Large CNC machine tools have thousands of parts. If one of the components fails, it will lead to abnormal phenomena in the machine tool and the connection of wires and pipes. A slight negligence will lead to problems. In addition, large and heavy CNC machine tools are bulky and can be used without a constant temperature workshop, so environmental impact can easily lead to failures. Therefore, the problem of "difficult maintenance" of CNC machine tools is in front of us. There are so many CNC machine tools imported and manufactured in China, how to find faults and hidden dangers quickly and eliminate them in time? How do we maintain these expensive equipments? I think we must first have a high sense of responsibility and a spirit of not being afraid of difficulties; Second, master the numerical control technology I think we should read more books, ask more questions, remember more, think more and practice more (more than five), and gradually improve our technical level and maintenance ability to adapt to various complicated situations, solve difficult problems and maintain numerical control machine tools.
A, want to see more numerical control data; Read more and understand the characteristics and functions of various CNC systems and PLC programmable controllers; Understand the alarm and elimination methods of numerical control system; Understand the significance of parameter setting of CNC and PLC machine tools; Understand the programming language of PLC; Understand the method of numerical control programming; Understand the operation of the control panel and the contents of each menu; To understand the performance of spindle and feed motor and the characteristics of driver, a lot of numerical control data are often needed. what do you think? I think it is important to highlight the key points and make clear the ins and outs. The key point is to thoroughly understand the basic composition and structure of CNC system and master the block diagram. The rest can be read through, but each part should be understood and mastered. Because the internal wiring diagram of CNC system is quite complicated, the manufacturer does not provide it. So there is no need to elaborate. For example, NX- 154 four-axis five-linkage blade processing machine adopts A-B 10 system, so it is necessary to focus on the functions of each part, the functions of each board, the direction of interface, the meaning of LED lights and so on. Nowadays, there are many types of numerical control systems, which can be updated quickly. Different manufacturers and models often vary greatly. To understand its * * * and personality (particularity). Generally, people who are familiar with the maintenance of Siemens CNC system are not necessarily skilled in troubleshooting A- B system, so they should read more books and constantly learn and update their knowledge.
Read more electrical diagrams and digest them; For each electrical component, such as contactor, relay, time relay, etc. , as well as the input and output of PLC, should be marked on the electrical diagram one by one. For a simple example, for example, 1A 1 is a contactor started by hydraulic pump motor 1M, and the direction of its normally open and normally closed contacts is generally indicated on the drawing. Therefore, the normally open or normally closed contact 1A 1 on a corresponding page can be marked as "hydraulic pump motor on", and the electrical diagram of a large CNC machine tool has dozens or even hundreds of pages. To understand, that is to say, the function of each component takes a long time. Sometimes you may not know the function of this ingredient once or twice, so you should read more and digest it before writing. Therefore, the startup of the hydraulic pump motor 1M mentioned just now should also clearly indicate which external output of PLC drives the contactor 1A 1, and the context should be clear. However, some block diagrams in the electrical wiring diagram, such as the drivers of each shaft, are just a block diagram. As long as you know some control conditions (on-off conditions), you can study things that consider details when you have time. The electrical symbols in different countries are different, so we must first understand them clearly. For several thick PLC statement tables written by manufacturers, we should also read more, master its programming language, and make Chinese comments and translations on the basis of understanding. This can greatly save the time of troubleshooting in the future. If you wait for the fault to get familiar with the electrical diagram and PLC statement table, it will take a lot of time and often lead to wrong judgment.
Read more hydraulic and pneumatic diagrams and digest them deeply; For the mechanical grinding, sand making machine and hydraulic pneumatic diagram of CNC machine tools, we should understand their functions and context. And note on the drawings one by one, for example, the installation of accessories and tools for CNC gantry milling in Coburg, Germany is complicated, and the drawings need to be decomposed, such as which solenoid valve is used to lock the tools? What are the corresponding PLC outputs and inputs? The drawings indicate that electrical and mechanical actions should be carried out to the end, and at the same time, the parts closely related to machinery and electricity should be emphasized. For example, Italy INNSE CNC milling machine adopts electro-hydraulic proportional valve technology, and its function and function, especially its adjustment method and data, should be emphasized. The current of proportional valve and the corresponding pressure of balance pump under static and dynamic conditions should be understood, and the electromechanical integration should be mastered, so that the ability to solve problems will be great and you should read more foreign languages. Do not know foreign languages, especially English. It is impossible to understand a large number of foreign technical materials, and it is often not ideal to rely solely on translation. It is difficult to read the technical materials in foreign languages at first, and there are many new words. Read more and remember more, so many commonly used professional words, and it will be easy to read in the future. A competent maintainer should basically master language tools.
Second, ask more questions and consult foreign experts; If you can have the opportunity to go abroad for training or foreign experts come to your factory to install and debug machine tools, you'd better have the opportunity to participate. This is the best learning opportunity, because you can get a lot of first-hand information, as well as the methods and skills of machine tool debugging. For example, how to carry out electrical correction after laser measuring the accuracy of each axis. Ask more questions and find out what you don't understand. Through this period of time, there will be great gains, and many internal materials and manuals can be obtained (confidential to users). When machine tools are put into formal production, we should always keep close contact with relevant foreign experts. Through fax and E-MALL, it is very beneficial to ask for further solutions and related materials, solve the difficult faults of machine tools, and get special and special spare parts. At the same time, we should also keep good relations with the agents of CNC systems such as Siemens and FANUC, ask more questions, get further information and related spare parts of CNC systems in time, and also have the opportunity to take special courses on CNC systems.
After a fault occurs, ask the operator's master about the whole process of the fault. Don't ask, or just ask. This often leads to wrong judgment and complicates the problem. So you need to ask more questions, ask in detail, understand the whole process of the fault (beginning, middle and end), what alarm signal was generated, what components were operated at that time, what was touched, what was changed, and so on. On the basis of fully investigating the site and mastering the first-hand information, the fault problems are listed correctly, and half of the problems have actually been solved, and then analyzed and solved. For experienced and skilled operators, it is very beneficial to be familiar with machine tool operation, processing procedures and common diseases of machine tools, and to work closely with them to quickly troubleshoot.
Ask other maintenance personnel more; When other maintenance personnel are repairing the machine tool and you don't go, when they come back, you should also ask more, what happened just now? How did he rule it out? Ask him to introduce its elimination method. This is also a good learning opportunity. Learn from other people's correct troubleshooting skills and methods, especially from experienced old maintenance personnel, learn their skills and improve their knowledge and level.
Thirdly, it is necessary to record more relevant parameters, especially the adjusted parameters of the machine tool, such as CNC machine tool parameters, PLC machine tool parameters, PLC programs (which can be stored in disk), current, voltage, speed and other data of the spindle and feed motor. Also pay attention to the status of relays and contactors in the electrical cabinet during power-on and formal processing (on or off), and the status of all input and output LEDs of PLC (bright and dark, flashing), or record whether the status IB (input bit) and QB (output bit) of PLC on the screen are 0 or 1, for example, IB1=: 0000065438. Recording it in this way is of great benefit to the analysis and judgment of faults in the future. For example, the Z-axis motor current relay action occurred in SCHIESS CNC vertical lathe in Germany. By checking the PLC status (0, 1) of the Z-axis motor in normal operation and comparing it with the abnormal situation, the cause of the fault can be found out quickly, because the status of 1 comparison relays is wrong, and the fault can be eliminated immediately through adjustment.
It is also helpful for adjustment and judgment to record the state of hydraulic and pneumatic, as well as the pressure of various pressure gauges and barometers and the disconnection state of solenoid valves when hydraulic and pneumatic are formally processed or not. For example, the static pressure of OPENsIDE MASTERHEAD CNC milling machine in ingersoll, USA adopts double membrane technology, and there are more than 100 pressure measuring points, which directly affects the normal function of the machine tool. It is very important to record static pressure and dynamic pressure.
Take a notebook with you to record the daily faults and how to eliminate them. The human brain is easy to forget after a long time. "A good memory is better than a bad pen", so it is helpful to record them. We found that some faults of CNC machine tools often occur repeatedly, and they are always these faults. Just check how to solve it at that time, and the fault can be eliminated in a few minutes, which is both fast and good. Our company has "Running Diary of CNC Machine Tool" and "Troubleshooting Record Book of CNC Machine Tool". Need to record these two data, this is a complete historical file of CNC machine tools.
Fourth, think more, think more, broaden your horizons, sometimes tinkering, not calm enough, not analyzing well, and get to the bottom of it. I remember that once the Y axis of Kebao gantry milling machine suddenly stopped working, and the screen repeatedly showed the alarm that the grating of 136 1Y axis was dirty. At that time, we actually cleaned the grating ruler and grating head twice, but the machine stopped. It took several days to solve the problem and finally found the real reason. The reason is that there is something wrong with the wire between the Y-axis grating head and the EXE amplifier. Because the snake skin tube was bent for a long time when the Y axis moved, there was a bad position feedback line, and the machine stopped when it broke at a certain position. At that time, we only paid attention to the static state and ignored the dynamic state. The control loop of 132 1 has an open circuit alarm, but it has not attracted enough attention. Therefore, it is necessary to list all the alarms and faults that have occurred, make comprehensive judgment and screening, predict the maximum possibility of faults, and then eliminate them. "There is no doubt that there is no road and there will be another village in the future." Think more and show you the way.
Think more and know why. Often when troubleshooting, we don't find the real cause of the fault, and then the fault continues to occur. I remember that the spindle Sl of ingersoll rotor blade root slot milling machine had an "automatic stop" failure after 2 hours of operation. At that time, foreign experts changed a serial disk, and the problem seemed to be solved. But after more than a month, the old problem was committed again, and a spare disk for the serial disk was changed, but the cause of the damage was unclear. After careful inspection, with the help of oscilloscope, we found that the anti-peak voltage of the photoelectric coupler corresponding to the "start" command is particularly high. After adding a ground wire separately, the anti-peak voltage of photoelectric coupler is greatly reduced. Since then, there has never been an "automatic stop" fault, because the anti-peak voltage is too high and the photoelectric coupler gradually fails after a long time.
Think twice, think ahead, and make spare parts according to the frequency, repeatability and service life of electromechanical equipment. This is an important work to ensure the continuous normal operation of the machine tool, and it must be done well. At the same time, for some devices, with the delay and elimination of time, there are no lottery tickets in the market or they are very expensive to buy. What should I do? Consider in advance. For example, in the early 1980s, there was a photoelectric reader for CNC machine tools, which read the machining program in a circular way, or it could be selected into the original tape (machine tool setting data) in the way of SPOOL. If it can't be sent in, the whole machine tool will become a "dead" machine with serious consequences. Because we were one step ahead, we cooperated with relevant units and adopted floppy disk processor to solve this problem after many experiments, which ensured that the machine tool can be used so far. Think more, give reasonable suggestions to leaders, try to improve the external environment of CNC machine tools, find ways from the aspects of temperature, dust and humidity, and take measures such as installing power regulator, electric control box and air conditioning room to greatly reduce machine tool failures.
Fifth, more practice means more practice.
Practice more, dare to do it, and be good at it. For maintenance personnel, be bold and cautious, dare to do it, only talk, can't do it, can't repair CNC machine tools. But you should be familiar with the situation before you start work, and don't be blind, otherwise it will enlarge the fault and cause an accident with unimaginable consequences. At the same time, be good at doing it. First of all, you should be familiar with the contents of the operation panel and various menus on the machine and operate freely, because the operation of various models and systems is the same. At the same time, we should make full use of the self-diagnosis technology of CNC machine tools to deal with and solve faults quickly. Now, with the development of numerical control technology, the self-diagnosis ability is getting stronger and stronger. For example, A-B 10 system has special diagnostic software, which can diagnose online.
We should practice more, cultivate practical ability and master experimental skills. Sometimes some faults look so vague that we can't tell whether they are electrical or mechanical. For example, in Coburg gantry milling, the Z-axis ram always moves down and gives an alarm. We adopted the "separation method" to completely separate the control of the electrical part from the original circuit. We remove the wire from the terminal of Z-axis DC motor and connect it to both ends of the motor with direct current (which can be given by AC 220V power supply through voltage regulator and rectified by four diodes). It is found that the motor can change the rotation direction according to the polarity change of DC, and the electrical fault is eliminated. After inspection, it was found that it was caused by the ram of mechanical friction plate. There are many other methods, such as "isolation method", "replacement method", "comparison method" and "knocking method", which can be used as effective means to help us find and eliminate faults. We should practice more and learn to use oscilloscopes, multimeters, online circuit detectors, short circuit detectors, computers, programmers and other related instruments to help us judge and check specific circuits, especially PLC programmers. This is very helpful for analyzing faults, especially complex faults, and solving problems.
It is necessary to practice more. When a component (such as selector switch, button, relay, etc.). If it is damaged in normal work and there are no spare parts for the time being, do it yourself as much as possible, and make the machine work normally by gluing or adopting temporary special methods until the spare parts come. & ltBR & gt For example, there are five miniature pressure switches for clamping behind the second knife of the German VDF CNC cart, and two of them were accidentally damaged, so there are no spare parts. We use "short connection method" to make the contact of pressure switch meet the input conditions of PLC, so that the machine tool can work normally without giving an alarm. Sometimes the machine is used for a long time, and the positioning accuracy is poor, which leads to positioning alarm. If it is impossible to readjust the machine tool, the parameters of the machine tool can be temporarily modified and the "tolerance zone" can be added to make it work normally. In short, there are still many such methods.
Practice more and make up the board by yourself. Generally speaking, the circuit board of CNC machine tools has good reliability and extremely low failure rate. Generally, when checking CNC machine tools, don't doubt the problem of the board card first. For example, in Siemens 850 system, sometimes there will be 4 1NC-CPU alarm or 43PLC-CPU alarm. In fact, the board is not faulty, and it can be eliminated by repeated tests such as unplugging, NC initialization, and cold and hot start PLC. If it does prove to be a circuit board problem, it should be repaired. These boards (usually without drawings) are expensive, usually thousands to tens of thousands of yuan. For every enterprise, "spare parts are difficult" and the price is too expensive to buy. Therefore, the quality of CNC machine tool circuit board is extremely important. Once the circuit board is damaged without spare parts, it will inevitably stop production, which will seriously affect production. Sometimes the circuit board is just a small fault. It is not difficult to find the problem as long as you check it carefully. We have found some faults many times, such as capacitor leakage, circuit board virtual welding, short circuit and so on. Some circuit board faults are more complicated, but they can be repaired by instrument inspection as long as it takes time. However, some circuit boards are in serious condition, especially large-scale integrated circuits, which are difficult to maintain. In addition, the original equipment has no spare parts, so we can only buy spare boards in advance or send them out for maintenance. It is very beneficial to make up the board by yourself. On the one hand, it can save costs for enterprises and solve urgent needs. On the other hand, it is very beneficial to be familiar with electronic circuits and cultivate your own analytical judgment and hands-on ability. After more than ten years of maintenance practice, we also feel that the CNC machine tools designed by foreigners, especially large CNC machine tools, are not perfect, and there are also many problems and defects. Through our study and in-depth study of CNC machine tools, we found problems, boldly improved some problems and achieved good results. For example, Germany VDF CNC cart, the original design of two hydrostatic supports works as soon as it is electrified, and the hydrostatic pump runs continuously, which consumes electricity and shortens the service life of the imported pump. We reformed it through PLC, and added two switches, which can open or close two static pressure brackets as needed for only tens of yuan, thus prolonging the service life of imported pumps and saving more than 20,000 kwh of electricity throughout the year. In the original design of ingersoll impeller slot milling, the main head and the auxiliary head only have reverse milling, but not the same direction milling. When machining the 20th stage impeller of high and medium pressure rotor, due to the small impeller spacing, reverse milling cannot be used, and only one head can be used for machining. After our research, the bidirectional limit wiring is skillfully changed and the PLC program is added. As a result, almost no money was spent and the same direction milling was realized. Now two heads can be processed at the same time, the working efficiency is doubled, and the task of processing the rotor is completed 3-4 days in advance. Therefore, we should further tap the potential of CNC machine tools and give full play to its power to serve production.
Although the faults of CNC machine tools are complicated and changeable, as long as we take them seriously and cultivate a high-quality maintenance team with mechanical and electrical integration, we can master the maintenance skills and master them by reading more books, asking more questions, thinking more, practicing more and accumulating more experience, and mainly rely on our own strength to maintain, use and manage CNC machine tools.