Elevated temperature forming method and preheater apparatus

A preheater apparatus for preparing sheet metal workpieces for forming, the apparatus comprising:

• a lower platen having a generally planar upper surface and configured to transfer heat into a workpiece carried on the upper surface;
• an upper platen disposed above the lower platen and having a generally planar lower surface disposed generally parallel to and spaced from the upper surface of the lower platen forming a gap between the platens, the upper platen being configured to transfer heat into a workpiece disposed between the upper platen and the lower platen, the upper and lower platens being disk-shaped and supported for co-rotation on a common axis;
• a shim spacing the lower surface of the upper platen from the upper surface of the lower platen by a distance greater than a thickness of a sheet metal workpiece to be heated by the platens, the shim being arranged to at least partially define a blank path for serially receiving, passing, and removing workpieces from between the platens while maintaining a constant desired gap distance between the upper and lower platens;
• and
• a circumferentially-spaced workpiece receptacle positioned between the platens, each such receptacle position being configured to receive a workpiece at an input station, to heat the workpiece to a desired temperature, and to carry the workpiece via platen rotation to an output station.