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Troubleshooting Example 1
The CNC machine has the following failures: the MPG can sometimes operate, sometimes fail to operate, or simply cannot work. The supplier stationed in Ho Chi Minh City sent experts back and forth to change the MP4 on site four times. The last time even replaced the IPC at any cost, but the problem still exists. Experts insist that the MPG was tested on the same type of machine tool in China and there is no problem. This makes all parties concerned very annoyed and has become a thorny issue in enterprise equipment.
We suspect that the electromagnetic environment of the mold shop has interference with the machine tool, and it is also suspected that there are certain design or process defects in the CNC engraving machine that are susceptible to interference. After observing and analyzing, the workshop wall and roof (foam insulation layer lined with the shop floor) are simple structures of color steel plates and can easily reflect electromagnetic waves; there are many facilities in the workshop, such as the processing center of Beijing Institute of Electrical and Mechanical Technology, GF AgieCharmilles, etc. Pulse electric discharge machine, Suzhou Sanguang's wire cutting machine, CNC machine tools such as numerical control lathes of Shenyang Machine Tool, and other Chinese companies' internal/external cylindrical grinding machines, tool grinding machines, variable frequency welding machines, band saws, and precision coordinate measurement Machines, Guilin Longmen Grinder with PLC expansion configuration, British high-precision high-speed scanner and Ningbo Haitian 650 large-scale injection molding machine, as well as two Chinese-made drilling machines and multiple power tools. When all kinds of machine tools in the workshop are in operation, the contactor and the brushed motor will generate spark interference. The interference of the electric processing machine and the welding machine is more serious, and its interference spectrum is very wide, the harmonic components are abundant, and the carrying interference energy is very large. Interference electromagnetic waves are superimposed on multiple reflections on the color plate surface and the roof, which will be strengthened in certain spectral bands. This is the external electromagnetic interference environment. However, due to the objective conditions in Vietnam, we cannot test the interference field strength of the workshop, so that accurate quantitative results can be obtained. Qualitative judgment of strong external electromagnetic interference can only be made based on experience. At the same time, we strictly inspected the CNC pulse and its output circuit. The signal cables inside the machine are all shielded - all use shielded cables, and one end is reliably grounded. However, the aviation plug and the MPG control box of the MPG cable were disassembled, and the cable sheathing was cut with a knife. The cable of the MPG cable was actually an unshielded cable (common multi-core cable), not to mention the single-end grounding. Then we used the same method to cut the 2nd MPG cable and also used unshielded cable. Based on past experience, we judge that this is the internal reason for the failure. The external electromagnetic interference signal is from the cable to the system signal, and it is superimposed on the small signal output circuit of the MPG (the output 5v pulse goes to the I port of the industrial computer), and then the input port of the IPC gets the error message.
We finally found the real cause of the malfunction that prevented the MPG from working properly. We asked the suppliers of CNC engraving machines to re-provision the new hand veins with shielding and good single-end grounding. After arrival, after appearance inspection, the transportation is not damaged, the cable jacket is bright and bright, and the model specifications are correct; the aviation plug inspection cable has a shielding structure and the single end is reliably grounded. After the replacement, the fault disappeared completely. The computer screen showed clear data in the three-dimensional coordinate system. The wheel of the MPG was rotated and the data immediately showed the exact position of the new coordinates in real time. The machine finally returned to normal operation after a period of downtime.
This example summarizes: The MPG is an important part of the CNC engraving machine. Now most NC machines have MPGs and as a standard configuration, it can even be said to have become an indispensable and important part. We believe that if there are strange irregularities in the function of the MPG (or other components) of the CNC machine under a complex electromagnetic environment, we should focus on the electromagnetic environment at the site, if there is electromagnetic interference, and then check the equipment easily. The site of the disturbance. Using this method, it is eliminated in a targeted manner, and it is easy to receive short-term and quick results. This failure was eliminated many times in a factory in Vietnam. In addition, external factors such as the quality of the power supply and whether the grounding meets requirements cannot be ignored.
At the same time, we hope that the CNC machine tool manufacturing plant will strengthen the design of the system's anti-interference performance when designing electrical and electronic circuits inside and outside the CNC system. Objectively speaking, some domestic companies have done relatively well. For example, other types of CNC machine tools introduced by the factory from China have always been able to work normally under the same strong electromagnetic interference. The reason is that these companies are relatively rich in funds and technical strength, corporate standardization work is in place, and the quality management system is relatively high. However, in individual companies, the anti-jamming design is often overlooked. For example, in this example, manufacturers use unshielded cable. Different countries have different economic developments, and plant exteriors and other external conditions are generally not the same, such as the standard factory building and the above-mentioned color steel plate plant (according to the author's knowledge, this kind of simple plant is a lot in the third world countries). The electromagnetic environment will be very different (sometimes even considering the country's power quality and various related factors such as grounding and climate). Our CNC machine tools can only work steadily under a variety of complex electromagnetic environment and climate environment, and can truly and effectively occupy the domestic and international market of CNC machine tools, and win the trust of users at home and abroad.
Troubleshooting Case 2
The computer numerical control engraving machine suddenly appeared a computer alarm signal, Y axis can not be reset to the origin, the computer displays:
The origin signal cannot be found on the Y axis origin search
The Y axis has not been returned to the origin
By examining the origin signal circuit, we found that there was no problem in the smoothness of the line and that all relevant cable plugs/sockets were also in good contact. However, it was found that the LEDs of the Y-axis magnetic induction switch (model: PS17-5DN, produced in Korea) were not emitting light normally. When the driver arrived at the sensing area, the LED light was normal; however, the LED was still slightly bright after removing the screwdriver. At this time, the correct state of the LED should be off, that is to say the Y-axis magnetic induction switch is not completely off at this time, there is still a signal output, and its RMS level exceeds its flip threshold level, causing the computer to alarm . After the arrival of the same type of magnetic induction switch provided by domestic suppliers, the appearance of the inspection was not damaged by transportation and the model specifications were verified correctly. After replacement, check that the wiring is correct (as long as the three wires of the same color are mated and insulated). Power on the system, with a magnetic screwdriver proximity sensor switch sensing parts, switch LED immediately normal light; the other hand, remove the screwdriver LED immediately extinguished, you can determine the magnetic sensor switch signal output back to normal.
Then Vietnamese maintenance personnel reported that the Y-axis could return to the origin. However, there is always the phenomenon of overshoot in the +Y direction after each operation. We have observed that many of the CNC engraving machine's buttons are jog-type. It works on the rising or falling edge of the pulse, which is totally different from the ordinary switch level control used by Vietnamese maintenance personnel, while the Vietnamese maintenance personnel It is assumed that the button must be pressed until the Y-axis returns to its original position. In fact, when the button is pressed, the computer continuously receives an external interrupt request signal (from the pressed button), so that the Y axis can not stop after returning to the origin, but can only be reversed - that is, move in the +Y direction, and +Y appears. Overshooting direction. After we explain, press the button Y axis to start immediately, execute the zero point return command, and the machine tool fully returns to normal.
This example summarizes: Maintenance of CNC machine tools seems to be difficult for general maintenance personnel, in fact, as long as it masters its structure, is familiar with the physical meaning of its various display signals, is good at analyzing the flashing of various signal LED, for example, is often Bright or not bright? Is it slightly bright or shiny, regular or random? Can solve the problem correctly. After fully understanding the lighting status and physical meaning of the above-mentioned various LEDs, the correct judgment can generally be obtained. In this example, the troubleshooting process is actually not even used by the multimeter, and a real fault is quickly found. Where Therefore, I believe that maintenance of CNC machine tools is not difficult, as long as the correct method to master often will do more with less, and sometimes even more than the maintenance of ordinary electrical and electronic electrical circuit even more convenient!
Two Cases of Troubleshooting of CNC Engraving Machine in Mold Shop
Editor's note: Yu Honghu's engineer is currently advising the director of a newly opened Vietnamese state-owned plastic mold factory in northern Vietnam. The situation in Vietnam is rather special, and the quality of maintenance personnel is generally low. High-quality supporting components must be supplied by Chinese manufacturers and cannot be guaranteed in time. Recently, a Mell-5060 type CNC engraving machine imported from China recently failed. Yu Gong recorded the method and process of troubleshooting 2 cases of CNC engraving machines, hoping to give it to Chinese experts working in the third world. A reference, but also for Chinese domestic, especially in the underdeveloped regions of the Midwest to engage in equipment maintenance and technical personnel to provide some reference.