Numerical control machine tool is an automatic machine tool with program control system. As a representative of advanced technology in the field of equipment manufacturing, it is widely used in equipment manufacturing. The following is the introduction information about fault diagnosis, analysis and maintenance of CNC machine tool servo system. Let's have a look.
The application of CNC machine tools has improved the automation, informationization and modernization level of equipment manufacturing industry, and brought broad development prospects for equipment manufacturing industry.
The servo system of CNC machine tools is an important system for controlling information processing and controlling the executive parts of machine tools, and its fault diagnosis, analysis and maintenance processing technology has always been highly valued by the equipment manufacturing industry.
Composition of servo system of NC machine tool
The servo system of NC machine tool consists of two parts: driving device and executing mechanism. The servo system of NC machine tool can realize the feed servo control and spindle servo control of NC machine tool. By receiving, amplifying and shaping the instruction information of the NC machine tool, the instruction of the controller is converted into the displacement movement of the machine tool actuator, so as to realize the cutting of the parts.
The servo drive device of CNC machine tools requires good fast response performance, which can accurately and sensitively track the digital command signals sent by CNC machine tools and execute the commands sent by CNC machine tools, so as to improve the dynamic tracking characteristics and static tracking accuracy of the system.
The servo system consists of two parts: driving device and actuator, and consists of spindle driving unit, feed driving unit, spindle servo motor and feed servo motor.
The servo system in the CNC machine tool system is an important link to convert the digital instructions of the controller into specific machining, so the servo system is not only complex in structure and principle, but also plays an important role in the machining and processing of workpieces.
The running stability of the servo system directly affects the running state of the machine tool and the machining quality of the workpiece. In order to improve the production efficiency of CNC machine tools on the premise of ensuring the machining accuracy and accuracy, the fault prevention, diagnosis and analysis of servo system have always been the key issues in the application of CNC machine tools.
Common faults and maintenance of water supply system
1. Fault type of feed servo system
The feed servo system has many components and complex functions, so the failure types of the feed servo system are also varied.
By summarizing and analyzing the faults of the feed servo system of CNC machine tools, the main fault types are as follows.
Alarm: When the feed movement exceeds the limit set by the software or the hard limit determined by the limit switch, it is mainly caused by over-travel alarm. In addition, when the load of the feed movement of the system is too large, the alarm will also occur due to the frequent forward and backward movement of the feed transmission chain and poor lubrication conditions.
When there is an alarm in the servo system, it means that there is something wrong with the servo system, and the staff needs to stop in time to avoid the quality problems of parts and the physical damage to the CNC machine tools caused by the untimely troubleshooting.
Jumping, crawling and vibration: Jumping, crawling and vibration are common faults in the servo system of CNC machine tools. Once jumping, crawling and vibration occur, it will directly lead to the decline of machining precision and accuracy, and affect the quality of parts.
Jumping is mostly caused by the instability of speed measuring signal or speed control signal caused by the fault of speed measuring device. In addition, poor terminal contact can also lead to power jump.
The main causes of creep are poor lubrication condition of transmission chain, low servo gain and excessive external load.
Most of the vibration phenomena are caused by too fast feed speed or too high feed acceleration.
Position error and drift: The position error is generated when the motion of the servo shaft exceeds the allowable position error range, and the position error includes following error, contour error and positioning error.
Drift refers to the phenomenon that the coordinate axis continues to move when the instruction value of NC machine tool is zero. Position error and drift will not only affect the machining quality of the workpiece, but also cause collision accidents and physical damage to the CNC machine tools.
Back-to-reference point fault: Generally, there are two kinds of back-to-reference point faults of machine tools: the reference point cannot be found or the reference point cannot be found accurately. Most failures back to the reference point are caused by not receiving the information or signal of the reference point deceleration switch.
2. Maintenance and treatment of common faults of feed servo system
Generally speaking, the failure of the feed servo system can be eliminated by referring to the operating instructions. If there are faults that cannot be eliminated by referring to the operating instructions, specific problems need to be analyzed and solved.
When vibration fault occurs, the mechanical device can be checked and adjusted, and the accuracy of speed and position detection of servo motor can be guaranteed. Because there are many electronic components in the CNC servo system, it is necessary to check whether there is external interference, and determine the fault type by checking the parameters of the drive unit.
If it is a mechanical failure, it should be solved in time. If it is an electrical fault, it is necessary to specifically confirm the location of the problem and repair the servo system fault by repairing or replacing parts.
If you can't return to the reference point, you can first check whether the deceleration switch signal of the reference point is accurate and effective. According to the problem of the deceleration switch signal of the reference point, use the principle analysis method or tracking analysis method to judge the position and repair it in time.
Fault and treatment of spindle servo system
1. Fault type of spindle servo system
The faults of DC spindle servo system mainly include stall, abnormal speed, motor vibration and overcurrent alarm of main circuit.
The main faults of AC spindle servo system are motor overvoltage and fuse blowing. The main reasons for this kind of fault are the overload of motor, poor contact or damage of cooling device, which leads to the high impedance of some components, or the failure of surge absorber of CNC machine tools.
2. Maintenance and treatment of common faults of spindle servo system
When the spindle servo system fails, we must first determine the type and location of the spindle system failure. When the spindle motor is not running, it is first necessary to determine whether there is a signal output from the CNC system, and then observe the I/O status to determine whether the starting conditions of the spindle are met.
If the servo motor is equipped with electromagnetic braking, it is also necessary to determine whether the electromagnetic braking is released. If the spindle speed is abnormal, first check the mechanical transmission mechanism to ensure the normal operation of the machine tool.
If there is no abnormality in the mechanical transmission mechanism, it is necessary to check the cable connection and status indicator light of the spindle driver and analyze whether there is any problem with the spindle driver.
If all the above reasons are eliminated, it is likely that the control panel is out of order.
When the high-speed rotation vibration of the spindle is too large, it is mostly caused by the failure of the electrical part of the spindle drive system. In order to solve this problem, the spindle drive and all electrical connections should be inspected comprehensively according to the electrical schematic diagram, and the fault parts should be determined and repaired.
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To sum up, CNC machine tool servo system, as the most complex system in CNC machine tool system, has an important influence on the smooth operation of CNC machine tools and the machining accuracy of mechanical parts.
When there is a problem in the servo system of CNC machine tools, we should first judge the fault type according to the fault phenomenon, and then investigate the fault location through certain technical means. When the cause and location of the fault are determined, reasonable maintenance should be carried out according to the fault type, so as to improve the stability of the CNC machine tool, ensure the quality of the workpiece produced by the CNC machine tool and improve the production efficiency of the CNC machine tool.
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