Titanium alloy grade 5, Ti6Al4V, is extensively gaining importance in the industrial environment, specifically in aerospace, medical and automotive domains, mainly due to its exceptional blend of mechanical properties like high hardness which is further heat treatable, high strength-to-weight ratio which makes it light, high corrosion and temperature resistance etc. However, the same properties undervalue Ti6Al4V as a conventionally difficult-to-machine material. Rapid tool wear, excessive heat generation, dimensional instability and loss of surface integrity are the issues that plague the conventional machining of Ti6Al4V. In view of these facts, non-traditional machining processes like electron discharge machining (EDM) -die sinking and wire cut prove to be a substitute for the conventional machining. In this study, an experimental optimization of EDM die-sinking electrode materials among copper, brass and graphite, is carried out. Experimental design is created using a statistical tool and actual machining is carried out to record the surface roughness, variations on the surface hardness and dimensional stability. Quality evaluation and statistical analysis substantiates graphite electrodes to produce better surface finish-Ra 2.05microns with minimal dimensional variation-less than 10%when operated at minimum spark gaps. It is inferred that graphite electrodes exhibit higher resistivity towards current than its counterparts thus passing minimum spark energy preventing excessive self-wear and a dimensionally accurate work piece. The depth of machining highly impacts the variations on the surface hardness post machining.

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Polishing of core and cavity surfaces after machining is a vital operation in the processing of plastic and metal cast products. It is carried out in order to achieve a certain degreeof surfacefinish-roughness or smoothness-on the machined surface, depending on its application as an end product and also for release from the cavities during ejection of the parts after moulding. Polishing is a high skilled manual time-consuming process in the overall cycle time of mould manufacturing. In this study, a CNC toolpath is generated in order to polish the core and cavity on the same machine where it is machined initially. The machine parameters for the polishing of the surfaces are optimized through a DOE set up. The surface finish achieved through machine polishing is inspected and recorded using a surface roughness tester and toolmaker’s microscope. It is observed, through the study that a combination of higher interference values between the tool face and the surface being polished along with higher feed rates proved to be determining factors in providing better surface finishes as high as 0.5μ Ra in machine polishing.

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