How to make a beautiful edge with punching and flanging

Punching and flanging is one of the processes in the production process of stamping parts, generally for the next step of tapping or other processes. And sometimes there will be some quality problems such as burrs, deformation, cracking, etc. So in order to better product quality, how can the punching company do the punching and flanging to turn out beautiful edges? 1. The degree of deformation of the inner hole flanging of the stamping part should not be too large. Punching flanging is a stamping method in which a hole is pre-punched on a blank (sometimes not pre-punched), and a vertical flange is turned along the edge of the hole. The dominant and mandatory deformation of the hole flanging is the tensile deformation of the material along the tangential direction, and the closer it is to the mouth, the greater the deformation and the greater the thinning. Therefore, the defect of hole edge cracking is prone to occur. In order to prevent the edge of the hole from cracking, the degree of deformation of the inner hole flanging of the stamping part should not be too large. If the height of the flanging is large, it can be divided into several flangings. 2. The flanging coefficient of punching and flanging should not be too small. In punching and flanging, the degree of deformation is expressed by the ratio of the aperture before flanging to the aperture after flanging, that is, the flanging coefficient K. Obviously, the larger the K value, the smaller the degree of deformation, the smaller the K value, the greater the degree of deformation, and the more likely the edge of the burr hole is to crack. The full value of the maximum degree of deformation that the hole edge can achieve without breaking during flanging is called the allowable limit flanging coefficient. In order to prevent edge cracking, the flanging coefficient of hole flanging should not be too small, and should be greater than the limit flanging coefficient. Production practice shows that the limit flanging coefficient is not only related to the type and performance of the material, but also to the processing properties and state of the prefabricated hole (drilled or punched, with or without burrs), the relative thickness of the blank, and the shape of the flanging punch, etc. The factor is related. 3. The flanging height of punching and flanging should not be too large. Generally, the height of punching and flanging should not be greater than the limit value, otherwise, the flanging edge is easy to crack. If the required height of the stamping part is greater than the limit value, it cannot be directly flanged at one time. At this time, if it is a small hole flanging of a single blank, a flanging with a thinner wall should be used, such as a self-tapping screw for flanging. If it is a large hole flanging, use the method of deep drawing, punching the bottom hole and then flanging. 4. The pre-holes of punching and flanging should not have large burrs. The processing quality of the pre-holes of punching and flanging has a great influence on the limit flanging coefficient. Pre-holes that are deburred after drilling have a small limit flanging coefficient, which is beneficial to flanging. For pre-holes punched with a punching die, if there are burrs, the limit flanging coefficient is large, which is unfavorable for flanging. At this time, if the required flanging coefficient is small, it is very easy to cause the flanging hole to crack. Take the side with the burrs up, and then carry out the flanging to reduce the phenomenon of flanging cracking. 5. The fillet radius of the punching and flanging punch should not be too small. For the flanging with prefabricated holes, the fillet radius of the punching punch should be as large as possible, and it can be made into a spherical or parabolic shape. In this way, the hole turning force is small, and the hole turning quality is also good. 6. The gap between the punch and the die of the hole flanging should not be too large. In order to avoid or reduce shrinkage, the gap between the convex and the die of the hole flanging should not be too large. If the mold gap is too large, the material does not move close to the die during flanging, resulting in greater shrinkage and residual bending deformation, which will affect the flanging quality of metal stamping parts. 7. When turning the hole, the thickness of the vertical side mouth can not be ignored. When turning the hole, the deformation zone is basically limited within the round corner of the die. The material in the deformation zone is elongated and deformed in the tangential direction under the action of unidirectional or bidirectional tensile stress. Greater than the radial compression deformation, resulting in material thickness reduction. The maximum thinning of the vertical edge of the hole, when the thickness is too thin, and the material elongation exceeds the ultimate elongation of the material, so-called p-rupture occurs. When punching and flanging, the smaller the flanging coefficient K value, the greater the degree of deformation, and the greater the thickness of the vertical side mouth is reduced, and the easier it is to break. Therefore, the thinning of the thickness of the vertical side mouth cannot be ignored when the hole is punched. [Related recommendation] Learn more: What are the methods for polishing the surface of stainless steel? 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