How to solve the burr problem of precision metal stamping parts

For mold designers, the quality of the cross-section of the precision metal stamping parts designed is very important. But first, let's talk about what is blanking. Punching is a stamping process that uses a punching die to separate sheet materials under the action of a press. In a broad sense, punching is a variety of separation processes such as punching, blanking, cutting, cutting, and cutting. The general term. But generally speaking, blanking mainly refers to blanking and punching processes. Punching is a basic process in the cold stamping process, and it has a wide range of applications. It can directly punch out the required finished parts or prepare blanks for other cold stamping processes. After the sheet is punched, it is separated into two parts, namely the punched part and the holed part. If the purpose of punching is to obtain a certain shape of the contour and the size of the punched part; this kind of precision metal stamping parts The blanking process is called the blanking process, and the remaining part with holes becomes waste. On the contrary, if the purpose of punching is to obtain an inner hole of a certain shape and size. At this time, the punched part becomes waste, with holes, The part is the workpiece, and this punching process is called the punching process. See the table below. The classification of blanking is divided into ordinary blanking and precision blanking according to the roughness of the cut surface or the accuracy of the blanking parts. Ordinary blanking is when the workpiece is separated, due to the pressure of the die. In addition to the shear deformation of the material between the convex and concave edges, there are also deformations such as stretching, bending, and transverse extrusion. The material is finally torn The form is separated. Therefore, the section of the ordinary blanking workpiece is relatively rough, and has a certain taper, and its accuracy is low. Due to the special punching structure of the precision blanking, the material at the edge of the convex and concave die is finally plastic The form of shear deformation is separated. The section of precision blanking parts is smooth and perpendicular to the board surface, and the accuracy is high. Although the blanking separation process is completed in an instant, the deformation separation is very complicated. The stamping separation deformation is mainly divided into the following three Stages: 1. In the elastic deformation stage, under the pressure of the punch, the material at the cutting edge will first be deformed by elastic compression, stretching, etc. The punch is slightly squeezed into the inside of the material, and the bottom of the sheet is also slightly squeezed. Into the cavity of the concave mold, the material under the punch is slightly bent. The material on the top of the concave mold begins to warp. If the gap between the punch and the concave mold is larger, the warpage and warpage will be more serious, but at this time, the material inside The stress has not reached the limit state. When the external force is removed, the material can still return to its original state. This stage is called the elastic deformation stage, and the plastic deformation stage As the punch drops, the pressure on the sheet continues to increase, and the stress inside the material also increases. The increase. When the internal stress reaches the yield limit of the material, it begins to enter the plastic deformation stage, when the male and female molds further rush into the material. Due to the existence of the gap between the edges of the male and female molds, the tensile stress and bending inside the material change Larger, the compressive stress component decreases, the material is further bent and stretched, and the material hardening in the deformation zone is intensified. When the blanking force continues to increase until the material near the edge begins to produce microcracks, the blanking force also reaches the maximum. The appearance of microcracks (cracks) indicates that the material has begun to be damaged and the plastic deformation stage has ended. 3. The separation stage. The punch continues to drop, causing the sheet to produce upper and lower cracks and expand continuously, and extend to the inside of the material, as shown in Figure 2.1 -3. When the upper and lower cracks of the sheet overlap, it means that the material fibers are all torn and broken, and the part sections begin to separate. When the punch is lowered again, the punched part of the sheet is pushed out of the cavity of the cavity, and the initial The formed burr is further elongated, as shown in Figure 2.1-4. At this point, the punch has risen to complete the entire blanking process. The cross-sectional characteristics of ordinary blanking parts are analyzed by the cross-sectional characteristics of ordinary blanking parts, and we can find such a law. The cutting surface and the surface of the part are not perpendicular, but with a certain taper; except for a very narrow part of the bright band, the rest are rough and dull. There are burrs and corners. We separate the areas on the cross-section of the blanking part It is called collapse zone (also called rounded zone), bright zone (also called shear zone), fracture zone and burr. a-rounded b-bright zone c-fracture zone d-burr zone High-quality blanking parts The section should be: the bright band is relatively wide, accounting for more than 1/3 of the entire section; the collapse angle, the fracture zone, the burr and the taper are very small, and the entire blanking part is straight without bending, but The factors that affect the quality of the punching section are very complex, which vary with the properties of the material, thickness, blade gap, die structure and punching speed.