Discharge Detection And Servo Control Of Dry Edm Under High Frequency Power Supply

As the manufacturing industry continues to develop green,Dry-EDM is considered as a new EDM technology to be a substitute for kerosene dielectric EDM because of its advantages of no pollution,low tool electrode loss,and large and shallow discharge crater.Some researchers have found that the discharge channel of the gas medium expands rapidly,and the energy is concentrated in the early stage of the formation of the discharge channel,and the low-energy discharge instead causes the energy to enter the spark with high efficiency.Therefore,it is necessary to further research the EDM of the gas medium at a high frequency and narrow pulse width.However,the spark discharge stability in high-frequency gas is poor,and the high short-circuit rate has become a key factor limiting its further improvement in processing efficiency.Therefore,on the basis of previous studies,this paper will analyze and study the machining characteristics of highfrequency Dry-EDM,and formulate detection and control strategies suitable for highfrequency Dry-EDM,so as to improve its machining efficiency.First,understanding the characteristics and machining characteristics of highfrequency Dry-EDM is an important basis for testing and control strategy formulation.By comparing the processing characteristics of gas medium and kerosene medium under high-frequency pulse power supply and analyzing,it is found that high-frequency DryEDM has the characteristics of high short circuit rate,discontinuous discharge pulse,and sensitivity to gap change.At the same time,the discharge waveforms were collected through the electric discharge machining experiment in gas,the discharge pulses and arc pulses at different pulse frequencies were analyzed and compared,the detection characteristics were determined,and the subsequent effective pulse detection circuit design was guided;Because high-frequency Dry-EDM is sensitive to the change of discharge gap,.The effects of multiple servo control parameters related to the gap state on the discharge state during the machining process were studied through experiments.It was found that the values of the servo reference voltage and the servo feed speed have a greater influence on the discharge state at different machining stages.Secondly,based on the analysis of the structure and function of the Dry-EDM machine tool,the CNC system software suitable for the Dry-EDM machine tool is designed,which provides a good software platform for the later introduction of fuzzy control algorithms and online adjustment.At the same time,referring to the analysis of the high-frequency gas spark discharge waveform in the previous article,an effective pulse detection circuit based on CPLD is designed to detect the breakdown delay time through threshold comparison.According to the rising edge and high level duration of the output signal of the comparator,CPLD determines the type of waveform,and carries out counting statistics and transmission to the host computer.Finally,in the Matlab2016 fuzzy control toolbox,the design and simulation of the fuzzy control algorithm with the discharge rate and short circuit rate as the input,and the servo reference voltage and servo feed speed as the output are completed.Based on the experimental analysis of the influence of servo control parameters on Dry-EDM in chapter 2,a fuzzy control rule table for different processing states in the early and late stages was designed based on the short circuit rate.Through the joint programming of Matlab2016 and Visual Studio,the realization of the fuzzy control algorithm is completed in the numerical control system,and the effectiveness of the system is verified by comparing the simulation results with the experimental results.