Common Defects and Solutions of Drawing Dies
Cracks at corresponding parts of punch shoulder
Due to insufficient strength of the material, this defect occurs when the deep drawing load reaches the material breaking load. The defect occurs at the corresponding part (rp) of the shoulder R of the punch, which is closer to rp than the impact mark line. The impact mark line of the ruptured part can be observed and checked for the following situations, as it is different from other parts: or it can be extended; Or there are shiny parts above and below the flange; Or wrinkles may occur. In addition, there are sometimes shiny parts on the side walls. Initially, it ruptured laterally and presented as a tongue like shape.
Causes and elimination methods:
(1) Product shape.
① Excessive deep drawing depth. At present, the limits for deep drawing of cylinders and square cylinders are determined during the design phase. Therefore, when conducting deep drawing near the limit, it is necessary to use materials with smooth and flat surfaces, combined with mold coordination and grinding, processing lubricating oil, buffering pressure, press accuracy, and other on-site conditions to conduct experimental deep drawing.
② The punch radius (rp) is too small. A Correct rp to the appropriate value. If the RP on the drawing is too small, first draw according to the appropriate value, and then add another process to form the required size.
③ The concave die size (rd) is too small. A Correct rd to the appropriate value. If the rd on the drawing is too small, first use the appropriate rd value for deep drawing, and then add another process to form to the required size.
④ The corner radius (rc) of the square cylinder is too small. Reduce the depth of drawing; Add an additional deep drawing process; Replace with higher grade materials; Increase the thickness of the sheet metal.
