Research On Detection And Servo Control Technology Of Micro-hole Edm Based On ZrB₂-based Ceramic

Micro-hole machining technology for ZrB₂-based ceramic,which is suitable to be aerospace composite,has been applied extensively in aerospace and instrument industries.We try to do research on micro-hole electric discharge machining?EDM?technology which can work well on ZrB₂-based ceramic.The characteristics of ZrB₂-based ceramic during micro-hole electric discharge machining was summarized by launching process experimental study.The control system was set up.The servo control method for micro-hole electric discharge machining on ZrB₂-based ceramic was completed.The depth to diameter ratios of the holes machined increase compared with the holes machined when the servo control method was not applied.So do the other indicators of machining process.The characteristics of ZrB₂-based ceramic during micro-hole electric discharge machining was summarized by launching process experimental study.An contrast experiment was launched in order to make out the differences between these materials during EDM,then the performance of ZrB₂-based ceramic during EDM was known.The main discharge waveforms happened during EDM on ZrB₂-based ceramic was collected.Four groups of experiments for single factor was launched to study the rule how each kind of waveform influences on machining process.The analysis of the results provides the basis for the establishment of control system.The CPLD module and the ARM module were built,so that machining process can be controlled.The CPLD module was built with CPLD as core.The voltage during machining was sent through voltage comparators and comparators output TTL level.Numbers of every kind of waveforms can be calculated from the TTL level.The ARM module was with ARM as core,its main function is controlling servo ac motor,so that the machine tool can work.After building the circuit board and writing the code,the whole tool was debugged and the function of every part was proved.Servo strategy of micro-hole EDM on ZrB₂-based ceramic was designed.The indirect self-correcting controller of adaptive control was selected,and the linear time-varying model was used to represent module of EDM process.The ARMAX model with time-varying parameters and interference terms was selected as the predicting model in this paper to calculate the predicting model,and the variance of prediction was used to calculate the control law.Combined with the actual experimental situation,the recursive least squares formula was used to calculate the predicted output at the next time.According to the principle of minimum variance,the steps of the algorithm was concluded,and the control algorithm flow chart was drew.The hardware and software were verified and evaluated by experiments.The optimal input combination of control system parameters alpha and beta was determined by response surface experiment.Experiments was carried out using both adaptive control method and average voltage method.The result was compared in five aspects.According to the experimental results,it can be concluded that when the adaptive control algorithm is adopted for machining,the ultimate depth-diameter ratio is larger,the discharge state tend to be better,the machining efficiency become higher,and the electrode loss become higher.By adding an adaptive jump to further optimize the machining system,micro-hole machining with a depth to diameter ratio of 23.0 was finally achieved,with more smooth chip discharge and better inter-electrode discharge state,which improved the processing depth to diameter ratio of EDM micro-hole machining on ZrB₂-based ceramic,and improved the efficiency and rate of discharge,and also improved the quality of wall of hole.