The Method of Punching Small Holes for Stamping Parts
In this paper, we will introduce the method and points for attention of punching small holes in the processing of stamping parts. With the development of science and technology and society, the previously commonly used machining method of micro holes has gradually been replaced by the stamping method. By making the punch firm and stable, improving the punch strength, preventing punch fracture and changing the stress state of the blank during punching, etc.
The ratio d/t of the punching diameter to the material thickness in stamping can reach the following values: 0.4 for hard steel, 0.35 for mild steel and brass, and 0.3 for aluminum.
When punching a small hole on a sheet, when the material thickness is greater than the punch diameter, the punching process is not a shearing process, but a process of extruding the material into the die through the punch. At the beginning of extrusion, part of the washed waste is compressed and squeezed into the area around the hole, so the thickness of the washed waste is generally less than the thickness of the raw material.
When punching small holes in stamping parts, due to the small diameter of punch punch, if common blanking method is used, the small punch is easy to break, so try to improve punch strength to prevent it from breaking and bending. The methods and precautions are as follows:
- The stripper serves as a guide plate.
- The guide plate and the fixed working plate are connected by a small guide post guide sleeve or directly with a large guide post guide sleeve.
- The punch shall be retracted into the guide plate, and the distance between the guide plate and the punch fixing plate shall not be too large.
- The bilateral clearance between punch and guide plate is less than the unilateral clearance between punch and die.
- The pressing force is 1.5~2 times greater than that of simple stripping.
- The guide plate shall be made of or inlaid with high hardness materials, and the thickness shall be 20%~30% compared with the normal situation.