an apparatus for thermal extrusion of a polymeric material to manufacture prototype mechanical elements from said polymeric material , said apparatus used for deposition of a liquefied ribbon of said polymeric material in patterned layers which solidify to form a three - dimensional prototype element , said apparatus comprising in combination , a mounting frame , said mounting frame including a mounting plate with a movable platen movable in the x and y directions , said frame further including an extrusion cylinder , said extrusion cylinder comprising a cylindrical housing having a uniform diameter cylindrical through passage , a head member having a uniform diameter bore connected with a reduced diameter , integral tip opening , said head member attached by a clamp to one end of the cylindrical housing to align the bore with the through passage , said - bore and through passage having an equal diameter , said head member including a circumferential heater to liquefy contents of the head member , a reciprocal piston slidably positioned in the cylindrical housing , and a piston actuator for driving the piston into the through passage to eject material through the tip opening .