Compression molding is used with thermosetting plastics. The thermoset plastic material may be in free-flowing granular form or viscous material. The material is placed in a hot mold, and the mold is closed by a hydraulic press. A typical compression molding process is performed at a mold temperature of 350°F and mold pressure of 100 psi (180°C and 700 kPa) with a curing time of 3 min. After the material is cured, the mold is opened and the plastic package is pushed out. Compression molding is a low cost process and is capable of high volume production.

It typically employs a matched metal tool in a heated (normally hydraulic) press to consolidate sheet materials or moulding compounds at relatively high pressures. Examples of composites that are commonly processed by compression moulding include thermosetting prepregs, fibre-reinforced thermoplastic [organ sheets", moulding compounds. Such as sheet moulding compound (SMC), and chopped thermoplastic tapes. It is also widely used to produce sandwich structures that incorporate a core material. Such as a honeycomb or polymer foam, although care must be taken not to use excessive pressure that might crush the core.