Abstract
This study investigates the milling by dry and near-dry electrical discharge machining (EDM) to achieve either the high material removal rate (MRR) or good surface roughness. Dry EDM uses the high velocity gas flow as the dielectric medium and near-dry EDM uses the mist spray of liquid-gas mixture as the dielectric medium. Different gas and mist dielectric fluids and electrode materials have been examined to achieve the desired high MRR and surface finish. Near-dry EDM exhibits the advantage of good machining stability at small discharge energy input and accordingly good surface finish. The liquid particles dispersed in the gas medium are considered to have similar effect as those particle additives in power mixed dielectric EDM. A 25-1 fractional factorial design was applied to study the effect of process parameters on dry and near-dry EDM. Discharge current, pulse duration and pulse interval were identified as the significant process parameters. Potentials and directions for further dry and near dry EDM process improvements were identified.