Draw Forming Method and Device

Abstract

A draw forming method for drawing a blank material ( 15 ). In this method, a restraint region ( 98 ) that is an outer peripheral section ( 21 ) of the blank material is held by a first holder means ( 22 ), and then a tension region ( 97 ) inside the outer peripheral section is displaced upward by a second holder means ( 23 ) relative to the restraint region. The displacement applies tensile force to a drawing region ( 96 ) that is the central section of the blank material.

1 . A draw forming method wherein a blank material set into a metal die unit is restrained by a blank holder and then drawn, the method comprising the steps of:
 setting the blank material into the metal die unit, the blank material having a stretching region and a restraint region set in the stated order outward and lined up with a drawing region subjected to pressure from an upper die and a lower die;   restraining the restraint region of the blank material with first holder means of the blank holder; and   applying tensile force to the drawing region and restraining the stretching region while second holder means of the blank holder displaces the stretching region in a shearing direction relative to the restraint region.   
   
   
       2 . A device for draw forming a blank material, comprising:
 a metal die unit comprised of an upper die and a lower die;   a blank holder for restraining the blank material set in the metal die unit; and   a press for applying pressure to the restrained blank material, wherein the blank holder comprises:   first holder means for restraining an outer peripheral section of the blank material at a first restraining position when the press is lowered; and   second holder means disposed inside the first holder means to restrain an inside section of the outer peripheral section of the blank material at a second restraining position when the press is further lowered.   
   
   
       3 . The draw forming device of  claim 2 , wherein:
 the press comprises a double-action press;   the first restraining position is a position in which the first holder means protrudes past the second holder means and in which the blank material is held by the lowering of the double-action press;   the second restraining position is the position in which the double-action press is lowered further from the first restraining position;   the upper die is held to be capable of sliding relative to the second holder means and is disposed separate from an inner slider of the double-action press; and   the first holder means and second holder means are fixed to an external slider positioned outside the inner slider.