微细电火花加工的材料蚀除特性及极性效应研究

Material Removal Characteristics and Polarity Effect in Micro EDM

为了进一步研究微细电火花加工的材料蚀除特性,对放电点处的热传导和材料蚀除过程进行了多物理场耦合仿真研究,并开展了微细电火花单脉冲放电实验验证.根据放电等离子体通道内部电子和离子的运动特性,对微细电火花加工中的极性效应进行了分析.结果发现,通过引入Marangoni对流模块可形成放电凹坑的边缘突起,仿真出的放电凹坑形貌和实测的放电凹坑形貌一致;微细电火花加工短脉冲放电时的能量利用率比较高,能量利用率随着放电持续时间的增加而逐渐降低;通过引入实际的放电条件对仿真模型修正,对放电凹坑半径的仿真精度可提高至7%以内;放电通道中电子的加速度和速度非常高,相同时间内电子轰击正极电极表面的次数是正离子轰击负极电极表面次数的40倍以上,所以正极的材料去除量明显高于负极,微细电火花加工表现出显著的极性效应.

To further investigate the material removal characteristics in micro electrical discharge machining(micro EDM),a multi-physical field coupled simulation was conducted on the thermal conduction at the discharge point and the material removal process,and single pulse discharge experiment was carried out for validation.Based on the motion characteristics of electrons and ions within the discharge plasma channel,the polarity effect in micro EDM was analyzed.The results show that the edge protrusion of the discharge crater can be formed by introducing Marangoni convection module,and the simulated discharge crater morphology is consistent with the measured discharge crater morphology.The energy utilization rate of short pulse discharge is relatively high,and the energy utilization rate decreases gradually with the increase of discharge duration.By introducing the actual discharge conditions to conduct the model correction,the simulation accuracy of the discharge crater radius can be improved to less than 7%.The acceleration and velocity of electrons in the discharge channel are very high,the number of times that electrons bombard the surface of the positive electrode in the same time is more than 40 times that of positive ions bombarding the surface of the negative electrode.Therefore,the material removal rate at the anode is significantly higher than at the cathode,and micro EDM exhibits a pronounced polarity effect.