Study Of Micro EDM Aided By Ultrasonic Vibration In Nitrogen Plasma Jet

As a new kind of dielectric,the atmospheric pressure cold plasma jet(APPJ)is proposed.When used as a dielectric,APPJ can obtain a larger discharge gap than other gas dielectric,thereby improving the interpolar state,reducing the abnormal discharge phenomenon and electrode loss,and improving the processing efficiency and quality.But compared with the liquid dielectric,the processing efficiency in APPJ is relatively low,and there are still frequent abnormal discharge phenomena during the processing.In view of the above problems,this paper proposes a method of using ultrasonic vibration(USV)assisted micro EDM in nitrogen plasma jet(NPJ),in order to obtain better processing performance than before.Based on the existing experimental equipment,an USV system was built,and the workpiece can achieve stable USV with an amplitude of 1?m and a frequency of 35kHz;an APPJ composite jet medium generating device was developed.USV assisted micro EDM can increase the breakdown distance to a certain extent,and due to the USV of the workpiece during the machining process,the ability of electrical corrosion products to be ejected from the surface of the workpiece is enhanced.When the dry type composite jet formed by high velocity air jet(HVAJ)and NPJ is used as the discharge dielectric,ultrasonic vibration-assisted processing can be performed normally,and compared with nonvibration-assisted processing,the introduction of USV improves the material removal rate(MRR)of EDM,reduces the roughness of the processed surface and tool electrode wear rate(TWR).In order to further improve processing efficiency,research on USV assisted processing in near-dry composite dielectric(NPJ + mist)was conducted.The mist is mixed into NPJ,which greatly improves the breakdown distance of micro EDM.After USV is applied,the breakdown distance can be further increased.Through the experiment of vertical groove milling,it is found that the mixing of mist into NPJ can increase the machining efficiency to 4-6 times of the original one;the introduction of USV can further improve the machining efficiency,even to twice of that without the aid of USV;after the application of the vibration,the TWR also tends to zero;USV has little effect on the surface roughness.Finally,the successful processing of complex three-dimensional cavity has verified the strong processing ability of this processing method.The technology of micro EDM aided by USV in NPJ + mist was used to process SUS 304.By comparing the experimental results of SUS 304 and brass,it is found that the processing performance of different workpiece materials is different.In the process of machining SUS 304,there are two machining phenomena,EDM and electrochemical machining(ECM).Due to the ECM in the process of machining,the MRR and surface quality of stainless steel are higher than that of brass.In this study,compared with EDM,ECM has higher MRR,lower surface roughness and TWR.Experiments prove that the introduction of USV and the reduction of mist flow will weaken the ECM during processing.In addition,although the NPJ is composed of charged particles,this is not the reason for the ECM.When using transistor pulse power supply or using deionized water as the dielectric with high processing energy to process stainless steel,no ECM occurs during the machining.