Punch, press processing device, and press processing method

Abstract

To provide a technology which can reduce an amount of chips generated during work and inhibit adhesion of a workpiece in press working in which a workpiece mainly composed of aluminum is punched by a punch.SOLUTION: A punch punches through a workpiece mainly composed of aluminum and includes: a shaft part having one end and the other end; and a protruding part protruding from the one end. A shape of the protruding part has a cone shape in which a bottom surface is formed at the shaft part side and a generator line of the protruding part inclines relative to a protruding direction of the protruding part so that a tip of the protruding part is disposed at a position overlapping with the bottom surface when the tip is projected on the bottom surface along an axial direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a punch, a press working device, and a press working method. [Background technology]

[0002] Conventionally, as one type of press working for manufacturing automobile parts and the like, a technique for punching a metal plate as a workpiece using a press working device equipped with a punch having a cutting blade and a die having a die hole capable of receiving the punch has been known (Patent Document 1). In this technique, a metal plate is placed on a die, and a punch is inserted into the die hole to cut the metal plate in a punching manner, thereby forming a hole in the metal plate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-78998 Summary of the Invention [Problem to be solved by the invention]

[0004] When punching aluminum-based workpieces using a press machine, the cutting edge of the punch rubs against the cut surface of the workpiece, generating chips from the workpiece and causing parts of the workpiece to adhere to the punch. When the workpiece adheres to the punch, the adhesion can cause the punch to wear and be damaged, or the adhered material can later fall off. The chips can adhere to the surface of the molded product, or punching a workpiece using a punch damaged by adhesion can scratch or deform the surface of the molded product. Therefore, coating the punch surface with diamond-like carbon (DLC) can reduce the frictional resistance when the punch comes into contact with the workpiece, thereby reducing the amount of chips generated and making adhesion less likely. However, when coating the punch surface with DLC by vapor deposition, the punch can become distorted due to heat, requiring adjustment work to correct the distortion. Furthermore, the coated DLC may peel off from the punch surface due to the force acting between the workpiece and the punch cutting edge when cutting the workpiece. Therefore, there is still room for research into methods to reduce the amount of chips generated and suppress adhesion when punching aluminum-based workpieces. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms. (1) According to a first aspect of the present disclosure, there is provided a punch for punching an aluminum-based workpiece, the punch comprising: a shank having one end and the other end, extending in an axial direction along a central axis; and a protrusion protruding from the one end, the shape of the protrusion being a cone with the shank as a base, the generatrix of the protrusion being inclined with respect to the axial direction so that when a tip of the protrusion is projected onto the bottom surface along the axial direction, the tip overlaps the bottom surface without passing through the center of gravity of the bottom surface, the generatrix direction of the protrusion is inclined with respect to the axial direction such that an angle formed between a generatrix direction along the generatrix of the protrusion and an orthogonal direction perpendicular to the axial direction corresponds to an inclination angle of the workpiece with respect to the orthogonal direction, the angle formed between the generatrix direction and the orthogonal direction is 18 degrees or more and 26 degrees or less when the inclination angle of the workpiece is within a range of 0 degrees to 4 degrees. (2) According to a second aspect of the present disclosure, there is provided a press processing apparatus for punching an aluminum-based workpiece, the press processing apparatus including the punch according to the above aspect and a die having a recess capable of receiving the punch, the die having a shape that conforms to the inclination angle of the workpiece. (3) According to a third aspect of the present disclosure, there is provided a press working method for punching an aluminum-based workpiece using a punch and a die having a recess capable of receiving the punch, the punch having one end and the other end, a shank extending in an axial direction along a central axis, and a protrusion protruding from the one end, the shape of the protrusion being a cone shape with the shank side as a bottom surface, the generatrix of the protrusion being inclined with respect to the axial direction so that when a tip of the protrusion is projected onto the bottom surface along the axial direction, the tip is positioned to overlap with the bottom surface, and the generatrix direction along the generatrix of the protrusion and an orthogonal direction perpendicular to the axial direction are inclined with respect to the axial direction. The angle between the punch and the recess is an angle corresponding to the inclination angle of the workpiece with respect to the orthogonal direction, and the press processing method includes: a first contact step of bringing the tip end of the protrusion, which is located on the opposite side to the shank side, into contact with the workpiece in an arrangement state in which the workpiece is placed on the recess in a state inclined by the inclination angle with respect to the orthogonal direction; a second contact step of pressing the punch toward the recess after the first contact step to bring the one end of the shank into contact with the workpiece; and a cutting step of further pressing the punch toward the recess after the second contact step to punch out the workpiece.

[0006] (1) According to a first aspect of the present disclosure, a punch is provided. The punch for punching an aluminum-based workpiece includes a shank having one end and another end, extending in an axial direction along a central axis, and a protrusion protruding from the one end. The protrusion has a conical shape with the shank as its base, and the generatrix of the protrusion is inclined with respect to the axial direction so that the tip of the protrusion overlaps the bottom when projected onto the bottom along the axial direction. According to this aspect, the tip of the protrusion can be pressed against the workpiece while in contact with it, and then the one end of the shank can be further pressed against the workpiece while in contact with it. This facilitates axial plastic deformation of the workpiece, thereby suppressing the formation of a secondary shear plane on the cut surface of the workpiece. This suppresses friction between the cutting edge of the punch and the cut surface of the workpiece. Therefore, the amount of chips generated can be reduced and adhesion can be suppressed without applying a coating such as DLC to the surface of the punch. (2) In the above embodiment, the angle between the direction along the generatrix of the protrusion and the direction perpendicular to the axial direction may be 9 degrees or more and 26 degrees or less. This embodiment makes it easier to plastically deform the workpiece in the axial direction. As a result, the amount of chips generated can be further reduced, and adhesion can be further suppressed. (3) In the above embodiment, the pyramidal shape may be a circular cone. According to this embodiment, one end of the shank contacts the workpiece in a generally circular shape during the process of pressing the punch against the workpiece. This allows the punch to apply a load to the workpiece more uniformly than when the protruding portion is pyramidal. This reduces the possibility of burrs or the like protruding from the cut surface of the workpiece. (4) According to a second aspect of the present disclosure, there is provided a press processing apparatus. The press processing apparatus punches an aluminum-based workpiece, and includes the punch according to the above aspect and a die having a recess capable of receiving the punch. According to this aspect, when punching an aluminum-based workpiece, it is possible to reduce the amount of chips generated and suppress adhesion without applying a coating such as DLC to the surface of the punch. (5) According to a third aspect of the present disclosure, there is provided a press working method. a first contact step of contacting the workpiece with the tip end of the protrusion, the tip end being located on the opposite side to the shank side, with the workpiece; a second contact step of contacting the workpiece with the tip end of the shank, the first contact step being pressing the punch toward the recess after the first contact step; and a cutting step of contacting the workpiece with the one end of the shank, the first contact step being pressing the punch toward the recess after the second contact step. According to this embodiment, when punching a workpiece whose main component is aluminum, it is possible to reduce the amount of chips generated and suppress adhesion without applying a coating such as DLC to the surface of the punch. The present disclosure can be realized in various forms other than the punch, press working apparatus, and press working method described above, such as a method for manufacturing a punch, a method for manufacturing a press working apparatus, a method for controlling the press working method, a computer program for realizing the control method, and a non-transitory recording medium on which the computer program is recorded. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing a schematic configuration of a press working device according to a first embodiment. [Figure 2] 1 is a flowchart showing a press working method. [Figure 3] FIG. 4 is a diagram for explaining the details of the second contact step. [Figure 4] A graph that virtually shows the relationship between workpiece distortion and tensile stress. [Figure 5] Enlarged view of the area in Figure 3. [Figure 6] FIG. 10 is a diagram showing a processing mode in a punching process using a conventional punch. [Figure 7] FIG. 10 is a diagram for explaining the tilt angle of a workpiece in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. First embodiment: 1 is a schematic diagram showing the overall configuration of a press working apparatus 10 in a first embodiment. The press working apparatus 10 is an apparatus that performs a punching process, which is a type of press working, on a workpiece W whose main component is aluminum. The press working apparatus 10 includes a punch 1, a die 2 having a recess 20 capable of receiving the punch 1, a workpiece holder 8, an elevating device 18 that raises and lowers the punch 1, and a control device 19.

[0009] In a state in which the workpiece W is placed on the recess 20 of the die 2, the punch 1 presses the workpiece W toward the recess 20 of the die 2 with a predetermined load N. The punch 1 is formed of a metal such as steel. The punch 1 includes a shaft portion 11 having one end 111 and the other end 117, and a protrusion 15 protruding from the one end 111 of the shaft portion 11.

[0010] The shaft portion 11 supports the protrusion 15. One end portion 111 of the shaft portion 11 and the other end portion 117 of the shaft portion 11 face each other in the axial direction along the central axis O. In this embodiment, the axial direction coincides with the direction of gravity. The shaft portion 11 is formed to extend in the axial direction along the central axis O from the one end portion 111 to the other end portion 117. In this embodiment, the shape of the shaft portion 11 is a cylinder extending along the axial direction. The other end portion 117 of the shaft portion 11 is connected to the lifting device 18.

[0011] The protrusion 15 is provided with a cutting blade (not shown) for pressing and cutting the workpiece W in a placed state. The shape of the protrusion 15 is a cone shape with the shank 11 side as the bottom surface, and the generatrix 155 of the protrusion 15 is inclined with respect to the axial direction so that the tip 151 of the protrusion 15 is positioned to overlap with the bottom surface when projected along the axial direction. Specifically, the protrusion 15 is formed integrally with the shank 11, with the end surface of the shank 11 forming one end 111 of the shank 11 as the bottom surface. The generatrix 155 of the protrusion 15 is formed so as to extend in the axial direction from the one end 111 of the shank 11 as a starting point. In other words, the shape of the protrusion 15 is a cone shape in which the angle α between the generatrix direction along the generatrix 155 of the protrusion 15 and the orthogonal direction perpendicular to the axial direction is an angle (acute angle) greater than 0 degrees and less than 90 degrees. That is, the tip 151 of the protrusion 15 is sharp. In this embodiment, the axial direction coincides with the direction of gravity, and therefore the orthogonal direction coincides with the horizontal direction.

[0012] The angle α between the generatrix direction and the orthogonal direction is preferably 9 degrees or more and 26 degrees or less. As will be described in detail later, by setting the angle α between the generatrix direction and the orthogonal direction to 9 degrees or more and 26 degrees or less, it is possible to more reliably reduce the amount of chips generated and suppress adhesion. In this embodiment, the angle α between the generatrix direction and the orthogonal direction is 18 degrees. Note that, in order to set the angle α between the generatrix direction and the orthogonal direction to a desired angle, the length L of the protrusion 15 is adjusted according to the dimensions of the bottom surface of the punch 1 (in this embodiment, the diameter of the bottom surface of the punch 1). Here, the "length L of the protrusion 15" refers to the shortest distance along the axial direction between one end 111 of the shank 11 and a tip end 151 of the protrusion 15 located on the opposite side of the shank 11.

[0013] Furthermore, in this embodiment, the shape of the protrusion 15 is a right circular cone. That is, the tip 151 of the protrusion 15 is located on the central axis O. A perpendicular line drawn from the tip 151 of the protrusion 15 to the bottom surface of the protrusion 15 passes through the center of gravity of the bottom surface of the protrusion 15 (in this embodiment, the center of the bottom surface of the protrusion 15). Therefore, in this embodiment, the protruding direction of the protrusion 15 coincides with the axial direction, and the orthogonal direction perpendicular to the axial direction coincides with the radial direction of the bottom surface of the protrusion 15.

[0014] The die 2 includes a support surface 2a that supports the workpiece W, a recess 20 that receives the workpiece W pressed by the punch 1 and the punch 1, and a cutting blade (not shown) for cutting the workpiece W pressed by the punch 1. The support surface 2a contacts the second surface W2 of the workpiece W. In this embodiment, the recess 20 is a bottomed hole that is open on the support surface 2a side and is formed by an inner wall surface 21i and a bottom surface 20i.

[0015] A predetermined clearance C (gap) is provided between the punch 1 and the die 2. The "clearance C" referred to here refers to the gap formed between the inner wall surface 21i of the recess 20 and the outer surface 11i of the shank 1 of the punch 1 when the punch 1 is housed in the recess 20 of the die 2. In other words, the clearance C is the shortest distance between the inner wall surface 21i of the recess 20 and the outer surface 11i of the shank 11 in the perpendicular direction.

[0016] The work holder 8 is a member for preventing displacement of the workpiece W placed on the recess 20 of the die 2. The work holder 8 is, for example, rod-shaped. The work holder 8 has a contact surface 8a that comes into contact with the workpiece W. The contact surface 8a comes into contact with the first surface W1 of the workpiece W. The work holder 8 is configured to be movable in the axial direction, for example, by a lifting device (not shown). During processing of the workpiece W, the contact surface 8a of the work holder 8 comes into contact with a portion of the workpiece W, allowing the press processing device 10 to move the punch 1 toward or away from the workpiece W in a stable posture.

[0017] The control device 19 applies a driving force to and controls each of the components of the press working apparatus 10 described above. Fig. 1 shows a representative schematic diagram of some of the electrical connections among the components of the press working apparatus 10 that are electrically connected to and controlled by the control device 19.

[0018] The lifting device 18 moves the punch 1 in an approaching direction D1 and a separating direction D2, which is the opposite direction to the approaching direction D1, in response to a lifting command from the control device 19. The approaching direction D1 is the direction in which the punch 1 and the workpiece W approach each other. The separating direction D2 is the direction in which the punch 1 and the workpiece W move away from each other.

[0019] 2 is a flowchart showing a press working method. In this embodiment, the press working device 10 punches out the workpiece W by executing a first contact step (step S1), a second contact step (step S2), and a cutting step (step S3) in this order. In the punching process, the workpiece W is broken by pressing with the punch 1, thereby forming a hole in the workpiece W. In this embodiment, a case will be described in which the punching process is performed in a state in which the flat workpiece W is horizontal (0 degrees), that is, in a state in which the workpiece W is arranged along the orthogonal direction.

[0020] As shown in FIG. 2, first, a first contact step (step S1) is executed. The first contact step (step S1) is a step of bringing the tip 151 of the protrusion 15 into contact with the workpiece W in the arrangement state in which the workpiece W is placed on the recess 20 of the die 2 shown in FIG. 1. Specifically, in the arrangement state in which the workpiece W is placed on the recess 20 of the die 2, the control device 19 sends a descending command to the lifting device 18 to move the punch 1 in the approach direction D1. As a result, the lifting device 18 moves the punch 1 in the approach direction D1, so that the tip 151 of the protrusion 15 and the workpiece W come into contact at one point.

[0021] 2, after the first contact step (step S1), a second contact step (step S2) is performed. The second contact step (step S2) is a step of pressing the punch 1 toward the recess 20 to bring one end 111 of the shaft 11 into contact with the workpiece W.

[0022] Fig. 3 is a diagram for explaining the details of the second contact step (step S2). Fig. 3 chronologically illustrates the states of the stamping apparatus 10 and the workpiece W at each point in time from the start to the end of the second contact step (step S2). Specifically, Fig. 3 schematically illustrates cross sections of the stamping apparatus 10 and the workpiece W from the start of the second contact step (step S2), through the first and second elapsed points, to the end of the second contact step (step S2).

[0023] The start point of the second contact step (step S2) coincides with the end point of the first contact step (step S1). That is, at the start point of the second contact step (step S2), the tip end 151 of the protrusion 15 is in contact with the workpiece W at one point (hereinafter referred to as the first contact state). Here, the control device 19 continues to lower the lifting device 18 until the end point of the cutting step (step S3), that is, until the workpiece W is punched and cut. This presses the punch 1 toward the recess 20 of the die 2.

[0024] 3 , when the punch 1 is pressed against the recess 20 of the die 2 while the tip 151 of the protrusion 15 is in contact with the workpiece W, the workpiece W extends from the tip 151 of the protrusion 15 as a starting point. In other words, the workpiece W is bent and deformed as if being pushed into the recess 20 from the contact portion WC with the tip 151 of the protrusion 15 as a starting point. As a result, the distorted portion WD of the workpiece W that has been distorted by the pressing is accommodated in the recess 20 of the die 2.

[0025] At this time, tensile stress F is generated inside the workpiece W due to the pressing force of the punch 1. FIG. 3 schematically illustrates the direction of action of the main tensile stress F generated inside the workpiece W. The direction of action of the tensile stress F generated inside the workpiece W coincides with the direction in which the workpiece W extends. The tensile stress F generated inside the workpiece W is a first direction component along the orthogonal direction, and includes a first direction component along the workpiece W and a second direction component along the axial direction. Hereinafter, of the tensile stress F generated inside the workpiece W by pressing starting from the tip 151 of the protrusion 15, the first direction component will be referred to as first tensile stress F1. Furthermore, of the tensile stress F generated inside the workpiece W by pressing starting from the tip 151 of the protrusion 15, the second direction component will be referred to as second tensile stress F2.

[0026] FIG. 4 is a graph G that virtually represents the relationship between the amount of strain ε of the workpiece W and the tensile stress F. Each graph G in FIG. 4 is a so-called stress-strain curve that shows the relationship between the tensile stress F and the amount of strain ε of the workpiece W that changes in conjunction with the tensile stress F. FIG. 4 illustrates the relationship between the amount of strain ε of the workpiece W and the tensile stress F at each time point in the second contact process (step S2) shown in FIG. 3 and at the end of the cutting process (step S3), separated into a first direction component and a second direction component. The horizontal axis of each graph G represents the amount of strain ε of the workpiece W. The vertical axis of each graph G represents the magnitude of the tensile stresses F1 to F3 in each directional component. The end point of each graph is the breaking point X at which the workpiece W breaks. In FIG. 4, the amount of strain ε of each directional component at each time point is plotted on graph G. At the start of the second contact process (step S2), both the tensile stress F and the amount of strain ε are zero. In addition, since the main component of the workpiece W to be processed in this disclosure is aluminum, it is assumed that no clear yield point appears on the stress-strain curve, and therefore the yield point is omitted from the illustration of each graph G in Figure 4.

[0027] At the first elapsed time point, the workpiece W is pressed by the punch 1 in a first contact state. In other words, at the first elapsed time point, the plate-shaped workpiece W is stretched in a state in which a load is applied to one point on the workpiece W by the pressing of the punch 1. Therefore, at the first elapsed time point, it is considered that the workpiece W stretches more in the perpendicular direction than in the axial direction. Therefore, at the first elapsed time point, it is considered that the first tensile stress F1 is greater than the second tensile stress F2 (hereinafter referred to as the first stress state). Note that at the first elapsed time point, neither the first tensile stress F1 nor the second tensile stress F2 has reached the breaking point X.

[0028] As shown at the second elapsed time point in FIG. 3, by continuing to press the punch 1 against the workpiece W at the first elapsed time point, the workpiece W is further deformed. At the second elapsed time point, the workpiece W is still pressed by the punch 1 in the first contact state. Therefore, it is considered that the first stress state is maintained at the second elapsed time point. Furthermore, since the second elapsed time point is later than the first elapsed time point, the strain amount ε of the workpiece W is larger than at the first elapsed time point. Therefore, as shown in FIG. 4, it is considered that both the first tensile stress F1 and the second tensile stress F2 at the second elapsed time point are larger than the first tensile stress F1 and the second tensile stress F2 at the first elapsed time point. Note that at the second elapsed time point, neither the first tensile stress F1 nor the second tensile stress F2 has reached the breaking point X.

[0029] As shown at the end of FIG. 3 , by continuing to press the punch 1 against the workpiece W at the second elapsed time point, the one end 111 of the shank 11 and the workpiece W come into contact. In this embodiment, since the shank 11 has a cylindrical shape, the load N is applied to the workpiece W in a generally circular pattern. At this time, the workpiece W has not yet broken. In other words, the one end 111 of the shank 11 and the workpiece W can come into contact before the first tensile stress F1 reaches the breaking point X. Then, the workpiece W is pressed into the recess 20 by both the tip 151 of the protrusion 15 and the one end 111 of the shank 11. As a result, in addition to the first tensile stress F1 and the second tensile stress F2, a tensile stress F3 is generated inside the workpiece W by pressing from the one end 111 of the shank 11 as a starting point, the tensile stress F3 having a second directional component (hereinafter referred to as the third tensile stress F3). Therefore, at the time when one end 111 of the shaft portion 11 comes into contact with the workpiece W, i.e., at the end of the second contact step (step S2), the tensile stress F related to the second direction component is equal to the sum of the second tensile stress F2 and the third tensile stress F3. As a result, after the end of the second contact step (step S2), it is considered that a state will be reached in which the tensile stresses F2 and F3 (second tensile stress F2 and third tensile stress F3) of the second direction components are larger than the tensile stress F1 (first tensile stress F1) of the first direction component (hereinafter referred to as the second stress state).

[0030] As shown in FIG. 2, the cutting step (step S3) is performed after the second contact step (step S2). The cutting step (step S3) is a step of punching out the workpiece W by pressing the punch 1 toward the recess 20 of the die 2 in a state in which two points, the tip 151 of the protrusion 15 and one end 111 of the shaft 11, are in contact with the workpiece W (hereinafter referred to as the second contact state). In other words, the cutting step (step S3) is a step of breaking the workpiece W and forming a hole in the workpiece W by further pressing the punch 1 toward the recess 20 in a state in which a first tensile stress F1, a second tensile stress F2, and a third tensile stress F3 are generated inside the workpiece W. The start point of the cutting step (step S3) and the end point of the second contact step (step S2) coincide with each other.

[0031] FIG. 5 is an enlarged view of region R in FIG. 3. FIG. 5 schematically illustrates the state of the workpiece W immediately before it breaks during the cutting process (step S3). At the start of the cutting process (step S3), none of the tensile stresses F1 to F3 shown in FIG. 4 have reached the breaking point X. That is, at the start of the cutting process (step S3), the workpiece W is in a state where the tensile stress F generated inside the workpiece W and the reaction force FR against the tensile stress F are in balance (hereinafter referred to as an equilibrium state), as shown in FIG. 5. Then, during the cutting process (step S3), the workpiece W in the second stress state is further pressed by the punch 1, causing a crack WS to form between the first surface W1 and the second surface W2 of the workpiece W. At this time, as shown in FIG. 4, the second-direction components of the tensile stresses F2 and F3 are considered to be greater than the first-direction component of the tensile stress F1. Therefore, the crack WS is likely to propagate in a direction dominated by the second-direction component, as shown in FIG. 5. In this way, as shown in FIG. 4, the tensile stresses F2 and F3 of the second directional components can reach the breaking point X before the tensile stress F1 of the first directional component reaches the breaking point X, thereby breaking the workpiece W. In other words, by further pressing the workpiece W in the second stress state, the direction in which the crack WS generated between the first surface W1 and the second surface W2 of the workpiece W extends can be made to be mainly in the axial direction. This allows the workpiece W to be punched out by plastic deformation mainly in the axial direction, thereby preventing the formation of a secondary shear plane on the cut surface of the workpiece W. This prevents the cutting edge of the punch 1 from rubbing against the cut surface of the workpiece W, thereby reducing the amount of chips generated.

[0032] FIG. 6 is a diagram showing a punching mode using a conventional punch 91. The conventional punch 91 is a comparative example of the punch 1 (FIG. 1) in this embodiment, and is a punch formed only by a shank 11 without a protrusion 15. In the conventional punch 91, the cutting edge is provided, for example, at one end 911 that contacts the workpiece W. When the punch 1 and the workpiece W are in planar contact with each other, i.e., when the punch 1 does not have a protrusion 15 (the angle α between the generatrix direction and the perpendicular direction is 0 degrees), a portion WD2 of the workpiece W corresponding to the distorted portion WD (FIG. 3) shown in FIG. 3 falls into the recess 20 of the die 2. Then, by pressing the workpiece W with the punch 1, the crack WS propagates in a convex shape. As a result, the workpiece W is not cut all at once, but is broken partway in the axial direction. Then, by further pressing the workpiece W with the punch 1, the cutting edge of the punch 1 scrapes off the convex portion WB, cutting the workpiece W. That is, if the punch 1 does not have the protrusion 15, a secondary shear plane is likely to be formed, and the cutting edge of the punch 1 is likely to rub against the cut surface of the workpiece W. Therefore, if the punch 1 does not have the protrusion 15, chips WG are likely to be generated, and adhesion is likely to occur.

[0033] Furthermore, even if the punch 1 has a protrusion 15, if the tip 151 of the protrusion 15 has a flat shape, the pressing force of the tip 151 is insufficient, i.e., the workpiece W comes into contact with the one end 111 of the shank 11 while the deformation of the workpiece W is small. "When the tip 151 of the protrusion 15 has a flat shape" refers to, for example, a case where the protrusion 15 is configured with a curved portion that protrudes from the one end 111 of the shank 11 in a convex curved shape with a predetermined curvature, and a flat portion that is connected to the curved portion and has a predetermined area. In this way, when the tip 151 of the protrusion 15 has a flat shape, the behavior is similar to that of the machining mode using the conventional punch 91, and it may be difficult to suppress the generation and adhesion of chips WG.

[0034] In contrast to this, as in the punch 1 of this embodiment (FIG. 1), for example, by setting the angle α between the generatrix direction and the orthogonal direction to 9 degrees or more, the punch 1 and the workpiece W can be easily brought into contact in a shape closer to a point rather than a planar shape. This makes it possible to more reliably deform the workpiece W by the tip 151 of the protrusion 15, and then bring the one end 111 of the shank 11 of the workpiece W into contact with the workpiece W. This makes it even easier to plastically deform the workpiece W in the axial direction.

[0035] Furthermore, if the tensile stress F1 of the first directional component reaches the breaking point X before the tensile stresses F2 and F3 of the second directional components, plastic deformation occurs mainly in the orthogonal direction, which may result in, for example, burrs. If the burrs come into contact with the cutting edge of the punch 1, the burrs may be scraped off and fall off.

[0036] In contrast to this, as in the punch 1 of this embodiment (FIG. 1), for example, by setting the angle α between the generatrix direction and the orthogonal direction to 26 degrees or less, it is possible to more reliably prevent the tensile stress F1 of the first directional component from reaching the breaking point X before the tensile stresses F2 and F3 of the second directional components. This makes it possible to more reliably cause plastic deformation mainly in the axial direction when punching the workpiece W.

[0037] In actual production, it is common to use a workpiece W with an oil film formed on its outer surface in order to further reduce frictional resistance. On the other hand, it has been confirmed that when a punch 1 is used in which the angle α between the generatrix direction and the orthogonal direction is set to be 9 degrees or more and 26 degrees or less, adhesion can be more reliably suppressed even for a degreased workpiece W, i.e., a workpiece W in which the oil film has been removed and frictional resistance is likely to occur. Therefore, it is more preferable that the angle α between the generatrix direction and the orthogonal direction be 9 degrees or more and 26 degrees or less.

[0038] According to the first embodiment, as shown in FIG. 1 , a punch 1 for punching an aluminum-based workpiece W includes a shank 11 having one end 111 and the other end 117 and extending in the axial direction, and a protrusion 15 protruding from the one end 111 side of the shank 11. The protrusion 15 is a cone shape with the shank 11 side as the bottom surface, and the generatrix 155 of the protrusion 15 is inclined with respect to the axial direction so that the tip 151 of the protrusion 15 overlaps with the bottom surface when projected axially onto the bottom surface. With this configuration, as shown in FIG. 3 , in the process of pressing the punch 1 against the workpiece W, the tip 151 of the protrusion 15 can be brought into contact with the workpiece W, and then the one end 111 of the shank 11 can be brought into contact with the workpiece W. In other words, the workpiece W is pressed in two stages: by the tip 151 of the protrusion 15 and by the one end 111 of the shank 11. As a result, as shown in FIG. 4, the tensile stresses F2 and F3 of the second directional components along the axial direction can reach the breaking point X before the tensile stress F1 of the first directional component along the orthogonal direction perpendicular to the axial direction reaches the breaking point X, thereby breaking the workpiece W. In other words, the workpiece W can be easily plastically deformed in the axial direction. This can prevent a secondary shear plane from being formed on the cut surface of the workpiece W, thereby preventing the cutting edge of the punch 1 from rubbing against the cut surface of the workpiece W during punching. This can reduce the amount of chips WG generated from the workpiece W when the cut surface of the workpiece W is scraped by the cutting edge of the punch 1.

[0039] Moreover, according to the first embodiment, it is possible to prevent a part of the workpiece W from adhering to the punch 1. This makes it possible to prevent the adhered material from the workpiece W adhering to the punch 1 from later falling off. Furthermore, it is possible to prevent the punch 1 from being worn down due to adhesion, thereby reducing the possibility of the punch 1 being damaged.

[0040] Furthermore, according to the first embodiment, the possibility of damaging the punch 1 can be reduced, and therefore it is possible to avoid punching the workpiece W using a punch 1 that has been damaged by wear due to adhesion, etc. This reduces the possibility of the surface of the molded product being scratched or deformed.

[0041] Furthermore, according to the first embodiment, it is possible to reduce the amount of chips WG generated and also reduce the amount of adhered material that falls off from the punch 1. This makes it possible to prevent the generated chips WG and adhered material from adhering to the surface of the molded product, thereby further reducing the possibility that the surface of the molded product will be damaged or deformed.

[0042] Furthermore, according to the first embodiment, it is possible to reduce the amount of chips WG generated and suppress adhesion without applying a coating such as DLC to the surface of the punch 1 to reduce frictional resistance. Therefore, the punch 1 can be used continuously without the need for adjustment work for distortion that occurs in the punch 1. Furthermore, it is possible to reduce the effort and cost of repainting when the coated DLC peels off from the surface of the punch 1.

[0043] Furthermore, according to the first embodiment, when the punch 1 in which the angle α between the generatrix direction and the orthogonal direction is set to be 9 degrees or more and 26 degrees or less is used, adhesion can be suppressed even for a degreased workpiece W. In other words, by performing punching using the punch 1 in which the angle α between the generatrix direction and the orthogonal direction is set to be 9 degrees or more and 26 degrees or less, adhesion can be suppressed even under conditions that are more severe than those during actual production. Therefore, by performing punching of the workpiece W using the punch 1 in which the angle α between the generatrix direction and the orthogonal direction is set to be 9 degrees or more and 26 degrees or less, adhesion can be more reliably suppressed.

[0044] Furthermore, when punching a workpiece W made of a metal material (for example, a metal material mainly composed of aluminum) that is less hard than metal materials such as steel, the surface of the formed product is easily scratched and deformed due to the generation and adhesion of chips WG. In contrast, according to the first embodiment, when punching a workpiece W made mainly of aluminum, the amount of chips WG generated can be reduced and adhesion can be suppressed. This makes it possible to suppress a decrease in the quality of the formed product obtained by punching a workpiece W made of a metal material that is less hard than metal materials such as steel.

[0045] Furthermore, according to the first embodiment, the shape of the protrusion 15 is a cone. As a result, in the process of pressing the punch 1 against the workpiece W, one end 111 of the shank 11 comes into contact with the workpiece W in a generally annular shape. In this way, the punch 1 can apply a load to the workpiece W more uniformly than when the shape of the protrusion 15 is a pyramid. This reduces the possibility of burrs or the like being formed that protrude from the cut surface of the workpiece W. Therefore, it is possible to reduce the possibility that the generated burrs will come into contact with the cutting edge of the punch 1 and fall off.

[0046] B. Second embodiment: FIG. 7 is a diagram illustrating the inclination angle β of the workpiece W in the second embodiment. When the workpiece W has a curvature, it may be difficult to arrange the workpiece W along the orthogonal direction, as shown in FIG. 1. Therefore, in this embodiment, a case will be described in which punching is performed with the workpiece W inclined at a predetermined inclination angle β from the orthogonal direction. The inclination angle β of the workpiece W is the inclination angle of the workpiece W with respect to the orthogonal direction that is perpendicular to the axial direction along the central axis O. Specifically, the inclination angle β of the workpiece W is an acute angle formed between the orthogonal direction and the extension direction of the workpiece W (in this embodiment, for example, the direction along the second surface W2). In this embodiment, too, the axial direction coincides with the direction of gravity. Therefore, the orthogonal direction in this embodiment coincides with the horizontal direction.

[0047] The flow of the press working method is the same as that of the first embodiment shown in Fig. 2. Also in this embodiment, the punch 1 has a cylindrical shank 11 extending in the axial direction and a protrusion 15 having a right circular cone shape protruding from one end 111 of the shank 11. The same steps and configurations as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0048] Regarding the shape of the protrusion 15, the angle α (FIG. 1) between the generatrix direction along the generatrix 155 of the protrusion 15 and the orthogonal direction is preferably determined, for example, according to the inclination angle β of the workpiece W. For example, when the inclination angle β of the workpiece W is 2 degrees, the angle α between the generatrix direction and the orthogonal direction is preferably 18 degrees or more and 26 degrees or less, and even more preferably 18 degrees. Furthermore, when the inclination angle β of the workpiece W is 4 degrees, the angle α between the generatrix direction and the orthogonal direction is preferably 18 degrees or more and 26 degrees or less, and even more preferably 26 degrees. In this way, the amount of chips WG generated and the probability of adhesion can be more reliably reduced.

[0049] 7, the shape of the die 2 may be shaped to conform to the inclination angle β of the workpiece W. In other words, the support surface 2a of the die 2 may be shaped to conform to the second surface W2 of the workpiece W. In this way, the stamping device 10 can move the punch 1 toward or away from the workpiece W in a more stable posture.

[0050] According to the second embodiment, by selecting the angle α between the generatrix direction and the orthogonal direction in accordance with the inclination angle β of the workpiece W, it is possible to reduce the amount of chips WG generated and suppress adhesion, even when punching is performed with the workpiece W inclined at the inclination angle β from the orthogonal direction. Therefore, even when it is difficult to arrange the workpiece W along the orthogonal direction, it is possible to perform punching satisfactorily without adjusting the arrangement of the workpiece W. This further improves the versatility of the punch 1 and avoids an increase in the amount of work required for punching.

[0051] Furthermore, according to the second embodiment, when the inclination angle β of the workpiece W is within a range of 0 to 4 degrees, by using a punch 1 in which the angle α between the generatrix direction and the orthogonal direction is 18 degrees or more and 26 degrees or less, it is possible to more reliably reduce the amount of chips WG generated and the probability of adhesion. In other words, when the inclination angle β of the workpiece W is within a range of 0 to 4 degrees, it is possible to use one type of punch 1 without preparing a punch 1 for each inclination angle β of the workpiece W, while more reliably reducing the amount of chips WG generated and the probability of adhesion. This simplifies the equipment required for punching the workpiece W.

[0052] C. Other Embodiments: C-1. Alternative embodiment 1: In the above embodiment, as shown in FIG. 1 , the shank 11 of the punch 1 has a cylindrical shape extending in the axial direction along the central axis O, and the protruding portion 15 of the punch 1 has a right circular cone shape with one end 111 of the punch 1 as the bottom surface. However, the present disclosure is not limited to this. The shape of the shank 11 of the punch 1 may be, for example, a rectangular column shape extending in the axial direction. Furthermore, the shape of the protruding portion 15 of the punch 1 may be a rectangular column shape. Even in such a form, in the process of pressing the punch 1 against the workpiece W, the tip 151 of the protruding portion 15 can be brought into contact with the workpiece W, and then the one end 111 of the shank 1 can be brought into contact with the workpiece W.

[0053] C-2. Alternative embodiment 2: In the above embodiment, as shown in FIG. 1 , the shape of the protrusion 15 is a right cone shape. However, the present disclosure is not limited to this. The shape of the protrusion 15 may be an oblique cone shape. When the shape of the protrusion 15 is an oblique cone shape, a perpendicular line drawn from the tip 151 of the protrusion 15 to the bottom surface of the protrusion 15 does not pass through the center of gravity of the bottom surface of the protrusion 15. In other words, the tip 151 of the protrusion 15 does not need to be located on the central axis O. Even when the shape of the protrusion 15 is an oblique cone shape, the angle α between the generatrix direction and the perpendicular direction can be determined depending on the inclination angle β of the workpiece W ( FIG. 7 ), the processing conditions, etc. The “processing conditions” referred to here include, for example, the thickness LW of the workpiece W, the magnitude of the load N applied to the workpiece W by the punch 1, the composition of the workpiece W, and the hardness of the workpiece W. Even in this configuration, during the process of pressing the punch 1 against the workpiece W, the tip 151 of the protrusion 15 can be brought into contact with the workpiece W, and then one end 111 of the shaft 11 can be brought into contact with the workpiece W.

[0054] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features of the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0055] 1...punch, 2...die, 2a...support surface, 8...workpiece holder, 8a...contact surface, 10...pressing device, 11...shaft portion, 11i...outer surface, 15...protrusion portion, 18...lifting device, 19...control device, 20...recess, 20i...bottom surface, 21i...inner wall surface, 91...conventional punch, 111...one end portion, 117...other end portion, 151...tip portion, 155...generator bar, 911...one end portion of conventional punch, C...clearance, D1...approach direction, D2...separation direction, F...tensile stress, F1...first tensile stress, F2...second tensile stress, F3...third tensile stress, FR...reaction force, G...graph, L...length, O...central axis, W...workpiece, W1...first surface, W2...second surface, WB...convex part, WC...contact part, WD...distorted part, WD2...part corresponding to the distorted part, WG...chip, WS...crack, X...fracture point, α...angle, β...inclination angle, ε...amount of distortion

Claims

1. A punch for punching a workpiece whose main component is aluminum, a shaft portion having one end and another end and extending in an axial direction along a central axis; a protrusion protruding from the one end, the shape of the protrusion is an oblique cone shape with the shank side as the bottom surface, and the generatrix of the protrusion is inclined with respect to the axial direction so that when a tip end of the protrusion is projected onto the bottom surface along the axial direction, the tip end overlaps the bottom surface without passing through the center of gravity of the bottom surface, The angle formed by the generatrix direction along the generatrix of the protrusion and the orthogonal direction perpendicular to the axial direction is an angle corresponding to the inclination angle of the workpiece with respect to the orthogonal direction, A punch wherein, when the inclination angle of the workpiece is within a range of 0 degrees to 4 degrees, the angle formed between the generatrix direction and the orthogonal direction is 18 degrees or more and 26 degrees or less.

2. 2. The punch according to claim 1, The punch, wherein the oblique cone shape is an oblique circular cone shape.

3. A press processing device that punches out a workpiece made primarily of aluminum, The punch according to claim 1 or 2; a die having a recess capable of receiving the punch; A press processing device, wherein the shape of the die is a shape that follows the inclination angle of the workpiece.

4. A press working method for punching an aluminum-based workpiece using a punch and a die having a recess capable of receiving the punch, comprising: The punch is a shaft portion having one end and another end and extending in an axial direction along a central axis; a protrusion protruding from the one end, the shape of the protrusion is an oblique cone shape with the shank side as the bottom surface, and the generatrix of the protrusion is inclined with respect to the axial direction so that when a tip end of the protrusion is projected onto the bottom surface along the axial direction, the tip end overlaps the bottom surface without passing through the center of gravity of the bottom surface, The angle formed by the generatrix direction along the generatrix of the protrusion and the orthogonal direction perpendicular to the axial direction is an angle corresponding to the inclination angle of the workpiece with respect to the orthogonal direction, When the inclination angle of the workpiece is within a range of 0 degrees to 4 degrees, the angle formed by the generatrix direction and the orthogonal direction is 18 degrees or more and 26 degrees or less, The press working method includes: a first contact step of contacting the tip end portion of the protrusion, which is located on the opposite side to the shaft portion side, with the workpiece in an arrangement state in which the workpiece is arranged on the recessed portion in a state inclined by the inclination angle with respect to the orthogonal direction; a second contact step of pressing the punch toward the recessed portion after the first contact step to bring the one end of the shaft portion into contact with the workpiece; a cutting step of punching out the workpiece by further pressing the punch toward the recess after the second contact step.

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