| Summary: | 碩士 === 國立虎尾科技大學 === 機械與電腦輔助工程系碩士班 === 105 === In recent years, with the rapid progress of industrial technology, high-speed machining has gradually become a trend, but for high-speed machining, the stability of the machine would decrease with spindle speed rising. The traditional experience method has not been able to deal with the variable processing conditions. The chatter prediction technique can be used to avoid the unstable speed area by numerical means, and obtaining the stable cutting conditions. Compared to domestic, this technology is more mature in foreign countries. The reason is that the technical standard is high, complex algorithm, the cutting parameters are not easy to obtain, and the calculation time is longer and so on, so most can not be widely used in the actual process. Therefore, this study intends to develop a simple and fast milling chatter prediction system that provides a basis for selection of machining conditions.This paper is divided into three parts. First, construction a relationship between the spindle speed and cutting depth by regenerative chatter theory and frequency respond function. Second, the modal parameters of the cutting tool system are estimated by curve fitting.Furthermore, we develop a processing stability prediction system with commercial software LabVIEW, The system include multi-modal parameter identification and chatter stability curve drawing function. In this study, uses the zero-order analysis method by professor Altintas and Lowest envelop method (LEM) to obtain the chatter stability curve diagram. Which can calculate by separately considering different dominant modes from the experiment of dynamic stiffness. The second part focuses on the identification of modal parameters, the experiment uses the hammer impact test to obtain the tool frequency response characteristics required for the analysis, and uses the global rational polynomial (GRFP) to perform the curve fitting of the response function to identify the damping ratio. Finally, the predicted chatter boundaries are compared to the experimental results in order to validate the modal and the stability analysis. The experiments show that under the condition of 100% radial feed, three of the eleven test points are not consistent with the predicted results, and the initial prediction accuracy is about 72%. In the phase difference measurement section, when the chatter occurs, the major frequency of the phase difference is greater than 60 degrees and the fluctuation range is also larger；In the case of stability, most of its major frequency located on the frequency of the tool passing frequency and its multiplier and the phase difference of the abnormal frequency is not more than 30 degrees.
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