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INTRODUCTION
With the advancement in rapid prototyping, investment casting has become the leading technology for producing high-quality castings quickly and inexpensively. Investment casting is also known as the "lost wax" process. This process uses wax patterns assembled in tree forms on a runner. The completed assembly is coated with a ceramic slurry, allowed to dry and then heated to melt out the wax leaving a ceramic mould into which the molten alloy is poured. Tolerances of 0.5 % of length are routinely possible, and as low as 0.15 % is possible for small dimensions. Castings can weigh from a few grams to 35 kg, although the normal size ranges from 200 g to about 8 kg. Normal minimum wall thicknesses are about 1 mm to about 0.5 mm for alloys that can be cast easily. Parts made with investment castings often do not require any further machining, because of the close tolerances that can be achieved.
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