Process for injection molding and apparatus therefor

Abstract

A process and apparatus for effecting injection molding of plastic resin products on an injection molding apparatus including a metal mold composed of a slidable mold element and a fixed mold element defining together the mold cavity, an actuator for sliding the slidable mold element and an injection nozzle for adjusting the nozzle flow path section, which comprises a first molding step of injecting a molten resin into the mold cavity which has been preset by the slidable mold element so as to include a post-compression margin to be compressed afterwards in a second molding step, to effect the injection under a reduced molding pressure, while causing a temperature elevation and, thus, a viscosity reduction of the molten resin, until the mold cavity has been filled up, and a second molding step of compressing the resin so charged in the mold cavity by operating the slidable mold element to compress the charged resin to compensate the post-compression margin, so as to allow an effective pressing force to be imposed onto the charged resin within the mold cavity also after the gate has been sealed.

Dependencies are inferred from the claim text.