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Plastics Processing: Rotational Molding

Rotational molding is used for molding very large hollow objects. The process is simple. There are typically three stations on a horizontal rotating unit called a carousel. At the first station, a liquid polymer or powder is placed in a mold which is essentially a metal tank. The mold moves to station two, an oven, where it is rotated about two axes simultaneously while being heated, typically by gas convection. As the plastic melts, it forms a homogenous layer of uniform thickness on the inside of the mold. The unit then moves to a third station, where it is cooled by water or forced air. Finally, the mold indexes forward to the first station, where it is unloaded and another charge of polymer is added.

Common Applications: large storage and feed tanks, trash containers, fuel and refuse tanks, light globes, camper tops, canoes, whirlpool tubs, mannequins