How to repair, use and manage CNC machine tools well

As we all know, CNC machine tools are the crystallization of the integration of modern high-tech machines, electricity, light, and gas. The electricity is complex, the pipelines are intersected, and the CNC systems are varied. The products are not interchangeable from the 1970s to the 1990s. Similarly, especially large and heavy CNC machine tools are expensive, each about several million dollars, and the installation and adjustment time is long (several months to more than 1 year). There are tens of thousands of components in a large-scale CNC machine tool. If one of the components fails, it will cause abnormal phenomena of the machine tool, as well as the connection of wires and the connection of pipes. A little negligence will cause problems. In addition, large and heavy CNC machine tools are bulky and used in the absence of a constant temperature workshop, and the influence of the environment can easily cause failures. For this reason, the problem of “difficult maintenance” of CNC machine tools is placed in front of us.
Our country has introduced and manufactured so many CNC machine tools, how can we quickly find faults and hidden dangers and eliminate them in time? How can these expensive equipment be repaired? I think that first of all, we must have a high sense of responsibility and the spirit of not being afraid of difficulties; second, we must strive to master CNC technology, and contact the author’s practice of maintaining CNC machine tools for more than ten years. Practice more (five more), gradually improve your technical level and maintenance ability, in order to adapt to various more complicated situations, solve difficult problems, and repair CNC machine tools.

One, read more

1. To read more CNC data
To read more, to understand the characteristics and functions of various CNC systems and PLC programmable controllers; to understand the alarms and troubleshooting methods of CNC systems; to understand NC and PLC machine tools The meaning of parameter setting; to understand the programming language of PLC; to understand the method of NC programming; to understand the operation of the control panel and the contents of each menu; There are a lot of information, what do you think? I think it is important to highlight the key points and figure out the ins and outs. The key point is to thoroughly understand the basic composition and structure of the CNC system and master the block diagram. The rest can be “toured” and read through, but each part of the content must be understood and mastered. Since the internal circuit diagram of the CNC system is quite complicated, the manufacturer does not provide it. Therefore, it is not necessary to find out in detail. For example, the A-B10 system is used on the NX-154 four-axis five-link blade processing machine tool. It is necessary to understand the function of each part, the function of each board, the whereabouts of the interface, and the meaning of the LED lights. Nowadays, there are many models of CNC systems and they are updated quickly. Different manufacturers and different models often have great differences. To understand its commonality and individuality (particularity). Generally, those who are familiar with the maintenance of SIEMENS CNC systems may not be proficient in troubleshooting A-B systems. Therefore, it is necessary to read more, keep learning, and update knowledge.
2. To see more electrical diagrams, digest electrical diagrams
For each electrical component, such as: contactor, relay, time relay, etc., as well as the input and output of PLC, it should be marked on the electrical diagram one by one. To give a simple example, for example, 1A1 is the contactor started by the hydraulic pump motor 1M, and the whereabouts of its normally open and normally closed contacts are generally noted below the figure. Therefore, the normally open or normally closed contact 1A1 on a corresponding page can be marked as hydraulic pump motor open, and there are dozens or even hundreds of pages of electrical diagrams for large CNC machine tools. To understand, it takes a long time to show the function of each component. Sometimes, the function of the component may not be clear after the first or second reading, and it is necessary to read more and then write it after digesting it. Therefore, when starting the hydraulic pump motor 1M just mentioned, it should also be clearly marked which external output of the PLC drives the contactor 1A1 to act, and the ins and outs must be clearly understood. However, some block diagrams in the electrical circuit diagram, such as the driver of each axis, are just a block diagram. As long as you know a certain control condition (on-off situation), you can study and consider the detailed things when you have time. The electrical symbols of each country are different, so it is necessary to understand clearly first. For the several thick PLC statement tables written by the manufacturer, you should also read more, master their programming language, and make Chinese annotations on the basis of understanding. This can greatly save the time for troubleshooting in the future. If you wait for a breakdown to get familiar with the electrical diagram and PLC statement table, it will take a lot of time and often cause wrong judgments.
3. Read more hydraulic and pneumatic diagrams and digest them in depth
For the mechanical, hydraulic and pneumatic diagrams of CNC machine tools, you must understand their functions and ins and outs. And indicate one by one on the drawing, such as the German COBURG CNC gantry milling accessories, the installation of the tool is more complicated, it is necessary to disassemble the diagram, such as which solenoid valve is used to lock the tool? What are the corresponding PLC outputs and inputs? Write it down on the diagram, in this way, from the electrical to the mechanical action, and at the same time, especially the parts that are closely related to the machine and the electricity should be understood. For example, the Italian INNSE CNC boring and milling machine adopts electro-hydraulic proportional valve technology, and its function and function, especially to understand its adjustment method and adjustment data, static and dynamic proportional valve current and corresponding balance pump pressure, understand both electricity and machine, mechatronics, and master a variety of skills, so that the ability to solve problems will be great up.
4. Read more foreign languages ​​and improve your professional foreign language reading ability
Do not know foreign languages, especially English. It is impossible to understand a large amount of foreign language technical materials, and it is often not ideal to rely solely on translation. Reading technical documents in foreign languages ​​is difficult at the beginning, and there are many new words. After reading and memorizing, there are only so many professional words in common use, and it looks fluent in the future. A competent maintenance personnel must basically master language tools. the

Second, ask more

1.Ask foreign experts more
If you 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 and methods and skills of machine tool debugging. For example, after measuring the accuracy of each axis by laser, how to make electrical corrections, etc. If you don’t understand, you need to ask more questions. Through this period of time, there will be great gains, and a lot of internal materials and manuals (which are kept confidential to users) can be obtained. After the machine tool is put into formal production, it should also keep in close contact with relevant foreign experts. Through FAX and E-MALL, it is very beneficial to inquire about further solutions and related materials to solve difficult machine tool failures, and to obtain special and special spare parts. You should also maintain a good relationship, ask more, and you can get further information and related spare parts of the CNC system in time, and you can also have the opportunity to participate in special learning classes about the CNC system.
2. After a failure occurs, you should ask the operator about the whole process of the failure. Don’t just ask, or just ask casually. In this way, you will often not get correct on-site information, which will cause wrong judgments and complicate the problem. Therefore, Ask more, ask in detail, understand the whole process of the fault (beginning, middle, end), what alarm number was generated, what components were operated at that time, what was touched, what was changed, and what was the external environment? On the basis of fully investigating the site and mastering first-hand materials, correctly list the fault problems, which has actually solved half of the problem, and then analyze and solve it. For experienced and skilled operators, They are familiar with machine tool operation, processing procedures, and common diseases of machine tools. Close cooperation with them is very beneficial for rapid troubleshooting.
3. Ask other maintenance personnel more
When other maintenance personnel are repairing the machine tool and you are not there, after they come back, you should also ask more, what happened just now? How was he ruled out? Ask him to describe his method of elimination. This is also a better learning opportunity. Learn other people’s correct troubleshooting skills and methods, especially learn from experienced old maintenance personnel, and learn their skills to improve your knowledge and level.

Third, remember more

1. To record various relevant parameters
Focus on recording various relevant parameters after the machine tool is adjusted, such as NC machine parameters, PLC machine parameters, PLC program (the above can be stored in the disk), as well as the spindle and each cutting motor Current, voltage, speed and other data. Also write down the state of relays, contactors, etc. in the electric cabinet during power-on and formal processing (closed or disconnected) and the state of all input and output LED light-emitting diodes of the PLC (bright and dark, flashing) or record whether the PLC status IB (input bit) and QB (output bit) on the screen are 0 or 1, such as IB1=: 00000001, that is, I1.0=1, I1.1-1.7=0. Recording it in this way is of great benefit for future analysis and judgment of faults. For example, the Z-axis motor current relay of the German SCHIESS CNC vertical lathe operates. We compare the PLC state (0, 1) when the Z-axis motor is working normally with the abnormal situation, and quickly find the cause of the fault. The reason is that there is only one comparison The state of the relay is wrong. After adjustment, the fault is eliminated immediately. ( all rights reserved)
2. It is necessary to record the hydraulic and pneumatic status
. Also record the pressure of various pressure gauges and air gauges and the suction and disconnection status of the solenoid valve when the hydraulic and pneumatic are in formal processing or not, which is also helpful for adjustment and judgment. very big. For example, the static pressure of INGERSOLL OPENSIDE MASTERHEAD CNC boring and milling machine in the United States adopts double-film technology, and there are more than 100 pressure measurement points.
3. Take a notebook with you, and record the failures that occur every day and how to eliminate them one by one. People’s brains tend to forget after a long time. “A good memory is worse than a bad pen.” The benefits of recording great. We found that the faults of CNC machine tools often appear repeatedly, and these faults are always there. Just check how to solve them at that time, and the faults can be eliminated in a few minutes, which is fast and good. Our company has a “CNC Machine Tool Operation Diary” and a “CNC Machine Troubleshooting Record Book”. These two books should be recorded well. This is a complete historical file of a CNC machine tool.

Fourth, think more

1. Think more, broaden your horizons
Often when you are repairing, you are not calm enough, you don’t analyze well, and you get stuck. I remember that once the Y-axis of COBURG gantry milling stopped suddenly during processing, and the 1361 Y-axis grating dirty alarm appeared on the screen many times. At that time, we cleaned the grating scale and the grating head twice in a matter-of-fact manner, but it still stopped. It took several days to solve it, and finally found the real reason. The reason is that there is a problem with the wire between the Y-axis grating head and the EXE amplifier. Because the snake tube is bent for a long time when the Y-axis moves, one of the position feedback wires is not working. Well, breaking off at a certain point causes the machine tool to stop. At that time, we only paid attention to the static state and ignored the dynamic state. There was a 1321 control loop open circuit alarm, but we did not pay enough attention to it. Therefore, we should list all the alarms and failures that have occurred, and conduct comprehensive judgment and screening by going from the outside to the inside, removing the false and saving the true, predicting the greatest possibility of failure, and then eliminating it. “The mountain is poor and the river is full of doubts and no way out, the willows are dark and the flowers are brightAnother village”, Duosi, pointed out the direction for you.
2. Think more, know why
Often when we troubleshoot, sometimes we fail to find the truth of the fault The reason, the failure continued to occur after that. I remember that the INGERSOLL rotor blade root groove milling machine, the spindle Sl had a failure of “automatic stop” after running for 2 hours. At that time, foreign experts replaced a sequence board, and the problem seemed to be solved, but after more than one A month later, the old problem was committed again, and the backup board of the sequence board was replaced, but the cause of the damage was not clear. We checked carefully, and with the help of an oscilloscope, we found the photocoupler corresponding to the “start” command The reverse peak voltage is particularly high. After adding a ground wire alone, the reverse peak voltage of the optocoupler is greatly reduced. Since then, there has never been an “automatic stop” failure, because the reverse peak voltage is too high. After a long time, the optocoupler gradually fails.
3. Think more, think one step ahead
According to the frequency of failure, repeatability, and the life of mechanical appliances , do a good job in spare parts. This is an important job to ensure the continuous and normal operation of the machine tool, and it must be done well. At the same time, some devices have been delayed or eliminated over time, and they are no longer available in the market or are very expensive to buy. What to do? You need to consider in advance, for example, if there is a photoelectric reader for CNC machine tools in the early 1980s, the processing program can be read in by LOOP mode, and the original tape (machine tool setting data) can be selected by SPOOL mode. The entire machine tool will become a “dead” machine, and the consequences will be very serious. Because we thought ahead and cooperated with relevant units, after many tests, we used a floppy disk processor to solve this problem and ensure that the machine tool can be used so far. Think more, think in advance, give reasonable suggestions to the leaders, try to improve the external environment of the CNC machine tool, think of ways from several aspects such as temperature, dust, humidity, etc. Measures to greatly reduce the failure of machine tools. #p#page title#e#

Five, practice more, that is, practice more

1. It is necessary to practice more, dare to do it, and be good at it.
For maintenance personnel, they must be bold and cautious, and dare to do it. But do it after familiarizing yourself with the situation, and don’t be blind, otherwise it will expand the fault, cause an accident, and the consequences will be disastrous. At the same time, we must be good at hands-on. First of all, we must familiarize ourselves with the operation panel of the machine tool and the contents of each menu, so that we can operate freely, because the operations of various models and systems are the same. At the same time, we must make full use of the self-diagnosis technology of CNC machine tools to quickly deal with and solve faults. Now the more development of numerical control technology, the stronger the ability of self-diagnosis. For example, the A-B10 system has special diagnostic software, which can be connected to the Internet for diagnosis.
2. Practice more, cultivate your hands-on ability and master experimental skills.
Sometimes some failures look very vague, and it is difficult to distinguish whether it is an electrical failure or a mechanical failure. For example, such a failure occurred in COBURG gantry milling. Whether the Z-axis is rising or falling, the Z-axis ram will always move down and give an alarm. We adopted the “separation method” to completely separate the control of the electrical part from the original circuit, remove the wires on the terminal block of the Z-axis DC motor, and connect another DC power supply (which can be rectified by 4 diodes through a voltage regulator through an AC 220V power supply) Given) connected to the two ends of the motor, it was found that the motor can change the direction of rotation according to the change of the polarity of the direct current, and the electrical fault was ruled out. After inspection, it was found that it was caused by the slippage of the mechanical friction plate and the drooping of the ram. There are many other methods, such as “isolation method”, “replacement method”, “comparison method”, “tapping method” and other methods can be used as an effective means to help us find and eliminate faults.
3. Practice more and learn to use relevant instruments
Such as oscilloscopes, multimeters, online circuit testers, short circuit testers, computers, programmers, etc. can help us judge and check specific circuits, especially plc programmers, The computer should be used proficiently, you can freely input and output machine parameters, online test related status, system initialization, etc. This is of great help in analyzing faults, especially complex faults, and solving problems.
4. It is necessary to practice more and carry out “small reforms and small reforms”
Often when a certain component is damaged during normal work (such as selector switches, buttons, relays, etc.) and there are no spare parts, do it yourself as much as possible Legal and other methods to repair or use temporary special methods to make the machine tool work normally, and then restore it after the spare parts arrive. For example, there are 5 miniature pressure switches for clamping in the second knife back of the German VDF CNC cart, and 2 of them are accidentally damaged, and there are no spare parts. In line with the input conditions of the PLC, the machine tool can continue to work normally without alarming. Sometimes after the machine has been used for a long time, the positioning accuracy is poor, and a positioning alarm is generated. When the machine tool cannot be readjusted, the machine tool parameters can be temporarily corrected, and the “tolerance” zone can be increased to make it work normally. a lot of.
5. You need to practice more and repair the board by yourself
Generally speaking, the circuit board of CNC machine tools has good reliability and the failure rate is extremely low. Generally speaking, when you check the CNC machine tool, don’t suspect the problem of the board first. For example, in the Siemens 850 system, sometimes 41NC-CPU alarm or 43PLC-CPU alarm occurs. In fact, it is not that the board is faulty. It can be generally ruled out by repeated tests such as dismantling, NC initialization, and hot and cold start of PLC. likeWhen it does turn out to be a circuit board problem, fix it. These boards (generally without blueprints) are expensive, generally costing thousands to tens of thousands of yuan. For every enterprise, “spare parts are difficult” and the price is too expensive to afford. Therefore, the quality of CNC machine tool circuit boards is extremely important. , Once the circuit board is damaged and there are no spare parts, and it cannot be repaired for a while, it will inevitably stop and seriously affect production. Sometimes the circuit board is only a very small fault, as long as it is carefully checked, it is not difficult to find the problem. We have found many faults such as leakage of individual capacitors, false welding of the board, short circuit, etc. Some circuit board faults are more complicated, but as long as time is spent, through It can still be repaired by inspection with instruments; however, there are still some circuit boards that are in serious condition, especially large-scale integrated circuits, which are difficult to maintain. In addition, there are no spare parts for the original components, so we can only buy spare boards in advance or send them out for repair. Repairing the board by yourself is very beneficial. On the one hand, it can save costs for the enterprise and solve the urgent needs. On the other hand, it can “dissect the sparrow” to become familiar with electronic circuits, and it is very beneficial to cultivate one’s 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 the large CNC machine tools, are not perfect, and there are many problems and defects. Through our study and deepening of CNC machine tools, we found out where the problems were, boldly improved some problems, and achieved good results. For example, the German VDF CNC cart originally designed two static pressure brackets to work as soon as the power is turned on, and the static pressure pump runs continuously, which consumes electricity and shortens the life of the imported pump. We modified it through PLC, added 2 switches, and only spent tens of yuan, so that the 2 static pressure brackets can be opened or stopped arbitrarily according to needs, which prolongs the life of the imported pump and saves electricity throughout the year. More than 20,000 degrees. In addition, in the original design of INGERSOLL impeller groove milling, the main head and auxiliary head only have reverse milling, but no co-direction milling. When processing the 20th stage impeller of the high and medium pressure rotor, due to the small distance between the impellers, reverse milling cannot be used, so only one head can be used for processing. After our research, we cleverly changed the two-way limit wiring and added a PLC program. As a result, the same direction milling was realized with almost no money spent. Now the two heads can be processed at the same time, the work efficiency is doubled, and the task of processing the rotor can be completed 3-4 days in advance. Therefore, we need to 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 complex and ever-changing, as long as we take it seriously, we will cultivate a high-quality mechatronic maintenance team. , we will be able to mainly rely on our own strength to repair, use and manage the CNC machine tools well.

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