combined and integrated unit so that the lock mechanism automatically becomes disengaged when the clutch mechanism is engaged, and the lock mechanism automatically becomes locked when the clutch mechanism is disengaged.

[0032] When the gear mechanism 422 of the cotter operating section 42 drives the nut member 421 in the forward direction, the screw feed mechanism drives the operating shaft 413 upward relative to the nut member 421. As a result, the entire cotter member 41 moves upward, and the adjustment slope 411 pushes the driven slope 31 forward against the biasing member. This causes the load cell 3 to move forward, and the position of the punch 26 is automatically adjusted to move closer to the die 23. Conversely, when the gear mechanism 422 drives the nut member 421 in the reverse direction, the operating shaft 413 and the entire cotter member 41 move downward. This causes the load cell 3 to move backward due to the action of the biasing member, and the position of the punch 26 is automatically adjusted to move further away from the die 23.

[0033] A common operating section 44, shown in Figure 3, is provided to operate the five sets of cotter operating sections 42. The common operating section 44 consists of an operating motor 441, an output gear mechanism 442, a spline shaft 443, a drive bevel gear 444, a drive shaft 445, a driven bevel gear 446, and a gear slide section 447. The operating motor 441 is located on the frame 21. The operating motor 441 can be switched between forward and reverse rotation. An output gear mechanism 442 is provided on the output shaft of the operating motor 441. The output gear mechanism 442 transmits the rotation of the operating motor 441 to the rotation of the spline shaft 443.

[0034] The spline shaft 443 is rotatably supported on the frame 21. The spline shaft 443 extends parallel to the reciprocating direction of the ram 24. Multiple spline grooves extending axially and parallel to each other are formed on the outer circumference of the spline shaft 443. The drive bevel gear 444 is provided to engage with the spline grooves of the spline shaft 443. The drive bevel gear 444 rotates together with the spline shaft 443 and is slidable in the axial direction of the spline shaft 443.

[0035] The drive shaft 445 is rotatably supported by the ram 24. The drive shaft 445 extends in the width direction of the ram 24 and engages with five cotter operating parts 42. The drive shaft 445 is positioned perpendicular to and opposite the spline shaft 443. Even when the ram 24 moves, the T-shaped positional relationship between the drive shaft 445 and the spline shaft 443 is maintained. A driven bevel gear 446 is provided at the end of the drive shaft 445 closest to the spline shaft 443. The driven bevel gear 446 meshes with the drive bevel gear 444.

[0036] The gear slide portion 447 is mounted on the ram 24 and engages with the drive bevel gear 444. The gear slide portion 447 moves in the forward and backward direction together with the ram 24, causing the drive bevel gear 444 to slide along the spline shaft 443. This ensures that the meshing state between the driven bevel gear 446 and the drive bevel gear 444 is always maintained, regardless of the position of the ram 24. This meshing state then transmits the rotation of the spline shaft 443 to the rotation of the drive shaft 445.

[0037] When the operating motor 441 rotates forward, the spline shaft 443 and the drive shaft 445 also rotate forward. Furthermore, the forward rotation of the drive shaft 445 is transmitted to the forward rotation of the gear mechanism 422 of the cotter operating unit 42, which is engaged with the clutch mechanism. Similarly, the reverse rotation of the operating motor 441 is also transmitted to the reverse rotation of the gear mechanism 422 of the cotter operating unit 42, which is engaged with the clutch mechanism. The forward and reverse rotation of the gear mechanism 422 adjusts the position of the punch 26 as described above. Therefore, the common operating unit 44 can automatically adjust the axial position of a selected punch 26 from the five punches 26 of the first to fifth forging processes using a single operating motor 441.

[0038] The storage unit 83, determination unit 84, and control unit 85 shown in Figure 4 are mainly configured using the software of the control device 8. The storage unit 83 receives and stores the waveforms of multiple machining forces detected by the five load cells 3. The determination unit 84 determines the feature quantities contained in each of the multiple machining force waveforms. In this embodiment, the feature quantities used are at least one of the five items shown in waveform V1 in Figure 5. That is, the feature quantities include at least one of the peak value P of waveform V1, the integral value S of waveform V1, the maximum value Dm and minimum value Ds of the derivative of waveform V1, the rising edge timing Tr of waveform V1, and the timing Tp of the occurrence of the peak value P.

[0039] The waveform V1 shown in Figure 5 is an example of a waveform detected by a load cell 3 in a cold forging process that produces a flanged hexagon socket head bolt W2 shown in Figure 7 from a workpiece W1 with the shape shown in Figure 6. Workpiece W1 has a head WH, a flange WF, and a shaft WA. The flanged hexagon socket head bolt W2 has a head with a formed hexagon socket WX, a flange, and a shaft, and naturally its shape and finished dimensions differ from those of workpiece W1. In this cold forging process, the die 23 and punch 26 shown in Figure 8 are used. Cold forging is also performed in processes other than this one.

[0040] The die 23 holds the shaft portion WA of the workpiece W1 inside the central processing mold. Meanwhile, the punch 26 consists of a center punch 265 and a ring-shaped punch 266 that can operate at different timings. The center punch 265 is positioned in the center so as to overlap with the axis and expands the pilot hole WH of the head of the workpiece W1 to form a hexagonal hole WX. By forming the hexagonal hole WX, the outer circumferential surface of the head WH of the workpiece W1 expands radially outward. The ring-shaped punch 266 is positioned around the center punch 265 and operates with a delay from the center punch 265. The ring-shaped punch 266 forms the outer circumferential surface of the expanded head WH of the workpiece W1 to a predetermined diameter and forms a flange portion WF in relation to the die 23. The center punch 265 is excluded from the adjustment target of the cotter adjustment mechanism 4, while the ring-shaped punch 266 is subject to adjustment by the cotter adjustment mechanism 4.

[0041] In waveform V1 of Figure 5, machining force is generated at time t1 and increases until time t2. Between time t2 and time t3, the machining force remains at a roughly constant value. After time t3, the machining force increases further, reaching its peak value P at time t4. After time t4, the machining force gradually decreases and disappears at time t5.

[0042] To elaborate on the relationship between the waveform V1 and the forging process, at time t1, the center punch 265 contacts the workpiece W1 and the forging process begins (plastic deformation of the workpiece W1 begins). From time t2 through to time t3, the forging process progresses, forming the hexagonal hole WX in the head WH. At time t3, the ring-shaped punch 266 joins the forging process, and the shaping of the outer surface of the head WH begins, with the processing forces from the center punch 265 and the ring-shaped punch 266 being added together. As time t4 approaches, the ring-shaped punch 266 forges the flange portion WF. Also, between time t1 and time t4, a chamfer is formed on the tip of the shaft portion WA of the workpiece W1 inside the die 23. At time t4, when the punch 26 reaches its dead center, the forging process ends, and thereafter the punch 26 retracts from its dead center.

[0043] In waveform V1 of Figure 5, the peak value P of waveform V1 indicates the magnitude of the machining force at time t4. The integral value S of waveform V1 indicates the area of ​​waveform V1 shown by the hatched lines. The maximum value Dm of the derivative of waveform V1 occurs slightly after time t1 and indicates the maximum upward slope of waveform V1. The minimum value Ds of the derivative of waveform V1 occurs slightly before time t5 and indicates the maximum downward slope of waveform V1. The rising edge timing Tr of waveform V1 coincides with time t1. The timing Tp of the occurrence of the peak value P coincides with time t4. It is preferable to express the rising edge timing Tr and the timing Tp of the occurrence of the peak value P of waveform V1 using the elapsed time from a reference timing. As the reference timing, for example, the timing when the punch 26 starts moving from its back dead center before time t1 can be used.

[0044] When the forging machine 1 repeatedly performs forging to continuously produce flanged hex socket head bolts W2 for a long period of time, the heat generated during processing causes the molds and other components (die 23, punch 26, etc.) to expand, and as a result, the finished dimensions of the flanged hex socket head bolts W2 gradually change. In this embodiment, the waveform of the processing force generated by the punch 26 is selected as a parameter directly related to the finished dimensions, and this waveform is repeatedly detected by the load cell 3.

[0045] To elaborate, the die 23 and punch 26 move closer to each other axially due to thermal expansion, so the space between the punch 26 and die 23 when they have advanced to their front dead center becomes narrower compared to when they are at room temperature. Consequently, the axial dimension (thickness) of the flange portion WF of the workpiece W1 tends to decrease, and the diameter tends to increase. In other words, the flange portion WF tends to become thinner and larger in diameter. If the forging machine 1 continues production as is, the finished dimensions of the flange portion WF may exceed the tolerance, potentially resulting in defective flanged hexagon socket head bolts W2. Conversely, if the die 23 and punch 26 shrink axially due to thermal expansion, the flange portion WF tends to become thicker and smaller in diameter.

[0046] On the other hand, when molds and other components undergo thermal expansion, a greater processing force is required than at room temperature. As a result, as shown by the solid line in Figure 9, the waveform V2 detected during thermal expansion tends to be offset to a larger value than the waveform V1 at room temperature, which is shown by the dashed line. The change from waveform V1 to waveform V2 often progresses gradually as the temperature of the mold and other components rises and the amount of thermal expansion increases. In reality, it is assumed that not only a simple offset but also waveform distortion occurs, but in any case, the following qualitative explanation is considered to be appropriate.

[0047] In the waveform V2 during thermal expansion, the peak value P and integral value S are larger than at room temperature. Conversely, an increase in the peak value P and integral value S indicates thermal expansion of the punch 26. Also, the maximum value Dm of the derivative tends to be larger than at room temperature, and the minimum value Ds of the derivative tends to be smaller than at room temperature (the absolute value becomes an even larger negative value). Furthermore, the rise time Tr of the waveform tends to become earlier as the die 23 and punch 26 approach each other. On the other hand, the timing Tp of the occurrence of the peak value P roughly coincides with the timing of the punch 26's last dead center, and therefore does not change significantly from room temperature. Nevertheless, depending on the shape of the workpiece and mold, the timing Tp of the occurrence of the peak value P may not coincide with the timing of the punch 26's last dead center. In this case, the timing Tp of the occurrence of the peak value P during thermal expansion may change from room temperature.

[0048] The determination unit 84 can obtain feature quantities from the waveforms (V1, V2) of the processing force detected by the load cell 3 each time the forging machine 1 repeats the forging process. The feature quantities may be any one of the five items described above, or a combination of multiple items. The determination unit 84 may also change the items of the feature quantities depending on the shape of the workpiece being produced and the type of mold used. Based on the changes in the feature quantities of the multiple waveforms (V1, V2), the determination unit 84 determines whether or not it is time to adjust the position of the mold.

[0049] To elaborate on the determination of the adjustment timing, the determination unit 84 uses either a first method to calculate a reference feature quantity as a determination criterion, or a second method to store a fixed reference feature quantity set in advance. When using the first method, the determination unit 84 calculates a reference feature quantity based on a predetermined number of feature quantities obtained from the waveforms of a predetermined number of workpieces immediately after the start of operation of the forging machine 1. For example, the determination unit 84 can calculate the reference feature quantity by arithmetic mean of 10 feature quantities obtained from 10 workpieces. However, it is not limited to this, and the determination unit 84 may also use an alternative method, such as excluding the maximum and minimum values ​​of the 10 feature quantities and averaging the remaining 8 feature quantities to calculate the reference feature quantity, or other calculation methods. According to this alternative method, the influence of abnormal value of feature quantities that may occur by chance can be suppressed.

[0050] Furthermore, the determination unit 84 may recalculate the reference feature quantities not only immediately after the start of operation of the forging machine 1, but also immediately after a predetermined update timing. For example, the determination unit 84 may set the production of 1000 flanged hex socket head bolts W2 as the update timing, and recalculate the reference feature quantities from the 10 waveforms detected after the production of 1000 bolts is completed.

[0051] On the other hand, the second method is applied when repeating production of a product for which a production record has already been established using the first method to calculate the standard feature quantities. When using the second method, the determination unit 84 registers the standard feature quantities used for the determination each time production of the product is completed. The determination unit 84 also stores the standard feature quantities set by the operator at the start of production of the product. The second method is not limited to repeat production, but can also be applied, for example, when the standard feature quantities have been estimated with sufficient accuracy in advance through detailed simulations in mold design.

[0052] The determination unit 84 calculates a reference feature using the first method or stores it using the second method, and then compares the feature obtained from the waveform of the workpiece with the reference feature to determine whether or not it is time for adjustment. Specifically, the determination unit 84 sets a good range RG and an adjustment-required range RM with the reference feature as the center. For example, as shown in Figure 10, the determination unit 84 can set the good range RG to be within ±A% of the reference feature as the center, set the range from +A% to +2A% outside the good range and the range from -A% to -2A% as the adjustment-required range RM, and set the area outside the adjustment-required range RM as the abnormal range RB.

[0053] The specific value of A% needs to be determined considering factors such as the size of the workpiece's tolerance dimensions and the degree of thermal expansion dependent on the mold's processing load, but it can be set to, for example, 5%. Furthermore, since changes caused by thermal expansion of molds, etc., are important, when using the waveform peak value P or area S as feature quantities, the range from 0 to +A% may be set as the good range RG, the range from +A% to +2A% as the range requiring adjustment RM, and everything else as the abnormal range RB. The methods for setting the good range RG and the range requiring adjustment RM can also be modified.

[0054] The determination unit 84 determines that the condition is good and not requiring adjustment if the characteristic quantity for determination is within the good range RG. Furthermore, the determination unit 84 determines that adjustment is required if the characteristic quantity for determination is outside the good range RG but within the adjustment required range RM. Additionally, the determination unit 84 determines that the condition is abnormal if the characteristic quantity for determination is outside the adjustment required range RM and within the abnormal range RB. Naturally, the determination unit 84 performs the determination for each forging process using different waveforms (V1, V2) and different reference characteristic quantities for each of the first to fifth forging processes. The determination unit 84 may omit the determination for idle forging processes where forging is not performed, or forging processes with small processing forces. In other words, adjustment of the mold position is omitted in these forging processes.

[0055] When the determination unit 84 determines that it is time for adjustment, the control unit 85 controls the cotter adjustment mechanism 4 to automatically adjust the position of the ring-shaped punch 266 (punch 26). The control unit 85 controls the cotter adjustment mechanism 4 to cancel out changes in the feature quantities. Following the control from the control unit 85, the cotter adjustment mechanism 4 switches the clutch mechanism of the cotter operation unit 42 to the engaged state and the lock mechanism to the released state for the forging process among the first to fifth forging processes that requires adjustment. Subsequently, the cotter adjustment mechanism 4 rotates the operation motor 441 to automatically adjust the position of the ring-shaped punch 266.

[0056] For example, if the change in feature quantities indicates thermal expansion of the die 23 and punch 26 due to repeated cold forging (plastic deformation), the control unit 85 controls the position of the ring-shaped punch 266 to move it axially away from the die 23. The cotter adjustment mechanism 4 automatically adjusts the position of the ring-shaped punch 266 by moving the cotter member 41 downward so that it moves away from the die 23. This makes it possible to return the thinned and enlarged flange portion WF to its original finished dimensions in the cold forging process that produces flanged hexagon socket head bolts W2. In addition, after the adjustment, the change in feature quantities is canceled out, and the detected waveform returns to approximately its original waveform shape.

[0057] Conversely, if the change in the feature quantity indicates thermal shrinkage of the die 23 and punch 26, the control unit 85 controls the position of the ring-shaped punch 266 to move closer to the die 23. The cotter adjustment mechanism 4 moves the cotter member 41 upward to automatically adjust the position of the ring-shaped punch 266 so that it is closer to the die 23. This makes it possible to return the thickened and reduced diameter flange portion WF to its original finished dimensions. In addition, after the adjustment, the detected waveform returns to roughly its original waveform shape.

[0058] The specific adjustment amount for the cotter adjustment mechanism 4 can be experimentally determined using an actual workpiece W1, or estimated from adjustment results for workpieces of similar shape. Furthermore, even if the adjustment amount is excessive or insufficient, the control unit 85 can recalculate the adjustment amount from the waveform detected thereafter and control the readjustment. This eliminates the need to verify the finished dimensions by sampling inspection of products, unlike conventional adjustment methods.

[0059] 3. Operation of the mold position adjustment device 7 of the embodiment Next, the operation of the mold position adjustment device 7 of the embodiment will be explained with reference to the operation flow in Figure 11. This operation flow is performed in parallel with the forging process of the forging machine 1. In step S1 of Figure 11, the forging machine 1 performs forging in each of the first to fifth forging processes. At this time, the load cell 3 detects the waveforms of the processing force (V1, V2). In the next step S2, the storage unit 83 acquires and stores the waveforms of the processing force from the load cell 3. In the next step S3, the determination unit 84 determines the feature quantities included in the waveforms of the processing force (V1, V2). That is, the determination unit 84 determines at least one of the peak value P of the waveform, the integral value S of the waveform, the maximum value Dm and minimum value Ds of the differential value of the waveform, the rising edge timing Tr of the waveform, and the timing Tp of the occurrence of the peak value P.

[0060] In the next step S4, the determination unit 84 proceeds to step S5 if it has not already stored the reference features, and skips step S5 and proceeds to step S8 if it has already stored the reference features (second method). In step S5, the determination unit 84 determines whether or not it is time to calculate the reference features and branches the operation flow. That is, if it is immediately after the start of operation or immediately after the update timing, the determination unit 84 branches the operation flow to step S6, and otherwise proceeds to step S8.

[0061] In step S6, if the determination unit 84 has not accumulated a predetermined number of features, it returns the operation flow to step S1, and the forging process is repeated. If the determination unit 84 has accumulated a predetermined number of features through the repetition of step S3, it proceeds the operation flow to step S7. In step S7, the determination unit 84 calculates a reference feature by, for example, arithmetic mean of the predetermined number of features (first method). After this, the determination unit 84 returns the operation flow to step S1.

[0062] Before executing step S8, the reference feature quantity is calculated in step S7 (first method), or the reference feature quantity is stored in advance (second method). In step S8, the determination unit 84 compares the feature quantity obtained in step S3 with the reference feature quantity, the adjustment range RM, and the abnormal range RB to determine whether or not there is an abnormality. If an abnormality is determined, in step S9, the control device 8 executes abnormality processing. For example, the control device 8 temporarily stops the forging machine 1 and keeps it in a standby state, and notifies the operator that there is an abnormality.

[0063] In step S10, if no abnormality is detected, the determination unit 84 compares the feature quantities obtained in step S3 with the good range RG and the adjustment range RM to determine whether or not it is time for adjustment. In step S11, if it is determined that it is time for adjustment, the control unit 85 sets the adjustment amount for the cotter adjustment mechanism 4. In step S12, the control unit 85 controls the cotter adjustment mechanism 4 to automatically adjust the position of the punch 26. After this, the control unit 85 returns the operation flow to step S1. Also, in step S10, if the feature quantities are within the good range RG, the determination unit 84 determines that the forging machine 1 is in a good operating state and returns the operation flow to step S1.

[0064] In the mold position adjustment device 7 of this embodiment, the load cell 3 can repeatedly detect the waveform of the processing force generated by the punch 26 as a parameter directly related to the finished dimensions of the workpiece. Here, the number of load cells 3 for detecting the processing force can be the same as the number of punches 26, so the number of sensors can be reduced and the configuration can be made simpler than in conventional technology that detects the temperature of each part inside the machine. Furthermore, the determination unit 84 can grasp the progress of how the characteristic quantities obtained from multiple waveforms (V1, V2) change gradually due to the influence of thermal expansion of the mold, etc., so it can accurately determine the timing of adjusting the mold position. In addition, since there is a cotter adjustment mechanism 4 that can automatically adjust the position of the ring-shaped punch 266 (punch 26), the control unit 85 can control the cotter adjustment mechanism 4 to automatically adjust the position of the ring-shaped punch 266.

[0065] 4. Variations of Feature Extraction In this embodiment, the integral value S, as well as the maximum and minimum derivative values ​​Dm and Ds, among the feature quantities determined by the determination unit 84, can be modified as shown in Figures 12 and 13. These modifications primarily improve the accuracy of the determination unit 84's abnormality detection. In Figure 12, the determination unit 84 divides the processing force waveform V1 into three time areas (TA1, TA2, TA3) (for example, into three equal parts). The determination unit 84 partially overlaps the three time areas (TA1, TA2, TA3), but overlap is not mandatory. The determination unit 84 determines integral values ​​(Ss1, Ss2, Ss3) for each area and uses them at least for abnormality detection. This allows the determination unit 84 to accurately determine abnormalities using the integral values ​​of the three quantities (Ss1, Ss2, Ss3). The determination unit 84 may also use the integral values ​​of the three quantities (Ss1, Ss2, Ss3) to determine the timing of adjustments.

[0066] For example, consider a case where an abnormal pattern occurs in which the machining force increases in one part of the waveform V1 and decreases in another part. In this case, the integral value S of one quantity in the embodiment appears to remain unchanged because the increase and decrease in the waveform V1 cancel each other out. Therefore, the determination unit 84 cannot accurately determine the abnormality based on this integral value S. On the other hand, with the integral values ​​of three quantities (Ss1, Ss2, Ss3), the determination unit 84 can accurately determine the abnormality based on one or more increased integral values ​​and one or more decreased integral values. Furthermore, by providing overlap, the risk that the change in machining force that occurs near the area boundary of the three time areas (TA1, TA2, TA3) will be dispersed into two areas and will not be able to be determined as an abnormality can be reduced.

[0067] Next, in Figure 13, the determination unit 84 divides the machining force waveform V1 into four time areas (TA5, TA6, TA7, TA8). The fifth time area TA5 is an increasing area where the machining force increases from time t1 to time t2. The sixth time area TA6 is a constant area where the machining force remains at a constant value that is not approximately zero from time t2 to time t3. The seventh time area TA7 is an increasing area where the machining force increases from time t3 to time t4. The eighth time area TA8 is a decreasing area where the machining force decreases from time t4 to time t5. The determination unit 84 may automatically divide the four time areas (TA5, TA6, TA7, TA8) from the obtained differential value, or it may perform area division according to the operator's settings.

[0068] The determination unit 84 determines the maximum values ​​Dm1 and Dm2 (strictly speaking, local maximums) of the derivatives for the increasing areas (fifth time area TA5 and seventh time area TA7), respectively. The determination unit 84 also determines the minimum value Ds1 (strictly speaking, local minimum) of the derivatives for the decreasing area (eighth time area TA8). Furthermore, the determination unit 84 determines the maximum value Dm3 and minimum value Ds3 of the derivatives for the constant area (sixth time area TA6). As a result, the determination unit 84 can accurately determine anomalies by individually comparing the multiple maximum values ​​(Dm1, Dm2, Dm3) and multiple minimum values ​​(Ds1, Ds3) of the derivatives with reference features, etc. The determination unit 84 may also use the multiple maximum values ​​(Dm1, Dm2, Dm3) and multiple minimum values ​​(Ds1, Ds3) of the derivatives to determine the timing of adjustments.

[0069] For example, consider a case where an abnormal pattern occurs in which the processing force (maximum value of the differential Dm3) cannot be considered constant within a certain area. In this case, the maximum value of the differential Dm in the embodiment coincides with the maximum value Dm1 in the fifth time area TA5. Therefore, the determination unit 84 ignores the maximum value Dm3 within the certain area, which is smaller than the maximum value Dm1 in the embodiment, and cannot accurately determine the abnormality. On the other hand, according to the modified example, the determination unit 84 separately calculates and determines the reference feature quantities for the maximum values ​​of the differential in the increasing area (Dm1, Dm2) and the maximum value of the differential Dm3 within the certain area, so it can accurately determine the abnormality. In other words, the determination unit 84 can accurately determine the abnormality when the maximum value Dm3 changes, even if the maximum value Dm1 has not changed.

[0070] Since the minimum values ​​of the derivative (Ds1, Ds3) are also separately evaluated by calculating the reference features, the effect of accurately detecting anomalies is the same. Furthermore, the determination unit 84 excludes the minimum value Ds of the derivative in the increasing area and the maximum value Dm of the derivative in the decreasing area from the features, thereby reducing the computational load.

[0071] Furthermore, similar to the case of integral values ​​(Ss1, Ss2, Ss3), the determination unit 84 may equally divide the waveform V1 of the machining force into multiple time areas without considering increases or decreases in machining force, and determine abnormalities by finding the maximum and minimum values ​​of the derivative in each time area. Also, in Figure 13, overlaps can be provided as in Figure 12. With this, even if the maximum or minimum values ​​of the derivative superimposed on the area boundaries of non-overlapping time areas (TA5, TA6, TA7, TA8) cause cases to be overlooked, the determination unit 84 can eliminate the risk of oversight by providing overlaps.

[0072] Furthermore, depending on the shape of the workpiece and mold, waveforms without a defined area may be detected. In this case, the determination unit 84 divides the waveform from the rising edge timing Tr to the peak value P generation timing Tp into increasing areas, finds the maximum value Dm of the derivative, and can use it for abnormality detection. In addition, the determination unit 84 divides the waveform from the peak value P generation timing Tp to the disappearance of the waveform into decreasing areas, finds the minimum value Ds of the derivative, and can use it for abnormality detection. In the application, in addition to the same effects as the embodiment (simple configuration, accurate determination of adjustment timing), the accuracy of abnormality detection can be improved.

[0073] 5. Modifications and Applications of Embodiments Furthermore, the present invention is primarily a technology for dealing with the axial thermal expansion of a mold. Therefore, the effect of applying the mold position adjustment device 7 of the embodiment is particularly noticeable for die 23 and punch 26 used for cold forging workpieces with shapes where the tolerance for axial dimensions is stricter than the tolerance for radial and circumferential dimensions. On the other hand, for workpieces with shapes where the tolerance for radial and circumferential dimensions is strict, other technologies for dealing with the radial thermal expansion of the mold will be applied. For example, mold design technologies that anticipate thermal expansion in advance to ensure good dimensional accuracy of the finished workpiece during mold thermal expansion, technologies for preheating the mold before operation, and technologies for interrupting operation or cooling the mold to keep the mold's thermal expansion below the allowable limit can be applied.

[0074] Furthermore, the cotter adjustment mechanism 4 may not have a common operating unit 44, and the operator may manually rotate the nut member 421. In other words, the cotter adjustment mechanism 4 may be modified into an adjustment mechanism that allows the position of the ring-shaped punch 266 (punch 26) to be manually adjusted. In this modified form, a notification unit can be provided instead of the control unit 85. The notification unit notifies the operator of the determination result of the determination unit 84. Furthermore, it is preferable that the notification unit notifies the operator of the adjustment method of the cotter adjustment mechanism 4 (for example, the rotation direction and amount of rotation of the nut member 421) to cancel the change in the feature quantity, in addition to the determination result that it is time for adjustment. In the modified form, the operator can manually operate the cotter adjustment mechanism 4 based on the determination result of the determination unit 84 and the adjustment method notified by the notification unit to adjust the position of the ring-shaped punch 266 in a timely and easy manner.

[0075] Furthermore, the cotter adjustment mechanism 4, which is positioned on the ram 24, can be moved to the frame 21 side to adjust the position of the die 23. In addition, the load cell 3 can be positioned on the die 23 side to repeatedly detect the waveform of the machining force generated by the die 23. The present invention and its embodiments are subject to various other modifications and applications. [Industrial applicability]

[0076] The mold position adjustment device 7 of this embodiment is not limited to the cold forging machine 1, but can be used in machine tools such as forging machines and presses. [Explanation of symbols]

[0077] 1: Forging machine 21: Frame 23: Die (fixed mold) 24: Ram 26: Punch (movable mold) 265: Center punch 266: Ring-shaped punch 27: Transfer device 28: Wire supply device 3: Load cell 4: Cotter adjustment mechanism 41: Cotter component 42: Cotter control unit 44: Common control unit 7: Mold position adjustment device 8: Control device 83: Memory unit 84: Determination unit 85: Control unit W1: Workpiece WH: Head WF: Flange WA: Shaft W2: Flanged hex socket head bolt WX: Hex socket head V1, V2: Waveforms P: Peak value S, Ss1-Ss3: Integral value Dm, Dm1-Dm3: Maximum value of the derivative; Ds, Ds1, Ds3: Minimum value of the derivative Tr: Rise timing Tp: Occurrence timing TA1-TA3, TA5-TA8: Time Area

Claims

1. A mold position adjustment device is provided in a machine tool that performs plastic deformation processing on a workpiece, having a fixed mold for holding a workpiece and a movable mold that reciprocates toward the fixed mold, and adjusts the position of the fixed mold or the movable mold, An adjustment mechanism that can automatically adjust the aforementioned position, A detection unit that repeatedly detects a waveform showing the temporal change of at least one of the processing forces generated in the fixed die and the movable die when the machine tool repeats the plastic deformation process, A determination unit determines whether it is time to adjust the position based on changes in the multiple waveforms that have been repeatedly detected, and which contains feature quantities in each of the multiple feature quantities. When the determination unit determines that it is time for the adjustment, the control unit controls the adjustment mechanism to adjust the position, A mold position adjustment device equipped with the following features.

2. The mold position adjustment device according to claim 1, wherein the control unit controls the adjustment mechanism to cancel the change in the feature quantity.

3. A mold position adjustment device is provided in a machine tool that performs plastic deformation processing on a workpiece, having a fixed mold for holding a workpiece and a movable mold that reciprocates toward the fixed mold, and adjusts the position of the fixed mold or the movable mold, An adjustment mechanism that allows the aforementioned position to be adjusted manually, A detection unit that repeatedly detects a waveform showing the temporal change of at least one of the processing forces generated in the fixed die and the movable die when the machine tool repeats the plastic deformation process, A determination unit determines whether it is time to adjust the position based on changes in the multiple waveforms that have been repeatedly detected, and which contains feature quantities in each of the multiple feature quantities. A notification unit that notifies the determination result of the determination unit, A mold position adjustment device equipped with the following features.

4. The mold position adjustment device according to claim 3, wherein the notification unit notifies, in addition to the determination result that it is time for adjustment, of an adjustment method for the adjustment mechanism that cancels the change in the feature quantity.

5. The mold position adjustment device according to any one of claims 1 to 4, wherein the detection unit detects the waveform of the processing force which may change due to the thermal expansion of the fixed mold and the movable mold accompanying the repetition of the plastic deformation process.

6. The mold position adjustment device according to claim 5, wherein the determination unit calculates a reference feature quantity based on a predetermined number of feature quantities obtained from the waveforms of a predetermined number of workpieces immediately after the start of operation of the machine tool or immediately after a predetermined update timing, and determines whether or not it is the adjustment time by comparing the determination feature quantity obtained from the waveforms of workpieces after the predetermined number with the reference feature quantity.

7. The mold position adjustment device according to claim 6, wherein the pre-determination unit determines that it is not time for adjustment if the feature quantity for determination is within a predetermined good range centered on the reference feature quantity, determines that it is time for adjustment if the feature quantity for determination is outside the good range but within the adjustment range, and determines that there is an abnormality if the feature quantity for determination is outside the adjustment range.

8. The mold position adjustment device according to claim 5, wherein the determination unit stores a preset reference feature quantity and compares the determination feature quantity obtained from the waveform of the workpiece with the reference feature quantity to determine whether or not it is time for the adjustment.

9. The mold position adjustment device according to claim 5, wherein the feature quantity includes at least one of the peak value of the waveform, the integral value of the waveform, the maximum and minimum values ​​of the differential value of the waveform, the rising time of the waveform, and the timing of the occurrence of the peak value.

10. The mold position adjustment device according to claim 9, wherein the feature quantity includes at least one of the integral value for each of the multiple time areas obtained by dividing the waveform, or the maximum and minimum values ​​of the differential value for each of the multiple time areas.

11. The mold position adjustment device according to claim 10, wherein multiple time areas partially overlap.

12. The mold position adjustment device according to claim 10, wherein the feature quantity includes at least one of the maximum value of the derivative in the increasing time area where the processing force increases, and the minimum value of the derivative in the decreasing time area where the processing force decreases.

13. The detection unit detects the machining force in a direction parallel to the axis passing through the center of the fixed mold and the movable mold. The adjustment mechanism adjusts the axial position of the fixed mold or the movable mold. The mold position adjustment device according to claim 5.

14. The mold position adjustment device according to claim 13, wherein the adjustment mechanism adjusts the position of the movable mold so as to move it away from the fixed mold in the axial direction when the change in the characteristic quantity indicates thermal expansion of the fixed mold and the movable mold due to repeated plastic deformation processing.

15. The machine tool is a forging machine that processes the workpiece by forging it using a plurality of forging processes, each having a fixed die and a movable die. The adjustment mechanism is provided in common to a plurality of the movable molds and adjusts the axial position of the selected movable mold. The detection unit is provided individually on each of the multiple movable molds. The mold position adjustment device according to claim 13.

16. The mold position adjustment device according to claim 15, wherein the fixed mold and the movable mold are used to press-form a workpiece having a shape in which the tolerance for the axial dimension is stricter than the tolerance for the radial dimension and the circumferential dimension.

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