| 摘要 |
PURPOSE:To form an accurately punched hole with a nicely sheared-off surface by a method wherein a molded item punched between a sprue bushing and a punch is compressed and sheared off by cooperating the sprue bushing and the punch with each other. CONSTITUTION:Molten resin is injected from a plasticizing cylinder 8 through a sprue bushing 7 so as to fill a cavity 11. After the dwell and cooling processes, a nozzle touching force P0 is changed to a force P2, which is smaller than P0. In addition, when a force P1, which is larger than the new nozzle touching force P2, is applied to a punch 21, the punch 21 advances so as to make the thickness of an opening hole part to be punched out thinner from ld or the opposing gap between the sprue bushing 7 and the punch 21 before its advancement to l'd. The punch 21 further advances by pushing back the sprue bushing 7 and finally punches the opening hole part (w) having the thickness of l'a out of a molded item W having a thickness of l0. Because the opening hole part to be punched out is made thinner and, after that, cut off, the punching, the sheared-off surface of which is accurately and nicely finished, is performed. |
