In order to improve the use of CNC machine tools, combined with the maintenance principles of CNC machine tools, this article discusses the general methods for the maintenance of CNC machine tools. The author sums it up as four methods: “look, smell, ask, and cut.” steel metal
That is, using the human sense organs such as hands, eyes, ears, and nose to find the cause of the malfunction. This is one of the simplest and straightforward methods.
When a CNC machine tool fails, it is first necessary to find out what happened and how it happened. If the fault can be reproduced, the process of the fault should be observed. Only knowing the first-hand situation can facilitate the elimination of the fault. steel metal
At the same time observe whether there is mechanical damage; and whether there are traces of burning, whether the resistance and wire have been discolored; whether there is abnormality in the operation and sealing parts, such as splashes, drops, spills, oil, smoke, Mars, etc.; Whether the relay trips, whether the fuse is blown, whether the power supply of the machine tool is missing, whether the three phases are severely uneven, whether the voltage of the machine tool is normal, and whether the parts on the electrical component are detached, disconnected, stuck, loose joints, etc.; Is it right? The operator’s processing procedures are correct. This step is the most intuitive for the maintenance inspection of CNC machine tools, and it is also the most important step to test the maintenance technician’s familiarity with the hardware construction of the machine tool.
Identify the presence or absence of odors. When the moving parts of the machine tool are violently rubbed, the electrical insulation layer will be burned, and the burnt smell of oil, smoke, gas, and insulating materials will also be generated. When the machine tool discharges, it will produce ozone and hear the discharge sound. steel metal
That is to say, when the machine tool fails. In the numerical control processing, it is best to formulate strict management measures, which stipulates that the operator can make detailed records in the event of a fault. In this way, it is possible to prevent the maintenance personnel from being around and accurately reflect the specific circumstances of the fault. When a numerically-controlled machine tool fails, it is necessary to stop the machine tool and protect the site. The operator should record the failure as detailed as possible. The important information must be observed and recorded in detail.
For example: the phenomenon at the time of failure, the location of the failure, the condition of the machine when the failure occurred, and the condition of the control system. If a fault occurs in the automatic machining mode, the machining program number at the time of the fault, the block number at which the fault occurred, and the tool number to be used for machining should be recorded. If there is a fault such as a machining accuracy error or an excessive contour error, the number of the workpiece being machined shall be recorded and unqualified workpieces shall be retained for specific analysis. In the event of a fault, if the system has an alarm display, the system’s alarm display and alarm code should be recorded. If a fault occurs during the machining of a part, the probability of a failure occurring when processing the same type of workpiece should be recorded. steel metal
That is to diagnose the fault phenomenon, so as to carry out maintenance, this step is also the most important step for maintenance of CNC machine tools.
Which can be divided into the following specific steps to complete.
4.1 system parameter inspection method
Now that the self-diagnosis function of the operating system of CNC machine tools has become stronger, most of the failures of CNC machine tools can be diagnosed and corresponding measures taken. When the CNC machine tool fails, sometimes the alarm information is displayed on the display. Sometimes there are alarm devices on the numerical control device, the PLC device, and the drive device. For example, the alarm light may flicker and beep. At this time, the maintenance manual must first be checked to see the corresponding parameter settings. Loss or incorrect setting of system parameters can cause changes in the machine’s performance or failure. For example, the FANUC system machine tool movement in the machine tool rest stop and the screen shows 500,501 alarm, query the parameter manual that the corresponding parameters for the storage stroke limit positive and negative limit exceeded, then you can change the machine to manual shaking Tool rest to the correct range of travel and correct the parameters, the alarm can be lifted. steel metal
4.2 reset machine tool method
During processing, due to the system alarm caused by the instantaneous fault, the hardware can be reset or the system power can be turned on and off in order to clear the fault. If the system working memory area is out of order due to power down, plugging out the circuit board or battery undervoltage, The system must be initialized and cleared. Before the removal, attention should be paid to the copying of important data. If the fault cannot be eliminated after the initialization, perform the hardware diagnosis.
4.3 Measurement Diagnosis
Measurement is the basic method for diagnosing equipment failure. We can use multimeters, oscilloscopes, logic testers and other instruments to measure electronic circuits. For example, when determining the phase sequence of a three-phase power supply of a digital control system, a phase sequence meter may be used to measure the three-phase power line to the phase sequence table. When the phase sequence is correct, the phase sequence table rotates clockwise, and vice versa. It is also possible to use a two-channel oscilloscope to measure, and if the phase sequence is correct, the waveforms of each two phases are 120° out of phase. steel metal
4.4 Principle Analysis
When other maintenance methods are difficult to solve the fault, you can proceed from the working principle of the machine tool step by step to check, and finally find the cause of the fault. For example, the author once encountered a machine tool using the FANUC 0iTD system, which had turbulence when machining threads. According to the basic principles of position control of the CNC system, it was basically possible to determine the fault on the rotary encoder, and it was very likely to be feedback. The signal is lost. In this way, once the numerical control device gives the command position of the feed amount, the actual position feedback will always be incorrect. The position error cannot always be eliminated, leading to problems with thread interpolation. When the pulse encoder was removed for inspection, the filament inside the encoder was found to be broken, resulting in no feedback input signal, which was consistent with the principle analysis. After replacing the encoder, the fault was eliminated. steel metal
4.5 Device Switching Method
For some failures involving the control system, it is sometimes not easy to identify which part is in question. In the case of ensuring no further damage can be taken on parts or components suspected to be faulty, on the same spare part or on the same type machine tool or The same parts or components of other parts of the machine are replaced to determine if a fault has occurred. If the fault is removed after replacing the device, it can be determined as a result of device damage. If the fault persists, the device is proved to be in good condition and can be detected by other methods.
These are just some of the author’s brief understandings, among which there are many immature places. CNC machine tool repair technology as a new industry, its direct purpose and end result is to restore the normal operation of the CNC machine tools, so as to ensure the smooth use of equipment. The development of CNC technology can be described with each passing day. New equipment and new systems emerge one after another. As the personnel involved in maintenance technology of CNC systems, they should constantly learn and master new knowledge and technologies, and sum up them to make them available. Sex and sustainable development provide reference for the rest of the industry so that everyone can make progress together. steel metal