| Micro electrical discharge machining(micro-EDM) is widely used in micromachining for its electrode easy to make, machining process easy to control and littlemachining influence of the material’s hardness and strength. But the low machiningefficiency and the slow machining speed also limit the application and development ofthe micro-EDM.In micro-EDM hole drilling and milling the spindle is generally rotated to improvethe machining speed, the rotational speed is normally hundreds to thousands rpm. It isconsidered that the spindle rotation is useful in flushing debris particles from the gapand cooling the electrode, avoiding localized discharge and abnormal arc, thus furtherincrease in the machining speed may be possible with increasing the spindle over tensof thousands rpm. However, in conventional RC pulse generator, the electric feedingmethod is contact using brush, it is difficult to supply electric power to the toolelectrode rotating with an extremely high speed without causing vibration of the spindlewhich lower the machining accuracy, so the contact electric feeding method limit thefurther increasing of the spindle rotation.The micro-EDM using electrostatic induction feeding method can realize thenon-contact electric feeding to the tool electrode, it can not only further improve theminiaturization in micro-EDM, but also could remove the electric feeding brush,offering a possibility for the application of the high spindle in micro-EDM.In this paper, through analysis of the principle of the micro-EDM usingelectrostatic induction feeding method, the micro-EDM experimental platform usinghigh spindle and the non-contact measuring device of the gap voltage were completed,verified the non-contact measurement could reflect the change of gap voltage exactly, itis also found that changing the inner diameter and the axial length of the feedingelectrode can adjust discharge energy effectively. Meanwhile the micro hole machiningflow field model using cylindrical electrode with high rotation speed was established,analyzed the forces on particles under different rotation, simulated the distribution ofthe particles in the gap flow field, it is found the higher rotation speed the spindle was,the more easily the particles were expelled from the gap. To adjust the gap widthautomatically, according to the discharge characteristics the servo control system of gapwidth was carried out. Meanwhile the influence of the servo reference voltage, the pulsefrequency and the spindle rotation speed to the machining speed in micro holemachining were investigated, and the electrode wear was investigated in machining themicro seam. |
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