Multi-response optimization and characterization for micro-EDM drilling of stainless steel (AISI 304) using a hybrid DFA-fuzzy logic approach

Due to high strength, biocompatibility and higher corrosion resistance, stainless steels are widely used in aerospace, medical, chemical, and automotive sectors. However, conventional machining of these materials does not produce higher accuracy because of their characteristics, which lead to the tendency of build-up edge formation, high tool wear and poor surface quality. Among numerous non-conventional machining techniques, electrical discharge machining is considered one of the highly efficient and economically viable methods for machining stainless steel. In the present study, microelectric discharge drilling is conducted on an AISI 304 stainless steel sheet using a 496 µm diameter WC tool electrode. The parametric impact of feed rate, voltage, and capacitance on performance characteristics like material removal rate, overcut, circularity error, and taper angle was studied after conducting a full factorial of 48 experiments. Capacitance has been found the most essential process parameter for influencing all machining outcomes considered in this investigation. Furthermore, a desirability function integrated with fuzzy logic is used to optimize all performance measures simultaneously. The optimal setting proposed by this approach is at voltage = 100 V, capacitance = 100 pF and feed rate = 20 µm/s. The field emission scanning electron microscope (FESEM) micrographs illustrate that lower discharge energy settings result in better geometrical accuracy and surface integrity. The energy-dispersive X-ray spectroscopy (EDAX) analysis revealed the migration of elements from the tool material and dielectric medium.