Maintenance methods for common faults of the hotte

2022-08-25
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Maintenance methods for common faults of CNC machine tools

maintenance methods for common faults of CNC machine tools: as the reliability of modern CNC system is getting higher and higher, the faults of CNC system itself are getting lower and lower, and most of the faults are caused by non system reasons. The external faults of the system mainly refer to the problems caused by the detection switch, hydraulic components, pneumatic components, electrical actuating components, mechanical devices, etc. The external faults of numerical control equipment can be divided into software faults and hard faults caused by external hardware damage. Soft faults are caused by improper operation and adjustment. Such faults often occur in the early stage of equipment use or during the adjustment period of equipment users. For CNC system, another trouble prone place is servo unit. Because the movement of each axis is realized by the servo unit controlling the servo motor to drive the ball screw. The rotary encoder is used for speed feedback, and the grating ruler is used for position feedback. Generally, the driving module of rotary encoder and servo unit is prone to failure. There are also individual system chaos caused by power supply. Especially for those systems with computer hard disk to save data. For example, Siemens 840C in Germany. Example 1: when a CNC lathe is just put into use, it must return to the reference point when the system is restarted after power failure. That is, when the axes are moved outside the non-interference area manually, the axes return to the reference point. Otherwise, a car crash may occur. Therefore, after processing every day, it is best to move the axis of the machine tool to a safe position. At this time, there will be no problem after operation or power failure. Faults caused by external hardware operation are common faults in NC repair. Generally, it is caused by problems in the detection switch, hydraulic system, pneumatic system, electrical actuator and mechanical device. Some of these faults can be found through the alarm information. For general CNC system, it has fault diagnosis function or information alarm. Maintenance personnel can use these information means to narrow the scope of diagnosis. Although some faults have alarm information display, it can not reflect the real cause of the fault. At this time, it is necessary to analyze and solve according to the alarm information and fault phenomenon. Example 2: the first turning unit in our factory adopts SINUMERIK840C system. The machine tool stops suddenly when it is working. Display spindle temperature alarm. After comparison and inspection, the fault occurred on the temperature instrument, and the alarm disappeared after adjusting the peripheral circuit. Then replace the new instrument and return to normal. Example 3: the same turning center, when working, CRT displays 9160 alarm "9160 no part with wiper 1 closed verify V". This refers to the alarm of not grabbing the workpiece. But in fact, the manipulator grasping the workpiece has grabbed the workpiece, but it shows that the manipulator does not grab the workpiece and alarms. Referring to the PLC diagram, this fault is caused by the measurement induction switch. After checking the position of the manipulator, the working stroke of the manipulator is not in place, and the incomplete sense of full depression should be caused by switching when trying to spend the critical period of innovation driven development. Then adjust the clamping force of the manipulator, and this fault is eliminated. Example 4: a vertical machining center adopts fanuc-om control system. 414 and 410 alarms will appear when the machine tool performs rapid movement of axis X under automatic mode. This alarm indicates that the speed control is off and the x-axis servo drive is abnormal. Since this fault can be eliminated by restarting after it occurs, it will alarm every time the x-axis moves fast. After investigation, the plug of the servo motor power line caused phase to phase short circuit due to arc creeping, and the fault was eliminated after repair. Example 5: improper operation of the operator is also an important reason for the quality of the fault experimental machine. We have our own evaluation criteria. For example, another CNC lathe with 840C system in our factory works normally on the first day, but it cannot be started on the next day. As soon as the working mode is switched to automatic mode, the alarm "missing selected mooe selector" will be given. After the finished workpiece is processed, the spindle does not stop, and the manipulator grabs the workpiece. Later, it is carefully checked that there is no problem in all parts, but a mode switch under automatic working conditions is in the wrong position. Therefore, when some alarms with unknown fault causes appear, be sure to check the switch position under each working mode. For the repair of CNC machine tools, it is important to find problems. Especially the external faults of CNC machine tools. Sometimes the diagnosis process is complex, but once the problem is found, it is relatively simple to solve. There are also some faults that do not produce fault alarm information, but the action cannot be completed. At this time, it is necessary to analyze and judge according to the maintenance experience, the working principle of the machine tool and the operation condition of PLC. The following two principles should be followed for external fault diagnosis. First of all, master the working principle and action sequence of the machine tool. Secondly, be able to use PLC ladder diagram. Cavonic company, the NC system located in Engel, Germany, has launched the status display function of iBT process or the external programmer to monitor the operation status of PLC. Generally, as long as the above principles are followed and care is taken, the NC fault of an experimental machine usually adopts hydraulic oil will be eliminated in time

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