METHOD FOR INJECTION MOLDING HOLLOW MOLDING, HOLLOW MOLDING AND SYSTEM FOR INJECTION MOLDING HOLLOW MOLDING

摘要

PROBLEM TO BE SOLVED: To provide a long hollow resin molding flexible in cross sectional shape, uniform in wall thickness and high in inner surface smoothness, and a method and system for injection molding the molding.SOLUTION: A method for injection molding a hollow molding comprises: charging a molten resin R into the cavity 2 of an injection molding die 10 in the state of closing a shut-off pin 3; injecting a compressible fluid G as a pressurized fluid while pressurizing the compressible fluid by an incompressible fluid W into the molten resin R in the cavity 2 in the state of opening the shut-off pin 3; discharging the excessive molten resin R into a waste cavity 4, pressurizing and holding the compressible fluid G into the molten resin R; and slowly cooling the inside of the molten resin R in the cavity 2.SELECTED DRAWING: Figure 4