Analysis and treatment measures of the problems existing in punching and turning holes

Analysis of problems existing in punching and turning holes and treatment measures 1. Cracking of punching and turning holes cracks on the circumference of the hole. The main reason is that the punched-out pre-hole section has a tearing surface, which produces burrs. There is a stress concentration point in this place, and the plasticity is poor in the process of drilling, and it is easy to crack. The use of materials with better elongation can increase the degree of deformation at the punching hole and reduce the hole cracking. If the molding allows, try to enlarge the pre-hole diameter, reduce the deformation of the hole, and help reduce the crack of the hole. If the structure permits, use thinner materials as much as possible to increase the relative diameter (D 0 /t) of the pre-holes, which helps to reduce the probability of cracking. When designing the mold, it is best to use a parabolic or spherical shape for the hole-turning punch, which can increase the allowable degree of deformation of the local material and reduce cracking. During the punching process, the direction of punching and turning holes can be opposite to the direction of punching pre-holes, so that the burrs are located on the inner side of the turning holes, which can reduce cracking. 2. After punching and turning the hole, the hole shrinks, the flange is not vertical, and the diameter of the hole becomes smaller, which will cause difficulty in screwing during assembly. The main reasons for the closing are the resilience of the material and the large gap between the punch and the die z/2. The material with better performance is used in the production, and the rebound is small, which can improve the closing problem. When designing the mold, select a suitable gap between the convex and concave molds to ensure that the flange of the turning hole is vertical. The gap between the male mold and the female mold is generally slightly smaller than the material thickness. 3. The height of the punching hole is insufficient. After the hole is turned, the height of the flange is insufficient, which directly reduces the screw length between the screw and the hole, and affects the reliability of the screw connection. The factors that affect the height of the punching flange include the pre-hole diameter is too large. Choosing a smaller punching hole diameter can increase the height of the punching hole. When the hole diameter of the pre-hole cannot be reduced, the method of thinning the hole can be adopted to make the wall thinner to increase the height of the flange of the hole. 4. If the root R of the punched hole is too large, the root R is too large after the hole is turned, which will cause a considerable part of the root to have no contact with the screw during assembly, which reduces the screw length between the screw and the hole and reduces the reliability of the screw connection. The excessive R at the root of the flanging hole is related to the material thickness and the fillet of the punching and flanging die. The thicker the material, the larger the root R will be; the larger the fillet at the entrance of the die, the larger the root R will be. To reduce the root R of the flanging hole, thin materials should be used as much as possible, and a smaller die entrance fillet should be designed in the mold design. When thicker materials are used or the fillet of the die entrance is less than 2 times the material thickness, the punching punch should be designed to increase the shoulder with shaping, and the root R should be shaped at the end of the stamping stroke, or the shaping process should be added separately. 5. When punching and boring waste material is used to process edging holes in the form of punching and boring, there is no corresponding structure matching on the die during punching, the material is broken, and the punching waste may randomly stick to the edge of the hole, causing frequent With the phenomenon of punching waste, the vibration of these waste materials is easily scattered on the mold working surface or parts, causing imprinting defects on the surface of the parts, requiring manual repair, and it is difficult to meet the requirements for the appearance of parts to be repaired and can only be scrapped Handling wastes manpower and materials; waste materials from flanging holes may be brought to the final assembly to cut the operator and affect the screwing; for electrical parts, such as waste materials from flanging holes, falling into electrical components during screwing may also cause short circuits This leads to electrical safety issues. Previous: Application of PVD Coating on Metal Stamping/Forming Die