1, the preferred sand mold precision casting:According to statistics, China or the world, in all casting production, 60 to 70% of the casting is made of sand mold production, and about 70% of them are using clay sand mold production.The main reason is that sand mold casting compared with other casting method of low cost, simple production process, short production cycle.So like a car engine cylinder block, cylinder head, crankshaft, etc are of clay green sand casting process.When wet can't meet the requirements to consider using clay sand table dry sand, dry sand mold or other mould.Coatings for green sand mold casting can be from a few kilograms to tens of kilograms of weight, and clay dry production castings can weigh up to dozens of tons.In general, for medium and large castings, cast iron pieces can use resin self-hardening sand mold casting parts can be production of water glass sand mold, can obtain the size precision, smooth surface castings, but the cost is higher.And, of course, the sand mold casting production casting accuracy, surface finish, material density and microstructure and mechanical properties are often poor, so when casting these performance requirements higher, other casting method should be used, such as casting, lost wax casting, die casting, low pressure casting and so on.