According to the structure, working principle and characteristics of the numerical control system, combined with our maintenance experience, the following analysis is carried out on the common defect location and defect site.
(1) The azimuth ring is a key link of the numerical control system. It is used to issue control instructions and compare them with the response value of the azimuth observation system to further complete the control task. The operation frequency is high, and the connection with peripheral equipment is prone to failure.
Common faults are:
Position control loop alarm: It may be that the measurement circuit is open, the measurement system is damaged, or the internal position control unit is damaged.
(2) Movements without instructions may be caused by excessive drift, positive response, failure of the position control unit; damage to the measuring element.
(3) The fault of the measuring element is usually displayed as a non-response value; the machine tool cannot return to the reference point; the leakage pulse alarm at high speed may be due to the grating or the reading head dirty; the grating is damaged.
(2) Servo drive system Servo drive system is related to power grid, mechanical system, etc. It is always in the state of frequent startup and operation during operation, which is also some more faults.
The main problems are:
The system is damaged. Usually it is because the grid voltage oscillates too much, or a voltage shock is formed. In some areas of our country, the quality of the power grid is not good, which will cause the overvoltage of the machine tool, especially in an instant. If there is no special voltage monitor, it is difficult to detect. When looking for faulty components, pay attention to it, some of which are damaged due to additional factors. For example, in a factory in northern China, many machine tool servo systems were damaged by lightning strikes at the factory's substation and broke into the power grid.
(2) There is no control command when the motor is running at high speed. The main reason for this defect is the opening or positive reaction of the velocity loop. For example, in a factory in Northeast China, a West Devotan rotor milling machine was introduced for debugging. The X-axis of the machine tool was running at high speed without instructions. After analysis, we believe that a positive response has been formed. Due to the drift of the system zero point, in the case of a positive reaction, it will quickly accumulate the high-speed operation of the motor, and we check it line by line and standard for complete accuracy. The technical workers of the machine tool factory believe that it is impossible to make mistakes. After sufficient analysis and inspection, We reversed the reaction line, and the result is that the f machine tool runs normally. Skilled workers in machine tool factories must admit Germany's mistakes. Another example is when we are training and giving lectures in a factory in Tianjin, we should repair a refiner because it cannot work normally after entering the factory at the request of the factory. The problem is that the machine tool works as soon as the motor starts, and does not start working until the maximum speed. We think this is because the speed loop is open and system drift cannot be formed. The key factor is that the speed response line is connected to the ground line.
(3) During processing, the requirements cannot be expressed outside the workpiece. When the circular interpolation axis changes direction, a boss appears, or the motor crawls or vibrates at low speed. This failure is usually caused by improper adjustment of the servo system, uneven gain system of each axis or improper coordination with the motor. The solution is to optimize and adjust.
(4) Safe combustion, or the motor is overheated and burned out. This defect is usually caused by excessive mechanical load or stuck.
(3) Part of the power supply is the power support for the normal operation of the system. The direct consequence of its failure or failure is the formation of system shutdown or the destruction of all systems. Usually in European and American countries, there are relatively few such titles, and there is not much thinking about planning elements. However, in my country, due to large power fluctuations and poor quality, there are hidden interferences such as high-frequency pulses, and human factors (such as sudden shutdown, etc.). These factors can result in power failure monitoring or damage. Otherwise, some operating data, setting data and processing programs of the CNC system are usually stored in RAM memory. When the system is powered off, the backup battery or lithium battery of the power supply is attached. Therefore, the downtime is relatively long, and the plug-in power supply or memory may cause data loss, making the system unable to run.
(4) PLC logic interface The logic control of the numerical control system, such as tool library management, hydraulic start, etc., is completed by PLC. To complete these operations, you need to collect status information
(5) The printed circuit shall not be blocked at will. Some maintenance work has a certain maintenance experience and the habit of checking broken wires for household appliances, but most of the circuit boards on CNC equipment are double-sided metal or multi-layer holes. The printing lines are fine. Once blocked, it is not easy to weld. When the tangent line is blocked, it is easy to block the adjacent line. In addition, when a certain line is blocked, it cannot be separated from the line, and multiple lines need to be blocked together. It's ok.
(6) The equipment shall not be disassembled and replaced at will. When there are no defective components, some maintenance personnel can only remove one component immediately by feeling that it is damaged, which results in a higher rate of misjudgment. The removed components also have a higher rate of man-made damage.
(7) When disassembling the parts, a tin suction device and a breather rope should be used. Don't use too much force. The same litter should not be heated for a long time and disassembled repeatedly to avoid damage to the litter.
(8) When replacing the new equipment, the pins should be properly handled, and acid welding oil should not be used during welding.
(9) Record the switch and jumper positions on the line, and do not change them at will. When performing comparison inspections above the north and south poles, or when exchanging components, pay attention to the components on each symbol board to avoid confusion and make good boards fail to work.
(10) Identify the power supply equipment and varieties of the printed circuit board, and supply power separately or all according to the inspection needs. High voltage should be paid attention to. Some circuit boards are directly connected to high voltage, or there are high voltage triggers in the board, which need to be drained properly. Be careful when operating.