IRONING AND FORMING METHOD OF SPLINE TOOTH PROFILE IN STEPPED SHEET METAL MADE PRESS FORMED PART AND SHEET METAL MADE CLUTCH DRUM IRONED AND FORMED BY SAME METHOD

摘要

PROBLEM TO BE SOLVED: To provide a ironing and forming method of a spline tooth profile in the sheet metal made press formed part not generating an excess metal in a different part in level. SOLUTION: Dies 24 (28, 30) having plural steps of ironing and forming surfaces 28a, 30a corresponding to the outer periphery of a sheet metal made pressed product is meshed in the axial direction with a punch having plural steps of ironing and forming surfaces 32a, 34a corresponding to the inner peripheral shape of the pressed product, the punch is divided into a first punch 32 ironing the small diameter peripheral wall with the die 28 cooperated and an outer peripheral punch 34 arranged in the outer periphery of the punch 32 and ironing the large diameter peripheral wall with the die 30 cooperated and descending and stopping at the position of a difference 29 in level of the die, the first punch and the outer peripheral punch are integrally descended, after the large diameter peripheral wall is ironed and formed, when the small diameter peripheral wall id ironed and formed, the pressing force of the outer peripheral punch is made smaller than the pressing force for ironing, whereby the small diameter peripheral wall is smoothly extended in the axial direction by the descending of the first punch (ironing), the flow of the material into the different part in level is reduced and the excess metal part is not generated in the different part in level.