METHOD AND APPARATUS FOR PRESSING CYLINDRICAL ARTICLES FROM POWDER Russian patent published in 1994 - IPC

FIELD: powder metallurgy. SUBSTANCE: method involves moving inner ring of die into outer ring; retaining split rings by means of retaining unit of die; filling powder into preliminarily prepared apparatus and mounting punch annular ring; securing stepped diameter mandrel by retainer. While applying pressing force to apparatus with sectors removed from below casing, punches are displaced. As a result article ends are sealed by annular protrusions. Then annular punch lower end is brought into contact with upper end of split ring and ring punch is brought into contact with stepped-diameter mandrel. Punch is displaced together with split ring and casing in downward direction and stepped-diameter mandrel is displaced upwardly together with punch to provide forming of article with predetermined geometrical shape and sizes. Simultaneously retainer is released and springs are compressed. In the process of pressing, powder is entrained by friction forces of inner surface of split ring and side surface of mandrel into space between stepped mandrel and split ring. At the end of pressing inner ring is moved into outer ring and split ring together with casing is displaced together with casing relative to sleeve. As a result die retainer unit is released and easily removed from sleeve. EFFECT: increased output of good articles and high quality of articles by eliminated crack formation and uniform distribution of powder material as well as enhanced reliability in operation. 2 cl, 4 dwg