Development and Performance Analysis of Hybrid Bio-Dielectric Fluids for Sustainable Electric Discharge Machining of P20 Tool Steel Using Taguchi-Based Regression Analysis

Abstract

Electric Discharge Machining (EDM) is a highly popular non-traditional machining technique to manufacture geometrically intricate shapes in hard, electrically conductive materials with high dimensional and geometrical accuracy. Traditionally, hydrocarbon- and synthetic-based dielectric fluids used in the process release toxic emissions that are very dangerous to the environment, health and safety of the operators. While vegetable oil-based bio-dielectric fluids have been explored as sustainable alternatives, their limited thermal stability and high viscosity restrict performance under high-energy machining conditions. Authors in this research paper have presented a novel approach to use Hybrid Bio-Dielectric (HBD) fluids; which are developed by blending kerosene (K) with Jatropha biodielectric (JBD) in three volumetric concentrations (HBD1: 75%K+25%JBD; HBD2: 50%K+50%JBD; HBD3: 25%K+75%JBD). And Density, Viscosity, Thermal Conductivity, Specific Heat, Breakdown Voltage and Flash Point were systematically characterised for the HBDs. Taguchi L25 orthogonal array was used to perform EDM experiments on P20 plastic mould steel with four variables like discharge current, pulse-on time (Ton), duty factor, and HBD composition; and Material Removal Rate (MRR), Tool Wear Rate (TWR), Surface Roughness (SR), and Surface Hardness (SH) were measured as response variables. The experimental findings indicate that HBD2 produced 30-40% improvement in MRR and 8-12% improvement in SH over pure kerosene. Results of HBD3 are found to be the best for overall productivity, tool life and surface quality. These were confirmed by the Analysis of Variance (ANOVA) at 95% confidence. The results establish the potential of hybridization of dielectric fluids as an effective approach towards achieving a balance between high machining performance and improved sustainability.