Patent Number: 6,332,932

Title: Punch, powder pressing apparatus and powder pressing method

Abstract: A powder pressing apparatus comprises a die having a through hole, an upper punch and a lower punch. At least one of the upper and lower punches has a punching surface having an edge portion provided with a projection. The projection has a tip chamfered by a width not greater than 0.5 mm. The punching surface has a slope having a surface roughness Ra not greater than 1.0 .mu.m. A rare-earth alloy powder is fed into a cavity formed in the through hole of the die. The rare-earth alloy powder in the cavity is oriented by magnetic field, and pressed by using the upper and lower punches. The upper punch and the lower punch are brought closest to each other at a minimum distance not smaller than 1.7 mm during the pressing. An obtained compact is used for manufacture of a sintered body and a voice coil motor.

Inventors: Kohara; Seiichi (Mishima-gun, JP), Kidowaki; Shinji (Osaka, JP)

Assignee: Sumitomo Special Metals Co., Ltd.

International Classification: B22F 3/03 (20060101); B30B 15/06 (20060101); B30B 11/02 (20060101); H01F 41/02 (20060101); H02K 15/03 (20060101); H02K 41/035 (20060101); H01F 001/053 ()

Expiration Date: 12/25/2018