JP2006088196A - Bulging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a bulged part having high bulging height on a thick work by a single process. <P>SOLUTION: By fixing the work on a die 2, inserting a bulging punch 1 on which a nose part 1a, an intermediate part 1b continuing to the nose part and a base part 1c continuing to the intermediate part are provided and a plastic flowing part for making the material of the work plastically flow toward the nose part of the bulged part 3b is provided into the die hole 2a of the die 2 when forming bulging on at least one side of the intermediate part 1b or the base part 1c, the bulged part 3b is formed while plastically flowing the material of the work in the direction of the nose of the bulged part 3b in a single operation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an overhang forming method.

  As an overhang forming method for forming an overhang portion by press molding from a flat portion, methods of Patent Documents 1 to 3 are known.

  Patent Document 1 discloses a method in which a hemispherical sphere head is stretched and then drawn into a cylindrical shape using a cylindrical punch. Patent Document 1 discloses a method in which a local part is formed in advance around a forming part and an overmolding process is performed using the surplus. In the former method, many steps are required to process the spherical head into a cylindrical shape. Further, since the drawing process is used, it is difficult to apply when the workpiece is thick.

  Patent Document 2 discloses an upper punch including a hemispherical tip portion and a body portion whose diameter is expanded from the tip portion via a taper portion. This upper punch forms an overhanging portion 21c on the outer periphery of the protrusion 21 in conjunction with the lower punch arranged coaxially, and is not for forming a protrusion with a high overhang height. The overhang portion 21c is different from the overhang portion of the present invention.

  Patent Document 3 discloses a press molding method in which a tapered boss formed by pressing a tapered tip punch into a plate material is redrawn to a predetermined diameter to form a pin-shaped boss. Many processes are required for redrawing. In addition, since a drawing process is used, it is difficult to apply to a thick workpiece.

Patent Document 4 discloses a method for manufacturing a tapered can. This taper can is manufactured by a male mold and a female mold having a tapered portion. Therefore, the taper part which exists in a male type | mold is for forming the shape of a taper can. In addition, it is premised on manufacturing from a very thin plate having a thickness of 0.2 mm.
JP-A-8-323429 (paragraph [0002], FIG. 6, claim 1, FIG. 3, 4) JP 2000-79422 A (paragraphs [0036] to [0041], FIG. 2) JP 2000-158053 A (Claim 1, [0019] to [0023], FIGS. 1 to 8) Japanese Patent Publication No. 8-32344 (FIG. 1)

  The present invention provides an overhang forming method capable of forming an overhang portion having a high overhang height on a thick workpiece in a single process.

  In order to solve the above technical problem, in the invention of claim 1, in the overhang forming method of forming an article having a flat portion from a workpiece and an overhang portion protruding from the flat portion using a punch and a die, the punch Are provided with a tip portion, an intermediate portion that is continuous with the tip portion, and a base portion that is continuous with the intermediate portion. At least one of the intermediate portion and the base portion is provided with the material of the workpiece during the overhang molding. The die is provided with a plastic flow portion for plastic flow, the die is provided with a die hole into which the punch is inserted, the workpiece is fixed on the die, and the punch is inserted into the die hole. The overhang forming method is characterized by forming the overhang portion while plastically flowing the material of the workpiece in the distal direction of the overhang portion by one operation.

  The invention according to claim 2 is characterized in that the outer peripheral surface of the intermediate portion is a tapered surface, and the material of the workpiece is plastically flowed in the direction of the tip of the overhanging portion by the taper surface during overhang forming. The overhang forming method according to Item 1.

  In the invention of claim 3, the cross-sectional area of the base portion orthogonal to the drive direction of the punch is a flange portion larger than the cross-sectional area of the portion of the intermediate portion continuing to the base portion, 3. The overhang forming method according to claim 1, wherein the material of the workpiece is plastically flowed in the direction of the tip of the overhang portion.

  According to the first aspect of the present invention, since the material of the workpiece is plastically flowed in the direction of the tip of the overhang portion by the plastic flow portion, not only the tip portion but also the plastic flow portion acts on the overhang forming. The site of action can be dispersed. Thereby, since the tensile stress acting on the overhanging portion can be dispersed, the overhanging portion having a high overhanging height can be formed on a thick workpiece in a single process. As the plastic flow part, the outer periphery of the intermediate part has a tapered surface that expands toward the base part, the outer diameter of the intermediate part suddenly increases in the middle, the outer diameter of the base part becomes larger than the intermediate part, and the flange Forming part.

  According to the invention of claim 2, since the intermediate portion having the tapered surface is a plastic flow portion, the plastic flow portion can be formed with a simple shape. Thereby, the manufacturing cost of a punch having a plastic flow part can be reduced.

  According to the invention of claim 3, since the flange portion is provided, and the material of the workpiece is plastically flowed in the distal direction of the overhang portion by the flange portion, the work of the portion where the flange portion abuts on the overhang portion being formed. Since the materials are collected and supplied to the overhanging portion, the tensile stress acting on the overhanging portion can be dispersed, and the overhanging portion with a high overhanging height can be formed on a thick workpiece in a single process.

  The present inventor has intensively studied an overhang forming method capable of forming an overhang portion having a high overhang height in a single process even with a thick plate, and has reached the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view for explaining an overhang forming process of the first embodiment, and FIG. 2 is an explanatory view for explaining a finish forming process of the first embodiment. These explanatory drawings form an overhang part from a flat plate.

  In the overhang forming step, the article 3 is formed by the overhang forming punch 1 and the die 2. The overhanging punch 1 is provided with a front end portion 1a, a taper portion (intermediate portion) 1b continuous with the front end portion 1a, and a base portion 1c continuous with the taper portion 1b. The outer peripheral surface of the tip portion 1a is a spherical surface. The outer peripheral surface of the taper portion 1b is a tapered surface whose diameter increases from the tip portion 1a side toward the base portion 1c side. The outer diameter of the base 1c suddenly increases from the connecting portion with the tapered portion 1b, and the diameter after the expansion is constant. That is, the cross-sectional area of the base portion 1c perpendicular to the drive direction (axial direction) of the overhanging punch 1 is larger than the cross-sectional area of the portion continuing to the base portion 1c of the taper portion 1b, thereby forming a flange portion. The die 2 is provided with a die hole 2a having an inner diameter that is the outer diameter of the overhang portion. An end portion of the die hole 2a that contacts the article 3 is an R portion 2b having an R surface.

  In the finish forming step, the overhang portion is formed into a final shape by the first finish forming punch 4 and the second finish forming punch 5. The first finish molding punch 4 has a cylindrical shape having an outer diameter of the inner diameter dimension of the final shape of the overhang portion, the tip portion is a flat surface, and the corner portion has an R shape. The second finishing punch 5 has a cylindrical shape having an outer diameter that is substantially the same as the inner diameter of the die hole 2a, and has a flat tip. The second finishing punch 5 slides in the die hole 2a of the die 2 and presses the tip of the overhanging portion.

  First, a flat plate is set on the die 2 and is moved so that the overhang forming punch 1 is inserted into the die hole 2 a of the die 2 by a drive unit (not shown). When the tip portion 1a of the overhanging punch 1 abuts against the flat plate and further advances over the overhang forming punch 1, the flat plate is plastically deformed along the shape of the overhang forming punch 1 to form the overhang portion 3b. At this time, the material of the workpiece is plastically flowed in the direction of the tip of the overhanging portion 3b by the tapered portion 1b. As a result, not only the tip portion 1a but also the tapered portion 1b acts to project the workpiece material in the direction of the tip of the overhang portion 3b, so that the working site of the overhang forming process can be dispersed. Therefore, since the tensile stress acting on the overhanging portion 3b can be dispersed, the overhanging portion 3b can be formed without breaking even if the overhanging height of the overhanging portion 3b is increased. The part 3b can be formed.

  When the projecting punch 1 is further advanced, the material of the workpiece is plastically flowed toward the tip of the projecting portion 3b by the flange portion in which the diameter of the connecting portion with the tapered portion 1b of the base portion 1c is increased. As a result, since the work material of the portion where the base 1c abuts is collected and supplied to the overhanging portion 3b to the overhanging portion 3b that is being formed, the tensile stress acting on the overhanging portion 3b can be further dispersed and a single process can be performed. The overhanging portion 3b having a high overhang height can be formed on a thick workpiece. Further, since the compressive stress acts on the overhanging portion 3b side by the flange portion, there is an effect that the tensile stress acting on the overhanging portion 3b can be reduced. Thereby, even if the overhang height of the overhang portion 3b is further increased, the overhang can be formed without breaking.

  Thus, since the taper portion 1b exists and the base portion 1c is a flange portion, a protruding portion having a high protruding height can be formed in a single process even if the plate is thick. When the shape as it is may be used, the article 3 having the flat portion 3a and the overhang portion 3b can be formed only by the overhang forming process. However, a finish forming step may be provided in order to make the shape of the overhang portion 3b a predetermined shape.

  In the present embodiment, as shown in FIG. 2, the overhanging portion 3b is shaped into a cylindrical shape with a closed tip. After the stretch forming, the stretch forming punch 1 is replaced with the first finish forming punch 4. While the article 3 is in contact with the die 2, the first finishing punch 4 is advanced so as to be inserted into the inner diameter side of the overhang portion 3 b, and at the same time, the second finishing punch 5 is inserted into the die hole of the die 2. It inserts into 2a from the front end side of the overhang | projection part 3b. The first finishing punch 4 and the second finishing punch 5 are moved to a predetermined position where the protruding portion 3b has a predetermined shape. The overhanging portion 3b is shaped by utilizing the surplus of the tip spherical portion of the overhanging portion 3b. In the present embodiment, the tip of the overhang portion 3b is flat, but in this case, the height of the overhang portion 3b after shaping is lower than the height immediately after the overhang forming step.

  Next, an example of this embodiment will be described. FIG. 3 is a cross-sectional view of a mold for overmolding according to the embodiment, and FIG. 4 is a cross-sectional view of a mold for finish-molding according to the embodiment. Since the basic structure of the punch and the die is the same as in FIGS. 1 and 2, the same reference numerals are used for the same parts. The overhang forming punch 1 and the first finish forming punch 4 are held by a lower die of a press device. The second finishing punch 5 is held by the upper die of the press device.

  A work holding plate 6 on which a work is placed is provided on the lower die of the press device. In the center of the work holding plate 6, a hole portion through which the overhang forming punch 1 and the first finish forming punch 4 slide is provided. That is, the overhang forming punch 1 and the first finish forming punch 4 move up and down relatively with respect to the work holding plate 6. A convex portion 6 a is provided on the outer peripheral portion of the work holding plate 6 facing the die 2. The workpiece is held by being sandwiched between the convex portion 6 a and the die 2.

  Prior to molding, the tip of the overhang forming punch 1 is lowered from the upper surface of the workpiece holding plate 6. First, the workpiece is placed on the convex portion 6 a and is sandwiched and fixed by the convex portion 6 a and the die 2. Next, the overhang forming punch 1 is raised to a predetermined position, and the overhang portion is overhang molded as described with reference to FIG. Thereafter, the stretch forming punch 1 is retracted and replaced with the first finish forming punch 4, and the first finish forming punch 4 is raised to a predetermined position and the second finishing punch 5 is lowered to a predetermined position. Finish molding.

  A 4 mm thick cold rolled steel plate SPC270 flat plate was used as the workpiece. Tool steel SKD11 is used as the material for the overhang forming punch 1, the first finish forming punch 4, and the second finish punch 5. The shape of the taper portion 1b of the overhang punch 1 is such that the diameter of the portion connected to the tip portion 1a is 6 mm, the diameter of the portion connected to the base portion 1c is 10 mm, and the portion connecting to the tip portion 1a to the portion connecting to the base portion 1c. The length is 10 mm. The outer diameter of the base 1c is 16 mm. The inner diameter of the die hole 2a of the die 2 is 10 mm. The overhang forming punch 1 was advanced until the height of the overhang portion 3b (the overhang height: the length from the contact surface between the die 2 and the flat portion 3b to the tip of the overhang portion 3b) was 12 mm. As a result, a high overhang portion 3b having a overhang height of 12 mm could be formed by a single pressing step without breaking. Thereafter, the overhang forming punch 1 is extracted, the first finish forming punch 4 having an outer diameter of 7 mm is inserted into the inner diameter side of the overhang portion 3b, and the second finishing punch 5 having an outer diameter of 10 mm is used for the first finish forming. Insert into the die hole 2a of the die 2 from the opposite side of the punch 4 and press the overhanging portion 3b with the first finishing forming punch 4 and the second finishing punch 5 so that the overhanging portion 3b has a height of 9 mm. did. Thus, an article 3 having an overhang portion 3b having an overhang height of 9 mm and an outer diameter of 10 mm was manufactured. By simply shaping the overhang formed in a single overhang process, the overhang of the desired shape can be formed from a thick material with a thickness of 4 mm. The formed overhang portion is used as a boss portion for caulking.

Comparative example

Test using a cylindrical overhang forming punch (material: tool steel SKD11) with an outer diameter of 8 mm to form an overhang portion with the same overhang height of 9 mm on the same workpiece as in the embodiment after the finish forming of the embodiment. As a result, it broke when it was molded to an overhang height of 5.5 mm. If the forming punch is stopped at a position where the overhanging height is 5 mm, it will not break, but the thickness of the overhanging portion will become extremely thin and there will be no practicality. When considering the thickness of the overhang, etc., the method of the comparative example could not obtain a practical overhang even with an overhang height of 3 mm.
FIG. 5 and FIG. 6 show the results of stress analysis applied to the overhang portion by the finite element method corresponding to the example and the comparative example, respectively. In the overhanging punch shape used in the stress analysis of the example, the diameter of the base is the same as the end on the base side of the tapered portion. That is, there is no flange portion. 5 and 6 are obtained by simply converting a color image into a black and white image. The black portion of the flat portion 3a indicates that the stress is very small. The overhang portion 3b indicates that the tensile stress increases as the concentration increases. As shown in FIG. 6, in the comparative example, a portion having a large tensile stress extends from the inner peripheral side to the outer peripheral side of the overhang portion 3b. For this reason, it is thought that it broke when it tried to shape the overhang | projection part with a high overhang | projection height using a cylindrical punch (a taper part does not exist). On the other hand, as shown in FIG. 5, in the embodiment, there is no high tensile stress portion extending from the inner peripheral side to the outer peripheral side of the overhang portion 3b. That is, the tensile stress in the overhang portion 3b is dispersed. For this reason, it is thought that even if the overhanging portion 3b having a high overhanging height was formed, it did not break. If the flange portion exists, the tensile stress is further dispersed.

  As described above, in the present invention, the intermediate portion is provided between the tip portion and the base portion, and at least one of the intermediate portion and the base portion is made to plastically flow the workpiece material in the tip direction of the overhang portion at the time of overhang forming. Since the plastic flow part is provided and the projecting material is plastically flowed in the tip direction of the overhang part by a single operation of inserting the punch into the die hole, the overhang part is formed. Even so, it is possible to form an overhang portion having a high overhang height in a single step. In the above description, the taper portion and the flange portion are plastic flow portions.

  As a material for forming the article of the present invention, in addition to the SPC 270 shown in the embodiment, it can be used for a steel plate having a rolling property such as a cold rolled steel plate of SPC 440 and SPC 590, an aluminum material having a rolling property, a magnesium material and the like. In particular, the steel plate has a high utility value because a large stress is applied when a large deformation is applied.

  There is no absolute restriction on the thickness of the portion that forms the overhang, but it is preferably 0.5 to 10 mm. In particular, 1-8 mm and 2-6 mm are desirable. When the plate thickness is thin, a protruding portion having a high protruding height can be formed even with a cylindrical punch, and the value of utilizing the present invention is small. If the plate thickness is too thick, it may break.

  The overhang height (distance from the side surface of the overhang portion of the flat portion to the tip of the overhang portion) of the overhang portion formed according to the present invention is 12 mm (three times the plate thickness of the flat portion) in the embodiment. It is not limited. In order to make use of the advantage of the present invention for forming an overhang portion having a high overhang height, the overhang height is desirably 4 mm or more, 6 mm or more, or 8 mm or more. In comparison with the thickness of the flat portion, the overhanging height is preferably equal to or greater than twice the thickness of the flat portion, more than twice, and more than three times.

  The taper angle (the apex angle of the cone formed by extending the taper surface of the taper portion) of the tapered portion of the example is 22.6 degrees. The taper angle can be selected from 10 to 40 degrees, 15 to 30 degrees, and 20 to 25 degrees. Note that the tapered portion does not have to be an exact regular conical shape. Moreover, you may have several taper part from which a taper angle differs. In this case, it is preferable to increase the taper angle as the distance from the tip portion increases. Even if the tapered portion is a concave curved portion as its ultimate shape, it belongs to the tapered portion of the present invention.

(Appendix)
The above description includes the following technical idea.

-In an overhang forming method of forming an article having a flat portion from a workpiece and an overhang portion protruding from the flat portion using a punch and a die,
The punch has a tip portion, a base portion having a cross-sectional area larger than the cross-sectional area of the tip portion perpendicular to the driving direction of the punch, and an intermediate portion provided between the tip portion and the base portion,
At least one of the intermediate part and the base part is provided with a plastic flow part that plastically flows the material of the workpiece in the tip direction of the overhang part during overmolding,
The die is provided with a die hole into which the punch is inserted,
Fixing the workpiece on the die and forming the overhang portion while plastically flowing the material of the workpiece in the distal direction of the overhang portion by a single operation of inserting the punch into the die hole. The overhang forming method characterized.

Explanatory drawing explaining the overhang forming process of 1st Embodiment Explanatory drawing explaining the finish molding process of 1st Embodiment Sectional view of the mold for overhang molding of the embodiment Sectional view of the mold for finish molding of the embodiment Results of stress analysis on the overhang by the finite element method corresponding to the embodiment Results of stress analysis on the overhang by the finite element method corresponding to the comparative example

Explanation of symbols

1 ... Punch for overhang forming (punch)
1a ... tip part 1b ... taper part (intermediate part) (plastic flow part)
1c: Base part (flange part) (plastic flow part)
2 ... Die 2a ... Die hole 3 ... Article 3a ... Flat part 3b ... Overhang part

Claims (3)

In the overhang molding method of molding an article having a flat portion and a projecting portion projecting from the flat portion using a punch and a die,
The punch is provided with a front end portion, an intermediate portion continuing to the front end portion, and a base portion continuing to the intermediate portion,
At least one of the intermediate part and the base part is provided with a plastic flow part that plastically flows the material of the workpiece in the tip direction of the overhang part during overmolding,
The die is provided with a die hole into which the punch is inserted,
Fixing the workpiece on the die and forming the overhang portion while plastically flowing the material of the workpiece in the distal direction of the overhang portion by a single operation of inserting the punch into the die hole. The overhang forming method characterized. 2. The overhang forming method according to claim 1, wherein an outer peripheral surface of the intermediate portion is a tapered surface, and the material of the workpiece is plastically flowed in the tip direction of the overhang portion by the taper surface during the overhang forming. . The cross-sectional area of the base perpendicular to the driving direction of the punch is a flange that is larger than the cross-sectional area of the portion of the intermediate portion continuous to the base, and the material of the workpiece is stretched by the flange during overhanging. 3. The overhang forming method according to claim 1 or 2, wherein plastic flow is performed in the direction of the tip of the protruding portion.

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