1. Adhesion and scratches: defects on the surface of the workpiece or mold due to the friction between the material and the punch or die;

2. Burr: mainly occurs in the shearing die and blanking die, and the gap between the cutting edges is large or small, which will produce burrs;

3. Line offset: When the part is formed, the first part that is in contact with the mold is extruded and a line is formed;

4. Concave and convex: there are foreign objects (iron filings, rubber, dust) mixed in the uncoiled line to cause convex and concave;

5. Twisting: due to uneven stress, poor matching of drawbeads or poor control of press sliders, etc., the r-corner or embossed parts of the workpiece are tortuous and strained;

6. Wrinkles: Wrinkles at the edges or r parts are caused by poor adjustment of the press slider, low press precision, inappropriate adjustment of the air cushion pressure, and large punch or r parts.

7. Other specific problems: In daily production, there will be situations where the punching size is too large or too small (may exceed the specification requirements) and the size of the punch is quite different, in addition to considering the design size of the forming convex and concave dies In addition to factors such as machining accuracy and blanking clearance, the following aspects should also be considered.

⑴. When the punching edge is worn, the tensile stress on the material increases, and the tendency of the stamping parts to turn over and twist increases. When the material is turned over, the size of the punching hole will become smaller.

⑵. The strong pressure on the material causes plastic deformation of the material, which will cause the size of the punching hole to increase. When the strong pressure is reduced, the size of the punching hole will become smaller.

⑶. The shape of the punch edge. If the end is trimmed with an inclined plane or an arc, due to the slowing down of the punching force, the punching piece is not easy to be turned over and twisted, so the size of the punching hole will become larger. When the end of the punch is flat (no slope or arc), the size of the punching hole will be relatively small.

8. The method of suppressing the turning and twisting of stamping parts

⑴. Reasonable mold design. In the progressive die, the arrangement of the blanking sequence may affect the forming accuracy of the stamping parts. For the blanking of small parts of stamping parts, generally a larger area of blanking is arranged first, and then a smaller area of blanking is arranged to reduce the impact of blanking force on the forming of stamping parts.

⑵.Press the material. Overcome the traditional mold design structure, open the material gap on the unloading plate (that is, when the mold is closed, the material can be compressed. The key forming part, the unloading plate must be made into a block-type structure to facilitate the problem of long The wear (pressure) loss caused by the pressing part of the stripper plate caused by the time stamping, and the material cannot be compressed.

⑶. Increase the pressure function. That is to increase the thickness of the pressing part of the unloading insert (the normal thickness of the unloading insert is H+0.03mm) to increase the pressure on the material on the die side, thereby preventing the stamping parts from turning over and distorting during punching.

⑷. The end of the punch edge is trimmed with a bevel or arc. This is an effective way to reduce buffering force. Reducing the buffer cutting force can reduce the tensile force on the material on the die side, so as to achieve the effect of inhibiting the turning and twisting of the stamping parts.

⑸. In the daily mold production, attention should be paid to maintaining the sharpness of the punching convex and concave mold edges. When the punching edge is worn, the tensile stress on the material will increase, so that the stamping parts tend to turn over and twist.

⑹. Unreasonable blanking gap or uneven gap is also the reason for turning over and twisting of stamping parts, which needs to be overcome.