Furnaces ensure high quality ceramic sheet production

GE Infrastructure Sensing, a leading manufacturer of thermisters, has increased its production facilities with the addition of a fourth Carbolite top-hat furnace for processing ceramic sheet at temperatures up to 1300°C.

The thermal sensors manufactured by the company, which are widely used in the automotive industry and in heating, ventilation and refrigeration equipment, incorporate several types of ceramics to suit different applications. The materials are produced from metal oxides mixed with binders, which are formed into thin sheets and then fired in the Carbolite furnaces.

Heating the sheets to 400°C over four hours burns off the polymer binders, after which the material is sintered at between 1200°C and 1300°C to form the new crystal structure. Sintering can last up to 20 hours, depending on the formulation and the performance characteristics required. After cooling, the sheets are cut with a diamond saw to the size required for the finished assembly.

The hearth, which can hold many sheets at a time, runs on a track and is driven by an electric motor, so it can be moved in and out of the furnace. The heating elements are in a ‘top hat’ structure, which is lowered over the hearth when a charge is being processed and raised at the end of a cycle.

The success of the sintering process depends on heating the material to very accurate and uniform temperatures, so the furnaces have been designed to provide a working area within the chamber 200mm wide x 600mm long x 350mm high where temperature uniformity is ±2°C at 1200°C. Access ports allow thermocouples to monitor load temperatures in the chamber.