Statistical modelling and process optimization of EDM electrode fabricated using pressureless microwave sintering and rapid tooling route

Abstract

The fabrication of customized products necessitates specialized setups, such as tools and dies, capable of accommodating complex shapes. In the present work, rapid tooling, an indirect 3D printing process along with pressureless microwave sintering was employed to fabricate complex shaped electric discharge machine (EDM) electrode. Copper spherical particles were used as the material for sample fabrication, and central composite design technique was utilized to conduct experiments. The investigation focused on exploring the impact of microwave sintering machine parameters – sintering temperature, heating rate and holding time – on crucial electrode properties, including density, volumetric shrinkage and electrical conductivity. The dominance of the sintering temperature on responses was revealed over the heating rate and holding time. Additionally, the effect of interaction between heating rate and holding time on electrical conductivity and density showed less effect of large holding time at slower heating rate. To investigate the particle bonding behaviour, scanning electron micrographs of the fabricated samples were also studied. The adopted methodology effectively sintered the particles without the need for applying pressure. Using genetic algorithm (GA), a multi-objective optimization was conducted to achieve an optimized set of microwave sintering machine parameters, aiming for maximum density, electrical conductivity and minimum volumetric shrinkage. A density of 7.32 g/cc, volumetric shrinkage of 8.36% and electrical conductivity of 73.88% IACS was obtained from samples sintered at optimized sintering parameters. The dimensions of the fabricated electrodes and machined cavity were then compared with the computer-aided design model. The results revealed an efficient process for fabricating complex shaped EDM electrodes.