Rubber Compression Molding

MID-STATES IS EQUIPPED WITH OVER 70 HYDRAULIC PRESSES.

Molds used in this process consists of a cavity shaped like the part to be produced and a top plate that presses down to form out the part. The heated mold is removed from the press and opened. A precut and weighed piece of custom mixed uncured rubber, is placed into the cavity. If the rubber is to be bonded to metal, the metal piece is placed into the cavity at the same time. The loaded mold is returned to the press and the press is then closed. The pressure exerted by the press pushes the plates together and forces the uncured rubber to flow into the shape of the cavity in the mold. The mold remains closed until the rubber is cured. A compression mold may have many cavities.

A variation on the compression mold is the transfer compression mold, usually used for small parts where a precut and weighed piece of custom mixed uncured rubber, is placed into a “pot” either above or below the part, and rubber is squeezed into the small cavity. This process uses more rubber and creates more scrap, but allows small parts to be made economically since hand loading a small slug of rubber in to dozens or hundreds of cavities would be too expensive.

Mold Design and Fabrication

The molds for customers’ products are designed and manufactured by independent tool shops with proven records of quality craftsmanship. The process of mold design and manufacture is a joint effort between Mid-States and the tool shop to ensure a mold that is durable, works smoothly and produces a quality product.

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  IATF 16949-Cert-MSRP (PDF, 331KB)