The principle of casting method selection in precision casting

1. Priority is given to sand precision casting. According to statistics, in China and internationally, 60 to 70% of all castings are produced with sand molds, and about 70% of them are produced with clay sand molds. The main reason is that the cost of sand casting is lower than other casting methods, the production technology is simple, and the production cycle is short. Therefore, automobile engine cylinder blocks, cylinder heads, crankshafts and other castings are produced using clay wet sand technology. When the wet type cannot meet the requirements, consider using the clay sand surface dry sand type, dry sand type or other sand types. The weight of castings made by clay wet sand can range from several kilograms to dozens of kilograms, while the weight of castings made by dry clay sand can reach dozens of tons. Generally speaking, for medium and large castings, iron castings can be produced with resin hard sand molds and steel castings with water glass sand molds. Castings with the correct size and clean surface can be obtained, but the cost is high. Of course, the casting precision, surface cleanliness, material density, metallographic structure, mechanical properties, etc. produced by sand casting are very poor. When the performance requirements of the castings are higher, other casting methods should be used.
2 Low pressure casting, die casting, centrifugal casting and other casting methods, equipment and molds are expensive and suitable for mass production. For small castings, a boxless high-pressure molding machine production line with horizontal or vertical parting can be used. The production efficiency of solid molding is high, and the middle part with a small area can choose a variety of boxed high-pressure molding machine production lines and air-punch molding lines. , To meet the requirements of fast and high-precision molding production line, you can choose the cold core box, hot core box, and large-scale castings of the shell in medium batches. The shape and core of the resin hard sand can be considered.
For heavy castings produced in small batches of a single piece, manual molding is still a very important method. Manual molding can adapt to a variety of complex requirements and is more flexible, and does not require a lot of process equipment. Sodium silicate sand molds, VRH method sodium silicate sand molds, organic ester sodium silicate hard sand molds, clay drying molds, resin hard sand molds, cement sand molds, and other single-piece recast parts. The pit molding method has low cost and fast production. Mass production or long-term production of shaped products are suitable for multi-box modeling and split-box modeling. The investment in molds, sand boxes, etc. is high, but it can be compensated in terms of saving modeling time and improving product quality.