| Electrochemical machining (ECM) is an anodic dissolution process to machine workpiece in a flowing electrolyte where the shape of the cathode (as tool) is copied onto the workpiece (as anode) with the removal of the anode in ions. Due to the tiny size of metal ion, this micro-dissolution process brings ECM tremendous potential in the micro-manufacturing field. As for wire electrical discharge machining (WEDM), because of tool wear, the metal wire with the diameter of more than 30μm must be used as the wire electrode of WEDM, and the wire must be move quickly for the compensation of the tool wear. Therefore, WEDM has great limitations for its applications in micro machining in the future.Wire electrochemical micro machining (WEMM), which is the combination of electrochemical micro machining and the idea of wire cutting, was proposed as a new method of micro machining in this dissertation. Because of no electrode wear in this process the micrometer scale metal wire can be used as the wire electrode in WEMM, and the micrometer or tens micrometer structure can be fabricated. The proposed technology can be used in the field of aviation & aerospace industry, precision instrument, biological and medicinal instrument. The dissertation consists of five sections, including:1. The fundamental theory of WEMM was investigated. Firstly, the characteristics of WEMM were summarized. Secondly, the theoretical model of WEMM was founded based on the Bulter-Volmer equation and Faraday'laws, and the top limit of the feed speed was studied. At last, the boundary layer theory of micro fluid was introduced into the analysis of the transport mechanism of materials in the micro scale gap of WEMM, and the solution to improving the discharge of materials from the micro gap.2. The machining system of WEMM was developed. The movement system, measuring system, wire electrode system, high-frequency short-pulse power supply and electrolyte system were designed. The two types of short-circuit: clogging short-circuit and unavoidable short-circuit was proposed, and the type of short-circuit can be determined by the locality distributing of short-circuit, then the state of the micro gap in WEMM was online measured and distinguished. The method of punitive function was used to optimize the velocity of feed forward, and the strategy of servo-control system were designed. Finally, the control system was founded using devices of virtual instruments, and the software of the system was designed based on Labwindows/CVI.3. The new method of the online fabrication of the micrometer scale wire electrode used in WEMM was investigated. A model about the process of electrochemical etching was developed, the diameter of wire electrode was real-time monitored by precisely measuring the variation in resistance of the electrode. Based on electric field analysis, the device of electrochemical etching was designed to ensure the uniform wear of the wire electrode, and a monitoring system used for fabricating the wire electrodes was developed based on virtual instrument technology. The online fabrication of wire electrode and the following process of WEMM were integrated into one system. Because of the compatibility of the technology, the machining accuracy can be improved. Finally, a tungsten wire electrode of 5μm in diameter was experimentally fabricated.4. The laws of machining process were experimentally investigated. The effects of various parameters on the machining accuracy, stability and surface quality were analyzed, and the impacts of feed speed, frequency of feed, electrical parameter, electrolyte and the diameter of wire electrode on the machining process were experimentally investigated. Besides, the slight vibration of workpiece took place along the direction of the wire electrode length for effectively refreshing electrolyte in the machining area. A slight vibration of workpiece taking place along the length direction of the wire electrode for effectively refreshing the electrolyte was experimentally proved to be able to improve the stability of WEMM.5. The micro metal structures were obtained. Two models of machining process: cutting slits and fabricating structures were proposed. In model of cutting slits, parameter curve was divided into micro line segments, the wire electrode fed forward following the profile at constant speed, and the various micro grooves in width of 15μm and aspect-ratio of 10 were obtained; In model of fabricating structures, the profile was deviated from the same distance, micro blades with the slit width of 20μm and micro sharp-angles structure with the radius of 1μm were machined.The proposed technique can provide a new manufacturing method for machining high-performance materials. Applying this technique to the fabrication of micro products would speed up the development of MEMS.
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