Influence of 4-dodecylbenzenesulfonic acid as a surfactant on a graphite-based dielectric in powder mixed electric discharge machining

A recent trend in micro-EDM is the addition of powders into the dielectric. The presence of powders helps to lower the dielectric breakdown voltage and, therefore, the discharge occurs early. As a result, the discharge energy is better distributed, resulting in a greater number of discharges, each with less energy. The main advantage of using this method is the improvement of both the process performance and surface finishing of the workpiece. In general, a critical aspect of the implementation of this technology is the management of the powder. In fact, to obtain advantages during the machining, the powders should be maintained dispersed into the dielectric to avoid their aggregation. This paper aims to study the concentration of the powder and the surfactant in the dielectric fluid on micro-EDM drilling performance. Titanium alloy was used as workpiece material, hydrocarbon oil as dielectric, graphite as powder, and 4-dodecylbenzenesulfonic acid as surfactant. The performance was evaluated considering the material removal rate, the tool wear ratio, and the geometrical characteristics of the holes (overcut and taper rate). Graphite content positively affected both material removal rate and tool wear ratio; a larger spark gap was observed as well. The use of surfactant is required for mix stability, but increasing its percentage generally reduces the effects of graphite and increases data dispersion as well.