PURPOSE: To make the metal flow uniform by setting a discard hole nearby the hole part for forming the thin wall part which is positioned at the thin wall forming hole part side than the drawing center of the modified shaped material forming hole having the thin wall part forming hole part and the thick wall part forming hole part.
CONSTITUTION: Because a discard hole 7 is set nearby the hole part 8 forming the thin wall part on the die for extruding the modified shaped material, a part of the extruding material concentrated in the neighborhood of the thin wall part forming hole part of the die during extrusion is to escape through the discard hole. The metal flow passing through the thin wall part forming hole part is made uniform to the metal flow passing through the thick wall part forming hole part of the relatively large sectional area. Therefore, the structure of the thick wall part and the thin wall part is made uniform, the difference of strength of both part can be eliminated or controlled, and if this shaped material is stretched, the generation of bent can be eliminated or controlled.
TANIGAWA MASAKAZU
MICHISAKA KOUZOU
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