Powder Mixed Near Dry Electrical Discharge Machining

To meet demand for precise and flexibility of EDM development, a Powder Mixed Near Dry Electrical Discharge Machining (PNDEDM) is presented in this paper. The study focuses on using gas-liquid-solid three phase mixtures as dielectric medium. In the process of PNDEDM, the tool electrode is a thin-walled pipe, the high pressure gas-liquid-solid dielectric medium is applied from inside. Material removal mechanism has been analysed. Due to the presence of liquid drop and powder in gas, dielectric strength of gas is reduced, gap distance is increased, the eroded particles are easily flushed out, and the probability of short circuit rate and arcing phenomenon is minimised, stability of the machining process becomes better, material removal rate (MRR) is improved. Due to discharge disperse effect of powder, crater depth become small, less globular appendage is generated on the surface, therefore, surface quality roughness is improved. Experiment results show that the MRR and surface roughness increases with the increase of pulse duration, peak current, MRR and surface roughness decreases as pulse interval or dielectric medium pressure increases.