Lucifer Furnaces, Warrington, Pa., has supplied several convection ovens to a manufacturer of small medical parts in the southern United States. Model 42-B18 has a working chamber size of 9x9x18 inches, and heats to 1200°F. Uniformity is achieved with recirculating air flow. A rear mounted heavy-duty fan directs air along side-wall heating elements, then through the working zone.
Parts are protected from heating elements with a 16 gauge stainless steel liner. Furnaces are insulated with 4.5 inches of multilayered firebrick and 2 inches of insulating cold face block with overlapped seams for reduced thermal loss. Controls onboard include a Honeywell UDC3500 digital time proportioning temperature controller with four 20-segment setpoint programs, as well as a Honeywell high limit controller to prevent temperature excursions.
Side wall heating element banks consist of coil-wound resistance wire in ceramic holders, making replacement easy. The furnace shell is constructed with heavy gauge sheet steel reinforced throughout to form a rigid freestanding floor model. A horizontal swing door with adjustable latch provides a firm brick-to-brick seal while the safety switch powers-off both fan and heating elements when door is opened.
