Method of injection molding a part using an inflatable mold core

A method of injection molding a part having an undercut surface portion, comprising the steps of:

• providing a source of molten wax;
• providing a source of pressurized gas;
• providing a reusable mold assembly actuatable from an open position to a closed position, the mold assembly including a first mold portion, a second mold portion matable with the first mold portion to define a substantially sealed cavity, an inflatable, supple, inelastic core member positioned within the substantially sealed cavity and secured to the first mold portion, a path from the source of pressurized gas through the first mold portion to the inflatable, inelastic core member, and a path from the source of molten wax into the cavity;
• introducing the pressurized gas into the inflatable core member at a first pressure and temperature to provide an inflated core member that defines a core boundary;
• maintaining the first pressure and temperature within the inflated core;
• injecting the molten wax under pressure into a space defined by the cavity and the core boundary at a second pressure and temperature, the second pressure being less than the first pressure, and the second temperature being greater than the first temperature;
• allowing the wax to harden, thereby defining a part;
• aspirating the pressurized gas from the inflated, inelastic core member;
• opening the mold;
• and
• removing the part from the mold assembly.