Optimization of wire electronic discharge machining parameters for AISI 1020 middle steel using taguchi method

Abstract

Although mild steel is generally easy to machine using conventional methods, achieving high dimensional accuracy and superior surface finish remains challenging due to its relatively low hardness and high chip formation tendency. Wire Electrical Discharge Machining (WEDM), a non-traditional machining process, offers improved precision for machining electrically conductive materials. This study investigates the optimization of WEDM process parameters for machining AISI 1020 mild steel. The key performance measures considered were material removal rate (MRR) and surface roughness. The selected process parameters include pulse-on time, discharge current, and voltage. Experiments were conducted using a HUADONG DK7740 WEDM machine at Ethio- Engineering Group, Addis Ababa. The experimental design was based on the Taguchi method using an L9 orthogonal array with three factors at three levels. The collected data were analyzed using MINITAB 19 software to determine the optimal parameter settings and the significance of each factor. The results revealed that peak current is the most significant factor affecting surface roughness, followed by voltage and pulse-on time, whereas voltage and pulse-on time have the greatest influence on material removal rate. The minimum surface roughness was achieved at Ton = 65 μs, Ip = 6 A, and V = 45 V, while the maximum material removal rate was obtained at Ton = 65 μs, Ip = 14 A, and V = 45 V. Regression analysis demonstrated good predictive capability, with a coefficient of determination (R² ≈ 0.87) for surface roughness. Validation through confirmation experiments and COMSOL Multi physics simulation showed prediction errors of less than 1%, indicating strong agreement between experimental and predicted results. The findings confirm that increasing discharge energy enhances material removal rate but adversely affects surface quality due to the formation of deeper discharge craters. Therefore, an optimal trade-off between productivity and surface integrity is necessary depending on application requirements. Regression models were developed to predict MRR and surface roughness, and their validity was confirmed through simulation using COMSOL Multiphasic software. The confirmation results showed good agreement between predicted and experimental values. In conclusion, the study demonstrates that proper selection of WEDM parameters significantly enhances machining performance, with pulse-on time and current identified as the most influential factors.