A mold apparatus comprising: a core portion comprising a core surface, a first induction coil, and an inner core, and wherein the core portion has a core portion mass; a cavity portion comprising a second induction coil and a cavity surface, and wherein the cavity portion has a cavity portion mass; wherein the inner core comprises a non-magnetic material, the core surface comprises a magnetic material, and a density of the non-magnetic material is less than a density of the magnetic material; and wherein the core portion mass and the cavity portion mass differ by less than or equal to than 5%.