INJECTION MOLDING METHOD FOR SYNTHETIC RESIN MOLDING, AND MOLD

摘要

PROBLEM TO BE SOLVED: To generate a sink mark in a cavity where a rear face is peeled so as to improve a commodity value by injecting to charge molten synthetic resin, then introducing compressed fluid between a mold of an opposite side to a mold for forming an appearance surface and the molten synthetic resin so as to peel it. SOLUTION: When a male mold 12 is joined with a female mold 11, a cavity of the same shape as a molding 1 is formed between both the molds 11 and 12. A predetermined quantity of a molten synthetic resin is injected to be filled in the cavity from a runner via a nozzle and sprue 14 of the mold 11. A valve is opened immediately after injection of the resin is finished, and pressurized compression fluid (air) is introduced into the cavity from a compression pump via a compression fluid channel 18. The compression air is fed between the unsolidified resin in the cavity and a cavity forming surface of the mold 12 to form an air gap 19. The molten resin is entirely continuously urged to the mold 11 side for forming an appearance surface. A sink mark is freely generated on a rear surface, and not generated at the apperance surface 2 side.