CompressionMolding

Compression molding is a molding process in which a preheated charge of material, typically a thermosetting resin or a preform, is placed in an open heated mold cavity. The mold is closed and pressure is applied to fill the cavity and cure or thermoform the material, producing a solid part with good dimensional stability. The method is well suited for large, thick, or complex components and for fiber-reinforced composites.

Materials used include thermosetting plastics such as phenolics, epoxies, and silicones; thermoplastics that are formed from preforms; and composite laminates with continuous fibers. Ceramics and ceramic-forming powders can also be processed by compression methods. The material is typically preheated and loaded into the mold cavity as a slug, sheet, or preform.

Process steps typically involve heating and closing the mold, placing the preheated charge in the cavity, applying high pressure to compact and fill the mold, and maintaining pressure during curing or forming. After the material attains the required properties, the mold is cooled, opened, and the part is ejected. Any flash at the parting line is trimmed.

Equipment consists of hydraulic or mechanical presses with heated platens and molds, capable of high clamping forces. Cycle times depend on material, part geometry, and cure requirements. Advantages include excellent surface finish, good dimensional accuracy, low scrap, and suitability for large parts with high fiber content. Limitations include limited ability to produce highly intricate 3D features, longer cycles, higher tooling costs, and potential for voids or residual stresses if not properly controlled.

Applications span automotive interior components, electrical housings, appliance covers, and other molded structural or insulating parts.