The common characteristics of special casting are: the casting size is accurate, the surface roughness value is low, closer to the final size of the part, so it is easy to realize less cutting or no cutting; the internal quality of the casting is good, the mechanical property is high, the wall thickness of the casting can be reduced; the metal consumption and the scrap rate of the casting can be reduced; the(except investment casting) can be simplified, so that the mechanization and automation of the production process can be realized; Improve working conditions and productivity. However, although the special casting technology has its outstanding advantages, but each process also has its disadvantages and limitations, not all parts are suitable for a certain casting method. For specific parts, specific analysis shall be carried out, which method shall be selected according to the following factors. In selection, the batch, material, size and structure of castings shall be fully considered.
(1) In small batch production of single piece, when the requirements of dimensional accuracy and surface quality are not high,should be considered first. After all, sand casting has lower cost, simpler production process and shorter production cycle than other casting methods. Therefore, castings such as engine cylinder block, cylinder head, crankshaft, etc. of automobiles are made by sand casting.
(2) For castings with small mass, small size and complex thin wall, investment casting can be considered when other methods are difficult to achieve. Its casting mass can be tens of grams to tens of kilograms, its minimum wall thickness can reach 0.3mm, and its minimum diameter can reach 0.5mm. Therefore, investment casting is very suitable for producing castings with low quality. Investment casting is mainly used to produce blades or impellers of steam turbines and turbo engines, cutting tools, and small parts of airplanes, automobiles, tractors, pneumatic tools and machine tools.
(3) Die casting can directly cast all kinds of holes, threads, tooth shapes, patterns and patterns, and also can die-casting inlays. Die casting is mainly used for mass production of aluminum, magnesium, zinc, copper and other non-ferrous metal small and medium-sized castings. It is widely used in automobile, tractor, electrical instruments, aviation, navigation, precision instruments, medical equipment, daily hardware, national defense industry and other departments.
(4) For the complex structure, the original sand casting needs a lot of sand cores, using EPC. There is no casting structure technological problem related to parting and stripping in EPC. The EPC has a strong adaptability to the casting structure. The economic benefit of EPC is very significant because of its complex structure and many cores.
(5) For castings with large batch, simple structure, high dimensional accuracy and surface quality, especially for non-ferrous metal castings, metal mold casting can be considered. This method has high productivity.