Performance optimization of D2 tool steel machining using novel multi-material cladded electrodes in electric discharge machining

• The study investigates copper and graphite multi-material cladded electrodes in two configurations (copper-in graphite-out and graphite-in copper-out) for electric discharge machining (EDM) of D2 tool steel. • Key performance factors such as material removal rate, surface roughness, overcut, tool wear ratio, and depth of cut were evaluated for both electrode configurations. • Taguchi L9 array was employed for experimentation, with discharge current, pulse time ratio, and spark voltage as control parameters. • The copper-in graphite-out configuration yielded a notable surface roughness differential of 3.1 µm and a maximum depth of cut difference of 0.8 mm, compared to 0.04 mm for the graphite-in copper-out configuration. • The interfacial gap between cladded electrodes was found to be minimal (∼5 % of the maximum gap), indicating that depth impressions can be generated without significantly affecting the electrode interface integrity. This work evaluates a novel approach of employing copper and graphite multi-material cladded electrodes in two configurations (copper in - graphite out and graphite in - copper out ) for their performance on material removal rate, surface roughness, tool wear ratio, overcut and depth of cut under electric discharge machining of D2 tool steel. Discharge current, pulse time ratio and spark voltage were taken as variable parameters and Taguchi L9 array was established to identify design of experiments (DOE) that are used for experimentation of each of the two configurations. It is found that the multi-material electrodes behave differently in different configurations under the same parametric conditions. Additionally, the differences as created on the machined surface by each of the material in either configuration yield interesting results which indicate feasibility of generating patterns/impressions in a single experiment run. The interfacial gaps as created between the cladded electrodes post machining are also quantified for evaluation of limitations. It is found that copper in - graphite out configuration gives a maximum surface roughness value differential of 3.1 µm between the sections machined by individual materials in this configuration at certain parametric condition. Also, discharge current 4A, pulse time ratio 1.5 and spark voltage 6 V generate impression/pattern with a maximum depth of cut difference in both configurations (0.8 mm for copper in - graphite out and 0.04 mm for graphite in - copper out ). The interface gap at experiment condition where maximum height difference Δh max. (mm) is achieved, is only around 5 % of the maximum interface gap for both configurations which indicates that the depth impressions could be generated without introducing much gap within cladded electrode interfaces.