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 skin, dust) mixed in the uncoiling line to cause convex and concave;
5. Twisting: due to uneven stress, poor matching of drawbeads or poor control of the press slider, etc., the r-corner or embossed parts of the workpiece are tortuous and strained;
6. Wrinkles: due to poor adjustment of the press slider, low precision of the press, inappropriate adjustment of the air cushion pressure, large punch or r part, the edge or r part wrinkle is caused
