How to realize double-sided burr-free blanking

Definition of blanking

For mold designer, the quality of the designed product section is very important. Blanking is a kind of stamping process which uses blanking die to separate the sheet metal under the action of press. In a broad sense, blanking is the general name of various separation processes such as punching, blanking, cutting, cutting and so on. But generally speaking, blanking mainly refers to blanking and punching.

Negative gap blanking: a method of double-sided burr-free blanking of stamping die

It is estimated that many friends have heard of negative clearance blanking, as long as they have been engaged in stamping die, but many friends don’t know the real principle. Generally speaking, our stamping products have burrs in only one direction. If we want to eliminate burrs in this direction, we can carry out the process of pressing burrs in the die. If we don’t do this, it seems that we can only pass the method of negative clearance blanking.

Burrs are always produced during blanking, and it is difficult to eliminate them. Therefore, burrs are often pressed after machining to eliminate them. In view of the problem of parting surface, there is an increasing trend of deburring recently.

Here is a machining method to eliminate burrs, which is usually called “flat pressing method”.

A half-blanking is carried out. Usually, the punch is slightly larger than the die. This state is called “negative gap”.

When the punch is pressed into the material, the collapse angle of the material is only formed when it is pressed out to one side of the female die. At this time, the pressing amount of the punch is very important, usually set to more than 75% of the thickness of the material.

The next process is the flat pressing process. The operation of the flat pressing process is very simple, but its content is very special. The material is in the state of half blanking. This shape is divided into three parts to consider.

The virtual punch part, the virtual die part and the part sandwiched by the virtual punch and the virtual die are used to punch the materials of these parts. The process of punching yourself and generating the corner collapse is the core of the flat pressing process.

In order to realize the ideal flat pressing process, it is necessary to have an appropriate half-pressing amount in the blanking process. If it is too shallow, a virtual punch or a virtual die cannot be formed, and if it is too deep, it will be punched out before the flat pressing process. The reason for choosing the negative gap is to avoid material occlusion in the flat pressing process.

In terms of the final size of machining, the overall size of the punched part is basically the same as that of the punch in the semi-quantitative blanking process, which is slightly different from the ordinary blanking.

In addition, in the blade part of negative clearance blanking, we need to design the stripper block in the lower die, so as to ensure the flatness of the product. Of course, it is not necessary if the product is very small.

 

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