| 摘要 |
PROBLEM TO BE SOLVED: To improve manufacturing efficiencies by shortening a molding cycle without deteriorating the external appearances of a hollow molded item when the hollow molded item is to be manufactured by a gas-aided injection molding method. SOLUTION: A movable core 16 for molding a reinforcing rib 8 is provided in a die 11 so as to retractably protrude toward a cavity, and a nozzle 17 is provided in the core 16. After gas is blown into the cavity from the nozzle 17 to expand a synthetic resin R into a hollow form, the core 16 is retracted before the resin R is cured completely. Since the nozzle 17 is provided in the core 16, even if a resin 28 in an uncured state flows reversely into a hole 27 from which the nozzle 17 has been drawn out, the resin 28 is confined in the hole 27 so as not to be exposed to the outside. Thus even if a molding cycle is shortened and the resin is removed from the die before it is cured, the external appearance of the resin is not injured. |
