Experimental Study And Mechanism Analysis On Submersed Gas-jetting EDM

In the process of EDM, dielectric medium has remarkable influence on material removal rate, surface quality of the workpiece and relative electrode wear ratio. The Traditional EDM can achieve stable discharging but the electrode wears dramatically, which decreases the EDM milling performance. Oil-based dielectric will generate noxious gas that pollutes the environment, while water-based dielectric will bring electrolytic reaction. EDM in gas can make less electrode wear, but its high short circuit ratio will lead to unstable process and thus low material removal rate. A kind of uncomfortable smell like burning can also be found in this process.To take the advantages of both EDM in liquid and in gas dielectric, a new method called submersed gas-jetting EDM is proposed in which the high-pressure gas blown throughout the inner hole of a tubular electrode worked as the dielectric medium, and water-based liquid around the gas helps cooling and debris evacuation but does not involve in the discharge process directly.To explore the principle of submersed gas-jetting EDM with dielectric medium, Volume of Fluid (VOF) model were used to analyze the air volume fraction of the working area between the electrode and workpiece. The results indicated that the working area is completely surrounded by the high-pressure gas and the discharge happens in the gas. In the experimental study of this method, the effects of dielectric media on minimum working gap, electrode surface and workpiece surface were analyzed, hence validated the numerical simulation results, and explained the reason that submersed gas-jetting EDM is similar with that of EDM in gas and the phenomenon of workpiece debris adhering on the electrode. To explore the law of submersed gas-jetting EDM, the preliminary experiment was conducted based on the research of counterparts all over the world, The effects and interaction of four critical factors named pulse duration, pulse interval, peak current and depth of cut, on material removal rate and relative electrode wear ratio were studied with methods of orthogonal experimental design and response surface. It was found that the factors are through a combination of ways to affect the overall EDM performance. It was also found that there are some kinds of relation between the machining abilities and gas pressure, relative speed between electrode and workpiece, wall thickness of electrode, depth of cut and so on.Through the milling machining of a plane, a new method named Submersed Gas-jetting High Speed Assist EDM Milling was finally proposed and its system structures were described. It was also discussed on the milling process planning and comprehensive machining performance. High Speed Assist Submersed Gas-jetting EDM revealed better machining performance compared with Traditional EDM and EDM in gas. This new method not only keeps lower relative electrode wear ratio but also achieves much higher material removal rate, without burning smell.It was proved that High Speed Assist Submersed Gas-jetting EDM Milling is an effective solution to solve high short circuit ratio problem of EDM in gas, and reveals good machining performance.