| 摘要 |
PURPOSE:To obtain a molded item having favorable external appearance with neither sinkmarks nor swirl pattern by a method wherein molten expandable resin is injected in a mold cavity under the condition that gas pressure is applied to the mold cavity and, after that, gas pressure in every part of the mold cavity is independently lowered to atmospheric pressure in a predetermined time. CONSTITUTION:After a mold is closed and a nozzle is touched, gas pressure 3 is applied through gas slits 13a and 13b in order to enhance the pressure in a mold cavity 1 higher than the blowing pressure of molten resin. Next, molten expandable resin 4 is injected so as to turn the resin into semi-hardened state by only cooling the resin surface in contact with the cavity surface. After that, by removing the pressure from the slit 13a just before the filling of a part 8a, the part 8a expands and completes the filling of resin therein. At this time, the part 8b is isolated by the expandable resin 4 and its expansion is suppressed. After that, by ending the injection just before the filling of the part 8b with resin and removing pressure from the slit 13b, the part 8b expands and the filling of the whole part is completed. By removing pressures in due order from independent gas slits as mentioned above, a molded item with neither sinkmarks nor swirl pattern on its surface is obtained. |
