Dewaxing / Investment Casting Autoclaves
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 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 heatup, there is a 15-20 minute dwell, and then a controlled depressurization at 15-30 psi/min (1-2 bar/min) 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 autoclave into a collection system using autoclave pressure.
In order to minimize ceramic shell cracking, the dewaxing autoclave must quickly transfer thermal energy into the ceramic shell and melt the surface wax so that it can be absorbed into the primary ceramic interface layer. This rapid absorption creates space for the remaining wax to expand and melt without cracking the shell.
ASC's dewaxing autoclave systems utilize engineered steam and pressure delivery system that quickly pressurizes the autoclave to 100 psig (6 bar) usually in under 3-4 seconds. This rapid increase in pressure and temperature 330 °F (165 °C) provides the proper environment to assure the initial interface melt and protection of the ceramic shell.
Fully integrated solution
ASC's dewaxing autoclave systems include the steam generator, accumulator, piping, valves, sensors, and advanced controls to fully automate the entire dewaxing process. Our dewaxing autoclaves come standard with our proprietary quick-opening door, assuring you of rapid and safe loading and commencement of the dewaxing process.
ASC's dewaxing autoclaves come equipped with proportional vent valve systems to provide programmable control of the venting process. This is critical in order to reduce cracking of the shells.
Control and data validation
ASC's dewaxing systems can be provided with our CPC computer control system for unequaled control of the process and data-collection and reporting to validate the dewaxing cycle.
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