MANUFACTURE OF INJECTION MOLDED FORM WITH REINFORCING RIB IN HOLLOW PART

摘要

PURPOSE: To efficiently obtain a molded form having a rib in a hollow part and excellent appearance by forming a protruding stripe of a special length from one surface of a cavity, and retracting part of a mold cavity when pressurized gas is press-fitted while molten resin remains a fluidized state to increase its volume. ;CONSTITUTION: Protruding stripes 10, 11 are formed from one surface toward the other surface of a cavity at a suitable position of a mold cavity 9. The heights of the stripes are so formed as to satisfy 1.2a/b5 when a gap of the surfaces of the cavity is a, and a gap between tops of the stripes 10, 11 and an opposed surface of the cavity is b. At the time of injecting, a movable mold 2 is retracted to increase a volume of the cavity 9. Its timing is set while the molten resin remains a fluidized state, before pressurized gas is press-filled in the molten resin or at the same time. As a result, a part B between the stripes 10, 11 and the surface of the cavity 9 is early cooled as compared with a part A having no stripe, the part A becomes hollow parts 13, 14, 15, but the part B is not swelled to become reinforcing ribs 16, 17.;COPYRIGHT: (C)1994,JPO&Japio