Research On The Reliability Analysis And Test Technologies Of Machining Center

Machining center is a kind of high speed and precision CNC machine tools which can realize many kinds of surface machining processes at the same time, it is a kind of important basic manufacturing equipment. At present, the machining accuracy of machining center in our country can reach the international advanced level, but the reliability level is far behind abroad, so the reliability research of machining center is very necessary. Due to the complexity of the structure in machining center, the actual working conditions are variable, the failure mode and the causes are complex, the collection of related reliability data is difficult, so the reliability of the machining center has been focused on scholars both at home and abroad.On the support of the domestic high grade CNC machine tools and basic manufacturing equipment of the national science and technology project: Research and development of 800 mm precision horizontal machining center and application of domestic functional components. This paper took the THM6380 precision horizontal machining center as study object, and the related technologies of reliability analysis and test were researched, then the results were applied into the work of the reliability improvement of machining center. The main contents are as following:(1) By analyzing the structure of the machining center, reliability model of the machining center was established by using reliability block diagram. Then the reliability index of machining center was calculated by collecting the reliability of the work site data, subsection triple Weibull distribution model was used to establish the distribution of the reliability data, by doing this the early failure period, reliability and failure rate function model was obtained.(2) Through research in the factory, the failure location, failure mode and failure cause of the machining center was analyzed. As the tool magazine system was the high failure location, the fault tree analysis was taken on it, and by the result of the analysis some reliability improvement advises was proposed. In view of the shortcomings of traditional failure hazard analysis method, an improved model of calculating the failure hazard based on group decision making and gray relational analysis was established,then the NC rotary table of machining center was taken as example to use this improved failure mode, effect and critical analysis, and the improved FMECA table was obtained,which provides the guidance for the reliability improvement of the NC rotary table.(3)According to the production process of the machining center, the reliability test system of machining center was established, then the pallet exchange system was taken as example to introduce the implementation of reliability enhancement test. In view of the early failure of machining center is frequent, optimization model of the early failure elimination test time based on minimum cost was established and then the optimal early failure exclusion test time was obtained. Through using the test time the corresponding early failure elimination test was designed, the test results were analyzed and corresponding reliability improvement measures were given.