What is Dewaxing autoclave in the investment casting process?
Casting wax is injected into a metal die in order to create a solidified wax positive of the part to be cast. This wax positive is called a “pattern”. The wax pattern is then dipped in a ceramic slurry to form an external ceramic shell negative. Once the ceramic shell is created, a Dewaxing autoclave is used to melt and remove the internal casting wax from ceramic shells. The ceramic shell is then fired and ultimately used as the mold cavity for the metal casting.
The dewaxing process occurs in a dewaxing autoclave which lead is tight with silicone inflatable seal and typically involves a rapid pressurization to 85 psi (5.8 bar) and in some cases a gradual increase to 140 psi (9.6 bar). After heat up, there is a 15-20 minute dwell, and then a controlled depressurization at 15-30 psimin (1-2 barmin) in order to reduce the possibility of cracking the shells. Once pressure has dropped to 15 psi (1 bar), the wax is forced out of the dewaxing autoclave into a collection system using autoclave pressure which is controlled by inflatable gasket