Wire electrical discharge machining (WEDM) is well known process for generating intricate and complex profiles in hard metal matrix composites. But damaged surface layer with poor surface integrity is a major disadvantage of WEDM. Beside poor damaged surface layer, after rough/first cut in WEDM, some surface area remains unmachined on work surface during intricate machining such as in die cutting. This paper presents a study on unmachined surface area named as surface projection, in die cutting after rough cut in WEDM. Using scanning electron microscope images, length of unmachined surface projections have been determined. In order to minimize these surface projections from small cavities having complex geometries, trim cutting operation is the best alternative. Results show that using more than one trim cut with appropriate wire offset value, surface projections can be minimized, successfully.

In this paper, wire electrical discharge machining of WC-Co composite is studied. Influence of taper angle, peak current, pulse-on time, pulse-off time, wire tension and dielectric flow rate are investigated for material removal rate (MRR) and surface roughness (SR) during intricate machining of a carbide block. In order to optimize MRR and SR simultaneously, grey relational analysis (GRA) is employed along with Taguchi method. Through GRA, grey relational grade is used as a performance index to determine the optimal setting of process parameters for multiple machining characteristics. Analysis of variance (ANOVA) shows that the taper angle and pulse-on time are the most significant parameters affecting the multiple machining characteristics. Confirmatory results, proves the potential of GRA to optimize process parameters successfully for multi-machining characteristics.