Transfer molding uses the same production processes as compression molding, with the exception of mold design. In addition to mold plates that encapsulate the outer part shape, there are additional plates inside the mold cavity.
This style of mold includes a pot in which unvulcanized rubber is placed. A piston (or plunger) forces the rubber into the closed part cavity through a small sprue hole.
Transfer molding results in more material waste than compression molding, but requires less material handling both before and after the molding process. Additionally, transfer molds cost more due to the additional material and machining time required to produce them.