Research On High Voltage Controlled Liquid Metal Electrode EDM

With the progress of society,industrial processing is developing towards the direction of micronization.The size of processing is getting smaller and smaller,and the precision requirement is getting higher and higher.Micro-EDM has been widely used for its advantages of no cutting stress,rigid,brittle materials and high machining accuracy.In order to achieve more micro-machining,micro-EDM needs more micro-machining electrodes,but on the one hand,the difficulty of micro-electrode processing leads to high processing costs,which limits the development of micro-EDM;on the other hand,the more micro-electrode,the greater the impact of electrode loss,and the current electrode loss compensation.The method of compensation is complex and the accuracy is difficult to guarantee,which limits the accuracy of micro EDM.Using liquid metal as tool electrode,on the one hand,can save the process and cost of fabricating micro-electrodes,on the other hand,it can use the fluidity of liquid metal to compensate for the loss of electrodes,which is a new method to solve the loss of electrodes.However,the problem of uncontrollable shape of liquid metal electrode end leads to low machining accuracy.Aiming at this problem,this paper studies the method to improve the machining accuracy of liquid metal electrode by experiments.The shape of the end of the liquid metal electrode is mainly affected by the surface tension of the liquid metal electrode and the electric field force caused by the processing voltage.The surface tension and electric field force at the end of the liquid metal electrode are analyzed theoretically.The formulas of the surface tension and electric field force at the end of the liquid metal electrode are obtained and analyzed.Effect of surface tension and electric field force on the shape of liquid metal electrode tip.It is found that the end of the liquid metal electrode will form a sphere under surface tension and an inverted cone under electric field force.By using COMSOL software,the shape change of the end of the liquid metal electrode is simulated.It is found that the end of the liquid metal electrode can maintain a stable inverted cone when the inlet pressure and the additional voltage are within a certain range.In order to analyze the factors affecting the processing accuracy of liquid metal electrodes,a comparative experiment was conducted on a laboratory platform using RC power supply and different needles.The effects of voltage,resistance,capacitance and needle diameter of RC power supply on the processing accuracy of liquid metal electrodes were analyzed.It is found that the accuracy of liquid metal electrode can be improved by reducing voltage(minimum 60 V),reducing capacitance(minimum 3.3 nF)and increasing resistance.Aiming at the problem of low processing accuracy of liquid metal electrodes,a method of adding DC high voltage is proposed,and the effects of adding DC high voltage on the processing accuracy of liquid metal electrodes are analyzed through comparative experiments.The processing accuracy of liquid metal electrodes can be significantly improved by adding DC high voltage and processing voltage below 60 V.