Enhancement of EDM performance for NiTi, NiCu, and BeCu alloys using a multi-criteria approach based on utility function

Introduction: Machining hard materials and shape memory alloys (SMAs), such as NiTi, NiCu, and BeCu, using conventional techniques is challenging due to excessive tool wear and poor surface finish. Non-conventional machining methods, particularly electrical discharge machining (EDM), offer improved precision and surface quality. However, the effectiveness of EDM is contingent upon the optimization of process parameters. The purpose of this study is to optimize EDM parameters to enhance the machining performance of SMAs by considering factors such as pulse-on time, pulse-off time, discharge current, gap voltage, and workpiece electrical conductivity. Methods. In this study, the Taguchi experimental design approach was employed to analyze the influence of key process parameters on the material removal rate (MRR), surface roughness (SR), and tool wear rate (TWR). Analysis of variance (ANOVA) was then applied to identify the most statistically significant factors affecting machining performance. A multi-objective optimization method, based on utility theory, was utilized to determine the optimal EDM settings that balance MRR, SR, and TWR. The results were validated through experimental trials. Results and Discussion. The experimental results indicated that Trial 15 achieved the highest MRR of 9.076 mm³/min, while Trial 1 produced the lowest SR of 2.238 µm. The minimum TWR of 0.041 mm³/min was observed in Trial 10, which contributes to increased tool lifespan. ANOVA revealed that gap voltage was the most influential factor, accounting for 85.98% of the variation in machining performance, followed by discharge current (4.76%) and pulse-off time (2.59%). The multi-objective optimization process successfully identified parameter configurations that optimize MRR while minimizing SR and TWR. The prediction model developed in this study demonstrated high accuracy, with an R² value of 93.3% and an adjusted R² of 89.7%. Validation experiments confirmed the effectiveness of the optimized parameters, resulting in an average MRR of 8.852 mm³/min, SR of 2.818 µm, and TWR of 0.148 mm³/min. The findings presented herein confirm that careful optimization of EDM parameters significantly enhances the machining performance of SMAs, considerably improving machining efficiency and tool longevity.