Injection and compression molding apparatus and molding methods therefor

摘要

The present invention relates to an improvement in an injection and compression molding apparatus and a method therefor which comprises the steps of supplying molten resin by injecting it into a cavity formed by molds and compressing the resin by applying pressure. In consideration of problems with respect to the occurrence of sink marks in molded products and the deterioration in precision which are caused by the escape of resin during compression and a change in the cavity distance between two molds, the present invention provides an injection and compression molding apparatus and a molding method therefor which is capable of resolving the problems and stably producing molded products with good productivity. In the present invention, a gate is closed during compression, and a supplemental amount of resin can be injected after the compression step so as to supply the desired amount of resin in the molded article. The rear side of a movable mold can be held by a mechanical fixing mechanism so that no change is produced in the distance between the molds owing to the pressure applied during injection, and resin is supplied by injection while the distance between the molds being maintained. It is thus possible to stably provide molded products with good appearance, dimensional precision and quality with good productivity.