Analysis of common failures of metal stamping parts

Stamping is the first of the four major processes, and its importance can be imagined. The quality of the finished products of the stamping factory will lay a reliable foundation for the appearance and performance of the whole vehicle. Therefore, the quality assurance of stamping parts has always been an issue that the automobile manufacturing industry attaches great importance to. According to the practical experience of quality management in our stamping factory, the author summarized the causes and countermeasures of common problems in the production of metal stamping products, hoping to provide some useful references for improving the quality of the stamping factories' counterparts. 1. Why do metal stamping parts appear to be twisted? The stamping part is formed in the progressive die by punching the remaining material around the stamping part to form the shape of the stamping part. The main reason for the turning and distortion of the punching parts is the influence of the punching force. When punching, due to the existence of the punching gap, the material is stretched on one side of the die (the material is warped upward) and compressed on the side of the punch. When using the unloading plate, use the unloading plate to compress the material to prevent the material on the die side from warping upwards. At this time, the force of the material changes accordingly. As the discharge plate increases its pressing force, the material on the punch side is stretched (compression force tends to decrease), while the material on the concave die surface is compressed (tension force tends to decrease). The overturning of the stamping part is caused by the stretching of the material on the die surface. Therefore, when punching, pressing and compressing the material is the key point to prevent the punching from turning over and twisting. The reasons and countermeasures for the turning and twisting of the stamping parts during bending: 1. It is caused by the burrs of the stamping parts produced during the punching. Need to study the cutting edge, and pay attention to check whether the blanking gap is reasonable. 2. The turning, distortion and deformation of the punched parts have occurred during the punching process, which leads to poor forming after bending, which needs to be solved from the punching and unloading station. 3. It is caused by the instability of stamping parts during bending. Mainly for U-shaped and V-shaped bending. To deal with this problem, guiding the stamping parts before bending, guiding during the bending process, and pressing the material during the bending process to prevent the stamping parts from slipping during bending are the key points to solve the problem. 2. Why do metal stamping parts cause tearing? Common tearing and skewing forms of metal stamping parts. The stamping process of the middle protective surface bracket is: blanking and punching-punching incision-flanging forming-incision-flanging. There are many forms of tearing and skew during the forming process of the middle protective surface bracket. The tearing parts are mainly distributed at the hole pattern of the workpiece, and the R arc at the corner of the side wall and the junction of the wall neck, etc., due to stamping and production The difference in process conditions, the proportion of each fractured part is different. The tear can be a one-time forming tear or a tear caused by the development of fatigue cracks, that is, invisible cracks. Reason analysis: According to the actual situation of the site, by inspecting the tearing position, fracture shape and degree of crushing of the part, it is believed that the tearing and skewing behavior of the part is mainly reflected in the flanging forming process. The reasons for this process are as follows :1. The forming process parameters are not in place. During the forming of the part, the process requires that the die, the pressing core and the two parts must be closely attached to each other. When the machine tool slides down, the sheet metal is compressed plastic deformation. Realize shaping. However, due to the shortcomings of the pressed parts such as unstable quality, it shows that the pressure of the machine tool is in a state of unbalanced pressure fluctuation during the production process. The main reason is that the processing technicians did not adjust the pressure of the machine tool in time at this stage in accordance with the requirements of the process designation, or did not communicate the machine pressure stability information with each other during the handover of each shift, resulting in poor quality of the parts. stable. 2. Defects in the design of the flanging forming mold. The mold is shared by the left and right parts of a mold with two cavities. Because the content of this process is not only the flanging, but also the shape forming content. In addition, the parts are particularly complex, the curved surface is narrow, and the forming requirements are concave. The molding core is consistent with the molding surface, etc., resulting in a large molding stroke of the mold structure and a small pressing area. In the initial mold design, the designer only considered the feature of small blanking surface, but ignored the guiding slide stroke of blanking core. 3. Why is the surface quality of metal stamping parts poor? There are many reasons for the surface quality problems of metal stamping parts. The surface quality of coils, sheets, and molds will affect the quality of the final stamping parts. The operation during the stamping process and the clamping and removal of station equipment may also damage the system. The surface quality of the parts, therefore, the details should be fully considered in each link of the entire manufacturing process, and try to avoid quality problems that affect the appearance of the final product. 1. The common undesirable phenomena of coiled materials mainly include the following aspects: (1) There is foreign matter on the surface or inside of the steel plate; (2) The foreign matter peels off and the coil is in a scar-like state; the coil is bad (3) The corners of the coil Damaged; (4) Corners (20～30mm) deformed or wrinkled due to uneven stress; (5) Scratches (caused by roller surface or foreign substances); (6) Roller slipping; (7) Irregular edges Damage; (8) After the foreign matter enters, the bulge is pressed out on the back of the coil (the foreign matter will disappear when it falls); (9) Roller traces (caused by foreign matter adhering to the roller); (10) Bad material beyond the rules; (11) Foreign matter causes obvious groove marks on the surface depth. According to practical experience, in the above content, items 5, 8, and 9 are the most frequently occurring product defects or reasons.