Simulation And Experiment Research Of Gap Flow For Micro-EDM Deep-Small Hole Machining

With the development of exotic materials and growth of demand in complex cavity structures, micro Electrical Discharge Machining (micro-EDM) is used in more and more occasions, currently has become one of the main methods in high aspect ratio micro hole machining, and is used widely in aerospace, die making, etc.In the process of EDM machining, because the particles emit difficultly from the gap in cylinder electrode machining, the discharge condition would become worse and restrict micro hole's aspect ratio, which couldn't meet the industry command. Then the methods of using flatted electrode instead of cylinder electrode or compounded with jump control are proposed. Although both the methods can increase the aspect ratio in a certain degree, the mechanisms are indistinct. In the whole machining process, particles are in the zone of gap flow field, thus the research of gap flow is the key of increasing the aspect ratio.The paper based on Finite Element Method (FEM) simulation, used Computational Fluid Dynamics (CFD) software to simulate the flow field of cylinder electrode machining of micro EDM, and made the conclusion that the gap flow was laminar flow in cylinder electrode machining process, and got the relationships between time and depth, also aspect ratio and efficiency through experiments.The method of simulating dynamic zone was used to get the flow field of flatted electrode. Compared to cylinder electrode, there were vertical velocities in the flow field, which could cause the particles move out of discharge gap and improve the discharge condition, and then, enlarge the aspect ratio. Relevant experiments were made to illustrate the influence of flatted level in flatted electrode machining, and proved the validity of simulation models.In EDM process, jump control could also enlarge the aspect ratio, which could be simulated with dynamic mesh method. The simulation model of jump control was established, and the vertical velocities were found. The reasons why jump control could enlarge the aspect ratio were explained with experiments. The simulation models could be the foundation of other models in EDM.