【正文】 of the premise, through the information input from the outside world or the system itself, through processing, judge the fault types, fault parts (ponents), as to estimate the possible failure time, severity, and the cause of the problem, you can even provide evaluation, decision making and maintenance advice. 　The main content of the modern fault diagnosis should include realtime monitoring technology, fault analysis (diagnosis) technology and fault repair methods of three parts. From information acquisition to fault location, and the fault exclusion, as separate areas of technology development, and the fault diagnosis technology of coordinated development. 　　2. Commonly used methods for nc machine tool fault diagnosis 　 (1) the intuitive method. Maintenance personnel use of sense organs, by the failure of various anomalies such as sound, light, taste, look at CNC machine tool system of each module and circuit, the presence of burn and injury, quickly to reduce the fault area on a module or a piece of printed circuit board. This is one of the most basic and monly used method. 　　 (2) CNC system since the diagnosis. The selfdiagnosis function, numerical control system has bee the important indicators of CNC system performance, the selfdiagnosis function of nc system real time monitor the working state of the numerical control system. Once the abnormal situation occurs, immediately on the CRT display alarming information, or through the leds indicate the fault reason, fault module, this is the most effective maintenance of CNC machine tool fault diagnosis and a method of directly. 　　 (3) function test program. Function program is to test method for the numerical control system monly used function and special function using manual programming or automatic programming methods, as a functional test program, into numerical control system, and then let the numerical control system to run the test program, so as to check the veracity and reliability of machine tools to perform these functions, and then judge the failure positions and failure causes of possible. (4) module switching method. Socalled module switching method is based on the analysis of the general causes of the failure cases, use spare copies of the printed circuit board, templates, integrated circuit chip replace the questionable part or ponent, will function the same template or unit exchanging, observation fault transfer situation, thus fast judgment fault positions method. 　 (5) the theory analysis. According to the principle of CNC ponent, start from the working principle of system ponents for analysis, and judgment, analysis from the logic relation between logic level and characteristic parameters of circuit failure suspects to determine fault positions method. This method does not need high maintenance personnel must be familiar with the working principle of the whole system or each ponent to fixing the fault parts. 　 (6) PLC procedure law. Alarm information based on PLC, consult about the PLC program, control stations corresponding module program, more relevant I/O ponent logic state, judge the fault. 　　Nc machine tool fault diagnosis methods and parameters of the test, measurement and parison method, tapping method, local ShengWenFa, isolation method and open loop test and so on, these methods have different characteristics, several methods often used at the same time the integrated use of maintenance, analysis, and gradually narrowing the scope of failure to achieve the purpose of troubleshooting. 3. Development trend of numerical control machine tool fault diagnosis technology 　　 (1) for the CNC lathe processing inplete information and inaccurate information, more emphasis on information integration strategies and processing technology, the representation method of knowledge。 (2) in view of the plication of modern CNC equipment, integration, automation degree rise and sustainable work ability and the improvement of reliability, more emphasis on integration of more intelligent technology and system level diagnosis technology, hybrid intelligent diagnosis technology research。 (3) in view of the expert system knowledge acquisition bottleneck problem, more emphasis on the adaptive ability and self learning ability research, online diagnostic technique, multisensor technology research. 　　Three, numerical control machine tool fault diagnosis 　　Nc machine tool fault diagnosis has been a problem in operation and maintenance personnel. Due to the work safety and reliability of nc machine tool for the benefit of the production units directly to produce very big effect, and application in the field of fault diagnosis expert system, based on human experts experience knowledge of equipment and system fault diagnosis technology. 　　CNC machine tools as a plex nonlinear system, fully considering the natural conditions change and manmade wrong operation, how to bine the advantage of fuzzy technology and artificial intelligence, summed up the more intelligent fault diagnosis methods, will be need to efforts in the direction of the later. 　With further improve equipment automation, its fault diagnosis is also being more plicated, especially for engineering machinery, to solve all fault is very difficult in the process of operation. In view of this situation, the technical strength of scientific research institutes to establish a system of remote fault diagnosis through the Internet and engineering machinery field connections, establish a realtime fault detection system, found the fault during the process of operation in a timely manner and quickly diagnose. In fault diagnosis of local system cannot solve, use the Internet access to remote fault diagnosis center, and through technical strength of scientific research institutes to deal with these failures, in time to resume production, and effectively implement the technical resources sharing, therefore the remote fault diagnosis system based on Internet will be a importa