Workpiece machining method

Abstract

To reduce or convert the tensile stress remaining on the cut surface of the workpiece into compressive stress. [Solution] A method for processing a workpiece W having a cut surface 10 cut by shearing at its end, wherein the end of the workpiece W is compressed and plastically deformed from a direction parallel to the shearing direction A of the shearing process, or from a direction inclined with respect to it.

Description

Technical Field

[0001] The present invention relates to a method for processing a workpiece.

Background Art

[0002] In recent years, for lower arms, intermediate beams, etc., which are known as automotive underbody parts, a method of forming parts using a single metal plate has been adopted for the purpose of cost reduction and the like.

[0003] In that case, first, the metal plate is punched by shearing to form a blank material, and then the blank material is press-formed to obtain a part with a predetermined shape. Further, as such a processing method, for example, in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2023-58927), a method of forming a lower arm using a blank material obtained by punching a metal plate by shearing is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, when a workpiece such as a metal plate is punched and formed by shearing, generally, tensile stress due to shearing is generated on the cut surface of the punched workpiece. Therefore, when a part is formed using such a workpiece, tensile stress remains at the end of the part. Thus, when additional tensile stress acts on the part thereafter, there is a risk that the part cannot withstand the tensile stress and damage such as cracking occurs.

[0006] Therefore, an object of the present invention is to reduce the tensile stress remaining on the cut surface of the workpiece or change it to compressive stress.

Means for Solving the Problems

[0007] To solve the above problems, the present invention provides a method for processing a workpiece having a cut surface at its end obtained by shearing, characterized in that the end of the workpiece is compressed and plastically deformed from a direction parallel to the shearing direction of the shearing process, or from a direction inclined with respect to it.

[0008] Thus, in the workpiece processing method according to the present invention, by compressing and plastically deforming the end of the workpiece in a direction parallel to the shearing direction of the shearing process, or in a direction inclined thereto, compressive stress in the direction parallel to the shearing direction can be effectively generated over a wide range. As a result, residual tensile stress at the end of the workpiece can be effectively reduced or converted into compressive stress, thereby preventing damage to the part due to tensile stress remaining on or acting on the cut surface of the workpiece. [Effects of the Invention]

[0009] According to the present invention, it is possible to prevent damage to parts due to tensile stress remaining on or acting on the cut surface of the workpiece. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view showing an example of an intermediate beam type suspension. [Figure 2] This is an enlarged cross-sectional view showing a magnified portion of the cross-section of the intermediate beam. [Figure 3] This figure shows a workpiece processing method according to the first embodiment of the present invention. [Figure 4] This figure shows the results of residual stress measurement tests conducted using the processing method according to the present invention and without using the processing method according to the present invention. [Figure 5] This figure shows the results of a workpiece durability test conducted using the processing method according to the present invention and without using the processing method according to the present invention. [Figure 6] This figure shows a workpiece processing method according to a second embodiment of the present invention. [Figure 7] It is a diagram showing a method for processing a workpiece according to the third embodiment of the present invention. [Figure 8] It is a diagram showing a method for processing a workpiece according to the fourth embodiment of the present invention. [Figure 9] It is a diagram showing the results of a durability test of a workpiece conducted when using the processing method according to each embodiment of the present invention and when not using the processing method according to the present invention. [Figure 10] It is a diagram showing a sample used in the durability test of the workpiece. [Figure 11] It is a diagram showing an example of pressing a pressing member from a direction inclined with respect to the shearing direction. [Figure 12] It is a diagram showing an example of compression processing of the edge of a through hole. [Figure 13] It is a diagram showing an example of pressing a pressing member from a direction orthogonal to the shearing direction.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described by taking, as an example, a method for manufacturing an intermediate beam mounted on a vehicle such as an automobile. Note that the method for processing a workpiece according to the present invention is not limited to being applied to the manufacture of an intermediate beam, but can also be applied to the manufacture of other suspension components such as lower arms, or the manufacture of other components.

[0012] <Configuration of an Intermediate Beam Type Suspension> First, the configuration of an intermediate beam type suspension in which an intermediate beam is used will be briefly described.

[0013] FIG. 1 is a perspective view showing an example of an intermediate beam type suspension.

[0014] The intermediate beam type suspension 1 shown in FIG. 1 includes a pair of left and right trailing arms 2 and an intermediate beam 3 that connects these trailing arms 2 to each other.

[0015] A pair of trailing arms 2 has a bush mounting portion 2a with a rubber bush mounted on one end side thereof, and an axle portion 2b to which a wheel is attached on the opposite other end side. One end (bush mounting portion 2a) of each trailing arm 2 is swingably attached to the vehicle body via a bracket and a fixing bolt in addition to the rubber bush.

[0016] The intermediate beam 3 extends in the width direction of the vehicle body and is coupled to the pair of trailing arms 2 at both ends in the extending direction. The intermediate beam 3 is formed as a longitudinal component that bends, for example, into a substantially U-shaped cross section.

[0017] By the way, in recent years, for the purpose of reducing manufacturing costs and weight of parts, a method of forming the intermediate beam using a single metal plate has been adopted. In that case, first, the metal plate is punched using a punch and a die to form a blank material of a predetermined shape, and then the blank material is bent by a press device into a substantially U-shaped cross section or the like to form the intermediate beam.

[0018] Thus, by forming the intermediate beam using a single metal plate, it is possible to reduce manufacturing costs and weight of parts. However, it has been found that there are the following problems regarding the durability of the intermediate beam when it is formed by a single metal plate.

[0019] <Problems regarding the durability of the intermediate beam> FIG. 2 is an enlarged cross-sectional view showing an enlarged part of the cross section of the intermediate beam 3.

[0020] As shown in Figure 2, in the intermediate beam 3 formed using a punched blank material, cut surfaces 10 are formed at both ends 3a and 3b of the cross-section of the intermediate beam 3 due to the shearing process when the metal plate is punched out. The cut surface 10 formed by the shearing process usually has a portion called a "burr" 11 formed by the tensile stress when the punch enters the workpiece (metal plate), a relatively smooth shear surface 12 generated by shearing, a rough fracture surface 13 formed as if the workpiece had been torn off, and a portion called a "burr" 14 where a part of the workpiece protrudes when the punch penetrates the workpiece. These portions are formed in the order of burr 11, shear surface 12, fracture surface 13, and burr 14 in the shearing direction A, which is the direction of movement of the punch 100.

[0021] Furthermore, in the cut surface 10 of a punched workpiece, tensile stress caused by shearing generally remains. Therefore, if a part is formed using a workpiece with residual tensile stress, there is a risk that the part may break, such as cracking, if further tensile stress is applied to the part afterward. In particular, if tensile stress is applied to the edge on the burr side 14 of the cut surface 10, stress concentration occurs at the burr 14 and the fracture surface 13, making it prone to cracking.

[0022] Therefore, measures are needed to prevent component failure, such as increasing the thickness of the component material to improve durability or polishing the cut surface to alleviate stress concentration. However, the former method has the problem of increased material costs and component weight due to the increased thickness of the material, while the latter method has the problem of decreased manufacturing efficiency due to the increased number of cumbersome polishing processes.

[0023] Therefore, the present invention proposes a workpiece processing method that can prevent damage without increasing the thickness of the component material or polishing the component. The processing method according to the present invention will be described below.

[0024] <Processing method according to the first embodiment of the present invention> Figure 3 shows a workpiece processing method according to the first embodiment of the present invention.

[0025] The workpiece W shown in Figure 3 is a plate-shaped workpiece having a cut surface 10 at its end, which is formed by shearing, and is a workpiece (blank material) before being formed into a desired part by press working. On the cut surface 10 of the workpiece W, a burr 11, a shear surface 12, a fracture surface 13, and a sharp edge 14 are formed in the direction of shearing A.

[0026] Furthermore, in Figure 3, the device indicated by reference numeral 20 is a compression device that presses a pressurizing member 21 against the end of the workpiece W, thereby compressively deforming the end of the workpiece W. The compression device 20 includes a pressurizing member 21 that pressurizes the end of the workpiece W, as well as a support member 22 that supports the workpiece W.

[0027] Furthermore, the pressurizing member 21 is configured to be movable in the direction of arrow B shown in Figure 3(b) and in the direction of arrow C shown in Figure 3(c) by a lifting mechanism (not shown). Here, the directions of movement of the pressurizing member 21, arrows B and C, are set to be the same as the thickness direction (vertical direction in Figure 3) of the workpiece W placed on the support member 22. In other words, the direction of movement of the pressurizing member 21 is set to be parallel to the shear direction A at the cut surface 10 of the workpiece W.

[0028] Furthermore, the pressurizing member 21 has a pressurizing surface 21a that is inclined toward its movement directions B and C (shear direction A). The pressurizing surface 21a is composed of a plane inclined at, for example, 45° with respect to the movement directions B and C. Note that the inclination angle of the pressurizing surface 21a is not limited to 45° and can be changed as appropriate.

[0029] To process a workpiece using the method according to the first embodiment of the present invention, first, as shown in Figure 3(a), the sheared workpiece W (blank material) is placed and fixed on the support member 22 of the compression device 20.

[0030] Next, as shown in Figure 3(b), the pressurizing member 21 is moved in the direction of arrow B to pressurize the end of the workpiece W. At this time, the pressurizing surface 21a of the pressurizing member 21 is pressed against the sagging 11 side of the workpiece W, and as the workpiece W is pressed, the end of the workpiece W is compressed in the shear direction A and undergoes plastic deformation. In addition, an inclined surface 15 following the pressurizing surface 21a is formed on the sagging 11 side of the workpiece W.

[0031] Subsequently, as shown in Figure 3(c), the pressurizing member 21 is moved in the direction of arrow C, retracting it from the workpiece W. This returns the pressurizing member 21 to its original position, and the machining of the workpiece W is completed.

[0032] As described above, according to the method of the first embodiment of the present invention, by compressing and plastically deforming the end of the workpiece W, a compressive stress (compressive stress) as described below can be generated.

[0033] <Residual stress measurement test> Figure 4 shows the results of residual stress measurement tests conducted using the processing method according to the present invention and when the processing method according to the present invention is not used.

[0034] In Figure 4, workpiece W1 shown in (a) is a comparative example workpiece that does not use the processing method according to the present invention. In contrast, workpieces W2 and W3 shown in Figures 4(b) and (c) are both workpieces processed using the processing method according to the present invention. Therefore, at the ends of each of the workpieces W2 and W3, which are embodiments of the present invention, there is an inclined surface 15 formed by compression processing.

[0035] Furthermore, in the respective workpieces W2 and W3, which are embodiments of the present invention, the size of the inclined surfaces 15 differs. Specifically, workpiece W2 in embodiment 1(b) of the present invention has inclined surfaces 15 that are compressed by 0.2 mm in both the longitudinal and transverse directions, while workpiece W3 in embodiment 2(c) of the present invention has inclined surfaces 15 that are compressed by 1.2 mm in both the longitudinal and transverse directions.

[0036] Furthermore, in Figure 4, (d) is a graph showing the residual stress values ​​measured for each workpiece W1, W2, and W3. In (d), the dashed line shows the residual stress value occurring in workpiece W1 of the comparative example in (a), the dashed line shows the residual stress value occurring in workpiece W2 of Example 1 in (b), and the solid line shows the residual stress value occurring in workpiece W3 of Example 2 in (c). Also, in (d), values ​​greater than "0" on the horizontal axis indicate tensile stress, and values ​​less than "0" indicate compressive stress. The vertical axis indicates the position in the thickness direction of each workpiece W1, W2, and W3.

[0037] According to the results of this measurement test, the tensile stress values ​​generated in workpiece W2 of Example 1 and workpiece W3 of Example 2 were lower than the tensile stress values ​​generated in workpiece W1 of the comparative example, particularly in the range indicated by symbol E. Furthermore, in workpieces W2 and W3 of Example 1 and Example 2, the residual stress changed from tensile stress to compressive stress, particularly in the region where the inclined surface 15 was formed (the compressed region). Thus, the reduction in residual tensile stress and the partial change in residual stress from tensile stress to compressive stress in workpieces W2 and W3 of Example 1 and Example 2 is thought to be due to the generation of compressive stress by the processing method according to the present invention. In other words, it is thought that the residual tensile stress was offset or reduced by the compressive stress generated at the ends of each workpiece W2 and W3 by compressing and plastically deforming them. It should be noted that the larger compressive stress over a wider range in workpiece W3 of Example 2 than in workpiece W2 of Example 1 is thought to be due to the greater compression in Example 2 than in Example 1.

[0038] <Durability Test> Next, Figure 5 shows the results of durability tests performed on workpieces using the processing method according to the present invention and without using the processing method according to the present invention.

[0039] In Figure 5, the dashed line is a graph showing the stress values ​​generated in a workpiece that does not use the processing method according to the present invention, and the solid line is a graph showing the stress values ​​generated in a workpiece that uses the processing method according to the present invention. In this durability test, tensile stress and compressive stress were repeatedly applied to each workpiece, and the values ​​of the tensile stress and compressive stress generated in the workpiece were measured.

[0040] First, in the workpiece that does not use the processing method according to the present invention (dashed line graph), a tensile stress of +α remains due to shearing, and tensile and compressive stresses are repeatedly applied based on this residual tensile stress (+α). In this case, at the peak value (maximum tensile stress value) where the maximum tensile stress is applied, the tensile stress value exceeded the durability threshold β of the workpiece.

[0041] In contrast, in the workpiece processed using the processing method according to the present invention (solid line graph), the residual stress is "0". That is, in the workpiece processed using the processing method according to the present invention, the residual tensile stress is canceled out by the compression processing of the end of the workpiece, resulting in a residual stress of "0". Therefore, tensile stress and compressive stress are repeatedly applied from a state of "0" residual stress. As a result, in the workpiece according to the present invention, even when tensile stress and compressive stress are repeatedly applied, unlike the comparative example, the peak value of the tensile stress did not exceed the durability threshold β.

[0042] As described above, the processing method according to the present invention makes it possible to reduce or convert residual tensile stress generated in the workpiece into compressive stress by generating compressive stress at the end of the workpiece, thereby lowering the peak value of tensile stress when tensile stress is applied to the workpiece. This makes it possible to prevent damage to the part when tensile stress is applied.

[0043] Furthermore, the processing method according to the present invention makes it possible to improve the durability of a part by simply compressing and plastically deforming the end of the workpiece. In other words, the processing method according to the present invention makes it possible to easily improve the durability of a part without increasing the thickness of the part material or polishing the part, thus avoiding the increase in material costs and part weight that would result from increasing the thickness of the material, as well as the decrease in manufacturing efficiency that would result from the increase in troublesome polishing processes. In addition, by improving the durability of the part, the number of maintenance and inspections can be reduced, thus reducing the costs associated with these.

[0044] Next, other embodiments of the present invention will be described. In the following description, we will mainly describe parts that differ from the first embodiment of the present invention, and descriptions of the same parts will be omitted as appropriate.

[0045] <Processing method according to a second embodiment of the present invention> Figure 6 shows a workpiece processing method according to a second embodiment of the present invention.

[0046] As shown in Figure 6, in the second embodiment of the present invention, unlike the first embodiment shown in Figure 3, the pressurizing member 21 is pressed against the workpiece W from the underside. That is, in the second embodiment of the present invention, the pressurizing member 21 is pressed against the workpiece W from the burr 14 side, rather than from the sag 11 side.

[0047] In this case, the pressurizing member 21 is pressed against the workpiece W from the burr 14 side, compressing the portion on the burr 14 side in particular, causing plastic deformation of the end of the workpiece W. In addition, an inclined surface 15 conforming to the pressurizing surface 21a is formed on the burr 14 side surface.

[0048] In this way, the workpiece W may be pressed from the burr 14 side. In this case as well, compressive stress can be generated at the end of the workpiece W, making it possible to reduce or convert the residual tensile stress generated during shearing into compressive stress. As a result, in the processing method according to the second embodiment of the present invention, it is possible to improve the durability of the part against tensile stress, similar to the processing method according to the first embodiment of the present invention.

[0049] <Processing method according to the third embodiment of the present invention> Figure 7 shows a workpiece processing method according to the third embodiment of the present invention.

[0050] As shown in Figure 7, in the third embodiment of the present invention, the shape of the pressurizing member 21 differs from that of the above embodiments. In this case, the pressurizing member 21 has a planar pressurizing surface 21a that is perpendicular to the thickness direction of the workpiece W or to the shear direction A of the workpiece W.

[0051] Therefore, in this case, when the pressurizing member 21 is pressed against the end of the workpiece W, a stepped surface 16 conforming to the pressurizing surface 21a is formed on the end of the workpiece W.

[0052] In this case as well, the end of the workpiece W is pressed, causing plastic deformation of the end of the workpiece W, which reduces the residual tensile stress of the workpiece W or changes it to a compressive stress. Therefore, in the processing method according to the third embodiment of the present invention, it is possible to improve the durability of the part against tensile stress, similar to the processing methods according to the above embodiments.

[0053] <Processing method according to the fourth embodiment of the present invention> Next, Figure 8 shows a workpiece processing method according to the fourth embodiment of the present invention.

[0054] In the fourth embodiment of the present invention shown in Figure 8, the workpiece W is pressurized using a pressurizing member 21 similar to that in the third embodiment shown in Figure 7, but the direction in which the workpiece W is pressurized is different from that of the third embodiment. That is, in the third embodiment shown in Figure 7, the sag 11 side of the workpiece W is pressurized, while in the fourth embodiment shown in Figure 8, the flank 14 side of the workpiece W is pressurized.

[0055] Thus, even when the workpiece W is pressed from the flank 14 side, compressive stress can be generated at the end of the workpiece W, thereby reducing or converting residual tensile stress into compressive stress, and improving the durability of the component against tensile stress.

[0056] <Durability of the workpiece according to each embodiment> Figure 9 shows the results of workpiece durability tests conducted using the processing methods according to each embodiment of the present invention and when the processing methods according to the present invention are not used.

[0057] In Figure 9, (A) is a graph showing the durability of a workpiece (comparative example) that does not use the processing method according to the present invention, and (B), (C), (D), and (E) are graphs showing the durability of a workpiece that uses the processing methods according to the first to fourth embodiments of the present invention, respectively.

[0058] In this durability test, multiple workpieces W (samples) were prepared, each having a through-hole 18 formed by shearing, as shown in Figure 10. In each embodiment of the present invention, the edges (cut surfaces 10) of the through-holes 18 were subjected to compression to form an inclined surface 15 as shown in Figure 3 or Figure 6, or a stepped surface 16 as shown in Figure 7 or Figure 8. A predetermined load was then applied to each workpiece W in the vertical direction as shown in Figure 10, and this was repeated. Figure 9 shows the maximum load at which the workpiece W did not break after repeating this load application a specified number of times. The determination of whether or not damage occurred was made based on the edges (cut surfaces 10) of the through-holes 18 of each workpiece. That is, it was evaluated whether or not damage occurred to the cut surface 10 formed by shearing.

[0059] As a result, as shown in Figure 9, when the processing methods according to each embodiment of the present invention were used (cases (B) to (E)), the durability of the workpiece was improved by 70% to 80% compared to when the processing methods according to the present invention were not used (case (A)). From this, it was found that the processing methods according to each embodiment of the present invention can significantly improve the durability of the workpiece.

[0060] As described above, the processing methods according to each embodiment of the present invention can significantly improve the durability of the workpiece and effectively prevent damage to the component due to tensile stress remaining on or acting on the cut surface of the workpiece. This is thought to be because the residual tensile stress generated in the workpiece can be effectively reduced or converted into compressive stress.

[0061] In the processing methods according to each embodiment of the present invention, as shown in Figures 3, 6 to 8, the pressing direction (movement direction B) of the pressing member 21 is set to a direction parallel to the shear direction A. In this case, when the pressing member 21 is moved in the pressing direction, the end of the workpiece W is compressed in a direction parallel to the shear direction A, so that compressive stress in a direction parallel to the shear direction A can be effectively generated at the end of the workpiece W. Furthermore, by compressing the end of the workpiece W in a direction parallel to the shear direction A, the range over which compressive stress is generated can be extended across the thickness direction of the workpiece W.

[0062] In contrast, as shown in Figure 13, when the pressurizing member 21 is applied to the workpiece W from a direction perpendicular to the shear direction A (direction of arrow B in the figure), it is difficult to generate compressive stress in a direction parallel to the shear direction A, and the range of compressive stress generation tends not to extend in the thickness direction of the workpiece W.

[0063] Accordingly, according to the processing method of each embodiment of the present invention, by compressing the end of the workpiece W from a direction parallel to the shear direction A, compressive stress can be generated over a wide range in the direction parallel to the shear direction A, and the tensile stress remaining at the end of the workpiece W can be effectively reduced or converted into compressive stress. As a result, damage to the part due to tensile stress remaining at or acting on the cut surface of the workpiece W can be prevented to a high degree, and durability can be greatly improved.

[0064] Furthermore, the direction in which the end of the workpiece W is compressed does not have to be perpendicular to the shear direction A; it may be parallel to the shear direction A, or it may be inclined with respect to the shear direction A. That is, as shown in the example in Figure 11, the workpiece W may be compressed by pressing the pressurizing member 21 in a direction inclined with respect to the shear direction A (direction of arrow B in the figure). In this case, by pressing the pressurizing member 21 in a direction inclined with respect to the shear direction A, a component force (applied pressure) can be generated on the workpiece W in a direction parallel to the shear direction A, and thus it is possible to generate compressive stress in a direction parallel to the shear direction A. Therefore, even in the example in Figure 11, the tensile stress remaining at the end of the workpiece W can be effectively reduced or converted into compressive stress compared to the example in Figure 13. To more effectively reduce residual tensile stress, it is preferable to set the compression direction of the workpiece W to be parallel to the shear direction A, as in the embodiments of the present invention described above.

[0065] As described above, according to the durability test results shown in Figure 9, there is no particularly large difference in durability among the processing methods according to each embodiment of the present invention. However, referring to the graph in Figure 4(d), the edge on the side against which the pressurizing member 21 is pressed (the inclined surface 15 side) can generate a relatively larger compressive stress than the opposite edge, so the processing method may be selected depending on whether the side on which tensile stress acts is the sagging 11 side or the burr 14 side. For example, if tensile stress is applied to the edge on the sagging 11 side of the molded part, the residual tensile stress mainly on the sagging 11 side can be effectively reduced or changed to compressive stress by compressing the sagging 11 side of the workpiece W, as shown in the example in Figure 3 or Figure 7. Conversely, if tensile stress is applied to the edge on the burr 14 side, the residual tensile stress mainly on the burr 14 side can be effectively reduced or changed to compressive stress by compressing the burr 14 side of the workpiece W, as shown in the example in Figure 6 or Figure 8. Thus, if the points where tensile stress acts on a molded part can be anticipated, the durability of the part can be effectively improved by changing the direction of pressure applied to the workpiece according to that prediction.

[0066] Furthermore, there is no significant difference in effect between the case where the pressing surface 21a of the pressing member 21 is a surface inclined with respect to the shear direction A (example in Figure 3 or Figure 6) and the case where it is a surface perpendicular to the shear direction A (example in Figure 7 or Figure 8). However, since the shape of the processing marks (inclined surface 15, stepped surface 16) formed on the workpiece W when the pressing surface 21a is pressed against it is different, the choice of which processing method to select may be appropriately determined depending on the shape and function of the part after molding.

[0067] Although the present invention has been described above, the present invention is not limited to the configurations of the above embodiments, and the design can be modified as appropriate without departing from the spirit of the invention.

[0068] In the descriptions of the embodiments above, an example was given in which a press member 21 is pressed against the outer edge (end) of a workpiece having a cut surface 10 formed by shearing to perform compression processing. However, the present invention is not limited to cases where the outer edge of a workpiece is compressed in this way. For example, as shown in Figure 12, the press member 21 may be pressed against the edge of a through hole 18 formed by drilling (shearing) in a workpiece W to perform compression processing. In this case as well, compressive stress can be generated at the edge of the through hole 18, so that the tensile stress remaining at the edge of the through hole 18 can be eliminated or reduced, and the durability of the workpiece W against tensile stress can be improved. Thus, the end of a workpiece to be compressed using the processing method according to the present invention may be the outer edge of the workpiece or the edge of a through hole. [Explanation of symbols]

[0069] 3. Intermediate beam 10 Cut surface 20 Compressor 21 Pressurizing member 22 Support member A Shear direction Double job

Claims

[Claim 1] A method for processing a workpiece having a cut surface at its end, which is cut by shearing, A method for processing a workpiece, characterized by compressing and plastically deforming the end of the workpiece in a direction parallel to the shearing direction of the shearing process, or in a direction inclined with respect to it.

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