Spin Casting

Spin casting is a technique of using centrifugal force or drive to produce castings from rubber mold. Spin casting is also referred sometimes as centrifugal rubber mold casting. Distinctively, a disfigured mold is spun along its central axis at a set speed. The casting material, commonly molten metal or liquid thermo-set plastic is then poured in through an opening at the top-centre of the mold. The packed mold then goes on spinning as the metal solidifies or the thermo-set plastic sets.

Defining characteristics

The two defining features of spin casting are semi-permanent rubber molds and the use of centrifugal drive. These make the process comparatively exceptional to machined die-based and expendable mold casting methods. These qualities also inspire operators to utilize casting materials particularly formulated for low melting points and viscosities. Most spin casting is performed with pewter and zinc alloys or thermo-set plastics.

The process of spin casting

The process distinctively employs vulcanized silicone or organic rubber as the mold-making substrate. Vulcanization is an integral step that happens halfway through the mold-making process. Prior to vulcanization, the mold rubber is a soft and malleable solid-like fluid in many ways very similar to silly putty. Due to the clay-like nature at this phase, the mold is effortlessly cut or shaped to house irregular models. Vulcanization serves two intentions such as establishing the negative space inside the mold as well as hardening the rubber so it will stay strong and rigid during casting.

Final product and competing process

After vulcanization and prior to using, the mold must be gated and vented. This comprises carving channels to make sure proper air and material flow during the casting process. Gating and venting is distinctively performed by hand using a sharp knife or scalpel and differs in time relying on the difficulty of the mold. The final product is a treated rubber mold that can remain anywhere from hundreds to over a thousand casting cycles before it requires substitution.

The casting materials commonly used for competing processes like metal die casting and injection molding are similar but not opt for spin casting. For instance, a distinctive zinc die casting alloy such as zamak 3 can be used but will solidify too quickly from a molten state when cast with centrifugal drive. As a consequent there occurs incomplete filling of the mold as well as a rough porous finish, knows as orange feel. Zamak 2, of a varied composition was enhanced as a gravity-cast alloy with greater finished strength but was found to work well with spin casting.

Questions:

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