Investigating the Performance of the Rotary Tool Near-Dry Electrical Discharge Machining Process through Debris Analysis

Rotary tool near-dry electrical discharge machining (RT-ND-EDM) process is an environmentally friendly EDM variant. A mixture of liquid–gas is employed as the dielectric medium. The literature reveals that the analysis of debris characteristics can reveal vital information about the EDM`s traits of material removal phenomena. Many factors ranging from the type of dielectrics used to the selected values of different process parameters affect debris characteristics in EDM. However, in the case of the RT-ND-EDM process, debris characteristics have not been investigated adequately. Therefore, this research characterizes the debris generated during the RT-ND-EDM of high-speed steel with two different dielectric combinations (i.e., water–air and glycerin–air) and expounds their formation mechanism. It investigates the parametric relationship of current, liquid flow rate, and tool rotation speed on the debris characteristics and then attempts to establish their relationship with the process performance. Surface roughness and material removal rate (MRR) were used for evaluating the process performance. The debris`s size, morphology, crystallinity, and elemental composition were characterized at the micro- and nano-metric scales. The experimental results revealed that the debris produced with glycerin–air was roughly three times bigger than those generated with the water–air. The air–glycerin combination gave higher MRR and rougher machined for given parameters.