Precision casting actually includes many ways. Here I briefly introduce the investment casting of silica sol process, which is the dewaxing method in some books. The technological process includes: wax injection, wax trimming, tree installation, slurry dipping, sand blasting, drying, dewaxing, heat preservation, sintering, melting, pouring, vibrating shell, door dismantling, sand cleaning, door grinding, sand blasting, passivation, heat treatment, shaping, quality inspection, renovation and welding. The above are some basic general process flows, but different structures are needed according to different customer requirements. The process is to use wax as a model, coat the surface with refractory, melt the wax at high temperature after drying to get the shape of the workpiece itself, and then melt the steel required by the guests and pour it into the dewaxed shell to make the casting.