JPH0459133A - Drawing method - Google Patents

Abstract

PURPOSE:To prevent generation of wrinkles by blank-holding a position deep in depth of draw at first, drawing this position a prescribed quantity, then, blank-holding a position shallow in depth of draw and preventing a shrinkage from being generated at a position deep in depth of draw. CONSTITUTION:A blank 1 is set on a lower die 22. When the blank 1 is set on the lower die 22, an upper die 21 is lowered, the outer peripheral part 1b of the blank 1 is blank-held by the upper die 21 and an outside cushion 23. When the outer peripheral part 1b is blankheld, the upper die 21 is lowered further under this state. At this time, when the moving stroke of the outside cushion 23 exceeds alpha, the central tart 1a of the blank 1 is blank-held by the upper die 21 and an inside cushion 24. Further, when the upper die 21 is lowered, the outer peripheral part 1b of the blank 1 is extended with the fall of the upper die 21. Consequently, the corner part of the outer peripheral part 1b is prevented from shrink flanging and generation of wrinkles at the outer peripheral part is prevented securely.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a drawing method for a material, and in particular to a drawing method that prevents wrinkles from forming when forming parts with different drawing depths. Related.

[Prior Art 1] Conventionally, there has been known a technique in which drawing is performed in two stages to suppress forming stress in drawing with different drawing amounts of materials. (Utility Model Application Publication No. 60-1514). Furthermore, a technique is known in which wrinkles are prevented from forming in the initial stage of forming by using a leading pin provided on the drawing punch so as to be movable back and forth (Japanese Utility Model Publication No. 60-38622).

Figures 8 and 9 show drawn material (steel plate) 1
It shows. The material 1 has a flat central portion 1a and a peripheral portion 1b, and a square hole 1C is formed in the central portion 1a. As shown in FIG. 9, the square hole 1C is formed in a separate process before being drawn. Center part 1a
An edge portion 1d extending in the circumferential direction is formed between the outer peripheral portion 1b and the outer peripheral portion 1b. The center portion 1a is located at a depth H4 below the top surface of the edge 1d, and the outer peripheral portion 1b is located at a depth H below from the top surface of the edge 1d.

That is, the outer peripheral portion 1b has a deeper drawing depth than the central portion 1a.

FIG. 7 shows a drawing die for forming the drawn product shown in FIG. 8 from a flat material. In the figure, 11 indicates an upper mold, and 12 indicates a lower mold.

The lower die 12 is formed with a protruding portion 12a extending in the circumferential direction. The upper die 11 is formed with a recess 11a into which the top of the protrusion 12a can enter. An outer cushion 13 is arranged on the outside of the protruding part 12a of the lower mold 12, and an inner cushion 14 is arranged inside the protruding part 12a.
is located. The outer cushion 13 and the inner cushion 14 are raised and lowered simultaneously by a plurality of cushion pins 15 on the press machine side. The movement strokes of the outer cushion 13 and the inner cushion 14 are both S.

In drawing forming using such a drawing die, first,
The material 1 is set on the lower mold 12 side. In this state, as shown in FIG. 7(a), the outer cushion 13 and the inner cushion 14 are raised by the cushion pin 15. When the material 1 is set, the upper die 11 descends,
As shown in FIG. 7(a), the material 1 is held blank by the upper die 11, the outer cushion 13, and the inner cushion 14. That is, the outer circumferential portion 1b of the material 1 is held blank by the upper die 11 and the outer cushion 13, and the center portion 1a of the material 1 is held blank by the upper die 11 and the inner cushion 14. The center portion 1a and outer peripheral portion 1b of this material 1 are blanked at the same time, and drawn by lowering the upper die 11, as shown in FIG. 7I.

[Problem to be solved by the invention] However, in the case of drawing forming as shown in Fig. 7,
As shown in Fig. 10, there are wrinkles 1e in the corners of the molded product.
There was a problem that something happened. As shown in FIG. 11, the cross section A-
Because the line length of the cross section B-B is shorter than the cross-sectional length p of A, if the center part 1a and the outer peripheral part 1b are held blank at the same time, they will be compressed to the outer peripheral part 1b with a deep drawing depth. This is because stress acts. In this way, the cross section B-B portion, which is the square portion of the outer circumferential portion 1b, shrinks as the upper die 11 descends to become a flange, and wrinkles 1e as shown in FIG. 10 occur.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a drawing method that can prevent the occurrence of wrinkles when forming parts of a single material with different drawing depths.

[Means for Solving the Problems] A drawing method according to the present invention that meets this objective is that in a drawing method in which parts with different drawing depths are formed on one material, the part with the deeper drawing depth is first formed. This method consists of blank-holding, squeezing the area by a predetermined amount, and then blank-holding the area where the drawing depth becomes shallow.

[Function] In the drawing method configured in this way, the area where the drawing depth is deep is held blank first, and after this area has been drawn by a predetermined amount, the area where the drawing depth is shallow is held blank. Since the material is held, tensile stress is generated in the deep drawing area during drawing. For that reason,
Areas with a deep drawing depth are elongated by the drawing process, thereby preventing wrinkles from forming as in the conventional case.

[Example] Hereinafter, a preferred example of the drawing method according to the present invention will be described with reference to the drawings.

First example FIG. 1 shows a first embodiment of the invention.

Since the cable material used in this embodiment is the same as the cable material shown in FIG. 8, the explanation thereof will be omitted by giving the same reference numerals.

In FIG. 1, 20 indicates a drawing die. Drawing die 2
0 consists of an upper mold 21 and a lower mold 22. Upper mold 22
A protruding portion 22a is formed on the upper die 21 so as to protrude toward the upper die 21 and extend in the circumferential direction. The upper mold 21 has a protruding mold part 2
A recess 21a is formed into which the top of 2a can be entered.

The upper die 21 is attached to a ram of a press machine (not shown). An inner cushion 24 is arranged inside the protruding part 22a of the lower mold 22. Inner cushion 24
is raised and lowered by the projection and retraction of a cushion pin 25 on the press machine side. The movement stroke of the inner cushion 24 by the cushion pin 25 is S. The cushion mechanism of the press machine used in this embodiment is a single-acting type having only one movement stroke S, and is not a double-acting type having two or more types of strokes.

A ring-shaped outer cushion 23 is provided on the outside of the protruding portion 22a of the lower mold 22. Outer cushion 23
is movable up and down by a biasing means 26 provided on the lower die 22. The biasing means 26 is the outer cushion 23
It has a function of always urging the upper die 21 toward the upper die 21.
For example, it is composed of urethane rubber, a compression spring, a cylinder filled with nitrogen gas, a hydraulic cylinder, etc. The outer cushion 23 has a movement stroke of S0α. As described above, S is the movement stroke of the inner cushion 23, and α is the movement stroke for drawing the inner circumference 1a after the outer circumference 1b of the material 1 has been squeezed by a predetermined amount. That is, in this embodiment, the drawing die 20 blank-holds the outer peripheral part 1b where the drawing depth is deep and narrows the moving stroke α, and then the inner peripheral part 1b where the drawing depth is shallow.
A is blank-held and drawing formation is performed.

Next, the procedure of the drawing method according to the present invention will be explained.

First, as shown in Figure 1 (a), either the material 1 or the lower mold 2
Set to 2. When the material 1 is set on the lower mold 22, the upper mold 21 is lowered, and the outer peripheral portion 1b of the material 1 is held blank by the upper mold 21 and the outer cushion 23.

When the outer peripheral portion 1b is held by one rank, the upper die 21 is further lowered in this state. Here, the outer cushion 23
When the movement stroke of exceeds α, the center 1a of the material 1
The blank is held by the upper die 21 and the inner cushion 24. Roughly speaking, when the upper die 21 is lowered, the outer peripheral portion 1b of the material 1 is stretched as the upper die 21 is lowered. In other words, in this embodiment, the outer peripheral part 1b of the material 1 is blank-held before the central part 1a, and tensile force is generated in this part first, so that the drawing depth is deep and shallow. During drawing forming in both cases, compressive stress is no longer generated in the corner portions of the outer circumferential portion 1b of the material 1 as in the conventional case. Therefore, the corner portion of the outer circumferential portion 1b is prevented from shrinking into a flange, and the generation of wrinkles on the outer circumferential portion 1b is reliably prevented.

FIG. 2 shows the state in which the molded product is taken out according to the conventional technique and the molding method according to this embodiment.

In this embodiment, since the movement stroke of the outer cushion 24 is S0α, the position of the outer cushion 24 becomes higher as shown in (2) in FIG. 2, and the molded material 1 is moved horizontally. It becomes possible to take it out. Therefore, as shown in FIG. 2A, the material 1 is no longer caught on the protrusion 12a of the lower die 12, which improves the work of taking out the material 1.

FIG. 3 shows an example in which the molding method of the present invention is applied to increase the rigidity of a vehicle pod. In the case of an integral structure of the rocker outer and the front 1 to pillar in the side member outer of the body, the D portion of the side member outer 31 is made shallower to prevent edge cracking during molding, as shown in Fig. 3 (a). It is necessary to mold the E part deeply in order to mold it and avoid improving the rigidity. However, conventionally, wrinkles occur when the depth of the drawing is different, so the cross-sectional shape of the side member outer 31a is inevitably limited to a substantially rectangular shape, as shown in (■) in FIG. It is difficult to increase the rigidity against the load F. Therefore, by using the molding method of the present invention, the shape of the site member outer 31b can be made into shapes with different drawing depths as shown in FIG. 3 (/deaf), without increasing the weight. It is possible to increase the rigidity.

FIG. 4 shows the development of molded products in the conventional technique and the molding method of the present invention. In recent years, the appearance of vehicles has become an issue, and for example, the flange portion that is joined to the spoiler 1 by welding is required to be made as difficult to see from the outside as possible. FIG. 4(a) shows a cross section of the rocker 35 formed by the conventional drawing method, and in this case, the flange portion 35a is visible at the angle θ.

However, in this case, it is necessary to attach resin or the like to the flange portion 35a to improve the appearance. On the other hand, in the molding method of the present invention, as shown at O in FIG. The portion 36a becomes difficult to see from the outside, and there is no need to take new measures to improve the appearance.

Second example FIG. 5 shows a second embodiment of the invention.

The difference between the second embodiment and the first embodiment is only the configuration of the biasing means, and other parts are similar to the first embodiment, so the same months as in the first embodiment are attached to the corresponding parts. The explanation of the parts that are the same will be omitted, and only the different parts will be explained. The same applies to other embodiments to be described later.

In FIG. 5, reference numeral 41 indicates a biasing means.

In the first embodiment, the biasing means 26 was provided directly on the lower die 22, but in this embodiment, it is attached to the top of the cushion bin 25 of the press machine.

As mentioned above, the biasing means 26 is made of urethane rubber or the like. In this embodiment, cushion bin 2
The reason why the biasing means 26 is attached to 5 is to allow the biasing means 25 to have a short stroke.

That is, for example, urethane rubber cannot have a large amount of elastic deformation, so when forming with a deep drawing depth, the stroke of the urethane rubber itself is insufficient and the forming becomes impossible. Therefore, as in this example,
By supplementing the stroke of the external cushion 23 during molding with the stroke of the cushion pin 25, deep drawing can be performed.

Third embodiment FIG. 6 shows a third embodiment of the invention.

In this embodiment, either the outer cushion 23 or the cushion pin 2
5, and is biased by the inner cushion 24 or biasing means 41.

In this embodiment, either the shorter movement stroke or the biasing means 4
1, the stroke of the outer cushion 23 is ensured by the stroke of the cushion pin 25 even in the case of a molded product with a relatively deep drawing depth. Other operations are similar to those in the first embodiment.

[Effects of the Invention] As explained above, when using the drawing method according to the present invention, the region where the drawing depth becomes deep is first held blank, and after this region is drawn by a predetermined amount, the drawing depth becomes shallower. Since the blank-hold portion is used, tensile stress can be generated in the portion where the drawing depth is deep. Therefore, during drawing, shrinkage does not occur in areas where the drawing depth is deep, and wrinkles can be prevented.

In this way, it is possible to form parts with different drawing depths in one material without creating wrinkles, so it is possible to obtain cross-sectional shapes that were previously impossible to form, and it is possible to form pressed products. Improved rigidity and appearance.

[Brief explanation of the drawing]

FIGS. 1(a) and (2) are cross-sectional views showing the steps of the drawing method according to the first embodiment of the present invention, and FIGS. 2(a) and (2) are the forming method using the drawing die of FIG. 1. 3(a) or 2) are cross-sectional views showing the state of taking out the molded product in the conventional forming method using a drawing die. A perspective view and a sectional view when applied to a die member, FIG. 6 is a sectional view of a drawing die for carrying out a drawing method according to a third embodiment of the present invention, and FIG. 6 is a sectional view of a drawing die for carrying out a drawing method according to a third embodiment of the present invention. , Figures 7(a) and (2) are cross-sectional views showing the steps of the conventional drawing method, Figure 8 is a perspective view showing an example of a molded product having parts with different drawing depths, and Figure 9 is a cross-sectional view showing the steps of a conventional drawing method. Sectional view taken along line IX-IX in Figure 8, No. 1
FIG. 0 is a partially enlarged perspective view showing the molded product shown in FIG. 8 with wrinkles, and FIG. 11 is a sectional view showing the cross-sectional length of each part of the molded product shown in FIG. 8. 1...Material 1a...Central part (portion with shallow drawing depth) 1b.
...Outer periphery (part with deep drawing depth) 1d-...
... Edge 20 ... Drawing mold 21 ... Upper mold 22 ... Lower mold 23 ... Outer cushion 24 ... Inner cushion 26 .41...Biasing means

Claims (1)

[Claims] 1. In a drawing method in which parts with different drawing depths are formed into one material, the part where the drawing depth becomes deeper is first held blank, and after that part is drawn by a predetermined amount, the part where the drawing depth becomes shallower. A drawing method characterized by blank-holding.