Causes and prevention methods of turnover and distortion of stamping parts

1. Causes of turnover and distortion during stamping

in the progressive die, the shape of the stamping part is formed by punching the remaining materials around the stamping part. The main reason for the turnover and distortion of stamping parts is the influence of blanking force. During blanking, due to the existence of blanking gap, the material is stretched on one side of the female die (the material warps upward) and compressed on the side of the male die. When the unloading plate is used, the unloading plate is used to compress the material to prevent the material on the die side from warping upward. At this time, the stress condition of the material changes accordingly. With the increase of the pressing force of the discharge plate, the material near the punch side is stretched (the compressive force tends to decrease), while the material on the die surface is compressed (the tensile force tends to decrease). The turnover of stamping parts is caused by the material on the die surface being stretched. Therefore, during blanking, pressing and compressing the material is to prevent the blanking parts from turning over and twisting

2. Methods of turning and twisting stamping parts

1) reasonable die design. The accuracy of the stamping process may be affected by the feeding sequence of the die. For the blanking of small parts of stamping parts, the blanking of large area is generally arranged first, and then the blanking of small area is arranged to reduce the impact of blanking force on the forming of stamping parts

2) press the material. Overcome the traditional die design structure and open the material holding gap on the discharge plate (that is, when the die is closed, the discharge plate fits with the concave die, and the gap between the discharge plate and the concave die at the place where the material is contained is t-0.03 ~ 0.05mm). In this way, the unloading plate moves smoothly during stamping, and the material can be compressed. For the key forming parts, the unloading plate is made into an insert structure to facilitate the solution of the wear (pressure) loss of the pressing part of the unloading plate caused by long-time stamping, and the material cannot be pressed

3) add strong pressure function. That is, thicken the pressing part of the unloading insert (normal unloading insert thickness H + 0.03mm) to increase the pressure on the material on the side of the female die, resulting in turnover, distortion and deformation of the stamping parts during punching

4) bevel or arc is made at the edge of punch. This is the way to slow down the blanking force. Reducing the buffer cutting force can reduce the tensile force on the material on the side of the die, so as to achieve the effect of turnover and distortion of the stamping parts

5) in daily die production, attention should be paid to maintaining the sharpness of the cutting edges of punching convex and concave dies. When the punching edge is worn, the tensile stress of the material will increase, and the tendency of turnover and distortion of the stamping parts will increase

6) unreasonable or uneven blanking clearance is also the cause of turnover and distortion of stamping parts, which needs to be overcome

3. Treatment of common specific problems in production

in daily production, the punching size will be too large or too small (possibly exceeding the specification requirements) and greatly different from the punch size. In addition to considering the design size, machining accuracy and blanking clearance of forming punch and die, it should also be solved from the following aspects

1) when the punching cutting edge is worn, the tensile stress of the material increases, and the tendency of turning and twisting of the stamping parts increases. When material turnover occurs, the punching size will become smaller

2) the strong pressure on the material causes plastic deformation of the material, which will lead to the increase of punching size. When reducing the strong pressure, the punching size will become smaller

3) punch edge end shape. If the end is trimmed with an inclined plane or arc, the punching part is not easy to turn over and twist due to the slow blanking force. Therefore, the punching size will become larger. When the end of the punch is flat (without inclined plane or arc), the punching size will be relatively smaller. In the specific production practice, specific analysis should be made for specific problems, so as to find out the methods to solve the problems. The above mainly introduces the causes and solutions of material turnover and distortion of blanking parts during blanking

4. Causes and Countermeasures of turnover and distortion of stamping parts during bending

1) caused by rough edges of stamping parts during blanking. It is necessary to study the punching cutting edge and check whether the blanking clearance is reasonable

2) during blanking, the blanking parts have been turned over, distorted and deformed, resulting in poor forming after bending, which needs to be solved from the blanking station

3) caused by the instability of stamping parts during bending. Mainly for U-shaped and V-shaped bending. The solution to this problem is to guide the stamping parts before bending, guide the stamping parts during bending, and press the material during bending to prevent the stamping parts from sliding during bending