MHD Convection as a Process Enhancer in ECDM: Mechanistic Study of Bubble Dynamics, Gas Film Evolution, and Microchannel Fabrication on Silica Glass

Abstract

Electrochemical Discharge Machining (ECDM) is a hybrid microfabrication process combining electrochemical etching and spark-assisted thermal erosion for machining electrically non-conductive materials. This study investigates externally applied Magneto-hydrodynamic (MHD) convection on bubble dynamics and microchannel fabrication in silica glass. The Lorentz force generated by ionic current density (J) and magnetic field (B) induces rotational electrolyte flow, reducing bubble residence time, departure radius, and gas film thickness while stabilizing discharge frequency. A mathematical model correlating departure radius with magnetic field strength was validated. Experiments were conducted using Response Surface Methodology (RSM) with a 28-run Central Composite Rotatable Design (CCRD), varying voltage, NaOH concentration, duty cycle, and feed rate. MHD convection reduced bubble departure radius by 46% and bubble coverage by 43%, improving Material Removal Rate (MRR) by 42%, Width of Cut (WOC) by 12.9%, surface roughness by 26.9%, and Heat-Affected Zone (HAZ) by 47% compared to conventional ECDM.