Balanced die method for metal powder compaction

Dramatic reduction of ejection forces in a metal powder compaction process has been achieved using a balanced die method. The approach uses a toolset consisting of a thin walled die in a fairly rigid metal, with a rubber sleeve capable of transmitting high radial pressure. By maintaining a pressure balance between internal compaction pressure and external 'bolstering' pressure across the thin wall die, the ejection forces were reduced to almost zero. With limited equipment available, the compaction process was carried out in incremental stages to produce cylindrical metal billets of 32 mm diameter by 20 mm height. Green densities of 6.49 Mg m(-3) were achieved for NC100 iron powder supplied by Hoganas at much lower compaction pressure than those reported elsewhere. (C) 1996 The Institute of Materials.