PURPOSE: To provide uniform and stable magnetic characteristics throughout identically press formed products by preventing large extension of a part to form the surface of a roll shaped magnet when it is press formed.
CONSTITUTION: The punch 6 of a press provides protrusions 6b under both ends of downward protrusions 6a having trapzoidal cross section, the lower die 7 is successively formed upward protrusions 7a having triangle-shaped cross section, a laminated member 5 is set on the press die for press forming so as to obtain a successive and cross sectionally fan-shaped block of magnet forming piece 8. At this time, the laminated member is extended to and contacted with the protrusions 6b in the order of 2W3% of the total, and after contacting as above, it extrudes and extends into the place where there are no protrusions 6b, recesses 13 are formed on the upper part of the both ends of each fan-shaped magnet forming pieces 8 by the protrusions 6b, thereby the upper surface of the magnet forming pieces 8 do not largely extend longitudinally in press forming works. Cutting the parts where the recesses 13 are formed, winding round the surface to form the wedge-shaped cutting 14 as an internal periphery, then the external periphery is fully magnetized.
KOETANI KOUJI
MIYOSHI NORIYUKI
MACHIDA KANJI
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