JP2017006967A - Manufacturing method of press machine and press machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a press machine capable of securing high accuracy equal to being processed after being integrated, on shape accuracy of a processing part, in a large-sized press machine having a frame constituted of a plurality of constitution members.SOLUTION: A manufacturing method of a press machine comprises a frame 1 constituted by fastening a plurality of constitution members by a tie rod 5, and in the manufacturing method of the press machine, at least one of the constitution members comprises a member processing process of independently processing in a state of causing stress equal to fastening time by the tie rod 5. By this manufacturing method, even the large-sized press machine can secure high accuracy equal to being processed after being integrated on shape accuracy of a processing part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a press machine manufacturing method and a press machine. More specifically, the present invention relates to a press machine manufacturing method and a press machine that can increase the shape accuracy of a processed part after assembly of a frame is completed.

  As in Japanese Industrial Standards, press machines are (1) using two or more pairs of tools, (2) placing work material between these tools and causing the tools to perform related motions, It is a machine that forms a processed material by applying a strong force to the processed material, and (3) is a machine that is designed to support the reaction force of the force generated between tools by the machine itself. Here, as described in Patent Document 1, the large press machine includes a frame on which a plurality of constituent members such as a base, a crown, and an upright are assembled.

  In this press machine, it is necessary to support a reaction force of a force generated between molds as tools in a frame. For this reason, the frame of a press machine is generally fastened by a tie rod with a force that is more than twice the above reaction force, with the base receiving the machining reaction force from the lower die and the crown receiving the machining reaction force from the upper die. Need to be. However, when the frame is tightened with such a tightening force, a large stress is generated in each member constituting the frame, and distortion is generated by the stress. In order to reduce the influence of the tightening force with such a tie rod, a relatively small press machine is subjected to finishing processing as a whole frame after being tightened with the tie rod.

  However, in a large press machine, it is impossible to finish the entire frame after tightening with a tie rod because the machine tool becomes very large. Therefore, in a large press machine, the thickness of the constituent members of the press machine is increased to such an extent that the influence of the tightening force by the tie rod can be reduced. And after processing these independently, the frame of a press machine is assembled.

  Even in this case, even if the components are thickened and the influence of the tightening force by the tie rods is reduced, the shape accuracy of the processed part cannot be completely affected, and the entire frame must be finished. There is a problem that it is difficult to obtain the same accuracy as that obtained by the above method.

JP2015-47622A

  In view of the above circumstances, an object of the present invention is to provide a manufacturing method of a press machine and a press machine that can increase the shape accuracy of a processed part even after a large-scale press machine is assembled.

A manufacturing method of a press machine according to a first aspect of the present invention is a manufacturing method of a press machine having a frame assembled by a plurality of constituent members being fastened by tie rods, wherein at least one of the constituent members is fastened by a tie rod. It has the member processing process processed independently by the state which has generate | occur | produced the stress equivalent to.
According to a second aspect of the present invention, there is provided a press machine manufacturing method according to the first aspect, wherein in the member processing step, the processing rod is inserted into the insertion hole of the tie rod of the constituent member, and the processing rod is tightened, whereby stress is applied to the constituent member. It is characterized by generating.
According to a third aspect of the present invention, there is provided a press machine manufacturing method according to the second aspect, wherein a spacer having a contact surface of the same shape as a contact surface with another component member in contact with the frame is assembled. It is characterized by being interposed between the nuts to be tightened.
According to a fourth aspect of the present invention, there is provided a press machine manufacturing method according to any one of the first to third aspects, wherein the component processed in the member processing step is a crown, and the upper die is driven to the crown in the member processing step. The mounting hole of the eccentric shaft to be processed is processed.
According to a fifth aspect of the present invention, there is provided a press machine manufacturing method according to any one of the first to third aspects, wherein the constituent member processed in the member processing step is an upright, and the upright includes an upper die and is arranged vertically. An operating slide guide surface is provided, and the guide surface is processed in the member processing step.
According to a sixth aspect of the present invention, there is provided a press machine manufacturing method according to any one of the first to third aspects, wherein the component processed in the member processing step is a bed, and the arrangement surface on which the lower mold is disposed on the bed. Is provided, and the arrangement surface is processed in the member processing step.
A press machine according to a seventh aspect of the present invention is a press machine having a frame assembled by fastening a plurality of constituent members by tie rods, and the constituent members generate stress equivalent to that at the time of fastening by tie rods. In the state, it was processed independently.
The press machine according to an eighth aspect of the present invention is the press machine according to the seventh aspect, wherein one of the plurality of structural members is a crown, and the crown is provided with a fitting hole for an eccentric shaft that drives the upper mold, and the crown is formed by a tie rod. The fitting hole is machined into the crown in a state where stress equivalent to that at the time of tightening is generated, and the fitting hole in the state where stress is generated has a cross section perpendicular to the axis of the fitting hole. The fitting hole in a state where the shape is a perfect circle and the stress is released is characterized in that the shape of the cross section perpendicular to the axis of the fitting hole is an ellipse.
A press machine according to a ninth invention is the press machine according to the seventh invention, wherein one of the plurality of constituent members is an upright, and the upright is provided with a guide surface of a slide that moves up and down with an upper die. The guide surface is processed into upright with the same stress as when tightened with a tie rod, and the guide surface in the state where the stress is generated is flat and the stress is released. The guide surface is curved.
The press machine according to a tenth aspect of the present invention is the press machine according to the seventh aspect, wherein one of the plurality of constituent members is a bed, and the bed is provided with an arrangement surface on which the lower mold is arranged, and the arrangement surface is at the time of tightening with a tie rod. Is processed into a bed in a state where the same stress is generated, the arrangement part in the state where the stress is generated is flat, and the arrangement part in the state where the stress is released is curved It is characterized by that.

According to the first invention, since one of the constituent members is processed independently in a state where stress equivalent to that at the time of fastening by the tie rod is generated, even if it is a press machine that is difficult to integrally process the entire frame, The shape accuracy of the processed part at the time of assembly can be made as high as the shape accuracy of the processed part when integrally processed.
According to the second invention, the stress is generated in the constituent member by inserting the processing rod into the insertion hole of the tie rod of the constituent member and tightening the processing rod, so that the stress of the constituent member is easy. The method is equivalent to that during assembly. From this, with respect to the processed parts of the component parts of the press machine, the shape accuracy of the processed parts at the time of assembly can be made equal to the shape accuracy of the processed parts when integrally processed.
According to the third invention, the spacer having the contact surface with the other component member that is in contact with the frame when assembling the frame and the contact surface having the same shape is interposed between the component member and the nut for tightening the processing rod. As a result, the stress of the constituent members becomes equivalent to that during assembly. From this, with respect to the processed parts of the component parts of the press machine, the shape accuracy of the processed parts at the time of assembly can be made equal to the shape accuracy of the processed parts when integrally processed.
According to the fourth invention, in the state where stress equivalent to that at the time of fastening with the tie rod is generated, by machining the fitting hole of the eccentric shaft that drives the upper mold in the crown, It is possible to ensure the same high shape accuracy as when the integral processing including the crown is performed.
According to the fifth aspect of the present invention, the guide surface of the upright is processed in an integrated manner including the upright by processing the guide surface of the upright in a state where the stress equivalent to that at the time of fastening with the tie rod is generated. High shape accuracy equivalent to that of the case can be ensured.
According to the sixth aspect of the present invention, the lower mold arrangement surface is processed integrally with the bed by processing the lower mold arrangement surface in a state where stress equivalent to that at the time of fastening with the tie rod is generated. It is possible to ensure the same high shape accuracy as when the process is performed.
According to the seventh invention, even if the component of the press machine is a press machine that is difficult to integrally process in the whole frame by being processed independently in a state where stress at the time of tightening by the tie rod is generated, A press machine with a high precision in the shape accuracy of the machined part when tightened by a tie rod can be obtained as in the case of integral machining.
According to the eighth invention, the crown constituting the component of the press machine is provided with the fitting hole of the crankshaft that drives the mold, and the fitting hole is equivalent to the stress at the time of tightening by the tie rod. Press machine that was able to ensure the same high shape accuracy as when the integrated processing including the crown was performed on the crown fitting hole by being processed into the crown in the state where the stress is generated It can be.
According to the ninth aspect of the present invention, the upright constituting the structural member of the press machine is provided with the guide surface for guiding the slide, and the guide surface is in the upright state in a state where the stress is generated when the tie rod is tightened. By being processed, it is possible to provide a press machine that can ensure high shape accuracy equivalent to that when the upright guide surface is integrally processed including the upright.
According to the tenth aspect of the invention, the bed constituting the constituent member of the press machine is provided with the lower mold arrangement portion, and the arrangement portion is processed in a state in which stress is generated when tightening by the tie rod. Thereby, it can be set as the press machine which was able to ensure the same high shape precision as the time of integral processing including the bed about the arrangement | positioning part of a bed.

(A) It is a side view at the time of independent processing of the crown which comprises the press machine which concerns on one Embodiment of this invention. (B) A side view showing the influence of the stress applied to the crown. The solid line shows the state when the tightening force is released after processing, and the two-dot chain line shows the state at the time of processing. (A) It is a side view at the time of independent processing of the upright which comprises the press machine which concerns on one Embodiment of this invention. (B) A side view showing the influence of the stress applied to the upright, where the solid line indicates the state when the tightening force is released after processing, and the two-dot chain line indicates the state during processing. (A) It is a side view at the time of independent processing of the bed which comprises the press machine which concerns on one Embodiment of this invention. (B) In the side view which shows the influence of the stress added to the said bed, the continuous line has shown the state when the clamping force is released after a process, and the dashed-two dotted line has shown the state at the time of a process. It is a front view of a press machine concerning one embodiment of the present invention. It is a side view of the press machine concerning one embodiment of the present invention.

Next, an embodiment of the present invention will be described with reference to the drawings.
(Press machine)
First, the basic structure of the press machine P according to an embodiment of the present invention will be described. 4 is a front view of the press machine P, and FIG. 5 is a side view. The side view of FIG. 5 shows only the frame 1.
The press machine P includes a frame 1. The frame 1 includes a lower bed 2, an upper crown 3, and an upright 4 provided therebetween. The upright 4 includes two support columns 4a into which tie rods 5 to be described later are inserted, and side frames 4b that connect the support columns 4a. The bed 2, the crown 3, and each upright 4 are provided with insertion holes for inserting tie rods 5. The tie rods 5 are inserted into the insertion holes, respectively, at both ends of the tie rods 5. By tightening the tie rod 5 with the provided nut, the bed 2, the crown 3, and the upright 4 between the screw mechanisms are firmly fastened. In the present embodiment, the two struts 4a arranged before and after the press machine P are connected and integrated by the side frame 4b. However, the side frame 4b is not provided, but the four uprights are used. Some are configured.

  A fitting hole 6 for fitting the main sleeve 16 is formed in the lower part of the crown 3, and an eccentric shaft 8 is rotatably inserted into a bush 7 provided in the main sleeve 16. The eccentric shaft 8 is a known eccentric shaft composed of the eccentric portion 8a at the central portion and the shaft portions 8b on both sides thereof, but is not limited to the eccentric shaft, and other types such as a crankshaft are also available. Applicable. The eccentric shaft 8 has a servo motor as a drive source 9 connected to an end thereof via a speed reducer 11. A variety of drive sources 9 can be used without particular limitation, but a servo motor with good controllability is suitable.

  The shaft portions 8 b located at both ends of the eccentric shaft 8 are fitted into the bush 7, and the eccentric portion 8 a located at the center of the eccentric shaft 8 is fitted into the connecting rod 17. A slide 15 is connected to the lower portion of the connecting rod 17 via a wrist pin 18. By rotating the eccentric shaft 8 around the shaft center of the shaft portion 8b, the eccentric portion 8b of the eccentric shaft 8 rotates in an eccentric state, and the connecting rod 17 moves up and down while being eccentric. The vertical movement of the connecting rod 17 is transmitted to the slide 15 via the wrist pin 18, and the slide 15 is guided by the guide member 10 provided in the upright 4 and moves up and down. FIG. 4 shows a state in which the slide 15 is at the bottom dead center position.

  An upper mold 12 is attached to the lower end of the slide 15. A lower mold 13 is attached to the upper surface of the bed 2 through a mold holder 14.

(Production method)
Next, a method for manufacturing the press machine P will be described. The manufacturing method according to the present embodiment mainly includes two steps, that is, a member processing step for processing the constituent member and an assembly step for assembling the processed constituent member.

  The press machine P according to the present invention includes a frame 1 that is assembled by fastening a bed 2, a crown 3, and an upright 4, which are constituent members, with a tie rod 5. These constituent members are processed independently in a state in which a stress equivalent to that at the time of fastening by the tie rod 5 is generated inside. Here, “independently” means that the main constituent members constituting the frame 1 are each processed in a single product state. That is, since members such as bolts and nuts are not main constituent members constituting the frame 1, even if they are processed together with them, it corresponds to being processed “independently”.

  In the present invention, even if the constituent members of the press machine P are processed independently while the stress at the time of tightening by the tie rod 5 is generated, the press machine P is difficult to be integrated with the entire frame 1. The shape accuracy of the processed portion when tightened by the tie rod 5 can be made as high as that obtained when integrally processing.

  With reference to FIG. 1 to FIG. 3, a member machining process of main components constituting the frame, which is one process of the manufacturing method of the press machine P, will be described in detail.

(crown)
FIG. 1 (A) shows a side view of the crown 3 constituting the press machine P according to an embodiment of the present invention, and FIG. 1 (B) shows the effect of stress applied to the crown 3. The solid line shows the state when the tightening force is released after processing, and the two-dot chain line shows the state during processing. Note that the solid line and the two-dot chain line shown in FIG. 1B are expressed larger than the actual amount of change in order to make the state of change easy to understand. An operator who processes the crown 3 performs an initial cutting process on the bearing surface of the nut of the tie rod 5 and the contact surface with the upright 4 on the crown 3 of the structure manufactured by casting or welding. Thereafter, the machining rod 21 is inserted into the insertion hole for the tie rod 5, and a predetermined stress is generated on the crown 3 by rotating and tightening the nut 26. This predetermined stress is a stress equivalent to that when the structural member is fastened by using the tie rod 5 and the frame 1 is configured.

  In order to generate a stress equivalent to that at the time of fastening by the tie rod 5, the lower part of the crown 3 has a contact surface with the upright 4 that is in contact with the crown 3 when the frame 1 is configured, and a spacer having a contact surface of the same shape. 22 is used. The upper part of the crown 3 is the same as the washer corresponding to the nut of the tie rod 5. When the spacer 22 is interposed between the crown 3 and the nut 26 for tightening the machining rod 21, and the same compression force is applied to the contact surface of the same shape by the machining rod 21, the tie rod is applied to the crown 3. Stress equivalent to that at the time of fastening by 5 is generated.

  In the above-described state, the cutting process is performed on the fitting hole 6 independently for the crown 3 by reducing the processing speed or reducing the machining allowance. When the crown 3 is machined alone, that is, when a stress equivalent to that at the time of fastening by the tie rod 5 is generated, the fitting hole 6 that holds the eccentric shaft 8 is perpendicular to the axis of the fitting hole 6. The shape of the cross section is a perfect circle (the two-dot broken line in FIGS. 1A and 1B). Then, in order to assemble the frame 1, the fitting hole 6 in a state where the stress is released has an elliptical cross-sectional shape perpendicular to the axis of the fitting hole 6 (solid line in FIG. 1B). . This ellipse is not limited to an ellipse that is strictly defined mathematically. However, the difference between the long axis and the short axis is larger than a general shape error caused by machining. For example, a general shape error caused by processing is 50 μm or less although it depends on a processing target, but the difference between the major axis and the minor axis of the ellipse is approximately 500 μm or more.

  In addition, although the case where compressive force is applied to the contact surface having the same shape as the contact surface with the upright 4 using the spacer 22 has been described, it is also possible to tighten using a nut and a washer without using the spacer 22. . In this case, it is necessary to determine the compressive force by the processing rod 21 by confirming the state of occurrence of stress using an analysis result such as FEM.

(Upright)
2A is a side view when the upright 4 is processed alone, and FIG. 2B is a side view showing the effect of the stress applied to the upright 4, and the solid line indicates that the tightening force is released after the processing. The two-dot chain line shows the state at the time of processing. Note that the solid line and the two-dot chain line shown in FIG. 2B are expressed larger than the actual amount of change in order to make the state of change easy to understand. An operator who processes the upright 4 performs an initial cutting process on the contact surface with the crown 3 or the bed 2 on the upright 3 of the structure manufactured by casting or welding. Thereafter, the processing rod 21 is inserted into the insertion hole for the tie rod 5 and a predetermined stress is generated on the upright 4 by rotating and tightening the nut 26. This predetermined stress is a stress equivalent to that when the structural member is fastened by using the tie rod 5 and the frame 1 is configured.

  In order to generate the same stress as that when the tie rod 5 is fastened, the upper part of the upright 4 has a contact surface with the crown 3 that is in contact with the upright 4 when the frame 1 is constructed, and a spacer having a contact surface of the same shape. 25 is used. Moreover, about the lower part of the upright 4, the spacer 23 which has a contact surface with the bed 2 and a contact surface of the same shape is used. When the spacers 23 and 25 are interposed between the upright 4 and the nut 26 for tightening the machining rod 21, and the same compression force is applied to the contact surface of the same shape by the machining rod 21, the upright 4 The same stress as that at the time of fastening by the tie rod 5 is generated.

  In the above-described state, the upright 4 alone is subjected to finish cutting on the guide surface of the guide member 10 by reducing the processing speed or reducing the machining allowance. When the upright 4 is processed alone, that is, in a state where a stress equivalent to that at the time of fastening by the tie rod 5 is generated, the guide surfaces processed into the upper and lower columnar portions of the upright 4 are flat (FIG. 2). (A) and the dashed-two dotted line of FIG. 2 (B)). In order to assemble the frame 1, the guide surface in a state where the stress is released is curved (solid line in FIG. 2B). More specifically, on the surface including the axis of the columnar portion of the upright 4, the guide surface has a shape in which the central portion between the upper and lower sides is recessed. This dent amount is larger than a general shape error caused by processing.

  In addition, although the case where a compressive force is applied to the contact surface having the same shape as the contact surface with the crown 3 or the bed 2 using the spacers 23 and 25 has been described, a nut and a washer are used without using the spacers 23 and 25. It is also possible to tighten. In this case, it is necessary to determine the compressive force by the processing rod 21 by confirming the state of occurrence of stress using an analysis result such as FEM.

(bed)
3A is a side view of the bed 2 before and after the single processing, and FIG. 3B is a side view showing the effect of the stress applied to the bed 2, and the solid line indicates the tightening force after the processing. The state when released is shown, and the two-dot chain line shows the state during processing. Note that the solid line and the two-dot chain line shown in FIG. 3B are expressed larger than the actual amount of change in order to make the state of change easy to understand. An operator who processes the bed 2 performs an initial cutting process on the contact surface of the bed 2 of the structure manufactured by casting or welding with the upright 4. Thereafter, the processing rod 21 is inserted into the insertion hole for the tie rod 5 and a predetermined stress is generated in the bed 2 by rotating and tightening the nut 26. This predetermined stress is a stress equivalent to that when the structural member is fastened by using the tie rod 5 and the frame 1 is configured.

  In order to generate the same stress as that when the tie rod 5 is fastened, the upper portion of the bed 2 has a contact surface with the upright 4 in contact with the bed 2 when the frame 1 is configured and a spacer having the same shape as the contact surface. 24 is used. The lower part of the bed 2 is the same as the washer corresponding to the nut of the tie rod 5. When the spacer 24 is interposed between the bed 2 and the nut for tightening the machining rod 21 and the same compression force is applied to the contact surface of the same shape by the machining rod 21, the tie rod 5 is applied to the bed 2. The same stress as that caused by fastening is generated.

  In the above-described state, a finishing cutting process is performed on the placement surface on which the lower mold 13 is disposed, by using the bed 2 alone to reduce the machining speed or reduce the machining allowance. When the bed 2 is processed alone, that is, in a state where a stress equivalent to that at the time of fastening with the tie rod 5 is generated, the arrangement surface of the lower mold 13 provided on the bed 2, that is, the upper surface of the bed 2 is flat. (The two-dot broken line in FIGS. 3A and 3B). In order to assemble the frame 1, the arrangement surface in a state where the stress is released is curved (solid line in FIG. 3B). More specifically, the upper surface of the bed 2 has a shape with a recessed central portion. This shape is larger than a general shape error caused by processing. The upper surface of the bed 2 may be disposed directly through the lower mold 13 or indirectly through the mold holder 14 or the like.

  In addition, although the case where compressive force is applied to the contact surface having the same shape as the contact surface with the upright 4 using the spacer 24 has been described, it is also possible to tighten using a nut and washer without using the spacer 24. . In this case, it is necessary to determine the compressive force by the processing rod 21 by confirming the state of occurrence of stress using an analysis result such as FEM.

  The operator configures the frame 1 by fastening the tie rods 5 to the main members that have been processed independently. The press machine P is manufactured by assembling other driving members and the like on the frame 1.

  Since the structural members are processed independently in a state where stress equivalent to that at the time of fastening by the tie rod 5 is generated, even the large press machine P that is difficult to be integrally processed by the entire frame 1 is tightened by the tie rod 5. In this case, the shape accuracy of the processed portion can be set to the same accuracy as the shape accuracy of the processed portion when integrally processed.

  In addition, the component members can be processed using a relatively small machine tool as compared to processing in a state where all the component members are assembled together. Cost can be reduced.

  In the above description, the bed 2, the crown 3, and the upright 4 are each processed in a state where stress equivalent to that at the time of fastening by the tie rod 5 is generated, but the present invention is not limited to this. . For example, only the crown 3 positioned at the uppermost part of the press machine P includes processing in a state where stress equivalent to that at the time of fastening by the tie rod 5 is generated.

DESCRIPTION OF SYMBOLS 1 Frame 2 Bed 3 Crown 4 Upright 5 Tie rod 6 Insertion hole 8 Eccentric shaft 9 Drive source 10 Guide member 15 Slide 21 Processing rod 22-25 Spacer

Claims (10)

A method of manufacturing a press machine having a frame assembled by fastening a plurality of components by tie rods,
At least one of the constituent members has a member processing step that is processed independently in a state where a stress equivalent to that at the time of fastening by the tie rod is generated.
A manufacturing method of a press machine. In the member processing step,
Inserting a machining rod into the insertion hole of the tie rod of the component member and tightening the machining rod to generate the stress on the component member;
The manufacturing method of the press machine of Claim 1 characterized by the above-mentioned. A spacer having a contact surface with another component member that is in contact with the frame during assembly and a contact surface having the same shape is interposed between the component member and a nut that tightens the processing rod;
The manufacturing method of the press machine of Claim 2 characterized by the above-mentioned. The component member processed in the member processing step is a crown,
In the member machining step, machining the fitting hole of the eccentric shaft that drives the upper die to the crown,
The manufacturing method of the press machine in any one of Claims 1-3 characterized by the above-mentioned. The component processed in the member processing step is upright,
The upright is provided with a guide surface of a slide that moves up and down with an upper mold,
In the member processing step, the guide surface is processed.
The manufacturing method of the press machine in any one of Claims 1-3 characterized by the above-mentioned. The component processed in the member processing step is a bed,
The bed is provided with a placement surface for placing the lower mold,
Processing the placement surface in the member processing step;
The manufacturing method of the press machine in any one of Claims 1-3 characterized by the above-mentioned. A press machine having a frame assembled by a plurality of components being fastened by tie rods,
In the state where the component member is subjected to the same stress as that at the time of fastening with the tie rod,
A press machine characterized by that. One of the plurality of components is a crown;
The crown is provided with a fitting hole for an eccentric shaft that drives the upper mold,
In a state where stress equivalent to that at the time of tightening by the tie rod is generated in the crown, the fitting hole is processed in the crown,
The fitting hole in a state where the stress is generated has a perfect circle shape in a cross section perpendicular to the axis of the fitting hole,
The fitting hole in a state where the stress is released has an elliptical cross-sectional shape perpendicular to the axis of the fitting hole.
The press machine according to claim 7. One of the plurality of constituent members is an upright,
The upright is provided with a guide surface of a slide that moves up and down with an upper mold,
The guide surface is processed into the upright in a state where stress equivalent to that at the time of tightening with the tie rod is generated in the upright,
The guide surface in a state where the stress is generated is flat,
The guide surface in a state where the stress is released is curved,
The press machine according to claim 7. One of the plurality of constituent members is a bed,
The bed is provided with a placement surface for placing the lower mold,
The placement surface is processed into the bed in a state where stress equivalent to that at the time of tightening by the tie rod is generated,
The arrangement portion in a state where the stress is generated is flat,
The placement portion in a state where the stress is released is curved,
The press machine according to claim 7.

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