Research On Technology Of Eliminating Early Failures For NC Machine Tools

The most typical feature of Machine Tools manufacturing industry in China is “big and not strong”.In recent years,the market share of home-made CNC Machine Tools has improved,but high-grade products are almost completely monopolized by western countries.The main difference between domestic CNC Machine Tools and imported CNC Machine Tools is reliability.The frequent early failures of domestic CNC Machine Tools let users suffer huge economic losses.Frequent early failures do harm to the reputation and images of domestic CNC Machine Tools among users.It can be said that eliminating the early failures is the main way to improve the reliability of domestic CNC Machine Tools.Regarding the domestic CNC Machine Tools as the research object,the paper systematically research on the early failures elimination technology,and provide ideas and methods for the early failures elimination of CNC machine tools.Combined with the national major scientific and technological special project for “high-grade CNC Machine Tools and Basic Manufacturing Equipment”,the main work of the paper were as follows:(1)Relying on a domestic CNC Machine tools manufacturing enterprise,set up a set of early failures elimination technology system for CNC Machine Tools.The system is based on the idea of “failure to return to zero” in FRACAS(Failure Reporting,Analysis and Corrective Action System),and uses the running failure date as the source of failure information,and integrates reliability evaluation,FMEA(Failure Modes and Effect Analysis),FTA(Failure Tree Analysis)and other reliability analysis techniques.It can be used to guide the work of early failures elimination technology when the enterprise lacks the necessary reliability test conditions.(2)In order to more accurately determine the early failures period of CNC machine tools,the NHPP(non-homogeneous Poisson process)theory and the “ bathtub curve” theory are used to calculate the early failures period of CNC machine tools under the hypothesis of “minimum repair”.(3)As a tool for production,CNC Machine Tools is often used to create economic value for the user.In view of the character of CNC Machine Tools,the effect of the failure is defined from the point of “economic loss”,and the traditional FMEA process is improved to make it more operable in the early failures elimination technology.(4)For the complex system of CNC Machine tools,the traditional FTA method has the disadvantages of complex building process,high requirement for analyst,and cannot indicate the degree of failure.The T-S FTA is used to the analysis of failure case,and the process of building the tree is simplified.At the same time,the multistate of the event can be considered,and the calculation method of relative importance is given.