Mold, mold manufacturing method, and mold inspection method

Abstract

Provided is a mold (10) comprising a die (20) and a punch (60), wherein: the die (20) is provided with a die side wall part (22) and a die flange part (24); when a portion where the die flange part (24) and the die side wall part (22) intersect is referred to as a die shoulder part (27) and a portion of the die (20) excluding the die shoulder part (27) is referred to as a die body part (28), the boundary between the die body part (28) and the die shoulder part (27) is a straight line (31), the outer surface of the die shoulder part (27) is a curved line (32) that protrudes outward, one end of the straight line (31) and one end of the curved line (32) are connected, and the other end of the straight line (31) and the other end of the curved line (32) are connected; and the die shoulder part (27) is constituted from a die hardened part (35) having a higher hardness than the die body part (28).

Description

Mold, Mold Manufacturing Method, and Mold Inspection Method

[0001] The present invention relates to a mold attached to a press machine.

[0002] For example, in a vehicle body manufacturing line, a metal plate called a blank material is plastically processed using a press machine. Through plastic processing, a molded product with a desired three-dimensional shape is obtained. A mold is used for this plastic processing.

[0003] Although a mold is made of a material harder than a metal plate, when attempting to manufacture a large number of molded products, the surface gradually wears. When this wear progresses to a certain depth, the mold is repaired or replaced with a new one. During the repair or replacement of the mold, plastic processing halts. This halt reduces the productivity of the molded product. The shorter the mold life (the period from replacement to the next replacement), the lower the productivity, and the longer the mold life, the higher the productivity. Therefore, a technique for extending the mold life is required.

[0004] One technique for extending the mold life is known to form a hardened layer harder than the mold on the surface of the mold (see, for example, Patent Document 1 (Figure 2)).

[0005] Patent Document 1 will be described based on the following figure. Figure 19 is a cross-sectional view of a conventional mold. As shown in Figure 19, the mold 200 consists of a mold body part 201 called a base part and a hardened layer 202 called a surface layer. The hardened layer 202 is made of a metal material harder than the mold body part 201. The hardened layer 202 is formed over the entire molding surface of the mold body part 201.

[0006] According to Patent Document 1, since the hardened layer 202 is hard, the mold 200 has the advantage of a longer life and increased productivity of the molded product.

[0007] However, the formation cost when forming the hardened layer 202 on the mold body part 201 is approximately proportional to the size of the volume of the hardened layer 202. In Patent Document 1, since the hardened layer 202 is formed over the entire molding surface of the mold body part 201, the volume of the hardened layer 202 becomes large, and the formation cost of the hardened layer 202 increases. That is, the technique of Patent Document 1 has the drawback of increasing the manufacturing cost of the mold 200.

[0008] In recent years, there has been a demand for cost reduction in vehicles, which in turn includes a demand for cost reduction in the vehicle body, and as part of that, a demand for reduction in the manufacturing cost of the mold 100.

[0009] Japanese Patent Publication No. 2016-137496

[0010] The objective of this invention is to provide a technology that can reduce the manufacturing cost of molds.

[0011] The invention according to claim 1 is a die and a punch, which plastically deform a metal plate into a hat cross-sectional shape, wherein the die comprises a die side wall portion extending along the movement axis of the punch, a die flange portion extending from the die side wall portion in a direction intersecting the movement axis of the punch, and a die top portion located behind the die side wall portion, the punch comprises a punch side wall portion facing the die side wall portion, a punch flange portion facing the die flange portion, and a punch top portion facing the die top portion, the portion where the die flange portion and the die side wall portion intersect is called the die shoulder portion, and the portion of the die excluding the die shoulder portion is called the die body portion, in cross-sectional view, the boundary between the die body portion and the die shoulder portion is a straight line, the outer surface of the die shoulder portion is a curved line that protrudes outward, one end of the straight line and one end of the curved line are connected, and the other end of the straight line and the other end of the curved line are connected, The die shoulder portion is composed of a die hardened portion that has a higher hardness than the die body portion.

[0012] The term "hat cross-section" refers to a cross-sectional shape similar to that of a hat-shaped steel as defined in JIS G 3350 Light Gauge Steels for General Structure.

[0013] In the invention according to claim 1, the die shoulder of the mold is a part that is always worn when a flat metal plate is bent into a hat cross-sectional shape, and is also the part that is subjected to the strongest pressure. Since the hardened part is limited to this die shoulder, the volume of the hardened part becomes very small. Because the volume of the hardened part is very small, the cost of forming the hardened part becomes very small. When the cost of forming the hardened part is small, the manufacturing cost of the mold decreases. In other words, the present invention provides a technology that can reduce the manufacturing cost of molds.

[0014] Furthermore, stress inevitably concentrates at the die shoulder. In the invention according to claim 1, the outer surface of the die shoulder is a curved line that protrudes outward. Since the corner portion is rounded, stress concentration is mitigated. As a result, the die of the present invention is effective and has a longer lifespan compared to conventional dies. In addition, the longer lifespan eliminates the need for unnecessary manufacturing, which not only reduces costs but also provides a manufacturing process with a lower environmental impact.

[0015] Incidentally, when a die consists of a die body and a die shoulder, the boundary between the die body and the die shoulder is determined by the design. This determination is important and requires advanced technology. However, in the invention according to claim 1, since the outer surface of the die shoulder is a curved line, the boundary is uniquely determined simply by connecting one end of the curved line with the other end of the curved line with a straight line. As a result, the boundary between the die body and the die shoulder can be easily determined based on the mold data. Since the shape is easily determined, advanced technology is not required for mold design.

[0016] (a) is a cross-sectional view of the mold according to the present invention, and (b) is an enlarged view of part b in (a). (a) to (e) are diagrams illustrating the method of manufacturing the die. This is a diagram showing an example of a build-up welding apparatus. (a) to (c) are diagrams illustrating the operation of the mold according to the present invention. (a) to (c) are diagrams illustrating a first modified example of the mold according to the present invention. (a) and (b) are diagrams illustrating further modified examples of the first hardened coating section. (a) and (b) are diagrams illustrating a second modified example of the mold according to the present invention. (a) to (c) are diagrams illustrating a third modified example of the mold according to the present invention. (a) to (e) are diagrams illustrating a fourth modified example of the mold according to the present invention, (c) is a view along the 9c-9c arrow in Figure 8, (d) is a cross-sectional view along the d-d line in Figure 9, and (e) is a cross-sectional view along the e-e line in Figure 9. (a) and (b) are diagrams illustrating a modified example of the third hardened coating section. (a) and (b) are diagrams illustrating a fifth modified example of the mold according to the present invention. This is a diagram illustrating a sixth modified example of the mold according to the present invention. This figure illustrates a seventh modification example of the mold according to the present invention. Figures (a) to (h) illustrate the wire frame and ruled surface. Figures (a) and (b) are cross-sectional views of the main mold and partial mold, figure (b) is a cross-sectional view of the partial mold, and figure (c) is a figure illustrating an example of a mold inspection device. This figure illustrates a modification example of the die hardening section. This figure illustrates a further modification example of the die hardening section. This figure illustrates a further modification example of the die hardening section. This is a cross-sectional view of a conventional mold.

[0017] Preferred embodiments of the present invention will be described below with reference to the attached drawings.

[0018] [Mold] As shown in Figure 1(a), the mold 10 consists of a die 20 and a punch 60. The mold 10 can be used to plastically deform a flat metal plate 12 into a hat cross-sectional shape.

[0019] [Die] The die 20 includes a die side wall portion 22 extending along the punch's moving axis 61, a die flange portion 24 extending from the die side wall portion 22 in a direction intersecting the punch's moving axis 61, and a die top portion 26 located at the back 25 of the die side wall portion 22.

[0020] [Punch] The punch 60 includes a punch side wall portion 62 facing the die side wall portion 22, a punch flange portion 64 facing the die flange portion 24, and a punch top portion 66 facing the die top portion 26.

[0021] [Die shoulder and die body] Figure 1(b) is an enlarged view of part b in Figure 1(a). As shown in Figure 1(b), the part where the die flange 24 and the die side wall 22 intersect is called the die shoulder 27. The part of the die 20 excluding the die shoulder 27 is called the die body 28. In other words, the die 20 is composed of the die body 28 and the die shoulder 27.

[0022] In a cross-sectional view, the boundary between the die body 28 and the die shoulder 27 is a straight line 31. The outer surface of the die shoulder 27 is a curved line 32 that protrudes outward. One end of the straight line 31 and one end of the curved line 32 are connected via a first inflection point 33, and the other end of the straight line 31 and the other end of the curved line 32 are connected via a second inflection point 34.

[0023] [Die Design] The procedure for designing the die 20 is explained below. First, a curved line 32 is defined. Next, the die side wall portion 22 is extended from one end of this curved line 32, and the die flange portion 24 is extended from the other end of the curved line 32. Finally, the first inflection point 33 and the second inflection point 34 are connected by a straight line 31.

[0024] As a result, the boundary between the die body 28 and the die shoulder 27 can be easily defined, the design of the die hardening portion 35 of the die 20 becomes extremely easy, and the design cost of the mold 10 having the die hardening portion 35 can be reduced.

[0025] [Die Hardened Section] The die shoulder 27 is composed of a die hardened section 35 which has a higher hardness than the die body 28. The material with high hardness is preferably high-speed tool steel or equivalent steel as specified in JIS G 4403. High-speed tool steel has a higher hardness than S50C after heat treatment, and an HRC of about 60 to 65 can be expected. This is because the higher the hardness, the better the wear resistance. HRC stands for Rockwell C scale hardness.

[0026] [Material of the die body] The material of the die body 28 is preferably carbon steel for machine structural use as specified in JIS G 4051 or equivalent carbon steel. Carbon steel for machine structural use is less expensive than high-speed tool steel, has flexible ductility, and has hardness (e.g., HRC25) that can withstand wear during press working even without heat treatment. S10C to S58C are standardized for carbon steel for machine structural use, but S50C, which has a carbon (C) component of 0.50%, is superior in terms of strength and hardness. S50C is more suitable for the die body 28.

[0027] [Die Manufacturing] The manufacturing method of the die 20 will be explained based on Figures 2(a) to (e). Figure 2(a) shows the first processing step. In this first processing step, the die material 41 is processed into a shape similar to the die 20 shown in Figure 1(b) to obtain the first intermediate product 42.

[0028] This first intermediate product 42 has a soft arched cross section 43 at its corner. This soft arched cross section 43 is the same shape as the die hardened section (Figure 1(b), reference numeral 35). Because it follows the shape of the die (Figures 1(a), (b), reference numeral 20), the data for the final product mold (Figure 1(a), reference numeral 10) can be used as is. Therefore, the manufacturing of the first intermediate product 42 becomes easier.

[0029] Figure 2(b) shows the second processing step. In this second processing step, the soft arched cross section 43 is removed from the first intermediate product 42. As a result, a second intermediate product 44 including the cut surface 44a can be obtained.

[0030] Figure 2(c) shows the third processing step. In this third processing step, a third intermediate product 46 is obtained by forming a build-up portion 45 on the cut surface 44a. The build-up portion 45 has the shape of the soft arched cross section 43 with excess material 45a added.

[0031] [Build-up welding] Build-up welding can be performed using arc welding with welding rods, or laser welding with welding powder (high-speed tool steel or equivalent steel powder, the same applies hereinafter). The latter (laser welding with welding powder) is more preferable. The welding powder is arranged neatly on the cut surface (ruled surface, described later) and melted with the heat of the laser (plasma arc heat). The amount of welding powder used can be optimized.

[0032] Compared to excessive use, the amount of welding powder used can be reduced, and the amount of carbon dioxide emitted can be reduced. Therefore, laser welding using welding powder enables environmentally friendly production (manufacturing) and is more preferable. Laser welding using welding powder will be discussed next.

[0033] [Welding apparatus] As shown in Figure 3, the welding apparatus 50 consists of, for example, a welding robot 52 equipped with a welding gun 51, a powder metering feeder 54 that supplies a predetermined amount of welding powder 53 to the welding gun 51, a high-voltage power supply 56 that supplies electrical energy to the welding gun 51 for the plasma jet 55 emitted by the welding gun 51, a gas container 58 that supplies argon gas for the shielding gas 57 emitted by the welding gun 51, and a control unit 59 that controls the welding robot 52, welding gun 51, powder metering feeder 54, high-voltage power supply 56 and gas container 58.

[0034] The control unit 59 supplies an appropriate amount of welding powder 53, argon gas, and electrical energy to the welding gun 51. A plasma jet 55, welding powder 53, and shielding gas 57 are ejected from the welding gun 51. This ejection causes the welding powder 53 to accumulate on the cut surface 44a.

[0035] The stacked welding powder 53 is sequentially melted by plasma heat. During this time, the shielding gas 57 prevents oxidation of the welding powder 53, and a sound build-up section 45 is formed.

[0036] Furthermore, there is no problem in using a multi-function processing machine such as a 3D (three-dimensional) printer. By using a multi-function processing machine, the manufacturing time can be shortened and hard materials can be laminated to form a hardened section. By using a multi-function processing machine, it becomes possible to automate the process of removing excess material 45a after the hardened section has been formed.

[0037] [Protruding portion] Preferably, as shown in Figure 2(d), the excess material 45a includes a protruding portion 45b that extends outward from the die body 28. The protruding length L of the protruding portion 45b may be approximately 0.1 to 5.0 mm.

[0038] Due to the presence of the protruding portion 45b, the boundary between the die hardened portion 35 and the die main body portion 28 in the fourth processing step shown in Fig. 2(e) can be finished into a smooth continuous surface without steps.

[0039] In addition, due to reasons such as insufficient amount of build-up, a V-shaped depression (notch) may occur at the boundary between the soft bow cross-sectional portion 43 and the outer surface of the die main body portion 28. This V-shaped notch will become a starting point for fatigue fracture if left unattended, which is not preferable. In this regard, by providing the protruding portion 45b, there is also an advantage that the occurrence of the notch can be more reliably prevented.

[0040] Fig. 2(e) shows the fourth processing step. In this fourth processing step, the die 20 is obtained by removing the surplus material 45a from the third intermediate product 46 shown in Fig. 2(c).

[0041] [Function of the Mold] The function of the mold 10 described above will be explained based on Figs. 4(a) to 4(c). Fig. 4(a) is a diagram showing the form at the start of pressing. As shown in Fig. 4(a), a metal plate 12 is placed on the punch 60. Then, the punch 60 and the die 20 are relatively moved. Although the punch 60 and the die 20 may be moved together, in this example, the punch 60 is stationary and the die 20 is moved toward the punch 60.

[0042] Fig. 4(b) is a diagram showing the form during pressing. As shown in Fig. 4(b), the punch top portion 66 of the punch 60 has entered the die side wall portion 22 of the die 20. As a result, the plastic processing of the metal plate 12 has started.

[0043] Fig. 4(c) is a diagram showing the form at the end of pressing. As shown in Fig. 4(c), the punch 60 has entered the die 20 sufficiently. The metal plate 12 has been sufficiently plastically processed. As a result, a molded product 13 having a hat cross-sectional shape is obtained.

[0044] From Fig. 4(b) to Fig. 4(c), due to the presence of the die hardened portion 35, the wear of the die 20 is suppressed. By suppressing the wear, the life of the die 20 can be extended.

[0045] Incidentally, in FIG. 4(c), the die main body portion 28 is softer than the die hardened portion 35. This is because wear resistance is not required for the die main body portion 28 more than the die hardened portion 35. The material cost of the die main body portion 28 can be reduced, and the material cost of the die 20 can be reduced.

[0046] However, when the wear of the die main body portion 28 in the die side wall portion 22 is larger than that of the die hardened portion 35, the following modification example is recommended.

[0047] [First modification example of the mold] Based on FIGS. 5(a) to 5(c), the first modification example of the mold 10 will be described. Note that FIG. 5(b) is an enlarged view of the b portion of FIG. 5(a), and FIG. 5(c) is a view showing a modification example of the first coating hardened portion 36.

[0048] As shown in FIG. 5(b), the first coating hardened portion 36 is embedded in the die side wall portion 22. One end of the first coating hardened portion 36 is connected to the die hardened portion 35.

[0049] [First coating hardened portion] The first coating hardened portion 36 is made of the same material as the die hardened portion 35 described above. The die side wall portion 22 is cut to a predetermined depth, build-up welding is performed on the cutting portion, and the surplus portion of the build-up welding is removed to obtain the first coating hardened portion 36. [[ID=1�]]

[0050] As shown in FIG. 5(a), the mold 10 is composed of a die 20 and a punch 60. In addition to the die hardened portion 35, the die 20 is provided with a first coating hardened portion 36. The hardness of the first coating hardened portion 36 is higher than that of the die main body portion 28. According to this first modification example, the wear resistance of the die 20 can be further enhanced.

[0051] In addition to the cross-sectional shape shown in FIG. 5(b), the first coating hardened portion 36 may have the cross-sectional shape shown in FIG. 5(c). That is, the first coating hardened portion 36 shown in FIG. 5(c) has a tapered shape in which the portion close to the die hardened portion 35 is thin and the portion away from the die hardened portion 35 is thick, and the thick portion bites into the die main body portion 28. Because it bites in, there is an advantage that the first coating hardened portion 36 is less likely to fall off from the die side wall portion 22 than in FIG. 5(b).

[0052] [Further Modification Examples of the First Hardened Film Section] Further modifications of the first hardened film section 36 are explained in Figure 6(a) and Figure 6(b), which is a cross-sectional view taken along the line b-b in Figure 6(a). As shown in Figure 6(b), the first hardened film section 36 may be a first projection 37 with an arc cross-section. That is, as shown in Figure 6(a), the first hardened film section 36 may be a first projection 37 extending along the moving axis 61 of the punch.

[0053] Since the first protrusion 37 is a projection, it can be added to the molding surface of the die 20 afterwards. This allows for minimizing the area of ​​hardened material on complex molding surfaces. Because it is minimal, it has the advantage of reducing the amount of expensive hard material used.

[0054] In Figures 4(b) and 4(c) described above, the edge of the metal plate 12 may come into contact with the punch flange portion 64 during the process from Figure 4(b) to Figure 4(c). When it is necessary to provide wear resistance to the punch flange portion 64, the second modification example described below is recommended.

[0055] [Second Modification Example of Mold] A second modification example of the mold 10 will be explained based on Figures 7(a) and 7(b). Note that Figure 7(b) is an enlarged view of part b of Figure 7(a).

[0056] As shown in Figure 7(a), the punch 60 has a second hardened coating portion 67 embedded in the punch flange portion 64. This second hardened coating portion 67 is made of the same material and formed in the same way as the first hardened coating portion (Figure 5(b), reference numeral 36). Therefore, the second hardened coating portion 67 has a higher hardness than the die body portion 28. The mold 10 consists of a die 20 and a punch 60. The die 20 includes a die hardened portion 35 and a first hardened coating portion 36. The punch 60 includes a second hardened coating portion 67.

[0057] As shown in Figure 7(b), the second hardened coating 67 exhibits wear resistance even when the edge of the metal plate 12 is rubbed. The punch 60 is protected by the second hardened coating 67.

[0058] [Third Modification Example of Mold] A third modification example of the mold 10 will be explained based on Figures 8(a) to 8(c). Figure 8(b) is an enlarged view of part b in Figure 8(a), and Figure 8(c) shows a modification example of the third coating hardening section 74.

[0059] As shown in Figure 8(b), the portion where the punch top portion 66 and the punch side wall portion 62 intersect is called the punch shoulder portion 71, and the portion of the punch 60 excluding the punch shoulder portion 71 is called the punch body portion 72. The boundary between the punch body portion 72 and the punch shoulder portion 71 is a straight line 31 in cross-sectional view. The outer surface of the punch shoulder portion 71 is a curved line 32 that protrudes outward in cross-sectional view. One end of the straight line 31 is connected to one end of the curved line 32, and the other end of the straight line 31 is connected to the other end of the curved line 32.

[0060] The punch shoulder portion 71 is composed of a punch hardening portion 73 which is harder than the punch body portion 72. A third coating hardening portion 74 which is harder than the punch body portion 72 is embedded in the punch side wall portion 62, and one end of this third coating hardening portion 74 is connected to the punch hardening portion 73.

[0061] The material of the punch body 72 may be the same as the material of the die body 28 described above. The material of the punch hardening part 73 may be the same as the material of the die hardening part 35 described above. The material of the third coating hardening part 74 may be the same as the material of the punch hardening part 73.

[0062] As shown in Figure 8(a), the mold 10 consists of a die 20 and a punch 60. The die 20 has a die hardening portion 35 and a first coating hardening portion 36. The punch 60 has a punch hardening portion 73 and a third coating hardening portion 74. According to this third modification example, both the wear resistance of the die 20 and the wear resistance of the punch 60 are improved.

[0063] Furthermore, as shown in Figure 8(c), the third hardened coating portion 74 has a tapered shape, being thin near the punch hardened portion 73 and becoming thicker as it moves away from the punch hardened portion 73, with the thicker portion biting into the punch body portion 72. Because it is biting in, the third hardened coating portion 74 is less likely to detach from the punch side wall portion 62 than in Figure 8(b), which is an advantage.

[0064] In Figure 8(b), the punch hardening portion 73 extends in the direction of the front and back of the drawing. When it is necessary to conserve hard material, the fourth modification described below is useful.

[0065] [Fourth Modification Example of the Mold] The fourth modification example will be explained based on Figures 9(a) to 9(e). Note that Figure 9(c) is a view taken along the 9c-9c arrow in Figure 8, and corresponds to a view from the die 20 side.

[0066] As shown in Figure 9(a), the molded product 13 is a frame member that has an overall T-shape and a hat-shaped cross-section. Also, as shown in Figure 9(b), the molded product 13 is a frame member that has an overall L-shape and a hat-shaped cross-section.

[0067] Figure 9(c) shows a punch 60 for plastically forming the L-shaped molded product 13 shown in Figure 9(b). The punch 60 for plastically forming the T-shaped molded product 13 shown in Figure 9(a) is omitted.

[0068] In Figure 9(c), the punch 60 has a first punch side surface 76 and a second punch side surface 77 that intersects with the first punch side surface 76. A bent portion 78 is located at the intersection of the first punch side surface 76 and the second punch side surface 77. During plastic deformation, the flow material accumulates from the first punch side surface 76 and the second punch side surface 77 to the bent portion 78.

[0069] As shown in Figure 9(d), the bent portion 78 is provided with a punch hardening portion 73 and a third coating hardening portion 74. In other words, in the bent portion 78, more material flows from the punch top portion 66 to the punch shoulder portion 71, causing the bent portion 78 to wear down more rapidly. As a countermeasure, the bent portion 78 is provided with a punch hardening portion 73 and a third coating hardening portion 74.

[0070] Figure 9(e) is a cross-sectional view of the part other than the curved portion 78. As shown in Figure 9(e), in the punch 60, the punch hardening portion 73 and the third coating hardening portion 74 are not provided in the part other than the curved portion 78. According to the fourth modification example, the cost of the punch 60 can be reduced by changing the partial curved portion 78 to a hard material.

[0071] [Examples of modifications to the third hardened coating portion] Examples of modifications to the third hardened coating portion 74 are explained in Figure 10(a) and Figure 10(b), which is a cross-sectional view taken along the line b-b in Figure 10(a). As shown in Figure 10(b), the third hardened coating portion 74 may be a second projection 79 with an arc cross-section. That is, as shown in Figure 10(a), the third hardened coating portion 74 may be a second projection 79 extending along the moving axis 61 of the punch.

[0072] Since the second projection 79 is a protrusion, it can be added to the molding surface of the punch 60 afterwards. This allows for minimizing the area of ​​hardened material on complex molding surfaces. Because it is minimal, it has the advantage of reducing the amount of expensive hard material used.

[0073] [Fifth Modification Example of Mold] In response to the need for cost reduction of mold 10, the fifth modification example provides a structure that can meet this requirement. The fifth modification example of mold 10 will be explained based on Figures 11(a) and (b). Note that Figure 11(b) is an enlarged view of part b of Figure 11(a).

[0074] As shown in Figure 11(a), the mold 10 consists of a die 20 and a punch 60. The die 20 includes a die recess 47 into which the punch 60 enters and a die flange portion 24 extending in a direction intersecting the movement axis 61 of the punch. The punch 60 includes a punch flange portion 64 facing the die flange portion 24. A second hardened coating portion 67, which has a higher hardness than the punch flange portion 64, is embedded in this punch flange portion 64.

[0075] The second hardened coating portion 67 has a higher hardness than the punch flange portion 64. As shown in Figure 11(b), the second hardened coating portion 67 exhibits wear resistance even when the edge of the metal plate 12 is rubbed. The punch flange portion 64 is protected by the second hardened coating portion 67.

[0076] In the invention based on the fifth modification, the punch flange portion 64, which is only a small part of the mold 10, is made into a hardened portion, so the volume of the hardened portion becomes very small. Because the volume of the hardened portion is very small, the cost of forming the hardened portion becomes very small. When the cost of forming the hardened portion is reduced, the manufacturing cost of the mold 10 decreases. In other words, the present invention provides a technology that can reduce the manufacturing cost of the mold 10.

[0077] [Sixth Modification Example of the Mold] A sixth modification example of the mold 10 will be described based on Figure 12. As shown in Figure 12, the mold 10 consists of a die 20, a punch 60, a blank holder 81, and a pad 82. That is, the mold 10 further includes a blank holder 81 that presses the metal plate 12 against the die flange portion 24. The pad 82 plays the role of relatively pressing the metal plate 12 against the punch 60.

[0078] The die 20 consists of a die body portion 28 and a die shoulder portion 27. The die shoulder portion 27 is a die hardened portion 35. The die hardened portion 35 enhances the wear resistance of the die 20. A holder hardened portion 83, which is harder than the die body portion 28, is embedded in the portion of the blank holder 81 facing the die flange portion 24. The holder hardened portion 83 enhances the wear resistance of the blank holder 81.

[0079] [Seventh Modification Example of the Mold] The seventh modification example of the mold 10 will be explained based on Figure 13. As shown in Figure 13, the mold 10 consists of a die 20, a punch 60, a blank holder 81, and a pad 82. Furthermore, the die flange portion 24 and the blank holder 81 are provided with a draw bead 85 that controls the inflow of the metal plate 12. The draw bead 85 is composed of a bead hardening portion 86 that is harder than the die body portion 28.

[0080] The draw bead 85 consists of a recess 87 and a protrusion 88. One of the recess 87 and the protrusion 88 is provided on the die flange portion 24, and the other is provided on the blank holder 81. Preferably, the recess 87 is provided on the blank holder 81 and the protrusion 88 is provided on the die flange portion 24.

[0081] Because the draw bead 85 strongly holds and pulls the metal plate 12, the material inflow is large. The greater the material inflow, the more severe the wear. Therefore, the draw bead 85 requires higher wear resistance than other parts. The draw bead 85 is composed of a hardened bead section 86 with high hardness, which enhances its wear resistance.

[0082] By the way, the identification or setting of the cross-section 44a, as explained in Figure 2(b), is important. This identification or setting can be done using a wireframe created with CAD (Computer-Aided Design). The wireframe will be explained in detail below.

[0083] Figures 14(a) to 14(h) illustrate a method for manufacturing a mold 10 using a wire frame and a ruled surface.

[0084] Figure 14(a) is similar to Figure 1(b), but for the sake of facilitating the following explanation, the reference numerals in Figure 1(b) have been changed and Figure 1(b) has been inverted. As shown in Figure 14(a), the die body 28 has a flat first surface 91 and a second surface 92 that is different from the first surface 91. The second surface 92 is also a flat surface.

[0085] [Wireframe] Wireframes are explained based on Figures 14(b) to (f), and ruled surfaces corresponding to cross-sections are explained based on (g) and (h). A ruled surface is a CAD term, written as "ruled surface" in English, and refers to a surface enclosed by a specific group of edges (the definition of an edge will be explained later). Since edges appear on the surface, a ruled surface is the same as a ruled surface.

[0086] Figure 14(b) shows vertex 93. This vertex 93 is a point set on the CAD screen. Figure 14(c) shows a straight edge 94. This edge 94 is a line connecting two vertices 93 with a straight line. Figure 14(d) shows a curved edge 95. This edge 95 is a line connecting two vertices 93 with a curve. The curve is defined by the radius of curvature R.

[0087] Figure 14(e) shows wire 96. Wire 96 is a broken or meandering line in which straight edges 94 are connected to each other, curved edges 95 to each other, or a straight edge 94 and a curved edge 95 are connected in series. Figure 14(f) shows wire frame 97. Wire frame 97 is a skeletal structure made up of multiple wires 96 arranged in a grid.

[0088] [Ruled Surface] In Figure 14(e), the vertical edge 94 is replaced with a straight edge 94v passing through the first surface, and the horizontal edge 94 is replaced with a straight edge 94h passing through the second surface. Then, the vertex 93 at the joint between the straight edge 94v passing through the first surface and the curved edge 95 connected to this straight edge 94v is defined as the first inflection point 98. Similarly, the vertex 93 at the joint between the straight edge 94h passing through the second surface and the curved edge 95 connected to this straight edge 94h is defined as the second inflection point 99.

[0089] Next, as shown in Figure 14(g), the first inflection point 98 and the second inflection point 99 are connected by a line 101. This line 101 corresponds to the straight line 31 shown in Figure 1(b) and also to the cross-section 44a shown in Figure 2(b). When the two-dimensional representation of Figure 14(g) is converted to a three-dimensional representation, it becomes Figure 14(h).

[0090] In Figure 14(h), the surface enclosed by the line 101 connecting the first inflection point 98 and the second inflection point 99, the wires 96, 96 perpendicular (including nearly perpendicular) to this line 101, and the line 102 in the background is the ruled surface 103. This ruled surface 103 corresponds to the cross-section 44a.

[0091] As described above, the press die is represented by a CAD wireframe 97, and a straight line (Figure 1(b), reference numeral 31) is defined by a line 101 connecting the first inflection point 98 and the second inflection point 99. As a result, the cross-section (Figure 2(b), reference numeral 44a) is uniquely determined, leaving no room for individual differences or human error.

[0092] [Method for manufacturing a mold using a wire frame] The method for manufacturing a mold using a wire frame can be summarized as follows. As shown in Figure 14(a), the die body portion 28 has a flat first surface 91 and a flat second surface 92 that is different from the first surface 91. The die shoulder portion 27 is provided between the first surface 91 and the second surface 92 and is composed of a curved ridge 95 on its outer surface.

[0093] As shown in Figures 14(b) to (h), the die is represented by a wireframe 97, which is defined by vertices 93 that are points on the screen, edges 94 and 95 that connect two vertices 93 with straight or curved lines, wires 96 that connect multiple edges 94 and 95 in series, and a skeletal structure composed of multiple wires 96.

[0094] Then, the vertex 93 located at the junction of a straight edge 94v passing through the first face 91 and a curved edge 95 connected to this straight edge 94v is defined as the first inflection point 98, and the vertex located at the junction of a straight edge 94h passing through the second face 92 and a curved edge 95 connected to this straight edge 94h is defined as the second inflection point 99, and the ruled face 103 is defined by the line 101 connecting the first inflection point 98 and the second inflection point 99.

[0095] Following the definition described above, the mold manufacturing method shown in Figures 2(a) to (e) is carried out. Specifically, the mold manufacturing method is provided, comprising: a first processing step to obtain a first intermediate product 42 processed into a shape resembling the die; a second processing step to obtain a second intermediate product 44 including the cut surface 44a by cutting off a soft arched cross section 43, which has the same shape as the die shoulder 27, along the cut surface 44a from the first intermediate product 42; a third processing step to obtain a third intermediate product 46 including a built-up section 45 with a cross-sectional shape that includes excess material 45a added to the soft arched cross section 43 by building up material with a harder material than the die body 28 on the cut surface 44a of the second intermediate product 44; and a fourth processing step to obtain the die by cutting off the excess material 45a from the third intermediate product 46.

[0096] According to this mold manufacturing method, the die shoulder and die body can be easily set by forming a wireframe on a CAD screen and setting ruled surfaces. Because it can be easily set, design costs can be reduced. When design costs are reduced, mold manufacturing costs are reduced. In other words, the present invention provides a technology that can reduce the manufacturing cost of mold 10.

[0097] Preferably, the build-up portion of the third processing step includes protruding portions that extend outwards to the first and second surfaces. The protruding portions are the same as the protruding portion 45b shown in Figure 2(d).

[0098] A mold 10 shown in Figure 1 is prepared, and a molded product 13 with a hat cross-section is obtained through the process shown in Figures 4(a) to (c). When the process shown in Figures 4(a) to (c) is repeated, the die hardened portion 35 shown in Figure 4(a) gradually wears down or chips. When this wear or chipping exceeds the permissible value, the mold 10 is repaired or replaced with a new mold 10. Inspecting the mold 10 as a whole and determining whether there are any abnormalities in the mold 10 while repeating the process shown in Figures 4(a) to (c) is time-consuming. Therefore, a mold inspection method that can replace the overall inspection is needed.

[0099] [Partial mold] As shown in Figure 15(a), the die 20 is preferably composed of a main mold 38 and a partial mold 39 that is removably attached to the main mold 38. A die hardening portion 35 is provided in the partial mold 39.

[0100] The metal plate 12 is plastically deformed using a mold (Figure 1(a), reference numeral 10) that includes such a die 20. After multiple plastic deformations, the bolts B are loosened and the partial die 39 is removed from the main die 38. Figure 15(b) shows the removed partial die 39.

[0101] Furthermore, the punch 60 may also be composed of a main mold 38 and a partial mold 39.

[0102] [Mold Inspection Device] A mold inspection device for carrying out a mold inspection method is shown in Figure 15(c). As shown in Figure 15(c), the mold inspection device 110 consists of, for example, a stand 111 on which a partial mold 39 is placed, a robot 113 that moves a non-contact type surface roughness meter 112 in three dimensions, a discrimination unit 114 that obtains roughness information from the surface roughness meter 112 and determines whether or not the roughness is within an acceptable value, and an alarm 115 that emits sound or light when the roughness exceeds an acceptable value.

[0103] [Surface Roughness Meter] The non-contact surface roughness meter 112 is a type of distance meter that emits a light beam such as laser light or infrared light, receives the reflected light, and measures the time it takes for the light to return. Based on the speed of light and time, the distance from the surface roughness meter 112 to the partial mold 39 is calculated. Moving either or both of the partial mold 39 and the surface roughness meter 112 changes the distance. This change in distance represents the roughness.

[0104] When a scratch occurs on the surface of the partial mold 39, the change in distance measured by the surface roughness meter 112 becomes significant. In other words, the depth of the scratch can be detected by the surface roughness meter 112. An acceptable value (threshold) for the depth of the scratch is determined based on the surface roughness of the normal partial mold 39. The discrimination unit 114 determines that an abnormality exists when the measured value exceeds the threshold. When the alarm device 115 receives abnormality information from the discrimination unit 114, it issues an alarm using sound, flashing light, etc.

[0105] [Mold Inspection Method] In other words, the present invention provides a mold inspection method as described below. As shown in Figure 15(a), the die 20 consists of a main mold 38 and a partial mold 39 that is detachably attached to the main mold 38, and the partial mold 39 is provided with a die hardening section 35. The mold inspection method comprises the steps of: removing the partial mold 39 from the main mold 38 after the metal plate has been plastically deformed by the mold including the die 20; an inspection step of detecting the depth of scratches occurring on the surface of the partial mold 39 with a surface roughness meter 112, as shown in Figure 15(c); a discrimination step of determining with a discrimination unit 114 that the partial mold 39 is sound if the detected scratch depth is within a threshold, and that the partial mold 39 is unsound if the detected scratch depth exceeds the threshold; and an alarm step of issuing an alarm with an alarm device 115 when the partial mold 39 is unsound.

[0106] While it is desirable to inspect the entire die 20 for abnormalities such as wear occurring in the die 20, this increases the inspection time. In this respect, the mold inspection method of the present invention has the advantage of shortening the inspection time because only the partial die 39 is inspected.

[0107] In addition, when inspecting the die 20 as a whole, if the die hardened portion 35 is formed in the back or corners of the die 20, it becomes difficult to inspect the die hardened portion 35. In this respect, the mold inspection method of the present invention has the advantage that the inspection of the die hardened portion 35 becomes easier because the removed partial mold 39 is inspected.

[0108] The above inspection method is suitable for inspecting the die 20, but can also be applied to the punch 60. Specifically, the punch 60 consists of a main die 38 and a partial die 39 that is detachably attached to the main die 38, and the partial die 39 is provided with a punch hardening section 73. The mold inspection method is provided, comprising the steps of: removing the partial die 39 from the main die 38 after the metal plate has been plastically deformed by the mold including the punch 60; an inspection step of detecting the depth of scratches occurring on the surface of the partial die 39 with a surface roughness meter 112; a discrimination step of determining with a discrimination unit 114 that the partial die 39 is sound if the detected scratch depth is within a threshold, and unsound if the detected scratch depth exceeds the threshold; and an alarm step of issuing an alarm with an alarm device 115 when the partial die 39 is unsound.

[0109] [Example of modification of the die hardening portion] As shown in Figure 16, when the maximum distance T between the curved line 32 and the straight line 31 in the die shoulder portion 27 is less than 1 mm, an arc groove 117 (or square groove) is made in the die body portion 28. Then, the die hardening portion 35 is made to protrude into the arc groove 117 (or square groove).

[0110] Alternatively, when the angle θ between the punch's moving axis 61 and the straight line 31 in the die shoulder portion 27 is less than 45°, an arc groove 117 (or square groove) is made in the die body portion 28. Then, the die hardened portion 35 is made to protrude into the arc groove 117 (or square groove).

[0111] The protruding portion 118 acts as an anchor. This anchor makes it difficult for the die shoulder portion 27 to detach from the die body portion 28. The structure shown in Figure 16 can also be applied to the punch shoulder portion (Figure 8(b), reference numeral 71).

[0112] [Further examples of modifications to the die hardening portion] The die hardening portion 35 shown in Figure 1(b) extends in the direction of the front and back of the drawing. However, as shown in Figure 17, the die hardening portion 35 may be dome-shaped. Dome-shaped die hardening portions 35 may be scattered along the same line.

[0113] Since it can be either a linear or dome shape, the design flexibility of the die hardening section 35 is increased. The structure shown in Figure 17 can be applied to the punch shoulder section (Figure 8(b), reference numeral 71).

[0114] [Further examples of modifications to the die hardening section] Also, as shown in Figure 18, the die shoulder 27 may be a two-humped camel-shaped die hardening section 35 having another curved line 32B next to the curved line 32. This increases the design freedom of the die hardening section 35. The structure shown in Figure 18 can also be applied to the punch shoulder (Figure 8(b), reference numeral 71).

[0115] The present invention is suitable for molds that include a die comprising a die body and a die shoulder.

[0116] 10...Mold, 12...Metal plate, 13...Molded product, 20...Die, 22...Die side wall, 24...Die flange, 25...Inside, 26...Die top, 27...Die shoulder, 28...Die body, 31...Straight line, 32...Curved line, 32B...Curved line, 33, 98...First inflection point, 34, 99...Second inflection point, 35...Die hardened part, 36...First coating hardened part, 37...First protrusion, 38...Main mold, 39...Partial mold, 41...Die material, 42...First intermediate product, 43...Soft arched cross section, 44...Second intermediate product, 44a...Cut surface, 45...Build-up part, 45a...Excess material, 45b...Protruding part, 46...Third intermediate product, 47...Die recess, 60...Punch, 6 1...Moving axis, 62...Punch side wall, 64...Punch flange, 66...Punch top, 67...Second coating hardened part, 71...Punch shoulder, 72...Punch body, 73...Punch hardened part, 74...Third coating hardened part, 76...First punch side, 77...Second punch side, 78...Bent part, 79...Second ridge, 81...Blank holder, 83...Holder hardened part, 85...Draw bead, 86...Bead hardened part, 91...First surface, 92...Second surface, 93...Vertex, 94...Straight ridge, 95...Curved ridge, 96...Wire, 97...Wire frame, 112...Surface roughness meter, 114...Discrimination part, 115...Alarm.

Claims

1. A die and a punch for plastically deforming a metal plate into a hat cross-sectional shape, wherein the die comprises a die side wall portion extending along the movement axis of the punch, a die flange portion extending from the die side wall portion in a direction intersecting the movement axis of the punch, and a die top portion located behind the die side wall portion, the punch comprises a punch side wall portion facing the die side wall portion, a punch flange portion facing the die flange portion, and a punch top portion facing the die top portion, the portion where the die flange portion and the die side wall portion intersect is called the die shoulder portion, and the portion of the die excluding the die shoulder portion is called the die body portion, the die body portion and the die shoulder portion are straight lines in cross-sectional view, the outer surface of the die shoulder portion is a curved line that protrudes outward, one end of the straight line and one end of the curved line are connected, and the other end of the straight line and the other end of the curved line are connected, and the die shoulder portion is composed of a die hardened portion which has a higher hardness than the die body portion.

2. A mold according to claim 1, wherein a first hardened coating portion having a higher hardness than the die body portion is embedded in the die side wall portion, and one end of the first hardened coating portion is connected to the die hardened portion.

3. A mold according to claim 2, wherein the first hardened coating portion is a first projection extending along the moving axis of the punch.

4. A mold according to claim 2, wherein the first coating hardened portion has a tapered shape in which the portion close to the die hardened portion is thin-walled and becomes thicker as it moves away from the die hardened portion, and the thicker portion bites into the die body portion.

5. A mold according to any one of claims 1 to 3, wherein the punch has a second hardened coating portion embedded in the punch flange portion, the hardness of which is greater than that of the die body portion.

6. A mold according to any one of claims 1 to 4, wherein the portion where the top of the punch and the side wall of the punch intersect is called the punch shoulder, and the portion of the punch excluding the punch shoulder is called the punch body, the boundary between the punch body and the punch shoulder is a straight line in cross-sectional view, the outer surface of the punch shoulder is a curved line that protrudes outward in cross-sectional view, one end of the straight line is connected to one end of the curved line, the other end of the straight line is connected to the other end of the curved line, the punch shoulder is composed of a punch hardened portion with a higher hardness than the punch body, and a third coating hardened portion with a higher hardness than the punch body is embedded in the punch side wall, and one end of this third coating hardened portion is connected to the punch hardened portion.

7. A mold according to claim 6, wherein the punch forms the metal plate into a molded product having a T-shape or L-shape and a hat-shaped cross-section, and the punch has a first punch side surface and a second punch side surface that intersects the first punch side surface, and has a curved portion at the intersection of the first punch side surface and the second punch side surface, and the punch hardened portion and the third coating hardened portion are provided only in the curved portion.

8. A mold according to claim 6, wherein the third coating hardened portion has a tapered shape in which the portion close to the punch hardened portion is thin-walled and becomes thicker as it moves away from the punch hardened portion, and the thicker portion bites into the punch body portion.

9. A mold according to claim 6, wherein the third hardened coating portion is a second projection extending along the moving axis of the punch.

10. A mold comprising a die and a punch for plastic deformation of a metal plate, wherein the die includes a die recess into which the punch enters and a die flange portion extending in a direction intersecting the movement axis of the punch, and the punch includes a punch flange portion facing the die flange portion, and a second hardened coating portion having a higher hardness than the punch flange portion is embedded in the punch flange portion.

11. A mold according to claim 1, wherein the mold further comprises a blank holder for pressing the metal plate against the die flange portion, and a holder hardening portion having a higher hardness than the die body portion is embedded in the portion of the blank holder facing the die flange portion.

12. A mold according to claim 11, further comprising a draw bead in the die flange portion and the flank holder for controlling the inflow of the metal plate, wherein the draw bead is composed of a bead hardening portion having a higher hardness than the die body portion.

13. A method for manufacturing a mold according to claim 1, wherein the die body has a flat first surface and a flat second surface different from the first surface, the die shoulder is provided between the first surface and the second surface and is composed of a curved ridge on its outer surface, the die is represented by a wireframe, the wireframe is defined by vertices which are points on the screen, ridges which connect two of the vertices by a straight or curved line, wires which connect a plurality of the ridges in series, and a skeletal structure composed of a plurality of the wires, the vertex located at the joint between a straight ridge passing through the first surface and a curved ridge connected to this straight ridge is defined as the first inflection point, the vertex located at the joint between a straight ridge passing through the second surface and a curved ridge connected to this straight ridge is defined as the second inflection point, and when the cross-section is defined by a straight line connecting the first inflection point and the second inflection point, A mold manufacturing method comprising: a first processing step of obtaining a first intermediate product processed to a shape similar to the die; a second processing step of obtaining a second intermediate product including the cut surface by cutting off a soft arched cross section, which is the same shape as the die shoulder, from the first intermediate product along the cut surface; a third processing step of obtaining a third intermediate product including a built-up section with a cross-sectional shape that includes excess material added to the soft arched cross section by building up material with a harder material than the die body on the cut surface of the second intermediate product; and a fourth processing step of obtaining the die by cutting off the excess material from the third intermediate product.

14. A mold manufacturing method according to claim 13, wherein the build-up portion of the third processing step includes a protruding portion that extends toward the first surface and the second surface.

15. A die according to claim 1, comprising a main mold and a partial mold detachably attached to the main mold, wherein the partial mold is provided with the die hardening portion, and comprising the steps of: removing the partial mold from the main mold after plastic deformation has been performed on the metal plate by a mold including the die; an inspection step of detecting the depth of scratches occurring on the surface of the partial mold with a surface roughness meter; a discrimination step of determining with a discrimination unit that the partial mold is sound if the detected depth of scratches is within a threshold, and that the partial mold is unsound if the detected depth of scratches exceeds the threshold; and an alarm step of issuing an alarm with an alarm when the partial mold is unsound.

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