| With the development of science and technology and Micro-Electro-Mechanical System (MEMS), parts and components become more and more miniaturized size. The system dimension, which is between 1 and 1000μm, is usually called micro system according to the scale features of the products. The corresponding micro machining technology has become a research hotspot in the industrially developed countries.The metal micro-structure is an important class of micro structures. Product miniaturization, precision and development of high-tech product have the urgent demand to the micro metal processing technology of micro scale complex structures. Therefore, the development for a micromachining technology, which has the capability to machining three-dimensional structures on metals and alloy materials, has become a hot issue in the micro-manufacturing field.Micro electrochemical milling (MECM), which is a combination of micro milling and electrochemical micro machining, is proposed as a new method of micro machining technology in this paper. Because of no electrode wear, the micrometer scale cylindrical electrode can be used as the tool in MECM, and the complex structures of micrometer or tens micrometer can be fabricated. The new technology can be used in the field of aerospace industry, precise instrument, biomedical devices and so on. The doctoral dissertation consists of five sections, including:(1) The fundamental theory of MECM is investigated. The theoretical model of MECM is founded, which is an important theoretical guidance for the following experiments, based on the charging process of interfacial electric double layer. In addition, the effects of various parameters on machining quality are analyzed, and then the correlative technical solutions are proposed.(2) A set of 3D machining system of MECM is established. The machining system has the following characteristics, such as micro-feeding with high-resolution and low speed, triaxiality linkage, high rotational accuracy, short-circuit detection and protection, vibration insulation and so on. The real-time control and data acquisition system for 3D micro electrochemical milling is founded using devices of virtual instruments, and the software of the system is designed based on Labwindows/CVI.(3) Two new methods of fabricating the micrometer scale electrodes used in MECM are investigated. First, the fabricated method of the micro multi-stepped cylindrical electrode is analyzed. Then, a mathematical control model for fabricating the micro multi-stepped cylindrical electrode is set up. It is proved that the experimental and theoretical values have a good agreement by the experiment of a third-stepped microelectrode. After that, based on the above multi-stepped cylindrical electrode, the type of micro cylindrical electrode with a spherical end, which has good roundness and mirror-class surface quality, is fabricated by using single electric discharge technology and through controlling the discharge parameters. Finally, based on electric field analysis, various applications are analyzed by using different micro electrodes.(4) Sets of experiments are carried out to fabricate micro complex structures on various metals, such as, nickelbase superalloys GH3030, nikel and stainless steel. The impacts of applied voltage, pulse on time, pulse period, electrode diameter, electrolyte parameters on the machining process are experimentally investigated. According to the theoretical model, strategy of milling by thin layer is applied. The impacts of layer thickness on the shape accuracy, machining stability and machining efficiency are experimentally investigated. Finally, using the optimized parameters, some high-precision micro 3-D staircase structures with minimum feature size of 5μm and hemispherical cavities are fabricated successfully.(5) A series of experiments are carried out to fabricate small structures on nickelbase superalloys GH3030. The effects of rotation rate on machining quality are experimentally investigated emphatically. In addition, the impacts of applied voltage, pulse on time, electrolyte concentration on the machining accuracy are experimentally investigated. Finally, using the optimized parameters, some small structures with high shape accuracy, good surface quality and minimum feature size of 40μm are fabricated successfully.
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