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Characteristics and maintenance ideas of imported CNC machine tool equipment

Some people think that imported CNC equipment is easy to use and difficult to repair, which is mainly caused by insufficient understanding of its characteristics. To maintain imported CNC equipment, we should first recognize its characteristics, and carry out maintenance ideas for these characteristics, which is beneficial to accurately and quickly judge the fault.
1. Don’t be blindly superstitious about the quality of imported CNC equipment

Most of the imported CNC equipment is the product of today’s most cutting-edge scientific and technological applications, but due to the hasty launch of the manufacturer, there is not enough timeliness test, and it is inevitable that there are imperfections in design and manufacturing. The cylinder bore honing machine purchased from GEHRING company in Germany adopts advanced CNC hydraulic servo technology to better solve the closed-loop control of anilox angle, depth, cylinder bore diameter and cylindricity. The company is a well-known and world-renowned company, and its newly developed laser honing technology is being tested at the Mercedes-Benz Automobile Plant and is known to be very successful. But the equipment produced by such a well-known company, after more than a year of use, often inexplicably sudden interruption of operation, equipment shutdown and other failures. Sometimes it reboots and then it goes back to normal, sometimes it takes several iterations to get normal, sometimes there is no problem for a period of time, and sometimes it has problems in a row. THE ALARM MESSAGE SHOWS THAT THE “SYSTEM COMMUNICATION” SYSTEM COMMUNICATION IS FAULTY.

This phenomenon is commonly referred to as a “soft failure”. At first, it was suspected that it was caused by power grid noise and harmonic interference, so the quality of the power grid was tested. The test report shows that the harmonics of the power grid exceed the standard, and it is recommended to filter it. In general, the harmonic quality of the power grid is mostly exceeded. Grid interference is only the external cause, and the overall anti-interference performance of the system is the internal cause. Most of the imported CNC equipment has a simple power grid noise filtering technology, and the problem occurs after more than a year of use, indicating that the system can resist external interference. Nowadays, either the external interference has become stronger, or the anti-interference performance of the system has deteriorated. Judging from the normal operation of other imported CNC equipment in the factory, it is likely to be a system problem. During the test of the GEH A25 module, it was found that the module had a barrier when the module was turned on and communicated, the connection speed was slow, and the anti-interference performance became poor, but it was ignored by the host. After replacing a new module, the equipment runs stably and the fault disappears.

It turns out that this CNC-GOP system is a patented product developed by GEHRING company and SIEMENS company, with strong special functions, convenient control and stable performance. Because it is a newly developed system, it has not passed enough aging tests, and the anti-interference and stability are poor. In fact, there are many manufacturers at the forefront of equipment manufacturing technology have similar problems. Therefore, we should not blindly worship Western high technology, and we must see that even advanced technology is still developing, and there may still be defects. The more advanced the technology, the more likely it is to be flawed. When maintaining imported CNC equipment, we must not only admit its technological advancement, but also see its shortcomings realistically.

Second, it is necessary to read the alarm information analytically

The control part of the CNC system of imported equipment is rigorously designed, and a seemingly small anomaly will also be included in the alarm entry, and it is possible to stop the machine. In the actual repair process of imported CNC equipment, reading the alarm information is the most basic and most convenient way to seek rapid repair. But not every piece of information is credible, and every piece of information can be used out of the box. In a wide variety of alarm information, many may be useless for maintenance and may even play a misleading role, we should be good at extracting the essence from this information, to keep the false and true.   For example, the CNC cam grinder produced by the German SCHAUDT company is a CBN grinder that grinds cam peach shapes. Every time you turn it on, there will be a whole bunch of alarms. In fact, it is all just started, and there are many preparations that have not been met for the time being, which is of little practical significance.

At one point, the machine alarm shows that the “Filter of oil dirty” hydrostatic system filter is dirty. The spindle slide table of the equipment adopts hydrostatic floating guide rails. Remove the filter and clean it, but it still alarms after installing it; I took a new filter and installed it, but the alarm still couldn’t be eliminated. I carefully checked the PLC alarm code, and found that the fault alarm condition was that the pressure sensor of the hydrostatic floating guide rail was not working. The explanation for the fault design is that when the pressure sensor does not sense pressure, it is understood that the filter is blocked. But upon closer inspection, the filter is good, and it is precisely the pressure sensor that is faulty, and it should have sent a signal but did not send a signal.

The given alarm information is obtained by the designer based on PC simulation, not his years of experience in on-site maintenance, but often designed according to conventional logic, with the designer’s personal understanding of the simulation results. However, the occurrence of failures is often unexpected, and it is still necessary to reason and judge according to the failure phenomenon and random data. The correct attitude towards the alarm information provided by the machine is: never distrust, but not all of it. Don’t trust the alarm information, and don’t fall into the trap of false alarm information.

Third, when the machine tool is first used, it is necessary to make a complete backup

Most of the imported CNC equipment applies modern microelectronic numerical control technology and uses PC for management, it should be said that the use of PC to manage CNC-PLC and OP system, the operation performance and maintainability of machine tools have been greatly improved. But if you forget to back up in time, it will cause trouble if the machine tool loses programs or parameters. Especially when various computer viruses are rampant, it is more necessary to back up the PC system.

After a holiday, an imported CNC equipment was turned on and the OP panel signal light flashed to alarm. After inspection, it was confirmed that all the internal CNC and PLC parameters of the SIEMENS system were missing. The program was then restored, and the data such as optical discs and floppy disks brought in the imported data were imported into the system, but the machine still could not operate. It turns out that most of these materials are the backup made by the manufacturer when leaving the factory, and after trial operation and debugging and on-site operation, some procedures, especially most of the parameters, have been greatly modified. In particular, the SIEMENS system requires the signing of the user agreement after the program is written in accordance with the requirements of European safety standards. If you don’t have an up-to-date backup at hand and you’re not familiar with the recovery system, you’ll be very reactive.

How can I avoid being passive when I lose a program? It’s about preparing for the worst-case scenario – hard drive corruption. When the hard drive is damaged, all efforts are impossible. Of course, it is also possible to remake a new system hard disk, but most of the hard disks in imported CNC equipment are non-standard. Some can be replaced with laptop hard drives, but this attempt is not very sure of success. Especially for automobile manufacturers, the equipment is required to be repaired in the shortest possible time, and it is impossible to give too much time to do hard disk recovery work.

In order to deal with the possible sudden loss of system programs, there are several effective methods: (1) Make a complete backup of the D disk of the PC hard disk, and it is necessary to mark the file name, product name, parameter type, date and other important identifiers. This is the most basic and convenient backup method, and can be restored immediately in the event of loss of machine programs or parameters. The disadvantage is that if the PC itself fails, it will not be possible to restore the program.

(2) In the D drive of the PC, make a GHOST backup to the system disk C disk. This is a simple and efficient way to deal with PC system failures (including virus damage), and sometimes all antivirus methods are not effective in restoring the system disk C drive GHOST once. GHOST USES V 7.50 TO RUN BETTER UNDER DOS.   (3) BURN THE GHOST BACKUP OF THE PC HARD DISK CONTENT INTO THE DISC. This method is safe and reliable, and it is a good way to back up files off-camera.

(4) Copy the hard drive. This is the safest and most reliable method. Buy a new hard disk that is exactly the same as your PC, keep it properly after copying it, and replace the backup hard drive with a backup hard drive in case of PC hard disk failure. The advantage is that it is fast and reliable, and the disadvantage is that it is costly.

Fourth, comprehensive and systematic consideration, scientific reserve of spare parts

In order to ensure the normal operation of imported CNC equipment in production, it is advocated to repair damaged devices by yourself. However, CNC devices generally have high technical content, most of them are protected by intellectual property rights, and cannot be easily repaired, so necessary spare parts must be reserved. The size of the spare parts reserve and the selection of varieties have always been a controversial topic, and the reserve is too large to occupy too much capital, forming a waste; The reserves are too small to meet the production needs. The spare parts reserve of imported CNC equipment can be determined according to the following factors:

(1) The reserve amount generally does not exceed 5% of the price of the equipment at the time of purchase, of course, this is a reference amount, and it should also depend on other factors of the equipment.

(2) Refer to the mechanical and electrical complexity coefficients of imported CNC equipment. If the complexity coefficient is large, the corresponding reserve can be slightly larger, and vice versa, it can be slightly smaller.

(3) Try to choose the CNC system of the same manufacturer when purchasing, which can greatly save the cost of spare parts.

(4) There is a difference in the software and hardware of imported CNC equipment. For products developed by some manufacturers, they should be stocked as much as possible according to the supply situation. Because these spare parts usually have narrow supply channels and long procurement cycles, they are “monopoly products”, and it is necessary to be “prepared”.

(5) Reserve according to market supply. Products such as SIEMENS and FANUC have sufficient market supply and can be appropriately reserved according to their procurement and delivery dates. If it can be purchased in the short term, the purchase can be suspended, and if the delivery time is longer, it can be purchased appropriately.

(6) Determine the amount of spare parts reserve according to the production output. Spare parts reserves, in the final analysis, are “insurance investment” to ensure that normal production is not interrupted, the larger the output, the greater the “insured amount”, which is in line with the laws of economy. The reserve of two-shift production should be larger than that of single-shift production, and on the contrary, an appropriate reduction can be considered.

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