| 摘要 |
PROBLEM TO BE SOLVED: To reduce a wasteful amount of resin which cannot be used for moldings and make effective use of natural resources by sending gas into a cavity after a molten resin is injected into the cavity of a mold by an injection unit and making the molten resin in the cavity flow back into the injection unit by a gas pressure. SOLUTION: A cavity 2 and a gas introduction aperture 3 connected to the former are formed in a mold 1. Then the screw 21 of an injection unit 20 is made to advance and a molten resin P stored in the tip of a heating cylinder 22 is injected into the cavity 2, and further, gas is supplied into the cavity 2 passing through the gas introduction aperture 3 from a gas feed device 5. The molten resin P in the cavity 2 is pressurized to flow back into the heating cylinder 22 to form a hollow part 4. Thus it is possible to take advantage of the merits of a conventional gas-assist injection molding process. The molten resin P which is flowed back is uncured, so that it can be utilized for a next injection operation and the resin can be effectively used without any waste. Further, the material cost can be saved and the natural resources be effectively utilized. |
