| 摘要 |
PURPOSE:To realize a hollow molded article excellent in dimensional accuracy by a method wherein molten resin is injected in a lump in a cavity before the closing of molds and, after gas is blown in to the lump, the resultant lump is compressed by clamping the molds so as to be turned into the molded article. CONSTITUTION:The set point S1 of starting position for blowing gas and that S2 of its finishing position are set in a setter 38. By means of signal sent from a controller 48, a movable platen 12 is moved to the midway position of mold closing and then stopped. Next, molten resin 30 is injected in a cavity C in a lump so as to envelop an air opening 20a. Injection is performed under low pressure and the moving position of an injection plunger 28a is detected so as to blow air in the molten resin 30, when the set point S1 of starting position for blowing gas coincides with the detected value of a position detector 32. Further, after the advancement of the injection of resin, the blowing-in of air is brought to an end, when the set point S2 of finishing position for pouring gas coincides with the detected value of the position detector 32, resulting in realizing a balloon-like resin 30a. By clamping the molds through the driving of the movable platen 12, the balloon-like resin 30a is turned into a hollow molded article 30b having a U-shape in cross section. |
