Punching processing method, method of manufacturing press-formed product, and press-formed product

Abstract

The punching processing method of the present invention is a punching processing method in which a metallic sheet material 1a is sequentially subjected to multiple punching processing steps by a punch and a die, comprising, in first step punching processing, forming a first step punched surface 2 on the sheet material 1a, and then in second step punching processing, forming a second step punched surface 3 on the sheet material 1a by punching the sheet material 1a such that the second step punched surface 3 and the first step punched surface 2 are crossed with each other, thereby forming matching portions 5 at positions where the first step punched surface 2 and the second step punched surface 3 intersect, wherein after the first step punching processing and before the second step punching process, the method further comprises subjecting the sheet material 1a to swaging processing that sandwiches and crushes matching portion forming portions 5a of the sheet material 1a, which will form the matching portions 5, from a top surface TS side and a back surface BS side of the sheet material 1a.

Claims

1. A punching processing method in which a metallic sheet material is sequentially subjected to multiple punching processing steps by at least one punch and at least one die, comprising the following steps in this order: a first punching processing step of forming a first punched surface on the sheet material; a swaging processing step that sandwiches and crushes one or more matching portion-forming portions of the sheet material from a top surface side and a back surface side of the sheet material, wherein the swaging processing step comprises pressing and crushing the matching portion-forming portions by a contact surface inclined at 30 to 85 relative to the top surface and the back surface of the sheet material; and, a second punching processing step of forming a second punched surface on the sheet material by punching the sheet material such that the second punched surface and the first punched surface intersect with each other, thereby forming one or more matching portions from the matching portion-forming portions at positions where the first punched surface and the second punched surface intersect.

2. The punching processing method according to claim 1, comprising, in the swaging processing step, sandwiching and crushing the matching portion-forming portions by pressing the matching portion-forming portions of the sheet material from the back surface side that is opposite to the top surface side of the sheet material, and in the second punching processing step, pressing the sheet material from the top surface side by a punch.

3. The punching processing method according to claim 2, wherein the swaging processing step comprises pressing and crushing at least one boundary portion between the back surface and the first step punched surface at the matching portion-forming portions.

4. The punching processing method according to claim 1, comprising carrying out the swaging processing step with a processing rate in a range of 30% to 90%, wherein the processing rate is a ratio of a thickness of the matching portion-forming portion after the swaging processing step to a thickness of the matching portion forming portion before the swaging processing step.

5. A method of manufacturing a press-formed product, comprising manufacturing the press-formed product using the punching processing method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is plan views of sheet materials showing an example where a sheet material is subjected to multiple punching processing steps.

(2) FIG. 2 is a plan view of a scrap discharged in a second step punching processing of the punching processing steps in FIG. 1.

(3) FIG. 3 is a plan view showing a press-formed product after the punching processing steps in FIG. 1.

(4) FIG. 4 is plan views of sheet materials showing the punching processing method according to one embodiment of the present invention.

(5) FIG. 5 is a view of the portion shown by the arrow A of FIG. 4(c).

(6) FIG. 6 is a view similar to FIG. 5, showing a matching portion of a press-formed product molded by a conventional method.

(7) FIG. 7 is an enlarged cross-sectional view taken along the line VII-VII in FIG. 4(b).

(8) FIG. 8 is a view similar to FIG. 5, showing a matching portion of a press-formed product molded by a method of another embodiment.

(9) FIG. 9 is a cross-sectional view taken along the line X-X in FIG. 8.

MODES FOR CARRYING OUT THE INVENTION

(10) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(11) In the punching processing method according to one embodiment of the present invention in which a metallic sheet material is sequentially subjected to multiple punching processing steps by a punch(s) and a die(s), first of all, a first step punched surface and a second step punched surface intersecting with the first step punched surface are respectively formed by a first step punching processing and a second step punching processing that is carried out after the first step punching processing and in a direction intersecting with the direction of the first step punching processing among the multiple punching processing steps, and corner portions called matching portions are formed at positions where the first step punched surface and the second step punched surface intersect.

(12) In addition, it is of course possible to carry out other punching processing or other processing before the first stage punching processing or after the second step punching processing, as well as it is also possible to carry out other processing between the first step punching processing and the second step punching processing.

(13) The punching method of the present invention can be effectively employed in high speed pressing for forming a sheet material into a predetermined shape by subjecting the sheet material to the multiple punching processing steps while intermittently feeding the sheet material in one direction mainly in a progressive press mold, and optionally imposition processing or bending processing, for example in order to manufacture a connector terminal or the like. Here, for the sake of simplicity, FIG. 1 illustrates an embodiment where the sheet material in a stationary state is subjected to punching processing for forming a circular shape as viewed from the plane at two stages with the position of the sheet material shifted.

(14) FIG. 1(a) shows a sheet material 1a after the first step punching processing that punches the sheet material sandwiched between a punch and a die (which are not shown) into a circular shape as viewed from the plane by the punch.

(15) By the first step punching processing, a first step punched surface 2 drawing a circular shape as viewed from the plane is formed around a disc-shaped void formed by cutting out the sheet material 1a.

(16) The above sheet material 1 is then subjected to the second step punching processing that punches the sheet material at a position somewhat shifted from the first step punched surface 2 to the right side in FIG. 1(a) so as to intersect with the first step punching processing, by the punch having the same size and shape, as shown by an imaginary lines in FIG. 1(b)

(17) The second step punching processing provides a press-formed product having a second step punched surface 3 with the same circular arc shape as that of the first step punched surface 2 as viewed from the plane, which is adjacent and contiguous to the first step punched surface 2, as shown in FIG. 1(b). As shown in FIG. 2, a scrap 4 discharged in the second step punching processing has a falcate contour shape as viewed from the planner.

(18) When such two punching processing steps are carried out, matching portions 5 as corner portions slightly protruding toward the void side will be formed in the press-formed product 1b at positions where the first step punched surface 2 and the second step punched surface 3 intersect, as shown in an enlarged plan view of FIG. 3. In the illustrated example, the first step punched surface 2 and the second step punched surface 3 intersect at two upper and lower positions in FIG. 3, and two matching portions 5 are formed at the positions, respectively.

(19) It is widely known in the art that the matching portions 5 cause molding defects such as the generation of burrs protruding toward the top surface side or the back surface side of the press-formed product 1b and the generation of metal powder resulting from peeling off of the burrs. Specifically, during the second step punching processing, the portions close to the punch for the second step punching processing on the first step punched surface 2 formed by the first step punching processing would be accompanied by the portion to be punched (the scrap 4) with the punch and plastically deformed to form burrs protruding toward the top surface side or the back surface side, and the portions plastically deformed and protruded would be scraped by the punch for the second step punching processing, thereby generating metal powder.

(20) In order to prevent the generation of burrs or metal powder at the matching portions 5, in this embodiment, the sheet material 1a is subjected to swaging processing after the first step punching processing and before the second step punching processing, as shown in FIG. 4.

(21) More particularly, after forming the first step punched surface 2 in the sheet material 1a by the first step punching processing and before performing the second step punching processing, the swaging processing is carried out by sandwiching and crushing at least portions where the first step punched surface 2 and the second step punched surface 3 to be formed by the second stage punching processing will intersect, that is, matching portion forming portions 5a where the matching portions 5 will be formed after the second step punching processing, from the top surface side and the back surface side of the sheet material 1a. In this embodiment, not only the matching portion forming portions 5a but also the entire edge portion facing the void including the first step punched surface 2 are pressed and crushed, as shown by an imaginary line in FIG. 4(b).

(22) After the swaging processing, the second step punching processing can be carried out in the same manner as described above, thereby forming the first step punched surface 2 and the second step punched surface 3 having good surface properties at the matching portions 5, as illustrated in FIG. 5.

(23) As can be seen from FIG. 5, the first step punched surface 2 and the second step punched surface 3 are comprised of two layers: shear surface regions 2a, 3a located on a top surface TS side of the press-formed product 1b and fracture surface regions 2b, 3b located on a back surface BS side, respectively. The shear surface regions 2a, 3a and the fracture surface regions 2b, 3b are arranged side by side to extend in the longitudinal direction (the left-right direction in FIG. 5) of the first step punched surface 2 and the second step punched surface 3.

(24) In general, the shear surface region would be formed by rubbing against the punch or the die when the sheet material is stretched in the thickness direction by punching processing to form a smooth surface having some linear patterns in the thickness direction. On the other hand, the fracture surface region would be generated by being torn off from the scrap discharged after being stretched by punching processing to form a dimple-like surface having irregularities thereon, which is clearly different from the shear surface region.

(25) According to this embodiment, the shear surface region 3a on the top surface TS side of the second step punched surface 3 gradually expands toward the fracture surface region 3b side as approaching the matching portion 5 in the longitudinal direction, and has longer length in the thickness direction (the up-down direction in FIG. 5) at the matching portion 5 than the length of the other portions, but it does not expand toward the fracture surface region 3b to reach the back surface BS side and is present within the second step punched surface 3, as shown in FIG. 5. The burrs at the matching portions are usually generated due to the shear surface area extending toward the fracture surface area side beyond the back surface and protruding from the back surface. In this embodiment, however, such burrs are not generated.

(26) In addition, FIG. 6 shows a press-formed product 51b molded by a conventional method in which two punching processing steps are similarly carried out with the exception that the swaging processing as stated above is not carried out, as a view similar to FIG. 5. As clearly shown in FIG. 6, the press-formed product 51b obtained by the conventional method has a burr B protruding from the back surface BS, because the shear surface region 53a of the second step punched surface 53 formed by the second step punching processing widely expands toward the fracture surface area 53b side beyond the back surface BS at the matching portion 55.

(27) Here, in the present invention, if the sheet material 1a is to be punched by pressing the punch from the top surface TS side of the sheet material 1a in the second step punching processing, it is preferable that in the above-mentioned swaging processing previously performed, the sheet material 1a is pressed and crushed from the back surface BS side opposite to the top surface TS of the sheet material 1a by a pressing member 20 or the like that is the swaging processing means indicated by an imaginary line in FIG. 7, as shown in the enlarged cross sectional view including the matching portion forming portion 5a in FIG. 7.

(28) The back surface BS side of the matching portion forming portion 5a of the sheet material 1a is thus pressed and crushed, so that by pressing the punch from the top surface TS side of the sheet material 1a in the subsequent second step punching processing, the expansion of the shear surface region 3a toward the fracture surface region 3b located on the back surface BS side at the formed matching portion 5 of the second step punched surface 3 can be suppressed and the generation of burrs at the matching portion 5 can be more reliably and effectively prevented.

(29) Although not shown, if the sheet material is punched by pressing the punch from the back surface side of the sheet material in the second step punching processing in contrast to the foregoing, it is preferable that in the swaging processing, the matching portion forming portion is pressed and crushed by the pressing member from the top surface side of the sheet material. In other words, it is preferable that in the swaging processing, the matching portion forming portion is pressed by the pressing member from the opposite side to the side where the punch is pressed in the second step punching processing. The matching portion forming portion may also be pressed from both sides of the top surface side and the back surface side by the pressing member.

(30) Here, when the matching portion forming portion 5a of the sheet material 1a is pressed and crushed by the swaging processing, the matching portion forming portion 5a may be preferably pressed in a direction inclined relative to the thickness direction of the sheet material 1a, rather than in a direction parallel to the thickness direction.

(31) As can be seen from FIG. 7, the contact surface of the pressing member 20 of the swaging processing means with the matching portion forming portion 5a may be inclined at a predetermined inclination angle relative to the top surface TS or the back surface BS of the sheet material 1a. As a result, the pressing member 20 is displaced along the thickness direction as indicated by a void arrow in FIG. 7, and when the sheet material 1a is pressed by the pressing member 20, pressing force PF is applied particularly to a boundary portion between the back surface BS and the first step punched surface 2 at the matching portion forming portion 5a in the pressing direction where the above inclined contact surface of the pressing member 20 is inclined relative to the thickness direction. Consequently, at the crushed matching portion forming portion 5a, a shape conforming to the inclined contact surface of the pressing member 20 is formed at the boundary portion between the back surface BS and the first step punched surface 2.

(32) In this embodiment, the fracture surface regions 2b, 3b are then inclined at a predetermined angle relative to the back surface BS at the matching portion 5 of the press-formed product 1b after the second step punching processing, and expansion of the shear surface regions 2a, 3a toward the fracture surface regions 2b, 3b side at the matching portion 5 can be suppressed to prevent the generation of burrs at the matching portion 5.

(33) The inclined contact surface of the pressing member 20 of the swaging processing means in contact with the matching portion forming portion 5a may have a flat surface shape as shown in FIG. 7, as well as a curved surface shape projecting outwardly or a curved surface shape recessed inwardly, although not shown.

(34) Further, when the pressing member 20 of the swage processing means is displaced as indicated by a void arrow in FIG. 7 and crush the sheet material 1a, the pressing member can be displaced in a predetermined amount of displacement from a position where the pressing member 20 is in contact with the sheet material 1a to a position where the displacement is stopped. The above amount of displacement herein can be preferably controlled such that a processing rate which is a ratio of the thickness of the matching portion forming portion 5a whose thickness has decreased after completion of the swaging processing relative to the thickness t of the matching portion forming portion 5a of the sheet material 1a before the swaging processing is from 15% to 90%. More preferably, the processing rate may be 30% to 85%.

(35) The adjustment of the inclination angle of the inclined contact surface in the swaging processing can lead to a press-formed product 11b having a small angle between the back surface BS and the fracture surface region 12b on the side of the first step punched surface 12 at the matching portion 15, and the like, for example as illustrated in FIG. 8. In this press-formed product 11b, the angle between the back surface BS and the fracture surface region 12b at the matching portion 15 is smaller than that shown in FIG. 5, as shown in the cross-sectional view of the first step punched surface 12 in FIG. 9.

(36) In order to adjust such an angle , the inclination angle of the inclined contact surface in the swaging processing may be, for example, 30 to 85, because the generation of burrs and the generation of metal powder at the matching portion 15 of the press-formed product 11b to be manufactured can be prevented more reliably.

(37) Further, the angle between the back surface BS and the fracture surface region 12b on the first step punched surface 12 side at the matching portion 15 may be preferably 30 to 85. This angle coincides with the inclination angle of the inclined contact surface of the pressing member 20 in the swaging processing. Measurement of the angle can be performed by measuring an angle at which a straight line connecting a point A1 where the fracture surface region 12b of the first step punched surface 12 near the matching portion 15 subjected to the swaging processing intersects with the back surface BS and a point A2 where the fracture surface region 12b intersects with the shear surface region 12 is inclined relative to the back surface B, as viewed in the cross section shown in FIG. 9.

EXAMPLE

(38) The punching processing method of the present invention was experimentally conducted and its effects were confirmed as described below. However, the description herein is for the purpose of illustration only and is not intended to be limited thereto.

(39) A test was conducted by subjecting the sheet material to the two punching processing steps with the processing position shifted, using the punch having the circular shape as viewed from the plane, as stated above. Since the degree of shifting greatly affected the generation of burrs at the matching portions, the test was carried out with a fixed degree of shifting.

(40) In Examples 1 to 9, the swaging processing was performed between the two punching processing steps under the conditions shown in Table 1. Here, in Examples 1 and 2, the same surface side as the surface pressed by the punch in the second step punching processing was pressed and crushed in the swaging processing before the second step punching processing. On the other hand, in Examples 3 to 7, the side opposite to the surface pressed by the punch in the second step punching processing was crushed in the swaging processing. In Examples 8 and 9, the top surface side and the back surface side were simultaneously pressed and crushed in the swaging processing.

(41) However, in Comparative Example 1, the swaging processing was not performed. In Comparative Examples 2 and 3, the swaging processing was performed after performing the two punching processing steps under each condition shown in Table 1.

(42) In the column of Presence or Absence of Burrs in Table 1, the symbol indicates that the burrs were sufficiently small or no formation of burrs was observed, whereas the symbol indicates that large burrs protruding on the top surface side or back surface side of the press-formed product were formed. Also, in the column of Metal Powder, the symbol indicates that a little amount of metal powder was generated, whereas the symbol indicates that a large amount of metal powder was generated.

(43) TABLE-US-00001 TABLE 1 Swaging Processing Results Surface Pressed InclinationAngle Presence or by Pressing () of Inclined Processing Absence Metal Timing of implementation Member Contact Surface Rate (%) of Burrs Powder Example 1 Between First and Second Punching Steps Top Surface 30 30 Example 2 Between First and Second Punching Steps Top Surface 63 70 Example 3 Between First and Second Punching Steps Back Surface 30 30 Example 4 Between First and Second Punching Steps Back Surface 60 50 Example 5 Between First and Second Punching Steps Back Surface 15 50 Example 6 Between First and Second Punching Steps Back Surface 85 50 Example 7 Between First and Second Punching Steps Back Surface 60 80 Example 8 Between First and Second Punching Steps Both Surfaces Top Surface 20 Side: 30 Back Surface Side: 24 Example 9 Between First and Second Punching Steps Both Surfaces Top Surface 35 Side: 50 Back Surface Side: 60 Comparative X X Example 1 Comparative After First and Second Punching Steps Back Surface 26 25 X X Example 2 Comparative After First and Second Punching Steps Back Surface 63 35 X X Example 3

(44) The results shown in Table 1 demonstrate that in Examples 1 to 9, both the generation of burrs and the generation of metal powder were well suppressed as compared with Comparative Examples 1 to 3. Specifically, in Examples 3 to 7 wherein the back surface side opposite to the surface pressed by the punch in the second step punching processing was crushed in the swaging processing, both the generation of burrs and the generation of metal powder could be more satisfactorily suppressed. Among them, Examples 4 to 7 in which the degree of processing was increased were particularly satisfactory.

(45) In Comparative Examples 2 and 3, the punched surface of the press-formed product after the punching processing had a defective shape due to the swaging processing performed after the first step punching processing and the second step punching processing.

(46) The above results demonstrate that since Examples 1 to 9 carried out the swaging processing between the two punching processing steps, the generation of burrs and the generation of metal powder were effectively suppressed as compared with Comparative Examples 1 to 3.

DESCRIPTION OF REFERENCE NUMERALS

(47) 1a sheet material

(48) 1b, 11b press-formed product

(49) 2, 12 first step punched surface

(50) 2a, 12a shear surface region

(51) 2b, 12b fracture surface region

(52) 3, 13 second step punched surface

(53) 3a, 13a shear surface region

(54) 3b, 13b fracture surface region

(55) 4 scrap

(56) 5, 15 matching portion

(57) 5a matching portion forming portion

(58) 20 pressing member of swaging processing means

(59) inclined angle of inclined contact surface of pressing member

(60) t thickness of sheet material

(61) angle between back surface and fracture surface region on first step punched surface side at matching portion

(62) TS top surface

(63) BS back surface

(64) PF pressing force