CNC machine tool repair technology as a new industry, its direct purpose and the end result is to restore the normal operation of CNC machine tools, thus ensuring the smooth use of equipment. CNC machine tools are an efficient automated machine tool, which integrates computer technology, automation technology. New technological achievements in various fields such as servo drive, precision measurement and precision machinery are an emerging mechanical control technology. Due to its good economic performance and high production efficiency, it is in an increasingly important position in production. However, due to the advanced nature of CNC machine tools and the instability of faults, most of the faults occur in the form of comprehensive faults. Therefore, the maintenance of CNC machine tools is difficult, and the maintenance work of CNC machine tools is not standardized, which makes CNC maintenance work in a kind of Chaos state, in order to improve the use of CNC machine tools, combined with the maintenance principle of CNC machine tools, this article will talk about the general method of maintenance of CNC machine tools.
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When a CNC machine tool fails, it is first necessary to understand the fault phenomenon, how it occurs and the process that occurs. If the fault can be reproduced, the process of the fault should be observed. Only when the first-hand situation is known can the fault be eliminated.
At the same time, observe whether there is mechanical damage; whether there are burning marks, whether the resistance and the wire have changed color; whether there are abnormalities in the running and sealing parts, such as spatter, falling off, spillage, oil, smoke, Mars, etc.; Whether the relay is tripped, whether the fuse is blown; whether the machine power supply is out of phase, whether the three-phase is seriously uneven, whether the machine tool voltage is normal, whether the parts on the electrical components are disconnected, broken, stuck, loose joints, etc.; Is it appropriate; the operator's machining program is correct. This step is the most intuitive for the maintenance inspection of CNC machine tools, and it is also a step to test the familiarity of the maintenance personnel on the hardware structure of the machine tool.
smell
Identify whether there is any odor. When the moving parts of the machine tool are severely rubbed, the electrical insulation layer will burn out, and at the same time, the oil, smoke, gas, and the burnt smell of the insulating material will be generated; when the machine tool is discharged, the ozone smell will be generated, and the discharge sound will be heard.
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That is, the situation when the machine tool fails. It is best to establish strict management measures during CNC machining, which stipulates that operators can make detailed records when they encounter failures. This can avoid the specific situation of the fault that can be accurately reflected when the maintenance personnel are not around when the fault occurs. When a CNC machine tool fails, the machine tool must first be stopped to protect the site. The operator should record the fault as detailed as possible. The important information should be observed and recorded in detail. For example, the phenomenon when the fault occurs, the fault location, And the state of the machine and the control system when a fault occurs. If the 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 used during machining should be recorded. If there is a fault such as excessive machining accuracy or excessive contour error, the workpiece number to be machined shall be recorded and the unqualified workpiece 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 it is a fault that occurs when machining a part, the probability of failure when processing the same type of workpiece should be recorded.
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That is to diagnose the fault phenomenon, so as to carry out maintenance, this step is also the most important step for CNC machine tool maintenance.
It can be divided into the following specific steps to complete.
4.1 system parameter check method
Now the operating system self-diagnosis function of CNC machine tools is getting stronger and stronger, and most of the faults of CNC machine tools can be diagnosed and corresponding measures are 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 will flash, beep, etc. At this time, first check the maintenance manual to see the corresponding parameter settings. Loss or incorrect settings of system parameters can cause changes or malfunctions in machine performance. For example, in the FANUC system automatic machining, the machine tool holder stops moving and the screen displays 500, 501 alarms. The parameter manual is queried to know that the corresponding parameter is the storage stroke limit positive and negative limit exceeded. At this time, the machine tool can be changed to the manual state. The tool can be released by correcting the tool holder to the correct stroke range and correcting the parameters.
4.2 reset machine method
During processing, due to system alarms caused by transient faults, hardware reset or powering on and off system power can be used to clear faults. If the system working storage area is chaotic due to power failure, plugging or unplugging the circuit board or battery undervoltage, The system must be initialized and cleared. Before cleaning, you should pay attention to the copying of important data. If the fault cannot be eliminated after initialization, perform hardware diagnosis.
4.3 Measurement Diagnostics
Measurement is the basic method for diagnosing equipment failure. We can use electronic instruments such as multimeters, oscilloscopes, and logic testers to measure electronic circuits. For example, when determining the phase sequence of the three-phase power supply of the numerical control system, the phase sequence meter can be used to measure, that is, the three-phase power line is connected to the phase sequence table. When the phase sequence is correct, the phase sequence table rotates clockwise, and vice versa. It can also be measured with a two-channel oscilloscope. If the phase sequence is correct, the waveform of each two phases is 120° out of phase.
4.4 Principle Analysis
When other maintenance methods are difficult to solve the fault, you can check the working principle of the machine tool step by step, and finally find out the cause of the fault. For example, I have encountered a machine tool using the FANUC0iTD system. When the thread is machined, the phenomenon of disordered teeth occurs. According to the basic principle of the position control of the CNC system, it is basically determined that the fault is on the rotary encoder, and it is likely to be a feedback signal. Lost, in this way, once the numerical control device gives the command position of the feed amount, the actual position returned from the feedback will always be incorrect, and the position error can never be eliminated, resulting in a problem with the thread interpolation. When the pulse encoder is removed for inspection, it is found that the filament inside the encoder is broken, resulting in no feedback input signal, which is consistent with the principle analysis. After the encoder is replaced, the fault is eliminated.
4.5 device exchange method
For some faults involving the control system, it is sometimes not easy to confirm which part is faulty. In the case of ensuring no further damage, it is possible to take the suspected faulty parts or components, using the same spare parts or the same type of machine or Replace the same parts or components in other parts of the machine to determine if a fault has occurred. If the fault is removed after replacing the device, it can be determined that the device is damaged. If the fault persists, the device is proven to be intact and can be detected by other methods.
CNC machine tool repair technology as a new industry, its direct purpose and the end result is to restore the normal operation of CNC machine tools, thus ensuring the smooth use of equipment. The development of numerical control technology can be described as ever-changing. New equipment and new systems emerge one after another. As relevant personnel engaged in CNC system maintenance technology, we should continuously learn and master new knowledge and technology, and summarize and summarize them to make them available. Sexual and sustainable development, providing reference for the rest of the industry.
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