Repair of no alarm fault in the hottest CNC machin

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Repair of no alarm fault in CNC machine tools

the control system of CNC machine tools has the function of fault self diagnosis. Generally, when a fault occurs, there is an alarm message. According to the control system used by the machine tool, the alarm content is different, but according to the fault handling method in the manual, most of the faults can be solved

there are also some faults of machine tools in actual use, which have no alarm and the phenomenon is not very obvious. For this situation, it is not as simple as it is documented

in addition, after some equipment fails, there is not only no alarm information, but also the lack of information required for maintenance. If some machine tools fail in use, if they are not careful, they will also cause batch scrapping of workpieces, so it is more difficult to deal with them. For this kind of fault treatment, when the repair personnel lack certain work experience, they often make wrong judgments, causing unnecessary economic losses or extending the repair time

in addition, sometimes due to the low frequency of faults, we will encounter great trouble when asking the special maintenance service department to deal with them. For this kind of fault, we think that when carrying out the tensile test, we must carefully check it according to the specific situation, analyze the tiny parts of the phenomenon, and find out the real cause

to find out the cause of this kind of fault, we must first find out its real phenomenon from the crisscross of various surface phenomena (this "phenomenon" is the real situation of the fault), and then find out the cause from the confirmed fault phenomenon. Comprehensive new materials can react to electrical signals, and the analysis of a fault phenomenon is an important factor to determine whether the judgment is correct. Before finding the cause of the fault, you must first understand the following:

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① whether the fault occurred in normal work or just after startup

② the number of occurrences, whether it is the first time or has occurred many times

③ confirm that the machining program of the machine tool is correct

④ whether other personnel have repaired or adjusted the machine tool

⑤ is there any difference between the fault phenomenon when requesting repair and the situation on site

the following are the handling and analysis methods of some non alarm faults we encounter in maintenance

fault - Zoje thy5640 vertical machining center found that there was abnormal sound at the spindle and gearbox when the spindle speed was below 500r/min during operation. By observing the power meter of the motor, it was found that the output power of the motor was unstable and the pointer oscillated greatly. However, the abnormal sound disappears when using more than 1201r/min. After starting up, the power meter of the motor will swing automatically without rotation command, and the motor will drift and rotate automatically. After normal operation, the braking time is too long, and the machine tool has no alarm

according to the observed phenomenon, the cause of the fault may be the loss of control of the spindle controller, and the cause of the mechanical transmission or motor cannot be eliminated. Due to the heavy workload of dismantling the mechanical part for inspection, the spindle controller of the electrical part shall be inspected first, and the controller is Siemens 6sc-6502. First check the preset parameters in the controller, and then check the control board. There is no abnormality. It is found that fine chemical industry is one of the most dynamic fields in the chemical industry today. It is found that the circuit board is dirty, and the circuit board is cleaned as required, but the boot fault is still the same after installation. Therefore, the cause of the fault in the controller can be temporarily eliminated. In order to determine whether the fault is in the motor or the mechanical transmission part, the motor must be separated from the machine. After separation, the startup and commissioning found that the continuous abnormal sound began to appear when the motor speed command was close to 450r/min, but the abnormal sound disappeared when the 1201r/min command was given. Therefore, we analyzed the main shaft part. The original 450r/min command given at low speed and the 4500r/min command given at high speed are the same for the motor at the highest speed, but the speed is reduced by gears at low speed, so the fault can be basically determined in the motor part. After analysis, the abnormal sound may be caused by poor bearing. The motor was disassembled for inspection, and it was found that the bearing was indeed damaged. At high speed, the bearing was stuck, causing the load to increase, causing the power meter to swing and deflect. After stopping, the motor drifted and braking was too slow. After inspection, the encoder disc was scratched. After replacing the bearing and encoder, all faults were eliminated.

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this fault is mainly caused by abnormal sound when the spindle rotates, so the sound source should be checked before troubleshooting. Abnormal sound is usually caused by mechanical friction, jamming and bearing damage

fault 2: the spindle orientation of the machining center is inaccurate or misplaced

the spindle orientation of machining center usually adopts three ways, magnetic sensor, encoder and mechanical orientation. When using magnetic sensors and encoders, in addition to adjusting the position of components, you can also adjust machine parameters. There is no alarm when orientation error occurs, and it can only be found when there is an interruption in the process of tool change. Once, there was a fault of inaccurate orientation on a modified machining center. At the beginning, the machine tool was often interrupted in the work, but the number of times was not very many. It could work again after restarting, and the fault occurred repeatedly. After careful observation of the machine tool after the fault occurred, it was found that the real cause of the fault was the position shift of the spindle after orientation. It was strange that if the spindle was touched by hand after orientation (similar to the situation when the tool was inserted into the spindle during tool change in work), the spindle would drift in the opposite direction. Checking that there was no alarm in the electrical part was the starting sign of the engineering utilization of modern hydraulic technology, and the mechanical part was very simple. The orientation of the machine tool uses encoder, so from the phenomenon of fault and possible parts, the possibility of electrical part is relatively small, and the most important mechanical part is connection. Therefore, it was decided to check the mechanical connection part. When checking the connection of the encoder, it was found that the set screw of the coupling sleeve on the encoder was loose, which made the coupling sleeve retreat, resulting in excessive clearance with the connecting part of the main shaft, which would lead to asynchronous rotation. After fixing the set screw as required, the fault is eliminated. In case of spindle orientation failure, analyze and deal with it according to the specific structure of the machine tool. Check the electrical part first, and then consider the mechanical part if it is confirmed to be normal.  

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