Causes and solutions for uneven height on both sides: 1. Material positioning should be accurate, 2. We need 3mm pistols. Adjustment of gap between punch and die. Reasons and measures for the polishing angle of the inner surface of the concave mold to be greater than 90 degrees: 1. The punch clearance is reasonable, based on the actual material thickness2. Negative angle of perforation is 1-2 degrees (88-89 degrees)3. If not, add an arc at the bottom. As a last resort, add plastic surgery.