The Reliability Of Tool Magazine And ATC

The tool magazine is one of the most important key function units of the machining center, which can reserve and help to auto-change the tools, whose reliability directly influences that of the machining centers. The tool magazines and ATC produced by our own country can meet the demands to a certain extent, yet the reliability has fewer advantages than that of the advanced products of the developed countries, which has been a key factor of the development restriction of the top-grade CNC machine tools produced by our country. So far, there is little reliability study of the tool magazine and ATC. Therefore, based on the national science and technology major projects "The Development Study of the Large Chain-type Tool Magazine, the High-speed Disk-type Tool Magazine and the Automatic Tool Changer", disc-type and chain-type tool magazines and ATC produced by Dalian Golden CNC Group Corp. are taken as the research object. Based on the research of the products and the gathering and analysis of the failure data, the reliability analysis tool is adopted to theoretically analyze the reliability of the main failure modes and the test research is done as well. Finally, the reliability analysis and testing scheme of the tool magazines and ATC are made, and the reliability evaluation methodology of the tool magazines and ATC is proposed. What has been done may be a reference of the improvement design of the tool magazines and ATC products and even the CNC machine tools.(1) The dissertation firstly introduces the background of the project and the current situation of CNC machine tools and the function units is analyzed as well, which is the theoretical foundation of the reliability study of tool magazines and ATC.(2) Based on the failure data got from field tracing, the FMECA analysis is conducted on YP disc-type tool magazines and ATC, and the failure modes, causes and criticalities are analyzed in detail. The failure positions which have the highest criticality are exposed, which offers the basis of the improvement design of the new products.(3) The modeling process of the distribution model of the time between failures is particularly presented. Based on the failure data of YP disc-type tool magazines and ATC, the distribution model is primarily elected, Weibull distribution is supposed to be complied, the parameters are estimated and the hypothesis is tested, and at last the hypothesis is proved to be reasonable by the fitting diagram’s comparison.(4) In order to expose the weak spots of the tool magazines and ATC faster, based on the characteristics of the large chain-type tool magazines and ATC, the reliability accelerated test program in the lab is made, which includes the previous preparation, the test requirement and the test specific items, etc. The rules of the judgment and the counting criteria of the failures are explicitly provided. The failure log sheet is made as well so that the failure data will be recorded and settled more easily.(5) The traditional reliability evaluation index are adopted to evaluate the YP disc-type tool magazines and ATC, and based on the failure data got from the reliability test of the large chain-type tool magazines and ATC, the evaluation index of Mean Tool Change Numbers Between Failures (MTCNBF) is come up with, which is a better evaluation index for tool magazines and ATC. For those failure data which do not include the tool change numbers, the traditional evaluation index are needed to evaluate the system’s reliability; while for those circumstances when there is the test with tools changed successively and there are counters in the tool magazine systems, the evaluation of mean tool change numbers between failures can be adopted to evaluate the system’s reliability.