Thermoset molding is an irreversible molding process by which malleable forms of plastics are forced into a heated mold and formed into their final shape. Thermoset Plastic Injection Molding Machine and Operator are different from thermoplastic molding.

The process for thermoset injection molding is quite similar to traditional injection molding with thermoplastics. Thermoset materials such as phenolics, MF etc. are gathered in a material hopper, and then fed through a hot screw and barrel at around 170F-240F depending on the material formulation. The material is injected into an hotter mold (around 350F) via sprue and runner system, feeding the cavity or cavities and filling the molded part. Other thermoset materials such as Expoxy, Urea-Formaldehyde, which are unsaturated polyesters and are fed to the screw and barrel using a hydraulic stuffer ram, and injected, molded, and cured the same way as phenolics.