The main reasons: ① The mold gap is too small, it is generally recommended that the total mold gap is 20% to 25% of the material plate thickness. ②The unevenness of the convex and concave molds is not good, including the lack of precision of the mold base and the mold guide assembly and the turret insert, which causes the mold to be poorly neutral. ③The temperature of the punch is too high, which is mainly due to the overheating of the punch due to the continuous stamping of the same die for a long time. ④ Improper sharpening method of the mold causes annealing of the mold and aggravated wear. ⑤ Partial unilateral punching, such as step punching, punching angle or shearing, the lateral force will bias the punch to one side, the clearance of this side is reduced, causing serious mold wear, if the machine tool mold installation accuracy is not high, serious Will cause the punch to overshoot the lower die, causing damage to the punch and die.