Patent ID: 9199402
Filing Date: 2015-12-01
Classification: B21C,B29C,B29K,B30B,H01F

Abstract:
1. A method for producing a plurality of permanent magnets, comprising: with a mandrel inserted in a through hole formed in an extrusion die, extruding a preform filled in the through hole into a filling space defined between an inner surface of the through hole and an outer surface of the mandrel by pressing the preform with a pressing punch, thereby forming a cylindrical extruded form in which at least more than two stress concentration portions extending in parallel along an extruding direction are formed so as to be spaced apart from each other in a circumferential direction; and applying an external force to the cylindrical extruded form obtained at two oppositely facing stress concentration portions to thereby divide the extruded form at the stress concentration portions into more than two permanent magnets; wherein said extruded form, which is formed so that a radial thickness T