Compression molding is a rubber manufacturing process that starts with mixed raw material or a special rubber compound. The compound material is either cut or weighed, or a pre-form is created. The pre-forms take the basic shape of the final product. Since the material is compressed between parts of a cavity, more material is required than will be in the end product. This ensures the entire cavity of the rubber mold is filled with compound when the custom rubber product is created.
Stern Rubber Company uses natural or synthetic rubbers (elastomers) that 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 pre-form of greater volume than the finished part will be.
The pre-forms, 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 pre-form is squeezed into the cavity shape.
Heated platens on the press help maintain mold temperature as the molded rubber 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.
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