L&L Special Furnace Co. shipped an ultrahigh-uniformity box furnace to a U.S./European dental laboratory for manufacturing implants. The primary purpose of the furnace is to evenly remove binders and cure ceramic blocks prior to being machined into teeth. The blocks are heated to 700°C (1292°F) to remove binder. The blocks are then heated to 1010°C (1850°F) to cure. The ceramic blocks shrink during the heating cycle, but the amount of shrinkage can be controlled with even heating. If there are variations in the temperature uniformity, it will cause irregularities in the product, resulting in waste and/or costly rework. During tests prior to shipment, the furnace was surveyed and indicated uniformity of ±2°C at 1010°C throughout the work envelope.
Many blocks and round ceramics can be placed in the furnace with a work envelope of 16 inches wide x 16 inches high x 24 inches deep. There is a 2-inch-diameter outlet in the top to which an afterburner can be attached. This allows for the binder to be burned off prior to venting. The furnace includes a secondary shell with a 300-CFM venturi, which is integrated with a motor control so the venturi speed can be adjusted to meet any required cooling curve.