Research On Maintenance Decision Of CNC Machine Tools Based On RCM

Over the years, CNC Machine Tools produced by our country are mainly in low andmedium-grade product and high-grade CNC machine tools rely on imports. The reasons are various,such as low level of design, low capacity of manufacture both in machine and key-functionassembly, the low reliability level is also an important reason. It is reported that the Mean Timebetween Failure (MTBF) of CNC Machine Tools produced by our country is about500hours.However, the MTBF of overseas CNC Machine Tools exceed2000hours. The gap is very great. Itseriously affects the users’ confidence on domestic CNC machine tools. The reliability of CNCmachine tools is depend on design, manufacturing (both of these define the inherent reliability ofthe CNC machine tools), but also related to the daily habits of use and maintain of CNC machinetools, Users of domestic CNC machine tools have not formed good habits of use and maintain ofCNC machine tools, not only because of the low level of professional level, the more importantreason is that the domestic CNC machine tool manufacturers have very little systematic study ofthe maintenance of CNC machine tools, and haven’t formed a effective maintenancedecision-making method. In order to improve the reliability level of the domestic CNC machinetools as soon as possible, this paper beginning with improving the quality of maintenance of theCNC machine tools in use, introduces the RCM theory into the maintenance decision-making ofCNC machine tools, presents a method for maintenance decision-making. Besides, in order tobetter and more targeted controlling of maintenance activities of CNC machine tool, this paperdesigns and develops the online maintenance decision-making system, providing actionableplatform for the protecting the operational reliability of CNC machine tools.First of all，it starting from the failure and maintenance theory, studied thecharacteristics of the failure and the maintenance activities of complex mechanical andelectrical products,pointed out that the six basic forms of the failure rate of thecomplex mechanical and electrical products as well as the basic types of maintenancework, and qualitative researched how each type of maintenance work affects thereliability of complex mechanical and electrical products.Then, it introduced reliability-centered maintenance (RCM) theory into thedecision-making of the CNC machine tools, divided the process into steps asinformation collection, decision of important functional units, FMEA, decision-makingof maintenance mode and forming the maintenance program. For key challenges ofeach step, it respectively established the mathematical model, provided tools for the quantitative study of the maintenance decision.Finally, based on the theory above, it respectively developed on-line maintenancedecision-making system for two different numerical control systems. The systemembedded into the CNC machine tools, automatic records failure and maintenance ofthe NC machine tool, and monitors the running state of CNC machine tools by sensors.According to the information above, it makes the decision of maintenance by itself.