1. Sring broke because Escape hole of spring and the blcking plate did not the center. Then the broke spring to abut between stripper plate and die holder while pumping. So it made the part forming incomplete.
2. The operator did not find the problem because they did not check this point. They concentrate at the knock hole position.
3. The QC did not find the problem because they did not inspect the last piece of part. (Standard did not define to inspection)