Research On Gap Characteristics And Servo Control System Of Dry EDM

The tremendous development of Electrical discharge machining(EDM)technology complements its irreplaceable role in the field of non-traditional machining.However,with the continuous extension of the green manufacturing,a series of environmental problems caused by EDM of traditional kerosene medium,such as the generation of harmful gases,the disposal of waste liquid,have received increasing concerns.The emergence of dry-EDM has opened up a new prospect for the sustainable development in EDM.However,the problems of poor discharge stability and low machining efficiency have always restricted the practical application of dry-EDM.Servo control is the key factor affecting the EDM performance.Therefore,based on the previous research,this paper focuses on the study about servo control of dry-EDM,aiming at further improving the discharge stability and the machining efficiency of dry-EDM,promoting its practical application and deep research.Understanding the gap characteristics is an important basis for the study of servo control of dry-EDM.Therefore,the experimental study is firstly conducted on discharge machining gap and pulse trains of dry-EDM,and the discharge gap and relative discharge rate of gas media are analyzed.Simultaneously compared with the related properties of kerosene medium,it is concluded that dry-EDM is more sensitive to the gap change,the reasons that the mismatch between the servo control of the traditional kerosene medium EDM and the dry-EDM are analyzed.Through the above research,two kinds of servo control strategies are proposed,namely the servo control strategy based on double-servo criterion of gap average voltage and short circuit rate(referred to as "improved strategy")and the servo control strategy based on PID algorithm.Secondly,according to the proposed control strategies,the overall design of the dry-EDM servo control system based on GTS is completed,that is to complete the hardware configuration and software design of the transistor pulse power,gap average voltage detection circuit,short circuit state detection and probability statistics module.On this basis,the design of the improved strategy for the dry-EDM and the control strategy based on the PID algorithm are completed.Simultaneously,the gap control model based on PID algorithm of dry-EDM is established,and the system simulation is completed with the help of Simulink,the control performance of P,PI,PD and PID are compared and analyzed,which provides a reference for the selection of the appropriate PID parameters.Finally,debugging experiments are performed for the overall system,and the servo parameters suitable for dry-EDM are determined in two servo control strategies respectively.Through comparison of different control strategies,the feasibility of the improved strategy and the control strategy based on PID algorithm is verified,it is thought that in the improvement of discharge stability and machining efficiency of dry-EDM,improved strategy,PD control and PID control are more effective.Based on the above studies,in order to further demonstrate the importance of the matching between the servo control and the dielectric properties of the EDM,the servo control characteristics of the different gas media are studied and analyzed,the optimization schemes corresponding to the gas medium are put forward and the effectiveness of the optimization schemes are verified by experiments.