| It has not been among the ranks of industrial power at the present stage of industry in our country. It’s still have certain difference between reliability level of domestic and foreign CNC machine tool, although China’s CNC machine tool leading enterprises, Shenyang Machine Tool, launched i5 series, but the market did not agree it. The key part of related technology is still seriously restricted the heteronomy and stable development of China’s industry. In the medium and long term development plan, our country has already made the CNC machine tool’s reliability technology as the key technology and the project, thus, the state of the machine tool industry development is still very important. Therefore, it is key transformation from manufacturing to manufacturing power in China to improve the reliability of CNC machine tool.The reliability theory of CNC machine tool is not completion. For this purpose, it was explored the suitable method for the comprehensive evaluation of the reliability of CNC machine tool based on the previous research. The followings are what this dissertation have done:1) The basic theory of reliability evaluation system of CNC machine tool was introduced, mainly covers the CNC machine tool failure distribution law of the typical, reliability evaluation, data collection methods, and extended data based on RBFNN.2) The equivalent failure rate and damage degree were introduced. And it has been given the harm degree analysis of equivalent failure rate calculation method, the method considered the differences between the design failure rate and the actual failure rate.3) The general process of reliability comprehensive evaluation is given. First, selecting the evaluation index based on the principle of reliability evaluation index of CNC machine tool. Then through the classical variation coefficient method to determine normalized weight or through the index value of inline dynamic weighting method to determine the non-normalized weight. Finally, two evaluation models are given:one is based on variation coefficient method and improved model by comprehensive reliability evaluation formula of repairable equipment, another is comprehensive reliability evaluation model based on dynamic weighting method. In addition, in order to facilitate determine the grade of CNC machine tool’s reliability, the reliability score threshold table of the evaluation model is given and that based on the threshold of reliability evaluation index.4) Three application examples are given, that is comprehensive reliability evaluation of CNC lathe VT-550 based on the variation coefficient method, comprehensive reliability evaluation of gantry machining center SIRIUS-1250 based on dynamic weighting method, and comprehensive reliability evaluation of domestic and foreign CNC milling machine based on dynamic weighting method. The results show that the reliability evaluation model based on variation coefficient method and the dynamic weighting method were better reflecting the real CNC machine tool’s reliability level, and it can intuitive see whether difference between evaluation objects in "quality" or not based upon dynamic weighting method of integrated reliability evaluation model. |
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