Sustainable electro discharge machining of aerospace materials using eco-conscious dielectric medium

The development of a sustainable EDM process depends on identifying alternative dielectric fluids that can enhance machining performance while minimizing the reliance on conventional petroleum-based fluids. In the present work, refined sunflower oil has been employed as the environmentally friendly dielectric fluid for the EDM process of SS304 stainless steel with an aluminium tool electrode. The mineral-based EDM oil has been employed as the conventional dielectric fluid. The experiments were carried out with the help of an orthogonal array of L16 for various levels of discharge current, gap voltage and pulse-on time. Machining response was analyzed in terms of Material Removal Rate (MRR) and Depth of Cut (DoC), while the dielectric behaviour and surface morphology after machining were investigated using FTIR, ICP-OES, and SEM analyses, respectively. The highest MRR rose from 33.33 mm 3 /min using EDM oil to 39.08 mm 3 /min using sunflower oil, while the highest DoC rose from 4.24 to 4.975 mm. Further analysis by Taguchi S/N ratio and ANOVA revealed that the dominant control factor changed from pulse-on time in EDM oil to discharge current in sunflower oil, with current responsible for about 43% of MRR and DoC using sunflower oil. The predicted optimal setting using sunflower oil would be 35 A current, 50 V gap voltage and 400 µs pulse-on time, resulting in predicted values for MRR and DoC of 42.62 mm 3 /min and 5.42 mm, respectively. Fourier Transform Infrared Spectroscopy (FTIR) results revealed higher retention of functional groups typical of triglycerides in sunflower oil after the machining process, suggesting high dielectric stability compared to mineral EDM oil. Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) analysis revealed lower concentration levels of selected metallic contaminants, including Pb, Zn, Cu, Al, Co and Mn, in the spent sunflower-oil media. These findings demonstrate that refined sunflower oil is a technically viable eco-conscious dielectric candidate for EDM of SS304, offering improved machining productivity, better post-machining chemical stability, and lower trace-metal contamination under the tested conditions.