Research On The Reliability Design System And The Key Reliability Technologies Of CNC Machine Tools

In recent years, as the work machine that integrated machine, electricity, liquid and control, the position of CNC machine tools in the process of the country industrialization promote a lot. Though a lot of efforts have made to promote the quality and reliability level of CNC machine tools, there is still a large gap for China’s machine tools industry in the design, manufacturing, quality control technology and innovation,when compared with developed countries. Besides, CNC machine tools products have complex structure and various components, its working state is very complex, and its reliability research work started so late that the relevant reliability data is seriously lacked, its reliability research has always been a difficult problem for scholars.On the support of the domestic high-grade CNC grinding machine reliability scale promotion project of the national science and technology project: high-end CNC machine tools and basic manufacturing equipment project, this paper take the home NC Grinding machine and its key functional parts as the research objects, and studied its reliability design system and the related technologies, through which, provide new reliability research direction and methods for CNC machine tool, and apply them on the engineering practice, so as to enhance the reliability level and market competitiveness of domestic CNC machine tools.The mainly contents are as following:① Based on the product design procedure, this paper integrated reliability model,reliability prediction, reliability allocation, reliability analysis and reliability test technology, and construct the framework of the reliability design system of CNC Machine Tools, which connect the product design by the reliability data and information.② As the reliability data are lacking during the initial design phase of CNC machine tools, and the factors that effected the reliability prediction are complicated and fuzzy, a fuzzy synthetic assessment model based on Vague sets(VSA) was proposed for reliability prediction. Based on the GO chart model, taking NC Grinding Machine as the example, adopt the VSA model to make quantitative analysis and prediction of NC machine tools, which verified the feasibility and applicability of the proposed method.③ According to the factors influencing the reliability allocation and their weights both have the characteristics of uncertainty, a subjective and objective combinationweighting method that combined the entropy method and Fuzzy analytic hierarchy process(FAHP) method was proposed. Taking NC Grinding machine as an example,adopt the fuzzy comprehensive allocation method that based on the new method to obtain the reliability allocation results, which was compared with the actual accumulated data, therefore, the feasibility and effectiveness of this method was verified.④ In order to overcome the problems that exist in the risk assessment of traditional FMEA, an improved risk preference function model was established. Which considers the relative weight, fault correlation of the risk factors and the relative weights to experts, then the interval analysis method and the Grey correlation degree method are adopted to evaluate the fault risks. At last, take the NC Grinding Machine as the example, use the improved risk preference function model to analyze and sort the key fault modes, then compared the result of traditional RPN method to verify the feasibility and correctness of the method proposed.