Multi-response optimisation of machining parameters in wire EDM process using grey relational analysis

Wire electrical discharge machining (WEDM) is extensively used in machining of materials when precision is of prime importance. It is a specialised process for cutting complex contours or fragile geometries that would be difficult to be produced using conventional cutting methods. In the present work, the WEDM machining of EN-31 alloy steel has been studied with multiple performance characteristics such as cutting rate (CR), surface roughness (Ra) and dimensional deviation (DD) using grey-Taguchi method. The process parameters considered for optimisation are pulse on time (Ton), pulse off time (Toff), wire feed (WF), wire tension (WT), spark gap set voltage (SV) and servo feed (SF). For experimentation Taguchi's L27 orthogonal array (OA) has been used. The application of grey relational analysis is adopted to convert multi-objective criterion into an equivalent single objective function; overall grey relational grade (GRG), which has been maximised by using Taguchi technique. Additionally, the analysis of variance (ANOVA) for GRG is utilised to determine the most significant process parameters. Optimal setting has been verified through confirmatory test; found good agreement with predicted value. The experimental results confirm that the proposed method effectively improves the machining performance of WEDM process.