Parametric effect on material removal rate and surface roughness of electrical discharge machined magnesium alloy

Magnesium and its alloys play a vital role in various applications such as automobile, aircraft, biomedical and military etc. Mg alloys have superior characteristics such as light weight, high strength, good damping capacity and easily castability etc. Eventhough it has attractive range of properties, the machining of magnesium alloys using conventional machining methods is difficult. To overcome that issue, non traditional machining is considered as a potential process. EDM is an electro thermal process extensively used for machining hard materials. In this investigation, the ZE41A magnesium alloy is machined using EDM with copper electrode. In order to improve surface characteristics such as material removal rate (MRR) and surface roughness (SR), various parameters namely current, pulse on time and pulse off time were selected. The regression values of MRR and SR are 97.20% and 99.62% respectively indicating an empirical relationship between the parameters and responses. Pulse off time was found as a significant parameter on the response followed by pulse on time and current. MRR and SR increased with increasing current, pulse on time and pulse off time. At a current of 5A, the produced spark density is high so that the removed quantity of material from the workpiece is high. At a pulse on time of 95 mu s, the spark intensity is high affecting the local temperature in the machined zone, and hence MRR increases. SR drastically increases at increasing current. At higher current, large size crater are observed on the machined surface that made the surface rough, and hence SR increases.