Natural or synthetic rubbers (elastomers) are compounded with additives to meet design use specifications and/or ease of processing. The compounded rubber, more technically a thermal set elastomer (TSE) is cut, weighed or extruded into a preform of greater volume than the finished part will be.

The preforms, at ambient temperature, are then loaded into each cavity of the open compression mold which has been preheated. The tool is closed and placed under the clamping pressure of the press as the preform is squeezed into the cavity shape.

Heated platens on the press help maintain mold temperature as the molded parts are given time to crosslink. The molded parts are removed from the tool and allowed to cool to ambient temperature before deflashing or final inspection.