JPH07303926A - Method and device for drawing - Google Patents

Abstract

PURPOSE:To prevent thinning of a bulging part and to enable forming of a work with a bulging part in one process by partially breaking a part to be discarded upon forming of a work with a breaking punch before the forming and then completing the forming of the work with a metallic die. CONSTITUTION:The die or drawing is provided with an upper die 1 and a lower die 2 in which die faces 1a, 2a are formed in accordance with the shape of a work having a bulging part to be formed; the upper die 1 is provided with a breaking punch 3 by which a part to be discarded upon forming of a work is partially broken before the completion of the forming; and the lower die 2 is formed with a recessed part 2b into which the tip end 3a of the breaking punch 3 can enter at the time of forming. Thus, a prescribed position is penetratingly broken, on the part to be discarded upon forming of the bulging part of the work, by the tip end 3a of the breaking punch 3 that is lowered with the upper die 1 before completing the forming of the work. Since the plate is extended outward as a result, cracks are prevented from generating which is caused by the thinning of the bulging part of the work at the time of completion of the forming.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a draw forming method and apparatus for forming a work having an overhang portion by press working.

[0002]

2. Description of the Related Art When a work having an overhanging portion such as a fuel tank upper of a vehicle is press-formed by a draw process, a usual draw forming operation causes a thin plate portion of the overhanging part to cause cracks. The overhang is formed in two steps.

By the way, the die for each press step arranged in series is sequentially fed continuously without cutting the plate material to perform required processing, and in the final step, the product is separated from the plate material. In a continuous press, it is known to prevent the material from being cut during draw forming by forming a slit in a portion to be cut in the final step before performing draw forming on a plate material (JP-A-58-61927). See the bulletin).

[0004]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention In the above-mentioned conventional method for draw-forming a work having an overhang,
Since the projecting portion is formed in two steps, the number of steps is increased. Further, the formation of slits as in continuous pressing cannot be applied as it is to a work in which an overhanging portion is formed in a circumferential shape.

[0005]

In order to solve the above-mentioned problems, the present invention has a tip formed in a polygonal shape, and a punching punch that pierces a part of a work before the completion of forming the work is provided in the upper die. Before the completion of the molding, a part of the portion to be discarded after the molding of the work was pierced by the piercing punch, and then the molding of the work by the mold was completed.

[0006]

[Function] Since a part of the work is pierced by the piercing punch before the completion of the forming of the work, the material is prevented from flowing into the overhanging part and thinning is prevented, so that the work having the overhanging part can be formed in one step and the piercing Since the tip shape of the punch is formed in a polygonal shape, the direction in which the cut runs can be controlled to some extent at the time of punching, and the material can be stretched substantially uniformly.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a cross-sectional view of a draw forming die to which the draw forming method and device according to the present invention are applied, FIG. 2 is an explanatory view for explaining the action at the time of draw forming, and FIGS. 3 to 6 are different shapes of punching punches. It is a perspective view and a front view showing.

The draw forming die has an upper die 1 and a lower die 2 on which die faces 1a and 2a corresponding to the shape of a work having an overhanging portion to be formed are formed. A piercing punch 3 for piercing a part of the workpiece to be discarded after molding is provided in the lower die 2, and the lower die 2 has a recess 2b into which the tip 3a of the piercing punch 3 can enter during molding.
Are formed.

The tip portion 3a of the piercing punch 3 is formed in a polygonal shape, for example, a triangular pyramid shape as shown in FIG. 3, a quadrangular pyramid shape as shown in FIG. 4, and an octagonal pyramid shape as shown in FIG. It is formed. In addition, a pentagonal pyramid shape, a hexagonal pyramid shape, or the like may be used. Further, it may have a cross shape as shown in FIG. 6, a Y shape, a star (*) shape, or the like.

When a work is formed using the draw forming die configured as described above, the processing plate is placed on the die face 2a of the lower die 2 and the upper die 1 is lowered as shown in FIG. As a result, the work W having the overhanging portion Wa is formed, but the portion to be discarded after forming between the overhanging portions Wa of the work W by the tip portion 3a of the piercing punch 3 descended together with the upper mold 1 before the completion of the forming of the work W. The predetermined position of is broken.

As a result, since the plate material extends in the direction of the arrow in the figure, it is possible to prevent the protruding portion Wa of the work W from becoming thin and cracking when the forming is completed. Therefore, the work having the protruding portion Wa in one step is prevented. W can be draw molded.

At this time, since the tip portion 3a of the punching punch 3 is formed in a polygonal shape, the running direction of the broken work W is from the center of the punch 3 to the polygonal corner portion. Since it is controlled substantially in the direction in which it extends, the elongation rate can be made substantially uniform from the breakthrough position. In this case, if the tip end portion 3a of the punching punch 3 is formed into a conical shape, the elongation does not become uniform because the directionality in the running direction of the cut does not appear, and a part of the protruding portion Wa of the work W becomes thin. Happens.

[0013]

As described above, according to the present invention,
The tip is formed in a polygonal shape, and a punching punch that breaks through a part of the work before the completion of forming the work is provided in the upper die,
Before the completion of forming the work, the punch punches through a part of the part to be discarded after forming the work, and then the forming of the work by the die is completed, so the thinning of the overhanging part is prevented and the overhanging part can be removed in one step. It is possible to form a work piece to have and reduce the number of steps. Further, since the tip shape of the punching punch is formed in a polygonal shape, the direction in which the cut runs can be controlled to some extent at the time of punching, the material can be stretched substantially uniformly, and the thinning of the overhanging portion can be made substantially uniform. Can be prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a draw forming die to which a draw forming method and device according to the present invention are applied.

FIG. 2 is an explanatory diagram for explaining the operation during draw molding.

FIG. 3A is a perspective view showing the shape of a punch for punching through;
(B) is a front view

4A is a perspective view showing another shape of the punch-through punch, and FIG. 4B is a front view.

5A is a perspective view showing another shape of the punch-through punch, and FIG. 5B is a front view.

6A is a perspective view showing another shape of the punch-through punch, and FIG. 6B is a front view.

[Explanation of symbols]

1 ... Upper mold, 2 ... Lower mold, 3 ... Punching punch, 3a ... Punching punch tip, W ... Work, Wa ... Overhanging portion.

Claims (2)

[Claims] 1. A draw forming method for forming a work having an overhang portion by press working, wherein an upper die is provided with a piercing punch having a polygonal tip, and the piercing punch of the work is formed by the piercing punch before the completion of the forming of the work. A draw forming method, characterized in that, after breaking through a part of a portion to be discarded after forming, forming of a work by a die is completed. 2. A draw forming apparatus for forming a work having an overhanging portion by press working, wherein the upper die is provided with a polygonal tip, and a piercing punch for piercing a part of the work is provided before the completion of the forming of the work. A draw forming device characterized in that