Patent ID: 7117704

Claim:
An impact extrusion molding method characterized by extruding a protrusion to be formed on the bottom of a semifinished product, which is being molded halfway alone molding process, in an equal direction to the progress direction of a punch when a cylindrical product is impact extrusion molded using a punch and a dice, and which protrusion is being molded while suppressing the metal-flow from the bottom of a slug set in the dice toward the side of the molded product article, wherein a convex portion, for forming an annular groove in the inner surface of the bottom of the molded product article, is provided on the top end of said punch, and wherein, when a protrusion extruded into the hole in the bottom of the said dice is cut around a portion of the annular groove formed in the inner surface of the bottom of the molded product article, a cut region is discharged from within the dice.