High-speed near dry electrical discharge machining

• A novel high-speed near dry electrical discharge machining method was proposed.
• Higher material removal rate, lower surface roughness and thinner width of overcut were obtained in this method compared with that of high-speed dry EDM.
• Debris deposition on the machined surface and electrodes were significantly reduced and an obviously thin heat affected zone was obtained.

High-speed near dry electrical discharge machining (EDM) is a novel and promising machining method, which obtains higher material removal rate, lower surface roughness and thinner width of overcut compared with that of high-speed dry EDM. Moreover, debris deposition on the machined surface and electrodes are significantly reduced and an obviously thin heat affected zone is obtained using the near dry dielectric (mist). In this study, a low-flux pump is utilized to supply deionized water at a controlled rate to the high-speed air pipe, which affords a mist dielectric to the machining process. Compared with dry EDM, the high-speed near dry EDM improves the cooling capacity and increases the dielectric strength of the dielectric. Furthermore, electrode injection flushing assisted by side flushing of high-speed mist was used to reduce debris deposition and improve cooling capacity. Comparative milling experiments of Ti6Al4V were conducted under the dry and near dry conditions using the different flushing ways. The effects of current, pressure, droplet size, electrode rotation speed, and droplet density on the material removal rate, surface roughness, width of overcut in continuous machining and material removal weight, trace length, trace width in single pulse machining were studied. In addition, scanning electron microscope, X-ray diffractometer, energy dispersive spectrometer, and micro-hardness tester were also used to study the micro-characters of the machined materials.