STUDY AND OPTIMIZATION OF ABRASIVE EDM PROCESS PARAMETERS WITH TOOL ROTATION

Abstract

Electrical Discharge Machining (EDM) is largely accepted advanced machining method in the domain of subtractive manufacturing processes across the globe. It caters lot of manufacturing applications involving generation of intricate shapes and machining hard to machine alloys in aerospace, defence, medical, and automobile industries. In this era of increasing competition, the developers and researchers are heading towards improvements of the method through various attempts. The focus area has always been the improvement of response measures. The literature reveals the successful attempts by researchers through modification to die-sinker electrical discharge machine by adding electrode rotation and with abrasive mixed dielectric fluid. The blend of these two alterations has been attempted through this research study. Two primitive materials, EN31 and D3 steel along with graphite and copper tool were taken for analysis keeping in view their wide scope of application in die industry. The aim is to provide a modified method which could be accepted for industrial usage. For this, a full factorial experimentation with three parameters i.e. tool rotation, current on time, and peak current at three levels each was planned. Three prominent responses were focused as output measures i.e. surface finish, electrode wear rate and material removal rate (MRR). The statistical model was generated which is effective in forecasting the response values. Analysis of variance revealed important parameters along with their interactions affecting response measures. The samples were also tested with scanning electron microscopy for surface morphology analysis. Abrasive mixed rotary electrical discharge machining (AREDM) enhanced the surface characteristics by attaining lower roughness values and recast layer thickness. In percentage terms, surface finish improved by 5.17% with variation of tool rotation from 1200 rpm to 1800 rpm while machining EN31 steel with graphite electrode. While with D3 steel, improvement in surface finish by 9.15% and 26.86% were recorded with graphite and copper electrode, respectively. For EN31 steel, a thin recast layer thickness of 32.29 µm was formed in AREDM compared to 62.25 µm in conventional EDM when machined with copper electrode. Comparing Recast Layer thickness (RLT) in vi AREDM with graphite and copper, graphite outperformed copper tool with RLT of 6.12 µm. Surface modification was also seen with the help of sub-surface micro hardness results. The sub-surface micro hardness increased from 514.59 HV0.5 to 533.23 HV0.5 in EN31 steel with graphite electrode and from 503.55 HV0.5 to 523.54 HV0.5 with copper electrode. Further, the surface morphology results at mid values of parameters were compared with conventional electrical discharge machining to see the improvements with existing methodology.

Finally, multi-objective optimization was performed with grey relational method and optimum parametric settings were obtained.