| With the rapid development of information technology and modern manufacturing techniques, the CNC machines, as the modern universal machine tools, are more comprehensively adopted by machine processing enterprises. Through years'efforts, the machine manufacturing industry has resolved a multitude of critical technologies and has acquired many advanced design and manufacturing techniques in means of cooperation with foreign enterprises, technology introduction and researches organized by the State, the integrated levels of CNC machine tools have improved greatly, the gap between CNC machine manufacturing industry of our country and foreign advanced enterprise has narrowed. However, we shall clearly realize that the CNC machine manufacture of our country still has a certain distance in aspects of reliability, high speed and high precision in comparison with foreign advanced enterprises. The key to improving the market share of domestic CNC machines is to enhance the availability of the machines, instead of simply laying importance on improvement of the reliability of the CNC machines.The availability refers to the degree of the machines in workable or available state at any time if necessary and when commencing a task, which has already included the maintenance utility. For the complicated and repairable system, the maintainability is the key, if the repairable system displays faults during completing a task, but can restore its operation after the faults being repaired within specified time, the faults of this sort are considered not to affect the system to complete its task. Prompt prevention measures adopted when the faults are about to occur also can ensure the completion of the task.At present, the researches on the reliability and maintainability of mechanical products are only confined to the levels of independent researches, from the views of the whole life cycles and benefits of the products, the reliability and maintainability are interrelated, which can affect the availability of the products at the same time, therefore, the researches on mechanical products'reliability and maintainability shall be done simultaneously.This research is based on the fourteenth CNC lathe among the modern machining facilities in the Engineering Training Center of Changchun Institute of Technology to carry out the reliability system research, and conduct field data collection for 20 months. Through analyses and researches, the reliability and maintainability can be combined in the form of building mathematical models to formulate preventive maintenance plans for facilities and data management library for spare parts.The contents of this paper are as follows:1. Founding of reliability database First,the definition of the various failures to distinguish, from the initial credited to the principles of the failures. Distinction between the classification of CNC machine tool failure is mainly reflected in the following three conditions: fault location, the nature of faults, Whether the failure occurred after the alarm display. The definition of fault location, fault model, fault cause lay the theoretical basis. The data collection process in order to remove them, which are not to be included in the analysis section of the fault conditions.Secondly,based on the principles of usability test data collection. Determine the CNC machine tool field use in the process of the failure data collection steps. According to the principle of availability of test data collection to determine the numerical control machine tool field use in the process of collecting fault data processing steps. Such as, data collection objects, data identifier, data recording, responsibilities, etc., and use them as a basis for fault log of CNC machine tool.Once again, commonly used in seven kinds of analysis methods on the availability of test data, such as: the vertical contrast, horizontal contrast, the overall balance, curve, the basic method of fuzzy theory, the basic theory of expert systems approach, primary and secondary analysis. Selected one from the most consistent with the current data collection unit of analysis of the actual situation, that is primary and secondary analysis, and the availability of test data analyze on it. In accordance with the above criteria and analysis methods developed subjects CNC lathe failure data summary table, and on this basis to establish, organize troubleshooting database.According to rely on the final index: mean time between failures, mean time to repair, the average effective degree formula. Then work on the following things, CNC Lathe between failure timetable,maintenance schedule, calculate the time between failures, mean time to repair, the average effective degree of value.2. FMECA Analysis (Fault Mode, Effect and Criticality) of CNC MachinesThis chapter is based on fault database that analytics in the last chapter. According on reliability analysis of the important qualitative method——Fault Mode and Effect Analysis(FMEA), done a detailed analysis on fault location, failure modes, failure causes in the first part of the overall machine failures. Found that failure-prone parts of CNC machine tools out, thay are mechanical transmission (34.2%), electrical control (16.7%), hydraulic and (13.6%), CNC system (12.7%). According to CNC machine tools failure mode analysis concludes that the initial fault detection of machine failure-prone form of the geometric precision of exceeding (11.5%), parts and components damaged (10.6%), CNC parameter disorder (9.7%), components damage (9.7%), positioning accuracy exceeding (9.3%), the detection system failed (8.8%). Through the CNC machine tools failure cause analysis concludes that the reasons for the failure-prone components damaged (23.6%), parts and components damaged (23.1%), dislocation (14.4%).Secondly, the fault-prone subsystems analyze about failure mode and failure cause. And the analysis of subsystems used in various parts of machine malfunction Criticality analysis, obtained the highest hazard mechanical transmission subsystems that affect the reliability of the series CNC lathe key components. Electric control part of the degree of hazard is also high, these two parts can be said that the series CNC lathe weaknesses. In addition, the hydraulic system is also relatively weak compared with other parts. To sum up its reliability to determine the main direction of improvement, but also to improve the reliability of the series provide the basis for CNC lathe.Analyze the situation according to cause of the malfunction can be seen in the production and processing machine operators in the quality of the machine's routine maintenance, repair, spare parts management, etc.-oriented is not enough yet to make up for deficiencies in this regard.3. Founding of Machine Maintenance Periods and Spare Parts StorehousesThe paper analyzes the disadvantages of the incompleteness existed in separate researches of reliability and maintainability, and puts forward to carry out repair, maintenance and spare parts management on the basis of reliability analysis. It creates corresponding mathematical models and combines the date in reliability database with installation and maintenance documents of the machine to calculate the quantity of each spare part through the medium of C language programming, found spare parts management database, and formulate routine maintenance plans for portions of spare parts.Finally, the Author hopes this research can provide powerful theoretical supports for reliability researches in repair, maintenance of the machines and founding of spare parts storehouses.
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