Transfer molding, unlike compression molding uses a closed mold system. The process begins with a piece of uncured rubber that has been preformed to a controlled weight and shape. The preform is placed into the portion of the mold called a "pot" located between the top plate of the mold and the ram (image right). The ram is closed which distributes (transfers) the uncured rubber into the cavity(s) through a runner and gate system. The material is held under high pressure and temperature to activate the cure system in the rubber compound (rubber is vulcanized). The cycle time is established to reach an optimal level of cure. At the end of the cycle, the parts are removed or ejected from the cavities and the next cycle begins.
Rubber Transfer Molding Steps:
1.) Uncured rubber is preformed to control weight, shape and specification
2.) Rubber preform is placed into pot
3.) Ram distributes (transfers) the rubber through the runner and gate system into the cavities
4.) Mold remains closed under pressure and temperature to reach optimal cure
5.) Parts are removed from the mold and the process is ready to begin again
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