1. Tooling Making
To achieve precision products by investment casting, making tooling is the first step to start investment castings. Such tooling or pattern will be precision machined by CNC center. Then the tooling cavity is polished, surface treatment (if necessary) in order to achieve the required surface quality of product.
2. Wax Injection
Wax sample is made by injection molding process, the liquid wax is injected into the mold (tool), after solidifying (by cooling), the wax sample is ejected from the mold.
3. Wax pattern assembly
The wax samples are then assembled into wax sample tree on the same sprue. Then, the wax sample trees are cured at room temperature.
4. Shell building
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.
5. Dewaxing and Heating the shell
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 800 - 1200 degrees Celcius. So investment casting also named as “lost wax casting”.
6. Casting
Casting is the key step in the whole investment casting process. After dewax, we will first melt the steel ingots into liquid status, and pour the liquid metal into the sprue, then cool it under room temperature for a while.
7. Knock out the shell
Break the ceramic shell and the casting products are taken out. The breaking shell process is done manually or using the ultrasonic vibration.
8. Remove the gate, sprue and runner system
Cut the individual investment castings from the sprue. Finally remove the excess metal from casting body by grinding.
9. Shot Blasting/Sand Blasting
To remove scales and achieve better surface finish, investment castings will be shot blasted or sand blasted by small steel balls. So all the foundries must be equipped with shot blasting machines.
10. Heat Treatment
To improve the mechanical properties of casting blanks, heat treatment is usually done after finishing castings. Main heat treatment processes are: Normalizing, tempering, annealing, hardening and tempering, carburizing, ect. The heat treatment is done as per the customer’s requirement.
11. Inspection and Quality Control
Inspection and Quality Control is also a necessary step in our investment casting process for qualified products. Our engineer will do dimensional inspection, 100% surface inspection, inner defects inspection and other inspection jobs according to requirements of products. Only ensure all the products are qualified, can we arrange delivery to our customers.
12. Anti-rust Oil Painting and other Surface Treatments
Normally, the stainless-steel products do not need to anti rust treatment. However, in order to protect products from rusting, the castings products will be dipped into anti-rust water or oil. Of course, other surface treatments can also be performed in this step like paint spraying, galvanizing, ect.
13. Package and shipping
As all the products are exported to overseas market. So, normally we will pack investment castings with polybags, and then put them into standard wooden cases. Of course, all the package must be carried out on the basis of free from damage. We can also supply custom package service according to customers’ special requirements.