Common methods for detecting faults of numerical c

2022-07-23
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Common methods for detecting and detecting NC equipment faults common methods for NC equipment faults

now NC equipment is more and more widely used, followed by how to ensure the effective utilization of the equipment. When the equipment fails, it is necessary to restore the equipment to normal use as soon as possible. In order to solve this problem, first of all, maintenance personnel should have high quality. They should not only have rich professional knowledge, such as electromechanical integration technology, computer principle, numerical control technology, PLC technology, automatic control technology, drag principle, hydraulic technology, but also master the common sense of mechanical processing and simple programming of numerical control devices. In addition, they should have a certain level of English and be able to read English skills, At this time, the unit of a is m/s2. There shall be sufficient data, including mechanical, electrical and hydraulic drawings, machine tool parameter backup, system operation and maintenance manual, PLC ladder diagram, etc. There should also be a certain amount of spare parts. In addition, maintenance personnel shall have certain experience and master certain maintenance methods. The author has been engaged in the maintenance of numerical control equipment for many years, has accumulated some experience, and has summarized a set of methods for the maintenance of numerical control equipment, which are introduced as follows for reference

to find out the fault phenomenon

when the numerical control equipment has a fault, first replace the hydraulic oil to find out the fault phenomenon, ask the operator about the situation when the fault occurs for the first time, observe the process of the fault when possible, and observe under what circumstances, how and what consequences the fault occurs. Only when we know the first-hand situation can we eliminate the fault. If we understand the fault process clearly, the problem will be solved in half. Find out the fault phenomenon, and then according to the working principle of the machine tool and CNC system, you can quickly diagnose the problem and eliminate the fault, so that the equipment can return to normal use

for example, when a CNC cylindrical grinder with teachable III system of American Bryant company is used for automatic machining, the grinding wheel will grind off a piece of the dresser. In order to observe the fault phenomenon and prevent the accident from happening again, the grinding wheel is removed from the running machine tool. At this time, the fault phenomenon is observed again. It is found that in the automatic grinding process, the grinding is normal. After the workpiece is grinded, when the grinding wheel is trimmed, the grinding wheel is fed normally, and the grinding wheel dresser rotates very fast, and soon press the upper limit switch. If the grinding wheel is not removed at this time, the grinding wheel must hit the dresser again. According to the working principle of the machine tool, the grinding wheel dresser is driven by the e-axis servo motor, and the rotary encoder is used as the position feedback element. Under normal conditions, when the dresser is dressing the grinding wheel, the z-axis slide table drives the e-axis dresser to move to the dressing position, and the dresser swings 30 ° ~120 ° to trim the grinding wheel. We have observed the fault phenomenon for many times and found that when pressing the upper limit switch of axis e, the coordinate value of axis E on the screen was only about 60 °, while the actual position was about 180 °. Obviously, there was a problem with the position feedback, but the problem was not solved by replacing the position control board and encoder. After repeated observation and test, we found that when the e-axis dresser is at the edge of the z-axis, there is no problem in returning to the reference point and rotating and swinging. It is necessary to use the alarm information of the system

now the self diagnosis ability of the CNC system is becoming stronger and stronger. Most of the equipment faults can be diagnosed by the CNC system, and corresponding measures can be taken, such as shutdown, which can generally produce alarm display. When the numerical control equipment fails, sometimes the alarm information is displayed on the display, and sometimes there are alarm indications on the numerical control device, PLC device and drive device. At this time, it is necessary to analyze these alarm information according to the manual. Some of the alarm information can be used to directly analyze the sensor failure of the spring fatigue testing machine. The most important and common cause of the problem is the overload of the experimental force. Confirm the cause of the failure. As long as the content of the alarm information is clear, the failure of the numerical control equipment can be eliminated

for example, a CNC channel grinder with German Siemens 810 system will generate No. 1 alarm display "battery alarm power supply" after startup, which obviously indicates that the CNC system is powered off to protect the battery. After replacing the new battery (Note: the battery must be replaced when the system is powered on), reset the fault and restore the machine tool to use. Another CNC grinder with Siemens 3 system did not display on the screen after startup. After checking the CNC device, it was found that a light-emitting diode on the CPU board flickered. According to the manual, the flickering frequency was analyzed and it was confirmed that the power-off protection battery voltage was low. After replacing the battery, restart the system. LANXESS plans to further strengthen efforts in the future to eliminate the fault

for example, a CNC lathe with FANUC 0tc system in Japan gives an alarm No. 2043, Display "hyd. pressure down ", indicating that the hydraulic system pressure is low. According to the alarm information, check the hydraulic system and find that the hydraulic pressure is indeed very low. Adjust the hydraulic pressure to restore the normal use of the machine tool.

the alarm information of other faults does not reflect the root cause of the fault, but rather reflects the result of the fault or other problems caused by it. At this time, the cause of the fault can be determined only through careful analysis and inspection. The following methods It is effective to detect such faults and some faults without alarm

use the PLC status display function of the CNC system

many CNC systems have PLC status display functions, such as the PC status function under the PC menu of Siemens 3 system, the PLC status function under the diagnosis menu of Siemens 810 system, and the PMC status display function of the dgnos param function of FANUC 0t system. These functions can be used to display the real-time status and contents of PLC input, output, timer, counter, etc. According to the working principle of the machine tool and the electrical schematic diagram provided by the machine tool manufacturer, some faults can be diagnosed by monitoring the corresponding status

for example, when a CNC lathe using FANUC 0tc from Japan breaks down once, it will give an alarm No. 2041 at startup, indicating that the x-axis exceeds the limit. However, it is observed that the x-axis does not exceed the limit, and the x-axis limit switch is not depressed. However, using the PMC status display function of the NC system, it is checked that the status of the PMC input x0.0 of the x-axis limit switch is "1", and the switch contact has indeed been connected, indicating that the switch has a problem, After the new switch is replaced, the machine tool fault is eliminated

for example, if a CNC lathe with Japanese Mitsubishi meldas L3 system fails once, the turret will not rotate. According to the working principle of the turret, when the turret rotates, the hydraulic cylinder floats the turret first, and then it can rotate. Observe the fault phenomenon. When the turret rotation button is manually pressed, the turret does not respond at all, that is, the turret does not float. According to the electrical schematic diagram, the output of PLC y4.4 controls relay K44 to control the solenoid valve, which controls the hydraulic cylinder to float the turret

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