A Control System for Microwave Processing of Materials

Abstract

This paper discusses a control system for microwave processing of materials. Microwave joining of ceramics and drying of timber are currently industry practices while microwave joining of engineering plastics and curing of epoxy adhesives are still being researched. In this study, all materials are processed in rectangular sections of waveguide fed by a magnetron with a maximum output power of 2 kW operating at 2.45 GHz. The most significant problems encountered when processing these materials are: (i) maintaining proper tuning to ensure maximum power transfer, (ii) thermal runaway, where the heating rate proceeds so rapidly that the material burns within a few seconds, and (iii) hot spot development, where localized regions heat up at a faster rate than adjacent regions. A computerized automated control system has been developed to alleviate these processing problems and has been successfully employed in joining a range of ceramics and engineering plastics, curing epoxy adhesives and drying wood. Results of preliminary tests obtained using the developed prototype are presented. [S1087-1357(00)71701-1]