1. Adhesion, scratches: defects that appear on the surface of the part or mold due to the friction between the material and the convex mold or the concave mold.
2. Burr: It mainly occurs in the cutting die and blanking die, and the gap between the cutting edges may be large or small, which will produce burrs.
3. Line offset: When the part is formed, the part that first contacts the mold is squeezed and a line is formed.
4. Concave and concave: foreign matter (iron filings, rubber, dust) mixed in the uncoiling line causes convex and concave.
5. Twisting: due to uneven stress, poor drawbead matching, or poor control of the press slider, the r-corner or embossed part of the workpiece is bent and strained.
6. Wrinkles: Wrinkles on the edges or r parts due to poor adjustment of the press slider, low press accuracy, improper adjustment of the air cushion pressure, large punch or r part, etc.
7. Other specific problems: In daily production, you will encounter situations where the punching size is too large or too small (may exceed the specification requirements) and the size of the punch is quite different, except for the design dimensions of the forming convex and concave molds. In addition to factors such as machining accuracy and blanking clearance, the following considerations should also be taken into consideration.
⑴. When the punching edge is worn, the tensile stress of the material increases, and the tendency of the stamping parts to turn over and twist increases. When turning over, the size of the punching hole will become smaller.
⑵. The strong pressure on the material causes plastic deformation of the material, which will cause the punching size to become larger. When the strong pressure is reduced, the punching size will become smaller.
⑶. The shape of the end of the punch blade. If the end is trimmed with a slope or arc, the punching force will be slowed down, and the punching part will not be easily turned or twisted. Therefore, the punching size will become larger. When the end of the punch is flat (no bevel or arc), the punching size will be relatively small.
8. Methods to restrain stamping parts from turning over and twisting
⑴. Reasonable mold design. In the progressive die, the arrangement of the blanking sequence may affect the forming accuracy of the stamping parts. For the blanking of small parts of stamping parts, generally a larger area of punching is arranged first, and then a smaller area of punching is arranged to reduce the influence of the punching force on the forming of the stamping part.
⑵. Hold down the material. Overcome the traditional mold design structure, open the material gap on the discharge plate (that is, when the mold is closed, the material can be compressed. The key forming part, the discharge plate must be made into a block type structure to facilitate the solution of long Time stamping causes abrasion (compression) loss at the pressure part of the discharge plate, and the material cannot be compressed.
⑶. Add strong pressure function. That is to increase the size of the press part of the unloading insert (normal unloading insert thickness H+0.03mm) to increase the pressure on the material on the side of the die, so as to prevent the stamping part from turning over and twisting during punching.
⑷. The end of the punch edge is trimmed with a bevel or arc. This is an effective way to reduce cushioning and cutting power. By reducing the buffer cutting force, the tensile force on the material on the side of the die can be reduced, so as to achieve the effect of suppressing the turning and twisting of the stamping parts.
⑸. In daily mold production, care should be taken to maintain the sharpness of punching convex and concave die cutting edges. When the punching edge is worn, the tensile stress on the material will increase, and the tendency of the stamping part to turn over and twist becomes greater.
⑹. Unreasonable or uneven blanking gap is also the cause of turning over and twisting of stamping parts, which needs to be overcome.
