Whole Investment Casting Process Steps
To achieve precision products, making tooling is the first step to start investment castings. Such tooling or pattern will be precision machined by the CNC center.
2.Wax Injection and Pattern Assembly
After a pair of casting patterns is completed, we will first make a wax pattern, such a wax pattern is obtained by injecting wax into the pattern. And you will see a model with the same dimensions of desired products. Again, we will repeat the injection job for more wax patterns. Then assemble these wax patterns onto the sprue. Finally, hang these pattern assemblies at room temperature for drying.
In this step, the pattern assembly will be dipped into a ceramic slurry and coated with a refractory material. This process needs to be repeated several times until reaching a certain thickness and strength. Thus, the ceramic shell is built and then dried in an atmospherically-controlled environment.
Placing the shell in a steam autoclave and rapidly heated, so that the wax will be melt and run out through the gate and pouring up under high temperature. The ceramic shell molds must be fired to burn out the last traces of pattern material and to preheat the mold in preparation for casting, usually in the range of 1600-2000 degrees Fahrenheit. So investment casting also named as “lost wax casting”.
Casting is the key step in the whole investment casting process. After dewaxing, we will melt the steel into liquid status, and pour the liquid metal into the sprue, then cool it under room temperature.
Break the ceramic shell, and cut the individual bucket tooth from the sprue. Finally, remove the excess metal from the casting body by grinding.
To improve the mechanical properties of parts, heat treatment is usually done after finishing castings. Main heat treatment processes are Normalizing, tempering, annealing, hardening and tempering, carburizing, etc.
9. Painting and other Surface Treatments like Anti-rust Oil Paint
Paint the bucket teeth and adapter to be yellow normally. Or make it green, black, red, etc. as customers require. To protect products from rusting, castings will be dipped into anti-rust water or oil.
As all the products are exported to overseas market, so we will pack all parts with polybags, and then put them into standard ply wooden cases. Of course, all the packages must be carried out on the basis of free from damage.