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English
According to the composition, working principle and characteristics of the vertical VTC7070 series lathe CNC system, combined with our experience in maintenance, the common fault parts and fault phenomena are analyzed as follows.
(1) Position ring
This is the numerical control system issued control instructions, and the position detection system feedback value comparison, further complete the control task of the key link. It has a high working frequency and is connected with peripherals, so it is prone to failure.
Common faults are: (1) bit control ring alarm: may be open measurement loop; The measuring system is damaged and the bit control unit is damaged internally. (2) no instruction on the movement, may be too high drift, positive feedback, position control unit failure; The measuring element is damaged. (3) Measuring element failure, generally no feedback value; Machine tools can not return to the reference point; At high speed, the possible reason for missing pulse alarm is that the grating or reading head is dirty; The grating is broken.
(2) Servo drive system
Servo drive system is associated with power grid, mechanical system and so on, and it has been in frequent start-up and operation state in the work, so it is also the part with more faults.
The main faults are: (1) system damage. It is usually caused by network voltage fluctuation or voltage shock. The power grid quality is not good in most areas of Our country, which will bring over the voltage limit to the machine tool, especially the instant over the limit. If there is no special voltage monitoring instrument, it is difficult to measure. When finding the cause of the fault, we should pay attention to it, and some are caused by special reasons. For example, in a factory in North China, many machine tool servo systems were damaged due to lightning strike in the factory substation and into the power grid. ② There is no control instruction, and the motor runs at high speed. The cause of this failure is velocity loop open loop or positive feedback. For example, during the commissioning of the rotor milling machine introduced from WOTAN Company in West Germany in a factory in Northeast China, the X-axis of the machine operated at a high speed without instructions. After analysis, we believe that this is caused by positive feedback. Because of the zero drift of the system, under the condition of positive feedback, the motor will be rapidly accumulated to run at high speed, but we checked the line according to the label and it was completely correct. The technical staff of the machine tool factory thought that it was impossible to connect wrong. After full analysis and detection, we reversed the feedback line, and the result was that the machine tool ran normally. Machine tool factory technician had to admit German side work error. There is another example, we in A factory in Tianjin training lectures, should be required by the factory to their factory since entering the factory has been unable to work properly after the maintenance of the precision grinding machine, the fault is: the machine starts the motor to run, and faster and faster, until high speed. We think that the system drift can not be controlled because of the open speed loop. After examination, the reason is that the speed feedback line is connected to the ground. (3) The workpiece surface can not meet the requirements during processing, the boss occurs when the arc interpolation shaft is reversed, or the motor crawls or vibrates at low speed. This kind of fault is generally caused by improper servo system adjustment, the gain system of each shaft is not equal or is not matched with the motor. The solution is to adjust. (4) insurance burn off, or motor overheating, and burn out, this kind of fault is generally mechanical load is too large or stuck.
(3) Power supply
Power supply is the energy support part to maintain the normal operation of the system. Its failure or failure directly results in the shutdown of the system or the destruction of the whole system. Generally, in European and American countries, there are few such problems, and few factors are considered in design. However, in China, due to the large fluctuation of power supply, poor quality, and hidden interference such as high-frequency pulse, coupled with artificial factors (such as sudden power failure). These causes can cause power failure monitoring or damage. In addition, the numerical control system part of the operation data, setting data and processing programs are generally stored in THE RAM memory, after the system power, rely on the power backup battery or lithium battery to maintain. Therefore, the downtime is relatively long, plug power or memory may cause data loss, so that the system can not run.
(4) Logic interface of programmable controller
The logic control of numerical control system, such as knife library management, hydraulic start and so on, is mainly realized by PLC. To complete these controls, it is necessary to collect the state information of each control point, such as electric breaker, servo valve, indicator light and so on. Therefore, it is connected with a wide variety of signal sources and executive components outside, changing frequently, so the possibility of failure is more, and the type of failure is also ever-changing.
(5) Others
Due to environmental conditions, such as interference, temperature, humidity beyond the allowable range, improper operation, improper parameter setting, may also cause shutdown or failure. The CNC equipment in one factory lost the READY signal of CNC soon after starting up, and the system could not work. It was found that the body temperature was very high after inspection, because the ventilation filter was blocked, which caused the temperature sensor to act. After the filter was replaced, the system worked normally. Failure to plug and remove the circuit board according to the operating procedures, or absence of esd protection measures, may cause downtime or even damage to the system.
In general, in the design, use and maintenance of numerical control system, it is necessary to consider the parts that often fail to give alarm. After the alarm circuit works, on the one hand, alarm information is given on the screen or operation panel. On the other hand, protective interrupt instructions are issued to stop the system from working in order to find out the fault and carry out maintenance.
3: increase the drawing Angle.
4: Lower the height of pouring solution on the landing lathe to reduce impact.
