Effect of process parameters on machining EN 47 spring steel through WEDM

Achieving good material removal rate (MRR) along with better surface roughness is a challenging task for the present machining industry. The present study proposes Taguchi-method-based multiple-response grey relational analysis to find the optimal combination of machining parameters for maximum MRR and minimum surface roughness (R-a) in wire electro-discharge machining (WEDM) of EN 47 spring steel. The effects of four process parameters - namely, pulse-on time, pulse-off time, gap voltage and wire feed - on the machining characteristics (MRR and R-a) were studied with the help of an L-27 orthogonal array, which was used to study the main effect as well as the interaction effect of the parameters. The grey relational grade was the performance index which is used to study the behaviour of machining parameters in WEDM of EN 47 spring steel with respect to the MRR and R-a. Signal-to-noise ratio analysis and analysis of variance are done by taking the grey relational grade as the combined response. It is observed that the pulse-on time was the most significant process parameter, whereas the pulse-off time had a moderate effect on the MRR and R-a. Moreover, significant interactions were found in all three cases in controlling MRR and R-a. The surface morphology and composition were studied with the help of scanning electron microscopy and chemical analysis.