Exploring the influence of powder particles in dielectric liquid of EDM: pulse train, discharge energy, material removal rate and surface topography

Abstract

A comparative study on the effect of adding molybdenum di-sulphide (MoS2) powders of diameters 40 μm, 90 nm size into an ultrasonic vibration induced dielectric liquid of electrical discharge machining (EDM) process is attempted. Discharge duration, peak current, gap voltage are selected as input variables and their impact is assessed using pulse train, discharge energy, material removal rate (MRR) and surface integrity which are considered as outcome measure. The outcome measures of powder mixed dielectric (PMD) are compared with that of pure dielectric. Through pulse trains, a new phenomenon of partial discharge is identified. The incidence of partial discharge are assessed using scanning electron microscope (SEM) images. By varying the discharge duration, peak current and gap voltage, the discharge energy reduces in contrast to pure dielectric by 4%, 21.01%, 8.35% respectively for 40 μm diameter PMD and 10%, 27.29%, 17.99% respectively for 90 nm diameter PMD. The increase of peak current and gap voltage magnitudes cause the discharge energy to rise whereas discharge energy drops with growing magnitudes of discharge duration. Compared to the pure dielectric, the PMD produced enhanced MRR for similar discharge energy levels. The peak current has shown greater influence on MRR than discharge duration and gap voltage. In comparison with pure dielectric, the machining performance has improved by 21% for 40 μm diameter PMD, whereas 84.21% for 90 nm diameter PMD. At higher discharge parameters, better surface topography is produced in PMD than pure dielectric.