Injection molding process for producing a box-shaped plastic housing

Abstract

An injection molding process for producing an integrally molded box-shaped plastic housing of a resin material. The housing includes integral portions of a bottom wall of a first thickness and an upright wall of a second thickness, the first thickness being in the range of from one-third to two-thirds of the second thickness and the bottom wall portion including at least one integral rib structure. A cavity is formed in a mold having cavity portions, respectively corresponding to the bottom and upright wall portions and the rib structure, in fluid communication. Fluid resin is injected through respective injection gates directly communicating with the rib structure cavity portion and the upright wall cavity portion, which provide passageways for flow of the liquid resin therethrough, thereby completely filling all cavity portions. Cavity portions corresponding to cylindrical bosses formed on the rib structures further are provided and knockout pins extend through the mold in alignment with the cylindrical bosses to release the secured housing from the mold. Porous knockout pins extend through the mold and communicate with bounded regions of the bottom wall cavity portion for selective release of gas therefrom, to assure complete filling thereof with liquid resin; the pins are actualable as ejector pins for releasing the cured housing from the mold.