Research On Several Basic Problems For Micro-EDM Of Micro Hole And Array Holes

The machining of micro-hole and array holes is always the difficult problem inthe field of mechanical processing. Micro-EDM technology has a feature of Non-contacting machining method, no obvious macroscopic applied force and goodcontrollability, and thus is an important means of machining micro-hole and arrayholes at present. So micro-EDM of micro-hole and array holes is one of theeffective approaches to solve the above processing problem.But micro-EDM of micro-hole and array holes has obvious limitations, forinstance, the heavy tool wear, the unstable discharge condition and low machiningefficiency, which hinder the machining process smoothly. In order to decrease toolwear and improve working efficiency and the discharge condition stability,processing strategies have been usually applied to improve discharge status, such astool electrode rotary, coated electrode, shaving electrode, shaking electrode, liftingelectrode, ultrasonic combined machining. However, there are still many problemsof the fundamental theory research in EDM process due to its complexity andrandomicity, especially material removal process and debris discharge processwhich have become bottleneck for EDM technology development and application.Therefore, according to numerous related literatures at home and abroad, theresearch on the temperature field distribution of single pulse discharge, finite pulsesdischarges and continuous pulse discharges and distribution of flow field of EDMof micro-hole and array holes was discussed by theoretical simulations andexperiments. Simultaneously the influencing factor on material removal process anddischarge process of debris has been analyzed to supplement and enrich the theoryof EDM technology.Single pulse discharge is the basis of knowledge and research of continuouspulse discharge processing. In this paper, the temperature field distribution of thesingle pulse discharge process was firstly discussed. Based on heat transfer theory,the time-varying radius, time-varying heat flow density of the temperature fieldmodel of electric spark single pulse discharge process has been established. Basedon temperature field simulation of the model, the influence law of the peak current and pulse width on the temperature field distribution and discharge crater size, andthe corresponding experiment has been carried out.Continuous pulse discharges process can be regarded as the superpositionprocess of countless times single pulse discharge process. But it is difficult to makesingle pulse discharge process results directly applied to continuous pulse dischargeprocess because of the complexity of continuous pulse discharge process. Therefore,the model of finite pulses discharge has been established based on the temperaturefield of single pulse discharge process. Through the temperature field simulation offinite pulses discharge model, the influence law of discharge position far and nearon the temperature field distribution of subsequent pulse discharge has been carriedout. According to the finite pulses discharge crater position distribution and thesimulation distribution of electric field, the random distribution principle of thecontinuous discharge position has been established. The temperature field model ofcontinuous pulse discharge process has been established, the temperature fieldmodel of continuous pulse discharge and the dynamic process of surface corrosionprocess and the formation process of surface topography has been simulated. Theinfluence laws of the each pulse discharge removal of crater and the highesttemperature and the pulse width and peak current on the material removal inprocess and processing surface morphology formation have been analyzed.In micro-EDM of micro-hole process, chamfered edge electrode and electrodelifting usually adopt to improve the discharge efficiency, which are closely relatedwith gap flow field. So gap flow field simulation model of micro-EDM has beenestablished. Through the numerical simulation of the particle movement rule in gapflow field, the influence of electrode shape differences and height of electrodelifting on machining efficiency have been analyzed, and the correspondingexperiment has been carried out.In micro-EDM of array holes process, the wear of tool electrode, the low ofworking efficiency, the difference consistency of array holes and the instability ofdischarge status has been limit micro-EDM of array holes technology. Micro EDMcompound ultrasonic processing method has been usually adopt to improve workingefficiency and the stability of the machining process. Therefore, combined withmicro-EDM compound ultrasonic processing experiment results, the flow fieldsimulation model of micro-EDM of array holes compound ultrasonic machiningprocess has been established. Through the numerical simulation of the particle movement of flow field, the influence law of ultrasonic amplitude and frequency onmachining efficiency has been analyzed, and the corresponding experiment hasbeen carried out.Sum up, the temperature field distribution of single pulse discharge, finitepulses discharge and continuous pulse discharge process has been carried out toexplore the mechanism material removal of EDM process. The flow fielddistribution of micro-EDM of micro-hole and array holes has been carried out tooptimize EDM process. The above research for further micro-EDM technologypotential laid a certain theoretical basis.