IRONING MOLDING METHOD FOR CYLINDRICAL PARTS AND DIE FOR IRONING MOLDING

摘要

PROBLEM TO BE SOLVED: To prevent the breaking of a blank while the inter-punch spacings of multistage punches for enhancing an ironing rate in ironing molding are approached. SOLUTION: A segment (cylindrical inner peripheral part Wc) where the ironing by the first stage of the punch 5a ends receives the reaction force R from a step part 4b of a cylindrical opening 4a. Consequently, even if the tension F acting on the cylindrical inner peripheral surface Wa in the ironing molding process step by the first stage of the punch 5a and the tension acting on the cylindrical inner peripheral part Wc in the ironing molding process step by the second stage of the punch 5b act simultaneously on the thinnest cylindrical inner peripheral part Wd, the tension described above is relieved. As a result, the breakage of the thinnest cylindrical inner peripheral part Wd can be prevented.