In the production process of metal stamping parts, we will encounter the situation that the punching size is too large or too small, and it is quite different from the punch size. In order to solve this kind of problem, we should not only consider the planning size, machining accuracy and blanking clearance of forming punch and die, but also think from the following aspects.

1. In the production of metal stamping parts, due to the rough edges of stamping parts during blanking, it is necessary to study the punching cutting edge and pay attention to check whether the blanking clearance is reasonable. It is mainly caused by the instability of stamping parts during bending. For U-shaped and V-shaped bending, the key to solve the problem is to guide the stamping parts before bending, guide the stamping parts during bending, and press the materials during bending to prevent the stamping parts from sliding during bending.

2. In the production of metal stamping parts, the tensile stress of materials increases, and the tendency of turnover and distortion of stamping parts increases. When material turnover occurs, the punching size will become smaller. The strong pressure on the material causes plastic deformation of the material, which will lead to the increase of punching size. When the strong pressure is reduced, the punching size will become smaller.

3. In the production of metal stamping parts, if the end is repaired with an inclined plane or arc, because the blanking force is relieved, the stamping parts are easy to turn over and smear, so the punching size will become larger. The punch end is flat, and the punching size will be relatively smaller.