Three in place principles in the most popular CNC

2022-08-09
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The principle of "three in place" in NC maintenance work

in order to adapt the NC maintenance work to the needs of the development of modern enterprises and improve the maintenance quality of NC equipment, we should achieve the following three in place: 1. Analyze the failure causes in place. In the past maintenance work, people used to take fault finding and troubleshooting as the content of maintenance work. However, this is only a part of completing the maintenance work. What is more important is to analyze and determine the cause of the fault, so as to take countermeasures to prevent the recurrence of similar faults. For example, our company has a CNC high-precision centerless cylindrical grinder manufactured by a German company. The PLC used is the product of Siemens company in order to minimize the impact of liquid on the stiffness of the whole machine. Less than a year after the machine tool was put into use, it will cause the in-depth adjustment of the world industrial pattern. Now an output drive transistor on the i/o unit of PLC was burnt out. As the equipment has not been out of warranty, the German manufacturer came to repair it. They only replaced the PLC output board, and when the machine tool operated normally, they quit work and returned home. As a result, about half a year later, the same fault occurred again. After our analysis, the load controlled by this output point is the grinding wheel automatic dressing feed control solenoid valve, the solenoid valve coil is DC24V, and the current is about 1.1a, while the rated continuous output current of the PLC output drive transistor is 0.5A, obviously, the load exceeds the rated value. It is the defect caused by the careless design of the machine tool. If we only replace or repair the PLC board, the same fault will occur again. Therefore, the circuit of machine tool must be improved

the degree of automation is very high. 2. Take measures in place. The so-called measures are to completely eliminate the cause of the failure, so that similar failures will not occur again. Measures in place refer to the effectiveness and reliability of measures. According to the principle of using mature technology or structure according to the existing conditions, pay attention to meeting the relevant national safety standards, and do not appear new unreliable links and generate new fault sources. There are many economically feasible measures in the above examples. Which one is better? The factors to be considered include: the maximum working frequency of the signal, whether the load form is resistive or inductive, the installation space in the electrical cabinet, the wiring space, the existing spare parts, etc. Based on the above factors, the method of adding relay drive is adopted. The relay coil is DC24V/40mA, the contact rated current capacity is 5a, the PLC I/O output rated current is 500mA, the relay coil load is 40mA and the relay contact rated current is 5a, the solenoid valve coil load is 1.1a, which is more than enough. Due to inductive load, relay coil freewheeling diode and solenoid valve coil freewheeling diode are set. After more than a year of operation, it has never failed again

3. Maintenance records should be in place. We stipulated that the specific contents of the maintenance record should include the following aspects: 1) fault phenomenon, 2) fault cause, 3) solution, 4) remaining problems, 5) date and downtime, 6) good dimensional accuracy) maintenance personnel. In addition, for improved and reconstructed machine tools, complete and accurate supplementary Drawings and relevant data are essential. In this way, in addition to the construction according to national standards in the transformation and maintenance, the wire number and device identification are available, which lays a good foundation for the maintenance of machine tools in the future. For example, in the example above, we have explained the changed circuit part on the electrical schematic diagram of the machine tool and supplemented the drawings, which will be very convenient no matter who will repair this machine tool in the future. Whether the "three in place" can be achieved directly reflects the working spirit of maintenance personnel, and is also the embodiment of technical quality. It is the basis for the standardization of maintenance work. Let us all take action to do a better job in the maintenance of CNC equipment

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