CNC machine tool is set high, refined, sharp technology in one, set machine, electricity, light, liquid in a high-tech products. With a high precision machining, stable and reliable processing quality, high production efficiency, adaptability, flexibility and many other advantages, widely welcomed in various industries, in use, is also more and more attention. But because it is a set of strong and weak in one, digital technology to control the integration of machinery manufacturing equipment, once some parts of the system fails, it is bound to make the machine downtime, affecting production, so how to properly maintain the equipment and failure can be timely Repair is to ensure the normal production of the key. 1 CNC machine tool maintenance For CNC machine tools, reasonable routine maintenance measures, can effectively prevent and reduce the risk of CNC machine tool failure. First of all, for each specific performance of the machine and processing object to establish operating procedures to establish work, failure, maintenance of the file is very important. Including maintenance and functional devices and components maintenance cycle. Secondly, the air in general workplaces contains contaminants such as oil mist, dust and even metal powders which can easily cause insulation resistance between components once they fall on a printed circuit or electronic device in a numerical control system Decline, even the components and printed circuit damage. So unless it is necessary to make the necessary adjustments and maintenance, under normal circumstances not allowed to open the door, but also not allowed to open the door during use. In addition, the numerical control system of the grid voltage to be implemented from time to time monitoring, once found beyond the normal operating voltage, it will cause the system can not work properly, and even cause damage to electronic components within the CNC system. Therefore, the distribution system in the equipment does not have automatic detection and protection of the case to have someone responsible for monitoring, as well as to improve the stability of the power distribution system operations. Of course, very important point is the use of DC servo motor drive and DC spindle servo drive, pay attention to the brush removed from the DC motor, so as to avoid corrosion due to chemical corrosion is the commutator surface corrosion, resulting in commutation performance Damaged, resulting in damage to the entire motor. This is a very serious and easy to cause malfunction. 2 NC machine general fault diagnosis and analysis 2.1 Check In the case of equipment does not work, we must first determine the specific location of the fault occurs and the causes, we can visual fault board, carefully check whether there is due to excessive current caused by the fuse blown , Charred components of charred, with or without debris cut-off phenomenon, causing the board over-current, over-voltage, short circuit. Observe the resistance capacitance, the semiconductor device pin with or without broken legs, Weld, etc., in order to find some of the more obvious faults, reduce maintenance range, determine the cause of the fault. 2.2 system self-diagnosis CNC system self-diagnosis function at any time to monitor the working status of CNC system. In the event of an anomaly, an alarm message is displayed on the CRT or the cause of the fault is indicated by a light-emitting diode, which is one of the most effective methods of service. In recent years, with the development of technology, a new interface diagnostic technology, JTAG boundary scan, has been introduced, which provides the ability to effectively detect parts on a circuit board with densely spaced leads and further improve the self-diagnosis capability of the system. 2.3 Function Test Method Function test method is to NC functions and special functions commonly used manual programming or automatically into the method, compiled into a functional test program, giving people numerical control system, and then let the numerical control system to run this test program, In order to check the accuracy and reliability of the machine to perform these functions, and then determine the possible causes of the failure. 2.4 Interface Signal Inspection By PLC online check the machine control system to pick up the signal and interface manual correct signal contrast, you can also find out the corresponding point of failure. 2.5 Replacement of Diagnostic Spare Parts With the development of modern technology, the integration of circuits is becoming more and more complex and the technology is more and more complicated. According to the conventional method, it is very difficult to locate the fault in a small area. In the event of a system failure, Reduce downtime, without the diagnosis of spare parts can be replaced or replaced with the same or compatible module module check, for modern CNC maintenance, more and more cases using this method for diagnosis, and then replace the damaged parts Module to make the system work properly to minimize downtime. The above diagnostic methods, there are no strict boundaries in the practical application, it may be possible to use a method to troubleshoot, may also need a variety of methods at the same time. The most important thing is to find out the key issue directly or directly according to the result of the diagnosis, or to repair or replace the production as soon as possible. 3 CNC machine tool fault diagnosis examples As part of the CNC machine tool drive power is one of the most prone to problems. Therefore, a brief introduction to the driving part: The driving part includes a spindle driver and a servo driver, a power module and a driving module. The power module boosts the three-phase AC voltage to a high-voltage DC, and the driving part is actually an inverse transform , The high-voltage tributary into three-phase AC, and drive servo motor to complete a servo axis movement and the operation of the spindle. Therefore, this part of the most prone to failure. To CJK6136 CNC machine tools and 802S CNC system failure phenomenon, for example, the main analysis of the control circuit and mechanical transmission interface fault repair. Such as CNC machine tools in the process, the spindle can sometimes return reference point sometimes can not. In the CNC operation panel, the spindle speed display sometimes without, the spindle is running normally. Analysis of the causes of the failure of the machine used frequency control, the speed signal is provided by the encoder, so you can rule out the possibility of damage to the encoder, or simply can not pass the speed signal. Only a problem with the encoder and its connection unit. Two considerations, one may be connected with the CNC system ECU connection loose, the second is that there may be mechanical problems with the spindle. This can start to solve the problem. First check the encoder and ECU connection. If there is no problem, remove the encoder to check whether the key of the main drive and the encoder is separated from the key slot, and the result is that this problem is solved. Fixing and reinstalling solves the problem. CNC machine tool failure is caused by a variety of reasons, mechanical problems, numerical control system problems, sensor components, drive components, the problem of the strong part of the line connection problems. In the maintenance process, to analyze the possible causes and scope of the fault, and then gradually ruled out until the fault point, do not blindly move, otherwise, not only can not solve the problem. It is also possible to further expand the scope of the problem. In short, in the face of CNC machine tool failure and maintenance problems, we must first take preventive measures unburned, CNC machine tools can not be a problem before they go to solve the problem, to do a good job of routine maintenance and understanding of the machine's structure and working principle, This can be targeted.