Abstract: A die spool for the extrusion of thermoplastic materials includes an axially split elongate spool body so as to be separable into first and second spool segments. The spool segments collectively establish the spool body and also define an axially oriented extrusion cavity through which thermoplastic material is conveyed. An alignment system ensures that only a single orientation of the extrusion axis is possible when the die spool is coupled to another similar die spool (or to an extrusion die associated with an extruder). A die spool assembly may therefore be provided which is comprised of a number of individual die spools. Preferably, a decreasing temperature gradient is established within the extrusion cavity of the die spool assembly (as may be accomplished by controllably operating electrical resistive heater elements) so as to at least partially solidify the thermoplastic extrudate therewithin.