EXTRUSION WORKING METHOD OF ANNULAR PART

摘要

PURPOSE:To work efficiently defect-free annular parts having no under fill by inserting a fitting member which fills the bore of a prepunched blank material into said bore and subjecting the blank material to extrusion working while acting back pressure from the counter extrusion direction. CONSTITUTION:A blank material 1 consisting of preliminary punching is set into a blank material holder PH. A main punch P1 and an auxiliary punch P2 are lowered and the punch P2 is first inserted into the bore of the material 1. On the other hand a lower punch KO is raisen from below to support the bottom surface of the material 1. Forming is thereafter started and the punch P1 is lowered together with the punch P2 to force the material 1 into the die LD while the back pressure against the punch P1 is exerted thereto from below by the lower punch KO. The defect-free annular part product having no under fill and collapsion of the bore is thus easily obtd. with one stage.