DESIGN OF A MICROWAVE CHAMBER FOR THE PURPOSE OF DRYING OF WOOD COMPONENTS FOR FURNITURE

A specialized multiple-magnetron, microwave chamber was designed and built to facilitate research into the drying of bent timber components for furniture manufacture. This article reports on the design of this chamber and the findings from experimental drying of wood components. The microwave chamber provides three power levels (2, 4, and 6 kW) by engaging appropriate numbers of standard 1 kW microwave magnetrons. Preliminary experiments revealed that good drying quality was achieved when the microwave power level was set to 2 kW and cycled such that microwave power was applied to the chamber for 30 s, followed by a 90 s relaxation time during which no microwave power was applied and internal heat and moisture diffusion could alleviate hot spots inside the wood samples. The use of microwave drying reduced the drying time from weeks or months to hours. Straight components that started with a low moisture content and all bent components, irrespective of their initial moisture content, were dried with no evidence of drying degrade or collapse. However, the straight components that started with a high moisture content showed severe surface collapse. This may have been because these samples were taken from poor-quality material that was considered unsuitable for bending.