4. Layered whitening around the face of the substrate
Cause
The blanking gap of concave and convex die is not suitable or the edge of concave mode becomes dull. When punching, it is difficult for the punched sheet to form a shear crack at the concave pattern edge.
The substrate has poor punching performance or is not preheated before punching.
Low pressure.
The leakage hole at the lower part of the die edge is blocked or the leakage resistance is large, which causes expansion and delamination.
Solution:
Reasonably expand the concave and punch punching gap;
Repair dull concave die edge in time;
Increase the pressing force;
Adjust the substrate preheating temperature;
Enlarge or hinge light leakage hole.
