Abstract: Disclosed is a method and apparatus for fabricating thermoplastic patterns for investment casting. The patterns define hollow objects and have contained within a very precisely located ceramic core. Thermoplastic is injected into the pattern die on either side of the core, thereby avoiding distortion, movement or breakage of the core. Multiple sprues are used; the sprues are individually fed from a nozzle having a single central bore. The configuration of the nozzle tip and the cavity from which the sprues emanate is such that a gate or bridge is not formed at the entrance to the die assembly. Accordingly, removal of the pattern from the die may be effected by pulling the part coaxially with the sprues, thereby avoiding the necessity of splitting the die where the sprues are located.