Study On The Terminal Position Precision Of Micro Electrode At Supercritical Speed In Edm Milling Process

In Micro-EDM milling process,the electrode requires pre-grinding to remove clamping errors,but with the improving of machining accuracy,machining efficiency decreases,and the wear of the electrode becomes more rapidly in the axial direction.In this paper,based on the self-centering effect of rotating shaft at supercritical speed,tube electrode at supercritical speed is used to improve machining accuracy.Firstly,the rotating vibration model of the tube electrode is established.By solving the differential equation,the frequency equation and mode function of the rotating vibration of the electrode are obtained,and the theoretical formulas of the critical speed and the optimal speed are derived.The effects of electrode length,rotating speed and installation angle on the steady-state response of the rotating vibration of the electrode are discussed.Then,the simulation of the rotating vibration of the tube electrode is carried out based on Ansys.The key parameters of the simulation model are modified by the idling experiment.Based on this model,the steady-state response shapes of the rotating electrodes and the changes of their terminal amplitudes under different lengths,initial installation angles and different rotation speeds are analyzed.The experimental results show that the critical speed range is in good agreement with the theoretical and simulation results,and the error of the terminal amplitude between experimental and the simulation results is within ±15%,which verifies the accuracy of the simulation model.Simulation and experimental results show that at the supercritical speed,the position precision of the rotating electrode can be significantly improved.Taking an 80 mm long electrode as an example,at a supercritical rotation speed of 7000 rpm,its terminal position deviation is 37.1% than that of 1000 rpm.Finally,machining experiments are carried out.The results of single-slot machining experiments with different lengths and rotation speeds of the electrode are studied,and the improvement of the terminal position precision of the electrode during the processing of supercritical rotation speed is verified.In view of the instability phenomenon of electrode appeared in the machining experiment,the main influencing factors of the electrode stability in deep groove machining are analyzed and discussed.The experimental results show that the performance of the servo system of the machine is insufficient,and the contact between the electrode and the side wall of the workpiece frequently occurs.As a result,the stability of the electrode is continuously destroyed,eventually resulting in the unreliable position precision of the terminal of the electrode.