1. Correction of eccentricity during punching
When punching, the hole diameter will be eccentric due to uneven anvil surface, skewed end faces of the punch and uneven heating of the blank. The correction method can be carried out by immersion method: during operation, the thin side of the hole wall is immersed in water to reduce the temperature, and then a punch is used to expand the hole. The thick side of the wall becomes thinner due to higher temperature and good plasticity, making the entire forging wall The thickness is uniform and the eccentricity is corrected. This method is suitable for materials with good plasticity.
2. The blank is out of shape during punching
That is, the metal under the punch is squeezed to all sides, the height of the blank is reduced, the diameter is increased, the upper end face is sunken, and the lower end face is convex. The degree of aliasing is related to the diameter D0, height H0 and hole diameter d1 of the blank before punching. The smaller D0/d1, the more serious the degree of aliasing. The correction method is: D0/d1 should be controlled to be ≥2.5~3. If the diameter of the hole to be punched is large, such as D0/dl<2.5, small holes are usually punched first and then expanded to obtain the required hole diameter.