Experimental Study And Mechanism Analysis Of Submersed Gas-Jetting EDM

In the past 60 years, electrical discharge machining (EDM) has achieved great development due to its strong ability in machining high-hardness material and complicated shape. Whereas the high electrode wear rate (EWR) and the low manufacturing flexibility are also its disadvantages.EDM in gas (Dry EDM) proposed by Kunieda in 1997 is a milestone of development of EDM. Dry EDM is environmental-friendly due to the using of harmless gas such as air and oxygen. It has much lower EWR and much better manufacturing flexibility compared with the traditional EDM. However, its poor machining stability and low material removal rate (MRR) prevented its application in industry.Based on the above-mentioned description, a new machining method named submersed gas-jetting EDM is proposed. In this new method, the tool electrode is a thin walled pipe from which the high-pressure gas is applied. In the process, the workpiece and the tool electrode are both submersed in the water-based machining liquid, and the high-pressure gas is used as its dielectric medium while water-based machining liquid plays a significant role which doesn't participate in discharge directly.In this study, the experiments to investigate the difference between submersed gas-jetting EDM and dry EDM, the influence of machining parameters and medium on machining results was implemented. The results indicate that compared with the dry EDM, the submersed gas-jetting EDM can result in higher MRR, better surface quality and the same low EWR. With various machining parameters such as pulse duration, pulse interval, peak current and gas pressure, its EWR can keep at a very low level, which is the most remarkable advantage inherited from dry EDM. The results also indicate that oxygen and W-EDM dielectric machining liquid can increase the MRR and the surface quality to a great extent. Furthermore, the machining mechanism was analyzed by numerical simulation method. According to the analysis, the fact was verified that the discharging process takes place in the gas medium, and the water-based machining liquid can improve the pressure of the discharge gap and enhance the cooling effect to the plasma channel etc.The study revealed that the submersed gas-jetting EDM possesses the advantages of both traditional EDM and dry EDM, and is a feasible EDM method worthy to be further investigated.