Performance enhancement of rotary tool near-dry EDM of HSS by supplying oxygen gas in the dielectric medium

Abstract

ABSTRACTThe present investigation was carried out with an objective to enhance the performance of the rotary tool near-dry EDM (RT-ND-EDM) process by adding oxygen gas in addition to the dielectric medium. The effects of the amount of oxygen, rotational speed of the tool, current, pulse on time, and liquid flow rate were investigated on the performance characteristics of RT-ND-EDM process using high-speed steel as work material. The material removal rate (MRR), hole overcut (HOC), and surface quality were chosen as performance characteristics to represent the viability of the process. Surface quality was measured and analyzed in terms of debris deposition, micro-globules on the surface, porosity, micro-cracks, blowholes, and flow marks. The analysis of experimental results of RT-ND-EDM process, when oxygen gas was used along with dielectric medium, revealed that the MRR was 203%, 110%, and 85% higher than that of MRR obtained by the dry EDM using air, dry-EDM using air-oxygen, and RT-ND-EDM process without oxygen, respectively. This can be attributed to the fact that the addition of oxygen in the water-air dielectric medium helped in more amount of melting due to the rapid oxidation of work material. The debris formed during the oxygen mixed RT-ND-EDM process, cross-sectional analysis of the machined surface and analysis of tool wear were also investigated.