Abstract: Apparatus for heating and cooling a mold onto which thermoplastic material is cast and fused to form a finished article includes a plenum having an inlet and an outlet for connection to a fluid heating and cooling system and a mold box having a plurality of cavities for selectively receiving interchangeable tube bundles that are selectively positioned in a movably sealed relationship within the mold box and wherein each tube bundle has a mold and a tube array that are maintained in a fixed relationship during interchange thereof into and out of said mold box so as to maintain individually heat balanced molds.

Abstract: A mold assembly for molding thermoplastic particles into a solid thin shell includes a metal shell having a cavity and including an outer surface exposed to a heat source and further including an inner surface on which thermoplastic material is cast and fused to form a thin layer thermoplastic shell. The heat transfer area of the metal shell is increased by providing a plurality of heat transfer pins connected to the outer surface; each of the heat transfer pins has an extended outside surface area exposed to the heat source for heating the metal shell and each of the heat transfer pins further includes a large diameter head portion which is joined to the metal shell by a capacitive weld nugget formed solely between the large diameter head portion and the outer surface of the metal shell without disrupting the metal shell at surface portions thereof formed between the heat transfer pins.