Achieving high machining speed and sustainability in micro-EDM using a two-phase three component dielectric

Abstract

This study presents a solution to the longstanding challenges of sustainability and slow material removal rate (MRR) in micro-electrical discharge machining (micro-EDM), proposing a two-phase, three-component dielectric composed of air, water, and glycerin. Significant enhancements, ranging from 7 to 19 times, are observed in machining speed (125 × 10⁻³ mm³/min), alongside a valuable reduction in environmental impact by over 7 times, compared to existing variants. Pressurized air efficiently flushes debris from the narrow inter-electrode gap, ensuring a clean machining environment. Water droplets enhance cooling and reduce the viscosity of the liquid phase, facilitating consistent material removal. Glycerin contributes additional energy through exothermic reactions, sustaining the melted puddle and boosting material removal efficiency with droplet explosions near the puddle. Single discharge crater experiments reveal unique material removal modes, indicating that complete melting before ejection of material may not be necessary. The study proposes a hypothesis suggesting that glycerin droplets burst upon contact with the work surface, promoting material spalling phenomena. Surface-sensitive morphology and chemistry analyses confirm traces of droplet explosions, validating the hypothesis. Parametric investigation demonstrates that the developed dielectric allows unprecedented use of extreme discharge energy (current up to 15 A) without concerns about damaging the machined surface or the micro-tool. The life cycle assessment (LCA) study reveals that the developed dielectric offers a sevenfold reduction in greenhouse gas emissions compared to existing variants. This research addresses challenges in micro-EDM and contributes to a circular economy by creating demand for excess glycerin, a by-product of bio-diesel synthesis. Overall, this study enhances sustainability and machining speed, aiming to pave the way for a more responsible future in micro-EDM.