PUNCHING METHOD IN HYDRAULIC BULGE FORMING OF CYLINDRICAL MEMBER

摘要

PROBLEM TO BE SOLVED: To provide a punching method by which an efficient and small shear- drop punching is carried out on a cylindrical member during a stage in which hydraulic bulge forming of the cylindrical member is carried out. SOLUTION: In the punching method of the cylindrical member which is made by working a long size extruded shaped material into a specified dimension is carried out when the hydraulic bulge forming is carried out or successively after the hydraulic bulge forming is carried out, after beforehand forming a slender embossed part by the hydraulic bulge forming around a part to be punched where is formed in a prescribed position of a surface to be worked, the punching is carried out by making the longitudinal direction of the embossed part coincide with the direction of a shear angle which is formed at both ends of the longitudinal section of a punching punch.