Vibration amplitude characteristics of tubular electrode in EDM drilling

In the drilling of electric discharge machining (EDM) by use of a tubular electrode with high-pressure dielectric fluid, the random electrode vibration causes short circuit and second discharge which have a bad effect on machining accuracy and efficiency. In this paper, the microscopic amplitude characteristics of the electrode vibration are researched by adopting methods of simulations, experiments and comparative analysis. Based on ANSYS simulation platform of finite-element software, a finite element model was established to simulate the vibration characteristics of the tubular electrode, and then the effects of multiple factors including hydraulic pressure of dielectric fluid, electrode-guide gap, drilling depth, discharge gap, spindle speed and electrode overhanging length on the electrode vibration amplitude were analyzed. In addition, the significant level of every factor was analyzed by numerical simulation under the condition of coupling these factors. The EDM drilling experiments were carried out to verify the simulation results. Our research shows that the guide gap, drilling depth and hydraulic pressure have positive correlation with the electrode vibration amplitude, and reducing the guide gap from 10 μm to 1 μm can effectively reduce 20 μm of the error of the aperture. By analyzing these coupling factors, the order of significance affecting the electrode vibration is drilling depth, hydraulic pressure of dielectric fluid, discharge gap, spindle speed and electrode overhanging length. This research provides a basis for optimizing machining process and spindle design of EDM drilling using a tubular electrode.