Spin casting is a way of making castings from a rubber mold using centrifugal force. It is sometimes called centrifugal rubber mold casting. The casting material is usually either thermosetting plastic or a metal alloy, though technically any low-viscosity material with a low melting point would work. Spin casting is done using a spin caster machine. A vulcanizer machine is used to prepare the mold before casting, and a melting furnace prepares the metal to be poured into the mold.
Centrifugal force is the outward force that exists when something is rotated. Many carnival rides depend on centrifugal force to pin riders against a wall or seat while the ride rotates at high speed around a center axis. In spin casting, the mold is spun at a set speed. As the casting material is poured into the mold, it is acted on by centrifugal force, spreading the material over the mold. Spinning must continue until the casting material solidifies; otherwise the force and thus the shape will be lost.
Either metal or plastic may be used as materials for spin casting. Operators have created special metal alloys that are ideal for use in spin casting. In order to work properly, the material must be malleable at low temperatures. High temperatures would cause the rubber mold to degrade and either crack or lose its shape. Spin casting materials must also have low viscosity, meaning the material flows with little resistance. For example, water has low viscosity, while molasses has a much higher viscosity.
Operators use a spin caster machine to ensure uniform speed and smooth motion during spin casting. A spin caster is basically a box enclosing a motor and clamping system. The box keeps hot molding material that splashes out of the mold from harming operators or other workers who may be nearby. The clamping system holds the mold in place while it spins at a predetermined speed.
Before spin casting metal, an operator uses a melting furnace to prepare the metal for casting. The melting furnace must have a fine temperature control to prevent overheating of the metal before it is placed in the mold. A vulcanizer is used to prepare the silicon molds for use in casting. It applies uniform pressure to the mold while maintaining high temperatures. This process takes several hours, but it is essential to cure the silicon to avoid mold deformities resulting from centrifugal forces.