Study On Integrated Micro Milling And EDM Process

Miniaturization of industrial products is an important research field of mechanical processing technology, and compound micro machining technology is the key to the realization of componen ts and parts. Because of the unique technology advantages,combined machining technology of micro milling and micro EDM technology becomes more and more important in the processing of micro structure. It has gradually become an important research branch in the field of micro machin ing.In this dissertation,combined machining technology of micro milling and micro EDM technology were researched. First, a composite precision machining system with the function of micro milling and micro EDM was designed and built. Then on-line wear monitoring of micro-milling tool, detecting the gap voltage of EDM, as well as complex machining technology of complicated micro structures were researched based on the composite precision machining system.Based on the analysis of the features and the requirement of the equipment of micro milling and micro EDM, a composite precision machining system with the function of micro milling and micro EDM was developed. For its control system, industrial control computer, data acquisition card NS6100 and multi-axis motion control board PMAC PC104 were used, and the software system was developed by VC++ based on Windows workbench. It can realize the function of data acquisition, pulse power control, machine motion control, machine state display, on-line detection, etc.According to the different fractal characteristics of wear conditions of micro milling cutters,a new method to realize on-line tool wear monitoring in micro-milling process was proposed. The calculation formula of the one-dimensional fractal dimension was deduced and its algorithm was also developed. At last, the pattern recognition classifier of wear conditions of micro milling cutter was established. To verify the above mentioned method, experiments were performed. The results show that the pattern recognition classifier can be used to identify the wear condition of micro-milling cutter in engineering practice.To improve the phenomenon of complex interference and severe signal degradation in the micro EDM discharging process, the discharge state detection method based on the correlation analysis was present. First, the calculation formula of the correlation coefficient of gap voltage was deduced. Then the detecting principle was analyzed in detail. Finally, experiments were performed to testify the validity of this method. On this basis, the judge rules of discharge state and the method of automatic machining control were established.To improve the efficiency and the depth to diameter ratio of micro hole for electro discharge machining(EDM), a new electrode morphology and structure named double helix electrode(DHE) was proposed and experimental verified. The experimental results showed that the material removal efficiency during machining micro hole is improved comparing to flatted electrode. As a result, the stability and efficiency of EDM process are improved, and the depth to diameter ratio of micro hole is increased. On the other hand, fluent software was used to simulate the flow-field of interstitial fluids of the DHE and the flatted electrode. Based on the simulated results, it is concluded that the morphology and structure of DHE strengthens the convective motion of interstitial fluid in axial direction, thus the chip removal efficiency is improved.Some typical micro structures were machined in the composite precision machining system, such as micro shaft electrodes, micro deep holes and micro needle array. They are greatly verified that the machining system have an excellent ability of fabricating miniature production with complicated micro structures especially which needed multi-process and multi-technology.