Twisting distortion

1. Causes of turning over and twisting during stamping

In the progressive die, the shape of the stamping part is formed by cutting the surplus material around the stamping part. The main reason for turning and twisting 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 die (material warps upward), and compressed on the side of the punch. 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 correspondingly. With the increase of the pressing force, the material on 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 turning of stamping parts is caused by the material on the die surface being stretched. Therefore, when punching, pressing and pressing the material is the key point to prevent the punching parts from turning over and twisting.

2. Methods to prevent the stamping parts from turning over and twisting

(1) reasonable mold design. In progressive die, the arrangement of blanking sequence may affect the forming accuracy of stamping parts. In order to reduce the impact of punching force on the forming of stamping parts, large area blanking is usually arranged first, and then small area blanking is arranged.

(2) press the material. In order to overcome the traditional mold design structure, the discharge gap is made on the discharge plate (that is, when the mold is closed, the discharge plate fits the die, while the gap between the discharge plate and the die at the place where the material is contained is t-0.03-0.05mm in material thickness). In this way, the discharge plate moves smoothly in stamping, and the material can be compressed. For the key forming parts, the discharge plate must be made into a inlaid structure, so as to solve the abrasion (compression) damage caused by the pressing part of the discharge plate caused by long-time stamping, and the material cannot be compressed.

(3) add strong pressure function. That is to say, the thickness of the pressing part of the discharge insert is increased (the normal thickness of the discharge insert is H + 0.03mm), so as to increase the pressure on the material at the die side, so as to prevent the stamping parts from turning over and distortion during punching.

(4) bevel or arc shall be made at the edge end of the punch. This is an effective way to reduce the punching force. By reducing the buffer cutting force, the drawing force on the die side material can be reduced, so as to achieve the effect of preventing the stamping parts from turning over and twisting.

(5) in daily mold production, attention should be paid to maintain the sharpness of punching convex and concave die edges. When the cutting edge is worn, the tensile stress of the material will increase, so that the tendency of turning over and twisting will increase.

(6) unreasonable or uneven blanking clearance is also the cause of stamping parts turning and twisting, which needs to be overcome.

3. Handling of common and specific problems in production

In daily production, the punching size is too large or too small (may exceed the specification requirements) and the difference with the punch size is large. In addition to the design size, processing accuracy and blanking clearance of forming punch and die, the following aspects should be considered to solve.

(1) when the cutting edge is worn, the tensile stress of the material increases, and the tendency of turning over and twisting of the stamping parts increases. When turning over occurs, the punching size tends to be smaller.

(2) the strong pressure on the material will cause plastic deformation of the material, which will lead to the increase of punching size. When the pressure is reduced, the punching size will be smaller.

(3) the shape of the edge end of the punch. If a bevel or arc is made at the end, the punching size will be larger because the punching force is slowed down and the punching parts are not easy to turn over and twist. When the end of the punch is flat (no bevel or arc), the punch size will be smaller.

In the specific production practice, it is necessary to analyze the specific problems and find out the solutions.

The above mainly introduces the causes of turning over and distortion of stamping parts and the solutions.