JPH0314531B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for punching out a thin plate material, and in particular aims to extend the life of a mold by punching out a workpiece material under a tensile load. It is something.

The basic structure of a conventional punching die is shown in FIG. The mold is usually divided into an upper mold part 1 which is fixed to the ram of a press machine and moves up and down, and a lower mold part 2 which is fixed to a bolster or press bed. Upper mold part 1
This includes a punch 3, a punch plate 4 that holds it, a stripper plate 5 that presses and holds the thin plate between it and a die (described later), and a spring that separates the stripper plate 5 and punch plate 4. 6 and an upper die set 7 for setting them on the ram of a press machine. The lower mold part 2 is composed of a punching die 8 and a lower die set 9 for attaching them to the bolster or press bed of a press machine.

When punching, a workpiece 10 is placed between the upper mold part 1 and the lower mold part 2, and the punch 3 and the punching die 8 are engaged to perform the punching process. , a workpiece 10 such as a hardened steel plate or amorphous metal is punched out. FIG. 2 shows a cross-sectional view of a typical punched product 10A. In the figure, surface 11
is the surface in contact with the punch, and a sagging portion 12, a sheared surface 13, a fractured surface 14, a burr 15, etc. are generally observed. The height h from the surface 11 to the tip of the burr 15 is the burr height. When punching is performed, as the number of punched sheets increases, the burr height h also increases, and eventually it becomes impossible to punch through. Then, the number of punched pieces until the burr height h reaches a certain value or the number of pieces punched until no more punching is achieved is the punching life per one grinding, and the tool part of the mold is ground again. , punching is performed, and this process is repeated until the end of the mold life.

Next, the process until the material breaks during punching will be explained with reference to FIGS. 3 and 4. FIG. 3 is a cross-sectional view when the cutting edges of the punch 3 and die 8 bite into the workpiece 10. As shown in the figure, when the cutting edge is bitten to a certain point, the material in contact with the side surface of the cutting edge receives a large tensile strain, and a small crack 16 is generated there.
When the punch 3 further bites into the workpiece, a small crack 16 grows and breaks. FIG. 4 shows a cross-sectional view when punching is completed. The punching life is largely due to wear of the punch 3 and die 8 due to friction with the workpiece during the above-described machining process. Therefore, conventionally, as a measure to extend the punching life, the material and shape of the punch 3 and die 8,
Studies have also been carried out on the oil used during punching.

The present invention focuses on the fact that shearing of the material is due to the occurrence and growth of cracks 16 due to local tensile strain of the workpiece, and that the punching life is due to the wear of the die tool part. Punching is performed while pulling the workpiece in the directions of
In addition, by reducing the wear of the tool part of the die, the punching life and, ultimately, the life of the die are extended.

Conventionally, as shown in FIG. 5, a method of punching out a workpiece while applying a tensile load to the workpiece is to press the workpiece 10 with a puncher pin 19 biased by a spring 18 in a punch 3. Punching was performed by applying a tensile load. However, in this case, there is a tendency for a larger hole to be formed in the workpiece 10 due to the curvature and pulling direction of the workpiece 10, and although the punch 3 suffers relatively little wear, the die 8 tends to wear more. In particular, the harder the workpiece 10 is, the more remarkable this becomes.

The present invention improves the above-mentioned drawbacks and further extends the life of the mold. The embodiment will be described below based on FIGS. 6 and 7. The basic structure of the mold is shown in FIG. As in the conventional case, the upper mold part 1 includes a punch 3, a punch plate 4, a stripper plate 5, an upper die set 7, and furthermore, presser plates 23, 23' and tension blocks 24, 24' on both ends or on the outer periphery thereof. The lower mold part 2 is composed of a grooved die 25, a lower die set 9, and the like. When punching, workpiece material 1
0 is placed between the upper mold part 1 and the lower mold part 2 as shown in the figure. When the upper mold part 1 descends, the presser plate 23,
23' and the die 25 press down both ends or the outer periphery of the workpiece 10. Next, tension block 24,
24' is lowered so as to fit into the recess of the die 25, in this case the groove 25A, and the workpiece 10 is deflected so that a tensile load is applied to the central portion. Next, the workpiece 10 is held down by the stripper plate 5, and punched out by the punch 3. Processing using this method promotes the occurrence and growth of cracks in the workpiece, and the product that is sheared and punched with low punch pressure is released from the tensile load, becomes smaller than the die hole size, and the skeleton side Since the hole is expanded by the tensile load, the friction against the punch 3 and die 25 is reduced, and the amount of wear is reduced.

In particular, by providing the tension blocks 24, 24' on the outer periphery of the punch 3, tension is applied radially around the punch 3, resulting in a greater effect.

FIG. 7 shows a state diagram of the main parts at the bottom dead center of the press. The punch 3 and die 25 are made of cold die steel that has been hardened to about 60 to 62 on the Rockwell hardness C scale, and has a micro Vickers hardness of 85.
0. Figure 8 shows the relationship between the number of punched sheets and the burr height when a plate with a thickness of about 40μ is punched using the conventional method without applying a tensile load. FIG. 9 shows the relationship between the number of punched sheets and the burr height in the case where the sheet is cut out. As is clear from this figure, if the punching process is performed while applying a tensile load to the workpiece, a punching life of more than 10 times can be obtained even if the same mold material is used.

In addition, as shown in FIG. 10, the die 25 has a stepped portion 2.
5B, the workpiece 10 is once held down by the holding plates 23, 23' and the die 8, and then the workpiece 10 is pressed against the stepped surface 25C one step below by the stripper plate 5, and the workpiece 10 is pressed down by the stripper plate 5. A similar effect can be obtained by punching holes with the punch 3 after stretching the material. In particular, by providing the presser plates 23, 23' on the outer periphery of the punch 3, tension is applied radially around the punch 3, resulting in a greater effect.

As described above, according to the present invention, after applying a tensile load to a thin plate, a hole is made, and the skeleton is kept under tension until the tip of the punch comes out of the stilton of the thin plate. It reduces wear and prevents the skeleton from sticking to the punch, which extends the punching life and has a great effect on extending the life of the mold.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the conventional mold structure, and Figure 2 is
Cross-sectional views of common punched products, Figures 3 and 4
The figure is a cross-sectional view showing the state of the die tool and workpiece during punching, Figure 5 is a cross-sectional view showing the state in which a puncher pin is attached in the punch and a tensile load is applied to the workpiece, and Figure 6 is a cross-sectional view showing the state of the die tool and workpiece during punching. FIG. 7 is a cross-sectional view of the mold structure of an embodiment of the present invention, and FIG. 7 is a cross-sectional view showing the state at the bottom dead center of the press. FIGS. FIG. 10 is a graph showing the number of punched sheets and burr height when punching is performed, and FIG. 10 is a sectional view of the main part of a mold of another embodiment of the present invention. 3... Punch, 5... Stripper plate,
25...Die, 25A...Groove, 25B...Step part, 25C...Step surface, 10...Work material, 2
3, 23'... Pressing plate, 24, 24'... Tension block.

Claims (1)

[Scope of Claims] 1. A punch that is attached to a punch plate and moves together with the punch plate to punch a thin plate into a predetermined shape between the punch plate and the die, and a presser plate and a tension block that are attached to the punch plate. , the thin plate is held on the outside of the recess by the die provided with the recess and the presser plate, and the thin plate is held between the entire circumference surrounding the recess or at least two places, and then the tension is Applying tension to the thin plate by protruding the thin plate into a concave portion of the die in a convex shape substantially parallel to the punching direction using a shock block, and further punching the thin plate into a predetermined shape using the punch and the die, A method for punching a thin plate, characterized in that a state in which tension is applied to the skeleton is maintained until the tip of the punch is removed from the skeleton of the thin plate. 2. A punch for punching a thin plate into a predetermined shape, a die having a predetermined-shaped hole at a position opposite to the punch, and a stripper located around the punch and holding the thin plate by sandwiching it between the die and the die. A thin plate punching device comprising a plate and a presser plate that holds the thin plate between the die and the die at the outer periphery of the stripper plate, wherein the die is provided with a step and the plate is held by the presser plate. The stripper plate projects the thin plate into a convex shape substantially parallel to the punching direction at the step between the stripper plate and the step surface of the step. A thin plate punching device configured to punch out a thin plate while holding it in between.