A Three-dimensional Micro-electrical-discharge-machining Process Based On Foil Queue Microelectrode

Micro-electrical-discharge-machining(Micro-EDM)is widely used in the fabrication of microholes and three-dimensional(3D)micro-structures due to its low macro cutting force.The dominant technique of 3D Micro-EDM is layer-by-layer scanning Micro-EDM using tiny electrodes with simple cross-section shapes.This technique can be used to fabricate complex3 D micro-structures,but it also has some disadvantages such as high electrode wear and low efficiency.In order to overcome these technical bottlenecks,a 3D Micro-EDM process based on foil queue microelectrode was proposed in this paper.Based on the 3D micro-structure,the 3D microelectrode was designed and dispersed into a group of foil queue microelectrodes,and then the microelectrodes were used in Micro-EDM in turn according to the planned path.Finally,the Micro-EDM results corresponding to each foil could be superimposed to fit a 3D microstructure.Compared with the existing 3D Micro-EDM technology,this process has the following advantages: The preparation of microelectrode is simple and can effectively improve the processing efficiency of the 3D micro-structure.The main work of this paper is as follows:(1)The characteristics of the process were investigated and optimized by preparing foil queue micro-electrode and performing Micro-EDM experiments under multi-group machining parameters.The experimental results showed that there were step-like machining marks on the surface of the workpiece,and the machining parameters had a significant effect on the machining quality of the micro-structure.(2)To conduct 3D Micro-EDM to investigate the wear characteristics of the foil queue microelectrode.It was found that the wear of each microelectrode decreased in turn in the Micro-EDM.The wear of the first three microelectrodes was larger,which had a greater influence on the shape accuracy.On the other hand,properly adjusting the wear of the microelectrode could make the edge wear of the microelectrode form a certain round corner,which was beneficial to reduce the step effect and improved the surface quality.(3)To prepare foil queue microelectrodes with tapered structure and to carry out Micro-EDM to eliminate step marks on the machined surface.The results showed that the surface quality of the workpiece could be improved effectively by using micro-electrode with tapered structure,and the improvement was related to the taper parameter and the surface slope of the microstructure.Meanwhile,the step on the surface of the workpiece could be eliminated gradually by increasing the number of layers of the 3D structure model and preparing the corresponding foil queue microelectrode.(4)To Use Fluent,a software package,to simulate the gap flow field of micro-electrode processing hemisphere structure,and carry on the experimental verification.The results showed that the gap flow field could be improved and the machining quality could be improved by increasing the inlet velocity properly and using ultrasonic vibration to assist machining.