METHOD AND APPARATUS FOR MOLDING MOLDED SHAPE WITH CASTING HOLE

PURPOSE:To manufacture a molded shape with a through-hole only by a molding process by advancing a punch into a cavity at a point of time when the injection of a molten resin is completed approximately and filling a residual space in the cavity with the resin. CONSTITUTION:A movable die 14 is engaged with a fixed die 12, and an extruding pin 26 is inserted into a hole 14d in the movable die 14 so that the upper surface of the pin 26 coincides with the base of a recessed section 14a in the movable die 14. A hydraulic cylinder 20 is driven and a driving plate 22 is brought into contact with a stopper 23. A cavity 10a is filled with a molten resin 30 through a sprue runner 12a while leaving small spaces 10b. The hydraulic cylinder 20 is driven to upward displace the driving plate 22, punches 24a, 24b are advanced into the cavity 10a, and the upper surfaces of the punches are brought into contact with the base of the fixed die 12. A small quantity of the resin is injected, and the cavity 10a is filled completely. The quantity of the resin injected after the punches 24a, 24b are projected is slight, and weld lines are not generated around the punches 24a, 24b. The resin in the cavity 10a is cured, and the punches 24a, 24b are retreated.