Similar to plaster mold casting, the pattern used in ceramic mold casting is made of plaster, plastic, wood, metal or rubber. A slurry of ceramic is poured over the pattern. It hardens rapidly to the consistency of rubber. This can be peeled of the pattern, reassembled as a mold. The volatiles are removed using a flame torch or in a low temperature oven. It is then baked in a furnace at about 1000 °C (1832 °F) yielding a ceramic mold, capable of high temperature pours. Additionally, the pour can take place while the mold is until hot.
Tolerances can be held to 0.4 %, surface finishes can be better than 2 - 4 µm (.075 - .15 µin). Add 0.3 mm (.012 in) for parting line tolerances. Wall thickness can be as small as 1.25 mm (.050 in), and the weights can range from 60 g (2oz) to a ton. Draft allowance of 1° is recommended.
This process is expensive, but can eliminate secondary machining operations. Typical parts made from this process include impellers made from stainless steel, bronze, complex cutting tools, plastic mold tooling.
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