Performance Investigation of Powder Mixed Electro Discharge Machining of Hypoeutectic Al-Si Alloy Using Brass Electrode

1. Introduction

In the conventional methods of machining, the basic principle of metal removing is the use of tool which is harder than workpiece material and material is removed by the compression shear chip formation. On the other hand, in advanced machining methods, there is not any direct contact between the workpiece and the tool and thus harder tool than workpiece is not needed.

EDM is a non-conventional machining process being largely used in tool and die making, aerospace, automobile and surgical instruments. EDM process utilizes thermal energy for machining all electrically conductive and high temperature high strength materials. In this process the material is removed from the workpiece due to erosion rapidly recurring spark discharge taking place between the workpiece and tool (Ojha et al., 2014).

PMEDM is a recent innovation in the EDM sector having more complex mechanism than conventional EDM (Talla et al., 2014). The powder fills up the spark gap between two electrodes under the influence of high electrical potential. Due to applied potential, these powder particles get energized and act as conductors which form chains in the sparking gap. This bridging of spark gap causes the reduction in the insulating strength of dielectric fluid and increases the gap size between tool electrode and workpiece. Due to easy short circuiting and hence more frequency of discharging, the material removal rate increases. The powder particles which are added into the dielectric also change the shape of channel carrying the discharge energy. The enlarging and widening of the discharge channel carry a more uniform discharge energy among the powder particles. This produces large number of small and shallow craters and reduces the surface roughness (Talla et al., 2014).