Defect Overview
Material failure at punch shoulder position occurs when drawing load exceeds material strength. Characteristics include visible failure at punch R position, stretched flange areas, and bright spots on sidewalls.
Product Shape Factors
Drawing depth too large requires smooth material and comprehensive testing. Small punch or die radius needs correction. Small corner radius needs depth reduction, extra passes, or better material.
Stamping Conditions
Excessive blank holder pressure causes bright flange surfaces - adjust roughness, clearance, oil type. Poor lubrication is critical for drawing success. Poor blank shape needs corner cutting. Poor positioning causes misalignment. Wrinkling-induced defects have multiple causes including holder pressure, radius size, and clearance.
Die Relationship Factors
Rough surface needs mirror finish for stainless steel. Contact must achieve uniform distribution. Poor draw bead needs modification. Small clearance shows bright spots. Galling needs film prevention. Insufficient rigidity needs rigid replacement.
Material Factors
Poor drawability needs better material selection. Thin sheets need thicker stock. Tolerance needs tighter control. Aging needs fresh material.
