One of the more commonly used precision castings is investment casting, also known as lost wax casting: use appropriate investment materials (such as paraffin) to make investment molds; repeat the steps of dipping refractory paint and sprinkling refractory sand on the investment mold to harden the shell and Dry; melt the inner investment mold to obtain a cavity; roast the mold shell to obtain sufficient strength and burn off the remaining investment material; cast the metal materials needed; solidify and cool, and clean the sand after shelling. In order to obtain high-precision finished products. According to product needs or heat treatment, cold processing and surface treatment.
Mass production factories should create conditions to adopt technologically advanced modeling and core-making methods. The old-fashioned shock-type or shock-type molding machine production line is not high in productivity, the labor intensity of the workers is large, the noise is large, and it is not suitable for the requirements of mass production, so it should be gradually reformed. 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 floor space is small; for middle parts, various box-type high-pressure molding machine production lines and gas can be used. Molding line to meet the requirements of fast, high-precision molding production line, core-making methods can be selected: cold core box, hot core box, shell core and other high-efficiency core-making methods.
Medium-volume large castings can consider the application of resin self-setting sand molding and core making.
For heavy castings produced in small batches of a single piece, manual molding is still an important method. Manual molding can adapt to various complex requirements and is more flexible, without requiring a lot of process equipment. Water glass sand molds, VRH water glass sand molds, organic ester water glass self-hardening sand molds, clay dry molds, resin self-hardening sand molds and cement sand molds can be used; for single-piece heavy castings, the pit molding method is used for low cost and put into production fast. It is more suitable for mass-produced or long-term shaped products to adopt multi-box modeling and split-box modeling. Although the initial investment in molds and sand boxes is high, it can be compensated by saving modeling man-hours and improving product quality.
Low pressure casting, die casting, centrifugal casting and other casting methods are only suitable for mass production due to the expensive equipment and molds.