| 摘要 |
PURPOSE:To obtain a perfect visor with no strain by a method wherein a gate is continuously provided on one side edge of a cavity and the visor is molded along the long side edge of an injection molding mold wherein a runner is connected with a sprue and an unnecessary belt-shaped runner part of the molded item is removed. CONSTITUTION:A synthetic resin raw material is injected from a sprue 5 to fill a raw material in a runner 3 and a cavity 2. As the boundary of the cavity 2 and the belt-shaped runner 3 forms a slit-like gate 4, when the raw material passes through the long gate 4, a pressure is applied uniformly over the whole line not to generate strain locally and the raw material spreads over into the cavity 2 without unevenness. On a molded item 6 taken out of the mold after heat curing, an unnecessary part 7 corresponding to the belt-shaped runner along the long upper side edge of a visor part 8 is formed. Therefore, the unnecessary part 7 is removed along the long upper side edge. Only a part with good quality is utilized thereby as the visor part and a part with inferior quality is thrown away to obtain a product with high quality. |
