Gas-assisted injection molding.

摘要

A thermoplastic article can be injection molded in a mold (10) which comprises a cavity (28) defining the shape of the article, at least one thermoplastic entry aperture (23) which is adapted to receive molten thermoplastic resin from a nozzle (22) of an injection molding machine (24), a thermoplastic flow path (21, 26, 30) communicating with the thermoplastic entry aperture and the cavity, and a fluid flow passageway (32, 34) extending into the mold. The fluid flow passageway extends from an exterior surface of the mold to the thermoplastic flow path. A low viscosity fluid such as a gas can be injected through the fluid flow passageway and into the thermoplastic flow path. An end portion (44) of the fluid flow passageway adjacent the thermoplastic flow path has a porous metal plug (50) disposed therein. The porous metal plug comprises a porous metal core (64) which permits the low viscosity fluid to flow therethrough but prevents the passage of molten plastic therethrough. The porous metal core can comprise a sintered metal. Alternatively, the fluid flow passageway can extend from an exterior surface of the mold directly to the mold cavity, rather than the thermoplastic flow path.