1. Adhesion and scratch: defects on the surface of part or tooling due to the friction between material and punch or die.
2. Burr: it mainly occurs in the shear die and blanking die. Burr will occur when the gap between cutting edges is large or small.
3. Deflection: Due to uneven stress, poor matching of tensile reinforcement, or poor control of the press slide, resulting in assembly corners or embossing parts have twists and turns, strain.
4. Uneven: Foreign matters (iron scurf, rubber and dust) are mixed in the coil front line to cause uneven.
5. Offset: When the piece is shaped, the site first contact with the mold was squeezed and a line was formed.
6. The punching size is too large or too small: In case of large difference from the punch size, the factors such as design size, machining accuracy and cutting clearance shall be considered.
