Compression Molding

Thermoset compression molding is typically a manual process that transforms compound of resins and glass fibers material (BMC, SMC or Phenolic) into molded shapes by adding material directly into an open mold cavity and then closing the mold. Closing the mold provides the force necessary to flow the material into the cavity voids; the heated mold (300° F and higher) initiates the chemical curing. Since there is no runner and gate system in a compression mold, the mechanical properties of compression molded parts are somewhat better than identical parts molded by transfer or thermoset injection molding.

Thermosets are materials that cure via an irreversible chemical reaction under heat and pressure, rather than cooling to a rigid state as thermoplastic injection molding materials do. This chemical reaction results in a strong highly cross-linked molecular structure and is the reason that thermoset materials have the ability to retain their properties at elevated temperatures. Typical applications are electrical connector housings, electrical insulators, automotive parts, cookware appliance handles and knobs.

Typically insert molding, or overmolding, requires accurately placing part(s) made from metal or other suitable materials (referred to as the insert) into the mold, closing the mold and then injecting the plastic into and/or around the insert(s). A typical application would be electrical connectors that incorporate machined metallic pins or sockets into a molded plastic housing. Most insert moldings utilize metal parts, including handles, threaded inserts or electrical contacts.