Compression Molding involves placing the uncured rubber compound into a heated, open mold cavity, then closing the mold under pressure (usually in a hydraulic press) to initiate vulcanization (curing). Transfer Molding requires the uncured rubber compound to be placed in a transfer chamber, heated, then forced into the mold cavity under pressure until cured. Injection Molding entails preheating uncured rubber in a chamber, then injecting it into a closed, heated mold.
Because transfer and injection molds remain closed throughout the molding process, they are generally capable of producing more intricate and consistent parts than compression molds. Though they’re more expensive to produce, transfer and injection molds also allow for higher temperatures, shorter cure times, and reduced finishing costs.