1. Eccentricity: Poor installation and improper adjustment of the second punch.
2. Tilt head: poor installation and improper adjustment of the first punch.
3. The head is not round: the selection of a punch is improper or the punch is not full enough.
4. Cracks in the mold: the mold is broken or the R angle of the mold is improper, so that the mold is scraped by the second impact.
5. Double layer on the head: poor forming in one punch.
6. Burr: poor forming in one punch, mainly caused by too large gap between punch and die hole or too short punch.
7. Crack angle: the punching needle is broken or the second punch is not heavy with the punching.
8. Cracked head: material problem, or the wrong use of a die, and the reason for lubricating oil.
