Research On Foundational Law Of Micro-EDM And Its Simulation

Electrical Discharge Machining (EDM) is a non-contact machining technique with little cutting force, which establishes its advantage station in the fields of micromachining. After continual development for decades, micro Electrical Discharge Machining (micro-EDM) is not only applied for machining micro-shafts, micro-holes and micro three dimensional structures, but also shows excellent potential for machining silicon materials. Study of micro-EDM technology is of great significance in the fields of micro-machine manufacture and been regarded greatly by researchers home and abroad. However, there is not systemic research on this technology at present, especially for its basic theory problems. There is no systematical theory model to illustrate the discharge process. For this reason, a discharge model is built in this research and computer simulation technology to analyze discharge process, relevant experiments were designed to validate the accuracy of the models.Discharge channel is the surrounding where discharge process occurs, so research on discharge channel is the basis of the research of discharge machining. Thereby, a discharge channel model based on particle in cell method is built. Forming process and oscillation characters of discharge channel are simulated and analyzed. From the simulation result plots, it can be clearly observed that electrical particles movement during the discharge process and particles'distribution under balance state vividly. Mechanism of channel's oscillation, composed of vertical oscillation and horizontal oscillation, is also demonstrated. Subsequently, influences of oscillation to electrode material erosion and influences of discharge channel's electromagnetic characters to particles'movement locus in deposition in gas are testified by discharge experiment.Because discharge process is instantaneous and microcosmic, microcosmic method has to be applied to measure the particles'movement in electrode surface. For this reason, molecular dynamics method is applied to simulate the pinpoint electrode forming process and electrode deposition process. From the simulation plot, it is found that during tungsten microelectrode self-sharpening process, single atom removing and bulk atom cluster removing both exist. Electric field force is a key factor for microelectrode shape forming. Influences of electric field force to microelectrode self-sharpening and temperature in discharge point to microelectrode self-sharpening process are discussed.In deposition experiments in air, it is found that with discharge current increases, energy of single discharge increase, correspondingly the deposited granule's size and deposition height both increase. However when discharge current exceeds a certain value, energy of single discharge is too excessive that deposition electrode is easy to burn, deposition height decreases, even to naught. From the simulation results it is found the same law. Simulation results show that the relation of emitting velocity to deposition height and relation of discharge electric field to deposition height of the simulation result are accordant to the trend of deposition height to discharge current in experiment. In the end it is found the critical values of discharge electric field and emitting velocity of depositing molecules of Cu. This research provides the reliable theoretical basis for further experimental study on the processing law of deposition and three dimensional deposition in air in Micro EDM.Electrode material erosion mechanism and how to measure the relationship of discharge energy and quantity of electrode erosion are the keys of research of EDM theory. In this paper, the heat conduction process in electrode is analyzed and a relatively rational model is built, in model both thermal current density load of gauss distribution and convection load are applied, material properties varying with temperature was considered, phase change is solved with enthalpy method. Analytic solution of temperature pattern of round heat sources is presented under the changing discharge channel radius with time and fixed input total power. The temperature fields of single pulse EDM are simulated by ANSYS and relation of crater shape and discharge parameters through simulation under different pulse-on time and current discharge condition is anylized. Finally, a single pulse power supply was designed and some corresponding experiments were done, the results show that the simulation results have the preferable precision of prediction, indicating a worthwhile theoretical foundation for continuous EDM simulation in further.