Experimental Investigation of Powder-mixed Dielectrics for Electrical Discharge Machining

Abstract

The addition of various micro/nanopowders in the EDM dielectric results in superior machining performance over the conventional pure liquid dielectrics. While most of the experimental studies on powder-mixed dielectrics in EDM have used conductive or semi-conductive powders, a few have shown merit in using non-conductive powders as well. However, unlike conductive powders, the specific mechanisms through which the non-conductive powders and their concentration affect the EDM process is poorly understood. The research presented in this paper investigates the effect of non-conductive powders and their concentration on the machining performance of powder-mixed dielectric-based EDM (PMEDM) in terms of material removal rate, tool wear, and surface roughness. Experiments are conducted with Alumina and SiC powder added to DI water at three different concentrations. It is observed that the material removal rate (MRR) and tool wear rate (TWR) of PMEDM is higher than conventional EDM with pure dielectric, while the electrode wear ratio is lower. The machined surface finish is smoother in PMEDM than conventional EDM. In Alumina-based PMEDM, an increase in the powder concentration leads to inter-electrode gap enlargement due to increased electrical conductivity, and leads to higher pulse frequency, stable machining conditions and improved MRR. In addition, dispersion of discharge energy due to the powder results in a better surface finish. The conductivity of SiC-mixed dielectric remains unaffected with changes in powder concentration, leading to no significant improvements in MRR. However, the energy dispersion mechanism leads to a smoother surface as the powder concentration increases.