JPH0523755A - Punching method for metallic plate and die - Google Patents

Abstract

PURPOSE:To suppress the generation of a burr by using a die of an extremely general and simple configuration which does not necessitate a complicated press equipment, and also, does not necessitate an especially strict management for a clearance and a blade tip, at the time of punching a metallic plate. CONSTITUTION:On the tip face of a punch 1, a projecting part 1a of a smaller shape than a punching shape is provided, and prior to punching shear by a cutting blade of the punch 1, the part positioned in the inside of a shearing scheduled line of a punching object part of a metallic plate P is overhung in the punching direction, and a bending deformation by a die 3 shoulder is applied to the shearing scheduled line part of the metallic plate concerned P. The shearing scheduled line part of the metallic plate is worked and hardened by a plastic distortion by the bending deformation, and generation of a burr at the time of punching and shearing by the cutting blade of the punch can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for punching a metal plate and a die.

[0002]

2. Description of the Related Art Pressing a metal plate for manufacturing automobile parts and the like always includes a punching process such as piercing and trimming by a press machine. But,
Generally, a burr (hereinafter referred to as a burr) occurs on the sheared end surface during punching, and if this burr becomes high, it may cause a defective combination of parts, or the paint may not ride well at the time of coating, resulting in deterioration of corrosion resistance. Adversely affect.

Therefore, in order to keep the height of the burr generated by punching a metal plate within an allowable value, the mold clearance has been made strict and the wear control of the cutting edge has been made strict. However, this is not always possible due to the shape of the mold and the shape of the parts. In practice, it is very difficult to finish the entire product to a certain clearance, especially in the case of a die with a contoured contour, because of precision problems in machining and assembling the die and mounting it on the press machine. Since a large clearance is unavoidable in some cases, a burr outside the allowable range is often generated in a part of the molded product. Further, as the clearance is reduced in order to prevent this, the wear of the cutting edge increases, and the possibility of causing serious trouble such as chipping increases. On the other hand, burrs generated during punching are also removed in another step such as polishing or grinding, but in this case not only the number of steps is increased, but also all burrs cannot be removed. Is included.

[0004]

In order to solve these problems, various studies have heretofore been made in various fields. For example, the precision shearing method and the vertical punching method described below, and further Pushing methods have been proposed. However, these methods have drawbacks in that a complicated mold and a pressing device are required and the shearing step is performed in multiple steps.

For example, in Japanese Laid-Open Patent Publication No. 1-293922, a punch or a die having one side has a radius of 0.2 mm or a rounded plate having a radius of about 0.2 mm or a thickness of a machined plate, or a chamfered die is used for precision punching. A method of processing has been proposed. However, with this method, it is very difficult to form a predetermined roundness on the cutting edge of the tool and to maintain the roundness.

Further, JP-A-63-157728 and JP-A-63-157728
In the -157729 publication, in press working of a magnetron ball piece or the like, when shearing the peripheral edge after molding, the stripper is provided with an inclination or the peripheral edge is bent to prevent burrs from being generated in the pushback process. Methods to prevent it have been proposed. However, this method is intended to prevent the generation of burrs in the pushback step after shearing, and it does not reduce burrs at the time of shearing, and has the problem that the structure of the mold becomes very complicated. .

Further, in Japanese Patent Laid-Open No. 64-34525, in the drawing process having an edging process, a die and a punch having a diameter slightly larger than that of the die are used to make a boundary portion of a member thin so that a product and a scrap are distinguished from each other. Then, a method of completely removing the burr in the subsequent tumbling process has been proposed. However, according to this method, since the punch diameter is slightly larger than the die diameter, unless the punch bottom dead center is precisely controlled, the die may be damaged by contact with the die, and a disaster may be caused by scattering of the damaged material. There is a possibility that it is not preferable.

The present invention has been made to solve the above-mentioned problems of the prior art, and does not require a pressing device having a complicated structure for punching a metal plate, and has a particularly strict clearance. It is an object of the present invention to provide a metal plate punching method and a metal mold that can suppress the occurrence of burrs with a metal mold having an extremely general and simple structure that does not require management of the blade edge.

[0009]

In order to achieve the above object, the present invention has the following constitution. That is, the punching method of the metal plate according to the present invention is, in the punching process of the metal plate using the punch and the die, prior to the punching shearing by the cutting edge of the punch, inward from the planned shear line of the punching target portion of the metal plate. It is characterized in that the portion located at is protruded in the punching direction and bending deformation due to the die shoulder is applied to the planned shear line portion of the metal plate.

Further, a metal plate punching die according to the present invention is a metal plate punching die comprising a punch and a die, wherein the punch has a protrusion having a shape smaller than the punching shape on its tip end surface. It is characterized by having.

[0011]

[Function] As many studies have been done so far on shearing of metallic materials, it is done by making the cutting edge of the tool bite into the work material, and if the biting amount exceeds the limit, cracks will occur from the cutting edge and separation will occur. Reach From the detailed analysis result of the stress state at this time, the crack is related to the stress generated in the material, and as shown in FIG.
It is known that it occurs just a little bit from the cutting edge to the tool side. As a result, burrs are always generated at the cut end of the product separated by shearing.

As can be seen from the burr formation mechanism, burr formation is inevitable as long as normal shearing is performed, but there are many factors that affect burr formation. As the processing conditions, as shown in the graph of FIG. 4, the clearance of the die and the wear of the cutting edge have a great influence, but the material factor is the material strength of the work material. The material strength has a relationship between ductility and strength. The lower the material strength is, the higher the ductility is, and cracks are generated at a position farther from the cutting edge toward the tool side, and burrs are easily generated.

The present inventor pays attention to this point, and before the start of shearing, that is, before the cutting edge of the tool bites into the material to be processed, the portion to be sheared is hardened to deteriorate the ductility. It is possible to suppress the occurrence of burrs with, and to harden the shearing part of the work material, we obtained the knowledge that it can be achieved by giving a plastic strain to the site and work hardening, and based on this finding The invention was completed. That is,
In the method of the present invention, prior to punching and shearing by the cutting edge of the punch, a portion of the metal plate located on the anti-product side from the planned shearing line of the punching target portion is projected in the punching direction, and the planned shearing line portion of the metal plate is provided. Since bending deformation due to the die shoulder is added to, the material of the part is work hardened by plastic strain due to bending deformation,
It is possible to suppress the occurrence of burrs when punching and shearing with the cutting edge of the punch.

Further, in the die of the present invention, the punch has a projecting portion having a shape smaller than the punched shape on the tip end surface thereof. Therefore, prior to the punching shearing by the cutting blade of the punch, the planned shear line of the punched portion of the metal plate is formed. The part located more inward is overhanged in the punching direction by the protruding part on the tip surface, bending deformation is applied to the planned shear line part of the metal plate by the die shoulder, and the material of the part is plasticized by bending deformation. It is possible to suppress the occurrence of burrs when work-hardening by strain and punching and shearing with the cutting edge of the punch.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. [FIG. 1] is a schematic explanatory view of a die according to an embodiment of the present invention and punching of a metal plate by the die.

The structure of the die of this example will be described with reference to FIG. 1 (a). The die of this example has a punch having a protrusion (1a) smaller than the punched shape on the lower end surface. Comprises (1), stopper (2) and die (3), punch (1)
It has a very general configuration except that a protrusion (1a) is provided at the lower end of the. Also, this mold is attached to a conventional press machine. In the figure, P is a metal plate as a workpiece, and the metal plate P is placed on the die (3) and punched.

Next, the process of punching the metal plate P will be described with reference to FIGS. 1 (b) to (d). First, as shown in (b), the stopper (2) is lowered to sandwich and hold the metal plate P with the die (3). Also, continue to punch
(1) is lowered.

When the punch (1) descends, as shown in (c), the protrusion (1a) at the lower end of the punch (1) causes
A portion of the metal plate P, which is located inward of the planned shear line of the portion to be punched, projects downward, and the planned shear line portion of the metal plate P is subjected to bending deformation by the die shoulder. And
Due to the plastic strain due to this bending deformation, the material of the portion to be sheared of the metal plate P is hardened and the ductility is deteriorated.

When the punch (1) further descends, as shown in (d), the cutting edge formed on the periphery of the punch (1) bites into the metal plate P to start shearing. Undergoes the same shearing as in ordinary punching, but in this example, since the ductility of the material in the shearing scheduled portion of the metal plate P has deteriorated, shear cracking occurs at a position closer to the cutting edge of the cutting blade. As a result, the occurrence of burrs can be suppressed to a very small level.

Next, under the above-mentioned structure, the thickness is 0.7 mm.
A specific example in which the cold-rolled mild steel sheet of (1) is punched into a hole shape having a diameter of 10 mm will be described.

The mold has a cutting blade with a diameter of 10 mm, the lower end surface has a diameter of 6 mm, and heights of 1.5 mm and 3.0 mm.
Two punches with the protrusions and the diameter of each punch hole are 10.10mm, 10.15mm, 10.24mm and 10.
A combination of 4 types of dies with a size of 32 mm was used. For comparison, a conventional punch having a cutting edge with a diameter of 10 mm and having no protruding portion on its lower end surface was used to cool the same as above using a die combined with the above four types of dies. In the same way, punching of a round hole shape with a diameter of 10 mm was performed on a rolled mild steel sheet.

These results are summarized in the relationship between clearance and burr height and shown in comparison with the graph of FIG. In the graph in the figure, the solid curve A has a height of 3.0 mm.
In this example, the punch B is provided with the protruding portion of
Shows the result of the present example using a punch provided with a protrusion having a height of 1.5 mm, and the broken line curve C shows the result of the comparative example.

As is clear from the graph in the figure, the punching process of this example has a smaller burr height than the comparative example at any clearance, and the greater the clearance, the greater the difference. From this, it was possible to confirm the excellent effects of the method and mold of the present invention.

In the above embodiment, an example in which simple round hole punching is performed has been described, but this is an example, and the present invention is not limited to this example, and a complex shape is not required. It goes without saying that it can also be applied to punching holes and trimming molded products with complicated outer shapes.

[0025]

As described above, according to the metal plate punching method and die of the present invention, there is no need for a pressing device having a complicated structure, and the clearance and the cutting edge are particularly strict. With a very general and simple mold configuration that does not require the management of, it is possible to suppress the occurrence of burrs due to the punching process of the metal plate, and to obtain an effect of high industrial value.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a die according to an embodiment of the present invention and a punching process of a metal plate by the die.

FIG. 2 is a graph showing a relationship between clearance and burr height according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a burr generation mechanism in shearing a metal material.

FIG. 4 is a graph showing the relationship between the clearance of a mold and the height of burrs in shearing a metal material.

[Explanation of symbols]

(1) --Punch (1a)-projection (2) --Stopper (3) --Die P --Metal plate

Claims (2)

[Claims] 1. In punching a metal plate using a punch and a die, prior to punching and shearing with a cutting edge of the punch,
A metal plate characterized in that a portion of the metal plate that is located on the side opposite to the product to be sheared of the portion to be punched is projected in the punching direction, and the portion to be sheared of the metal plate is subjected to bending deformation by a die shoulder. Punching method. 2. A punching die for a metal plate comprising a punch and a die, wherein the punch has a protrusion having a shape smaller than the punched shape on the tip surface thereof. Punching die.