Compression Molding

Compression molding is a process that involves taking a rubber compound or mixed raw material and creating "pre-forms" in the basic shape of the end product. The pre-forms provide a surplus of material to be placed in the cavity, thus ensuring a total cavity fill. Once in place, the mold is then closed, applying both heat and pressure to the pre-form and allowing it to fill the cavity. When the cavity is filled, excess pre-form material spills out into overflow grooves. Following this step the rubber is then demolded, usually by hand, leaving us with the molded rubber product.

Compression molding is often chosen for medium hardness compounds in low volume production or in applications requiring particularly expensive materials. This process helps to minimize the amount of overflow, or flash created during the rubber molding process.

In creating compression molded rubber products, the pre-forms can be difficult to insert into more complex mold designs. Furthermore, the compression molding process does not lend itself well to the material flow requirement of harder rubber compounds.

Benefits of Compression Molding

• Cost effective tooling
• Maximized cavity count
• Economical process for medium precision

Compression molding can be a cost effective solution in situations where:

1. The tooling already exists
2. The cross-section of the part is very large and requires a long cure time

Applications of compression molding range from simple o-ring drive belts to complex brake diaphragms with diameters of more than 10 inches. Timco can also offer a variety of other molded rubber products through compression molding.