Abstract
This study investigates the near-dry electrical discharge machining (EDM) process. Near dry EDM uses a precision minimum quantity lubrication (MQL) dispenser to supply a minute amount of liquid droplets at a controlled rate to the gap between the workpiece and electrode. The dielectric fluid used in this study is the water mist, the mixture of air and deionized water droplets. The wire EDM cutting and EDM drilling are investigated under the wet, dry, and near dry conditions. Near-dry EDM exhibits advantages over dry EDM in higher material removal rate (MRR), sharper cutting edge, and no debris deposition. Compared to the wet EDM, near-dry EDM has higher MRR at low discharge energy and generates smaller gap distance. However, near-dry EDM has the disadvantage of high thermal load on the electrode, which causes the wire breakage in wire EDM and high electrode wear in EDM drilling. A mathematical model, assuming that the gap distance consists of the discharge distance and the material removal depth, was developed to quantitatively correlate the dielectric strength and viscosity of the water mist to the generated gap distance.