Simulation of Surface Integrity for Nanopowder-Mixed Dielectric in Micro Electrical Discharge Machining

The use of powder-mixed dielectric for electrical discharge machining (PMD-EDM) and micro-electrical discharge machining (PMD micro-EDM) has been shown to reduce machined surface roughness and surface defects, such as, recast layer thickness. However, these were mainly empirical studies which had limited capacity to elucidate the physics and characteristics of the PMD-EDM process. In the current study, a new numerical model has been developed to describe the PMD micro-EDM process. The model has taken into account the larger expansion of the plasma channel and reduction in heat flux distributed to the workpiece because of the presence of powder particles. It has been analyzed using finite element methods (FEMs) and based on the multiple discharge approach. The heat source expansion factor due to the presence of powder particles has been estimated to be 1.07 at 0.02 g/L powder concentration. The fraction of heat flux to the workpiece has been found to decrease from 0.24 at 0.02 g/L to 0.11 at 0.2 g/L powder concentration. For model validation, simulated Rmax and recast layer thickness values were compared with their corresponding measured values. The simulated and measured results varied with the same general trend which suggested that the proposed process model for PMD micro-EDM was fundamentally sound.