Investigation on the influence of different types of dielectrics in electrical discharge machining

EDM is a special type of non-traditional machining technique in which material removal takes place due to repeated electrical discharges at short intervals in the presence of a dielectric medium. It is used in high precision machining of all types of conductive materials such as metals, metallic alloys, graphite and even some ceramic materials. In EDM, the main output parameters are the material removal rate (MRR), electrode wear rate (EWR), and surface roughness (Ra). It is generally desirable to obtain the maximum MRR with minimum EWR with good surface finish. The dielectrics play a vital role in machining. Even though EDM process has been traditionally used in die sinking industry mostly for machining hard materials, lighter materials like Ti alloy are machined more recently. In some cases, components made out of soft metals like Aluminium alloys are machined in EDM due to the intricacy of profiles, blind prismatic holes and inaccessible areas by other machining methods. This paper aims to investigate the effect of using different dielectrics, viz., biodiesel, transformer oil and kerosene on the material removal rate, electrode wear and surface roughness in EDM. Based on Taguchi’s design of experiments, machining were carried out on Aluminium Alloy 6063 specimens using a die-sinking EDM machine fitted with a copper electrode. The results show that the biodiesel as a dielectric has better performance in MRR, EWR and surface finish in comparison with kerosene and transformer oil. However, performance sustainability and the environmental effect of biodiesel have to be studied.