Precision casting method refers to the general term for casting methods that use non-metallic molds with higher product dimensional accuracy than ordinary sand mold castings. It includes three categories: dewaxing method, plaster mold method, and ceramic mold method. Among them, there are two major types of dewaxing casting methods: solid mold method and pottery shell mold method, the latter is an improved method of the former. The pottery shell mold method is widely used by the current dewaxing precision casting industry because it has the following advantages
- Better dimensional stability
- Less refractory materials are used
- Light weight, easy to transport, handle and make large castings
- The process can be partially automated to save manpower and increase production rate
- Lower production cost
- The ceramic shell mold is thinner, and the cooling rate of the casting after pouring is higher and uniform, so its mechanical properties are better.
The characteristics and advantages of precision casting by dewaxing are as follows:
- The maximum limit length of castings is 700mm, and the easy-to-make length is less than 200mm. The maximum weight of the casting is about 100 kg, usually less than 10 kg.
- The dimensional tolerance of castings is 20mm±0.13mm, 100mm±0.30mm, 200mm±0.43mm, and the dimensional accuracy of small parts cannot easily reach ±0.10mm. The angle tolerance is ±0.5~±2.0 degrees, and the minimum thickness of the casting is 0.5~1.5mm. The surface roughness of the casting is about Rmax4S~12S.
- There are almost no restrictions on the materials of precision castings, such as aluminum alloys, magnesium alloys, titanium alloys, copper alloys, various steels, cobalt-based and nickel-based heat-resistant alloys, and hard materials.
- To produce workpieces with complex shapes, with good dimensional accuracy and less cutting.
- Save material waste, and can be mass produced.
Dewaxing precision castings are widely used in jet engines, gas turbines, steam turbines, aircraft parts, internal combustion engines, vehicles, food machinery, printing machinery, paper machinery, compressors, valves, pumps, measuring instruments, sewing machines, weapons, Business machines, and other machine parts.