Investment casting refers to making a pattern in a fusible material, coating the surface of the pattern with several layers of refractory material to make a mold shell, and then melting the pattern out of the mold shell to obtain a mold without parting surface. Casting solution is prepared for sand filling. The types of alloys that can be produced by investment casting are carbon steel, alloy steel, heat-resistant alloy, stainless steel, precision alloy, permanent magnet alloy, bearing alloy, copper alloy, aluminum alloy, titanium alloy and ductile iron. Investment casting can meet CT4-6 tolerance