The compression moulding or pressing process is the traditional process for the production of rubber moulded parts. An amount which corresponds with the finished part of the unvulcanized rubber mixture is usually manually added to the heated vulcanisation mould.
The mould is then shut under pressure in a press. Through the mould pressure and the temperature, the mixture softens, flows and fills the mould part hollow room (nest). At temperatures of 140 – 200°C, the Vulcanisation of the rubber mixture takes place. The vulcanized (cross-linked) moulded part is then taken out hot. As opposed to the Injection moulding process (IM) the CM process in general requires clearly longer heating times since the heating of the added cold rubber mixture to the vulcanization temperature follows exclusively from the mould wall. A further development of the CM process is the Compression transfer moulding process (CTM).