See Figure 148. Molding is when rubber is shaped, cured, and bonded to a case via heat and pressure (14). There are three main methods: compression, transfer, and injection molding. Compression molding involves putting the uncured rubber compound into a heated, open mold cavity, then closing the mold under pressure (usually in a hydraulic press) to initiate vulcanization. In transfer molding, the uncured rubber compound is put in a transfer chamber (pot), heated, then squeezed down through a sprue, runner, and gate system leading into a closed mold cavity. With injection molding, the preheated rubber is injected under pressure through a runner system and into a closed, heated mold.

They differ in how the rubber enters the mold, but all three methods can be used to make shaft seals. Our illustration shows compression molding. Each cavity of the mold is loaded with a metal case and a rubber pre-form, then the mold is closed for simultaneous shaping and curing of the rubber, as well as bonding of the rubber to the case.

HOW A SHAFT SEAL IS MADE MAIN PAGE