Development of a novel micro w-EDM power source with a multiple Resistor-Capacitor (mRC) relaxation circuit for machining high-melting point, -hardness and -resistance materials

This study presents the development of a novel micro-wire electric discharge machining (w-EDM) power source for machining high-melting point, -hardness and-resistance materials. The relaxation circuit power devised with a multiple Resistor-Capacitor (mRC) is triggered by a Programmable Logic Device (PLD) to generate a high-peak, short-pulse-time current train. The mRC relaxation circuit is characterized by high density discharge-spots per unit of time for swiftly removing material and creating fine discharge craters. Three microstructures made of tungsten carbide, WC-based cermet, and Boron-Doped Polycrystalline Composite Diamond (BD-PCD), respectively, are machined to validate the novel relaxation circuit. Experimental results demonstrate the 3RC relaxation circuit reduces machining times by 25%-35%, resulting in a more time efficient micro w-EDM process. Compared with a transistorized power source, the heat-affected zone is smaller and surface finish is better when using the 3RC relaxation circuit. A set of metrics for helping measure important electro-thermal machining related properties during micro w-EDM is proposed in this study. These are the 'Spark Erosion Rate (SER)', 'Electro-Thermal Machinability (ETM)', and 'Cutting Performance (CP)'. An extensive examination of the quantitative and qualitative properties of material erosion mechanisms, material removal rates (MRR), and, cobalt deposition for machining of difficult-to-machine materials is undertaken and the results discussed in detail. (C) 2016 Elsevier B.V. All rights reserved.