Compression moulding is the only plastic moulding process that can mould thermosetting plastics because due to their cross-linked structure, preheating as used in other moulding processes would make the product assume the wrong final shape, by 'curing' earlier in the process. Thermosetting plastics possess excellent electrically insulative properties because they can not burn, only decompose.

The widely application of the Compression moulding is the SMC, that is Sheet Moulding Compound. SMC is used within the production of oil sumps and automotive engine covers. SMC is a fibre-reinforced composite material in sheet form. It primarily consists of a thermosetting resin, glass fibre reinforcement and filler. Additional ingredients such as low profile additives, cure initiators, thickeners and mould release agents are added to enhance performance of processing the material. As with any material system, be it metallic or plastic, SMC can be formulated to meet specific performance requirements of a particular application, such as tensile loading or class "A" surface. SMC is a sheet product which when ready to be used, is laid on to a cutting table and cut into pieces of pre-determined size and shape. The cut pieces are then stacked and assembled in a charge pattern that has been determined to gain the optimum fill, fit and fibre strength within the mould cavity. After charge placement within the mould, the mould is closed and the SMC material is compressed. Typical mould pressures for low-profile SMC are around 50-100 bar.