Optimisation of Wire Electrical Discharge Machining (WEDM) Process Parameters for AISI D2 Tool Steel Using Taguchi Method and Grey Relational Analysis

Abstract

Wire Electrical Discharge Machining (WEDM) is a precision non-contact thermal material removal process essential for machining hard, electrically conductive materials such as hardened tool steels, cemented carbides, and high-temperature alloys. This paper presents a systematic experimental investigation into the optimisation of WEDM process parameters for AISI D2 high-carbon, high-chromium cold-work tool steel (hardness 60 HRC) using a Taguchi L27 orthogonal array design with five factors at three levels: pulse-on time (Ton: 105, 115, 125 µs), pulse-off time (Toff: 45, 55, 65 µs), peak current (IP: 120, 160, 200 A), wire feed rate (WF: 4, 6, 8 m/min), and wire tension (WT: 6, 8, 10 N). Response variables measured are material removal rate (MRR), surface roughness (Ra), kerf width, and wire breakage occurrence. Analysis of Variance (ANOVA) identifies pulse-on time (41.6% contribution) and peak current (27.5%) as the dominant factors for MRR, while peak current (42.1%) and pulse-on time (38.4%) govern surface roughness. Grey Relational Analysis (GRA) resolves the conflicting single-response optimal settings into a unified multi-response optimal combination (Ton = 115 µs, Toff = 55 µs, IP = 160 A, WF = 6 m/min, WT = 8 N) that simultaneously maximises MRR, minimises Ra and kerf, and prevents wire breakage. Confirmation experiments validate GRA predictions within 4.2% error. Regression models for MRR and Ra are developed with R² > 0.96.