Early vacuum furnace designs began as single-chamber technology in which the heating and cooling required in a typical cycle were performed in the same chamber. While this is a cost-effective furnace design, there are dueling and sometimes completely incompatible design features that are necessary for optimum heating and optimum cooling. Better and thicker insulation helps with heating efficiency, but it likewise impedes the cooling rate and potentially the evacuation rate. Less or even no insulation is highly desirable for faster cooling rates and faster pump-downs, but this design creates havoc with uniform and efficient heating. High pressures and high velocities of cooling gases enhance cooling but are very detrimental to conventional hot-zone construction materials by causing erosion and distortion. Furnace designs with multiple chambers of other technologies are common (as seen with BIQ furnaces in atmosphere heat treating). This concept was the next logical progression in vacuum technology as well....