Analysis and treatment measures for the existing problems of punching and turning
1. The cracks on the orifice of stamping hole are cracked. The main part of the pre hole section is tear surface, burr, where there is a stress concentration point, where the hole is poor in plasticity and easy to crack. The material with better elongation can increase the deformation degree of punching hole and reduce the hole cracking. In the case of molding permission, it is necessary to increase the diameter of the pre hole and reduce the degree of deformation of the hole. Under the condition of structural permission, thin material is used as far as possible to increase the relative diameter of the pre hole (D 0 /t), which helps to reduce the probability of turning and cracking. In the design of the die, the parabolic or spherical shape is best adopted for the flanging convex die, which can increase the degree of partial deformation of the material and reduce the cracking. In stamping process, the direction of punching hole can be opposite to the direction of the punch hole, so that burrs are located in the inner side of the turning hole, so that the cracking can be reduced.
2. The hole orifice of the punching hole is contracted, the flange is not vertical, and the diameter of the orifice becomes smaller. The main reasons for the closure are material springback, gap between punch and die, z/2 and so on. The material with better performance and less springback in production can improve the closing problem. When the die is designed, the proper clearance between the punch and die can be selected to ensure that the flanging flange is vertical. The gap between the punch and the concave die is generally slightly smaller than the material thickness.
3, the height of stamping hole is not enough after turning holes, which directly reduces the screwing length of screws and holes, and affects the reliability of screw connections. The factors that affect the flange height of stamping hole are too large pre pore diameter. The hole height can be increased by selecting a smaller punch hole diameter. When the diameter of the pre hole can not be reduced, the form of thinning and turning holes can be adopted to make the wall thinner to increase the height of the flanging flange.
4. The root R is too large after the R overturn hole in the root of the punching hole, which will cause a considerable part of the root of the assembly to have no contact with the screw, which reduces the screw length of the screw and the hole, and reduces the reliability of the screw connection. The excessive R in the root of the flanging hole is related to the thickness of the material and the rounded corners of the stamping die. The thicker the material is, the greater the R will be in the root. The larger the corner of the die, the greater the R will be. To reduce the root R of flanging holes, thin materials should be chosen as far as possible. When the thickness of the material is less than 2 times the thickness of the thick material or die entrance, the shaper should be designed to increase the shoulder of the plastic and plastic the root R at the end of the stamping stroke, or to increase the shaping process separately.
5. When punching holes are used to process flanging holes in the form of punching and turning holes, there is no corresponding structure on the die when punching holes. The material is broken and the punching waste may be randomly attached to the edge of the hole, which often causes the phenomenon of punching and cutting, and the vibration of these wastes is easily scattered at the die face or zero when the material is taken and carried. On the part, it causes the stamping defect on the surface of the parts. It needs to be repaired manually. It is difficult to meet the requirements for the rework of the external parts. It can only be scrapped and waste human and material. The scrap of the flanged hole is taken to the operator of the assembly easily and the screw is affected, and the electrical parts, such as the scrap of the edge hole, fall to the electrical appliance. It is also easy to cause short circuit in components and cause electrical safety problems.
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