Research On Micro EDM System Based On Linear Motor And Its Key Technologies

Miniaturization is one of the most important trends of industrial production. Micro electro-discharge machining (EDM) gives it the ability to machine many difficult-to-cut materials. Its unique advantages of non-contact and less-cutting-force are useful in micro machining field. Micro-EDM is not only applied to machining micro-shafts, micro-holes and micro slots, but also to machining 3D micro structures and micro freeform. Therefore, micro-EDM has become one of the most important branches in the field of micro machining and receives worldwide attention.Precise micro-EDM system is the essential equipment for micro-EDM research. Nowdays, Micro-EDM machines have stepped into the stage of industry application and commercial distribution in some developed countries, whereas, these machines are prohibited goods to our country. Thus, it is urgent for us to develop high performance micro-EDM equipments.Based on the analysis of the features and the requirement of the equipment of micro-EDM, a set of micro-EDM system based on linear motor is developed. It composed of a mechanical system and a control system. The mechanical system consists of a precise granite body and a worktable, a three-dimensional servo mechanism based on linear motor, a precise rotary spindle and a discharge grinding unit, etc. The control system includes a control computer, a RC pulse generator, a discharge detecting circuitry, a motion controller, motor drivers and a CCD microscopic vision system, etc.Servo mechanism and its control system play an important role in micro-EDM system. The properties of many types of servo mechanism are discussed, and linear motor is adopted in the micro-EDM system because of its excellent performance of high resolution, high precision, high speed and quick response. The servo mechanism and control system can improve the machining efficiency and decrease relative electrode wear ratio of micro EDM.As to ED-milling, slicing strategy, arrange method of tool path and method to compensate electrode wear are proposed in this dissertation. A special CAM software package for ED-milling 3D micro structures is developed. Electrode manufacturing technique is the fundamental of micro-EDM, hence is systematically investigated in the dissertation. Micro shaft with a diameter of 5μm is achieved by block electrode discharge grinding (BEDG). A new tool manufacturing method named edge electrode discharge grinding (EEDG) is presented in this dissertation. EEDG is proved to be more effective than WEDG because of its simple structure, low cost, quick setting, high machining efficiency and good surface quality. Micro shaft with a diameter of 3.5μm is manufactured by using this method.Extensive processing experiments have been conducted on this micro EDM system. The effect of electrical parameters, spindle speed and dielectric on machining efficiency, relative electrode wear rate and surface roughness has been systematically investigated, and many micro-EDM machining rules have been achieved. A great number of experiments have been carried out on this micro-EDM system, the results show that micro shaft with a diameter of 3.5μm, micro hole with a diameter of 8μm and micro slot and micro slit with a width of 15μm can be obtained steadily. With the aid of the special CAM software package for ED-milling, 3D micro structures such as micro gear, micro mouse are machined on this micro-EDM system. The micro machining capability of this micro-EDM system and the performance of the CAM software packages are verified by these experiments.