基于场致发射理论的EDM平板电容模型及其参数

Plate-capacitor Model of Electrical Discharging Machining Process Based on Field Electron Emission Theory and Its Parameters Analysis

基于场致发射理论提出描述电火花加工(Electrical discharging machining,EDM)过程的平板电容模型,将单脉冲放电周期依次划分为极间电场建立、极间通道击穿、正常放电加工与消电离四个阶段,并分别进行各阶段的极间电场强度、极间电子自由程、极间介质介电常数和极间电流变化规律的理论分析。讨论EDM加工能量大小的影响因素,并给出基于该模型的极间电压与放电电流变化的仿真步骤与方法集。设计通孔加工试验和实时电流与电压采集电路,并基于该模型对极间电压与电流的变化曲线进行Simulink仿真程序设计。试验结果表明,相同加工参数实测曲线与仿真试验图形实现了较好的吻合,而且试验结果统计分析表明,该模型对不同电极材料与加工参数对加工效率的影响可做出合理解释且对加工效率有着良好的预测能力,证明了该模型的合理性与有效性。

Based on the field emission theory,a plate-capacitor model is constructed to describe the electrical discharging machining（EDM） process.In this model,the discharging pulse period is divided into four stages,successively as the establishment of the interelectrode electrical field,the formation of the interelectrode discharging channel,the stable EDM and deionization,and the correlative parameters of each stages,such as the intensity of interelectrode electric field,the mean free path of interelectrode electrons,the interelectrode medium constant,and the varying rules of discharging current etc.,are analyzed.The distribution of EDM energy and its influencing factors are discussed,and the simulation methods of interelectode voltage and current based on this model are given in details.For the purpose of single factor analysis,a set of through-hole experiments and real-time measuring circuit are designed and carried.The good agreement of experimental results with simulation data and the fact that the model can well explain the differences of machining efficiency with tool pole and different machining parameters,demonstrate that the model is reasonable and effective.