| Machining center is an automatical machine of high efficiency, which processes complex parts. It has an important position in the high-end equipment manufacturing industry. But, with the advance of the function level on the mechanical equipment and automation, it is bigger and bigger for the possibility of failure happened. Reliable problems restricted the development of nc machine tools. Key parts of the machining center is an important part of the machine tool, its reliable level affects directly the reliability of the whole machine, such as tool changing system, electrical system and the spindle system,etc. Once these key parts break down, they will affect directly the processing efficiency of the machining center or the economic benefits of the user. The reliability of key parts has become a bottleneck for the further development of China’s machine tool industry.The automatic tool changer system is an important part of the high-end machining center, which is an important symbol of reflecting the performance on high-end machining center. Although domestic automatic tool changer system can meet basically the functional requirements, the level of its reliability cannot be compared with advanced foreign products, which restricts seriously the development of nc machine tools. Therefore, if it is able to improved for the reliability of the automatic tool changing system, it will help to promote the reliable level of domestic high-grade CNC machine tool. In the study of the reliability of the whole machine, domestic scholars have a certain theoretical basis. For the purpose of the short-term rate of return on investment for domestic enterprises on machine tool, domestic scholars are unable to track experiments for many years in automatic tool changer system, which leads to have no access to getting reliable and enough failure data. It limits the related research of the reliability. Moreover, it is relatively less for the literature of reliability modeling study on automatic tool changer system. In addition, it is not overall on the research and there are a lot of shortcomings. Therefore, it is necessary for the reliability research on the automatic tool changer system. It can help to shorten the reliability growth period of the automatic tool changer system. It can provides a theoretical reference for the reliability design of the product and fault diagnosis or maintenance. At the same time, it has great reference value for the related research of similar products in engineering.Based on the failure data obtained from field tracking experiment, multiple and different types of data is pretreated by total failure time method, which can provide a more accurate data basis for the subsequent reliability analysis. Through using the experience modeling theory, choosing three-parameter weibuU distribution model, and bringing in the least square approximation method, the right approach, the K-S inspection, they, respectively, who are the reliability model based on time between failures of the whole machine, the reliability model based on time between failures of the automatic tool changer system, and the reliability model based on the first failure time of the automatic tool changer system, are established. It is obtained for more accurate reliability model; Combined with the above three models, they are respectively obtained for the MTBF of the whole machine, the MTBF and MTTFF of the automatic tool changer system by the point estimation method; They are respectively analyzed for the failure mode for the whole machine and the automatic tool changer system by improved criticality analysis method, which can get a more reasonable experimental results; By posterior probability model on the Bayes method, it is established for the posteriori probability model between the automatic tool changer system and the whole machine; By grey relation analysis, it is established for the inner link between the automatic tool changer system and other systems. |
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