Reliability Research Of CNC Machine Tool Electrical Controlling And Driving System

As a carrier of advanced manufacturing technology, the CNC machine tool is concerned by public about it’s development trend. Our country is a country that consumes lots of CNC machine tools, however, there is a great gap in reliability of high-grade CNC machine between our country with developed countries. Therefore, if we want to change from CNC machine tools consuming country to the manufacturing country, we must start from improving the reliability of domestic CNC machine tools. According to statistics, electrical controlling and driving system is the subsystem whose failure occurs most frequently in the CNC machine tools. Therefore, it is of great importance to strengthen the research on reliability of electrical system in order to improve the reliability of domestic CNC machine tools.Fault tree analysis method is one of the main system reliability analysis methods, whose application has been penetrated into all kinds of fields. Fault tree analysis method not only can be used to find events which can cause system failure, but also to look for the top event occurrence probability and the importance of basic events, find the key parts, then the anlysis results can provide suggestions for system reliability improvement. Therefore, the structure and working principle about the electrical controlling and driving system of CNC machine tools are introduced in this paper, then the system schematic diagram is drawn in this paper. Then the center frame motion controlling system of electrical controlling and driving system is taken as an example, and the fault tree analysis technology is used to carry on the system reliability analysis.Traditional fault tree analysis can’t consider the dynamic relationship of component failure. So in this paper, according to the system principle diagram and the dynamic failure behavior about the electrical controlling and driving system, as one of the key subsystems, the center frame motion controlling system is taken as an example to carry on the dynamic fault tree analysis. Firstly, the dynamic logic gates are added into the center frame motion controlling system, and the dynamic fault tree model is established. Then the dynamic fault tree analysis method based on modular thinking and dynamic fault tree analysis method based on Bayesian Networks are researched. In the dynamic fault tree analysis method based on modular thinking, fault tree is modularized into independent static and dynamic modules firstly. Then qualitative analysis and quantitative analysis are carried for the static and dynamic modules independently. Finally, the analysis results of the all static and dynamic modules are integrated to analyze the system reliability. Dynamic fault tree analysis method based on Bayesian networks not only can build the Bayesian network model, but also can solve the system reliability as well as carry on the bidirectional probabilistic reasoning for the model, and then the weak links of the system are found, which can provide reference for the system reliability improvement. The analysis results show that the dynamic fault tree analysis method can solve reliability analysis and evaluation problem for the complex system with dynamic failure characteristics more accurately compared with the traditional fault tree analysis method.The basic knowledge and the specific implementation process of 3F technology are discussed in the end. On the basis of finishing FMECA(Failure Mode,Effects and Criticality Analysis) and FTA(Fault Tree Analysis) about the center frame motion controlling system, FRACAS(Failure Report Analysis and Corrective Action System) process and the related data are used to complete the example analysis. Then the failure analysis results, corrective actions and feedback information, etc. can be gotten, which are conducive to the product reliability growth.