Troubleshooting CNC machines is a complex and systematic process that requires maintenance personnel to have rich theoretical knowledge and practical experience. When a CNC machine fails, the first thing to do is to confirm the fault phenomenon. This includes checking the fault record, asking the operator about the entire process of the fault, and investigating the fault site to fully grasp the fault information.
The intuitive inspection method is the most basic troubleshooting method. By directly observing the situation before and after the fault occurs, some obvious problems can be found, such as whether the equipment has abnormal sounds, vibrations, smoke, etc. When diagnosing a fault, certain principles should be followed. First, you must understand the structural characteristics and working principles of CNC machine, and then check the possible causes one by one according to the fault phenomenon. There are many common types of faults in CNC machine, and the causes are also very complicated.
1. Electrical system failure: Check whether electrical components such as power lines, relays, and transformers are working properly.
2. Mechanical system failure: including wear of mechanical parts, improper installation, debugging errors, etc. These problems usually lead to mechanical transmission failures, friction of guide rail movement, etc.
3. Hydraulic problems: Failures in the hydraulic system may cause the machine tool to fail to work properly, such as damage to hydraulic components, hydraulic oil leakage, etc.
4. Pneumatic problems: Failures in the pneumatic system may cause the machine tool to fail to start or run normally, such as damage to pneumatic components, open circuit of pneumatic lines, etc.
5. Cooling problems: Failures in the cooling system may cause the machine tool to overheat, such as leakage in the cooling system, fan failure, etc.
6. Software problems: programming errors, software fault detection and repair, etc. Programming errors may cause machining accuracy to fail to meet standards, and software faults need to be diagnosed and repaired by professional tools.
7. Hardware problems: tool breakage, spindle overheating, travel switch failure, etc. These problems need to be solved by checking and replacing the corresponding hardware components.
When a CNC machinefails, the following ideas are generally used to troubleshoot:
When a CNC machinefails, maintenance personnel should not rush to handle it blindly. First, they should check the fault record and ask the operator about the whole process of the fault. After confirming that powering on the system is not dangerous, they should turn on the power and observe in person to determine the main fault information, including any abnormalities in the system, especially the alarm content displayed on the CRT, such as:
(1) What is the alarm signal and alarm prompt when the fault occurs
(2) If there is no alarm, what working state is the system in, what is the system working mode and diagnostic results
(3) In which program segment does the fault occur, what instructions are executed, and what operations were performed before the fault occurred;
(4) At what speed does the fault occur? What position is the machine tool axis in? How large is the error with the instruction value?
(5) Has a similar fault occurred before, are there any abnormal phenomena on the site, and does the fault occur repeatedly?
(6) Observe the appearance of the system and whether there are any abnormalities in the internal parts, etc.
When analyzing the fault, maintenance personnel should not only focus on the CNC part, but should also conduct a detailed inspection of the machine tool's power, mechanical, hydraulic, and pneumatic parts, and make a comprehensive judgment to formulate a troubleshooting plan to achieve the purpose of rapid diagnosis and efficient troubleshooting. When analyzing the cause of the fault, attention should be paid to:
(1) The thinking must be broad. Whether it is the CNC system, power part, or machine, hydraulic, gas, etc., all possible causes of the fault and each possible solution must be listed, and then integrated, judged, and screened;
(2) Based on an in-depth analysis of the fault, predict the cause of the fault and formulate a troubleshooting plan based on the content, steps, and methods of the inspection.
Based on the predicted cause of the fault and the predetermined troubleshooting plan, use the experimental method to verify, gradually determine the fault location, and finally find the root cause of the fault.
According to the fault location and possible causes, use reasonable troubleshooting methods to troubleshoot the fault and restore the performance of the CNC machine.
In order to accurately determine the fault location and troubleshoot safely and quickly, the following principles should be followed:
After the machine tool fails, the maintenance personnel should calm down and formulate an analysis plan before taking action. The maintenance personnel should first ask the machine tool operator about the process and status of the fault, and read the machine tool manual and drawing materials before finding and handling the fault.
After determining the plan, the faulty machine tool should be powered off and static state of the machine tool should be observed, tested and analyzed. After confirming that it is a non-vicious cycle fault or non-destructive fault, the machine tool can be powered on. Under the operating conditions of the machine tool, dynamic observation, inspection and testing should be carried out to find the fault. For malignant destructive faults, the danger must be eliminated before power can be turned on, and dynamic diagnosis should be carried out under operating conditions.
When the machine tool with a fault is powered on, you should first check whether the software is working properly. Some faults may be caused by the loss of software parameters or the operator's incorrect use and operation methods. Avoid dismantling the machine at the beginning, which may cause greater consequences.
CNC machines are mechanical, hydraulic, and electrical integrated machine tools, and their failures must be reflected in the three aspects of mechanical hydraulics and electricity. The maintenance of CNC machines requires maintenance personnel to master the principle of first the outside and then the inside, that is, when the CNC machinefails, the maintenance personnel should first use methods such as looking, smelling, listening, and asking to check one by one from the outside to the inside. For example: in CNC machines, the external travel switches, button switches, hydraulic and pneumatic components, printed circuit board plug sockets, edge connectors and external or mutual connection parts, electrical control cabinet sockets or terminal blocks, these electromechanical equipment connection parts, due to their poor contact, cause signal transmission failure, which is an important factor in the failure of CNC machines. In addition, due to the large changes in temperature and humidity in industrial environments, the pollution of components and circuit boards by oil or dust, and the vibration of machinery, etc., will have a serious impact on the connectors of the signal transmission channel. Pay attention to these factors during maintenance, and first check these parts to quickly eliminate more faults. In addition, try to avoid unsealing and disassembly at will. Inappropriate large-scale disassembly and disassembly will often expand the fault, cause serious damage to the machine tool, lose precision, and reduce performance.
Since CNC machines are advanced mechanical processing equipment with a high degree of automation and complex technology. Generally speaking, mechanical failures are easier to detect, while the diagnosis of CNC system failures is more difficult. Mechanical first, then electrical means that in the maintenance of CNC machines, first check whether the mechanical part is normal, whether the travel switch is flexible, and whether the pneumatic and hydraulic parts are normal. From experience, a large part of the failures of CNC machines are caused by mechanical failure. Therefore, before troubleshooting, first eliminate mechanical failures one by one, which can often achieve twice the result with half the effort.
Common problems often affect the whole world, while special problems only affect the local part. For example, if several feed axes of a machine tool cannot move, the common parts such as CNC, PLC, power supply, hydraulic pressure, etc. shared by each axis should be checked and eliminated first, and then the local problems of a certain axis should be eliminated. For example, the failure of the power grid or main power supply is global, so the power supply part should be checked first to see if the fuse is normal and the DC voltage output is normal. In short, only by solving the main contradiction first, the local and minor contradictions can be easily solved.
When multiple faults are intertwined and covered, and it is difficult to start for a while, the easy problems should be solved first, and then the more difficult problems should be solved. Often in the process of solving simple faults, difficult problems may become easy, or when you are inspired by the elimination of simple faults, you will have a clearer understanding of complex faults, and thus have a solution.
When eliminating a certain fault, you should first consider the most common possible causes, and then analyze the special causes that rarely occur. For example: When the zero return of the B axis of the CNC lathe is inaccurate, it is often caused by the movement of the deceleration block position. Once this fault occurs, the position of the block should be checked first. After eliminating this common possibility, check the pulse encoder, position control and other links.
In short, after a CNC machinefails, as long as you master the correct troubleshooting ideas, follow reasonable troubleshooting principles, and use flexible judgment and analysis methods, you can quickly and timely eliminate the fault and achieve twice the result with half the effort.
Regular maintenance is the key to ensure the long-term stable operation of CNC machines. Through regular inspection and maintenance, potential problems can be discovered and solved in time, thus avoiding the occurrence of failures.
It is very important to keep CNC machines clean. Regularly cleaning dust and debris on the machine tools can reduce the wear and failure rate of mechanical parts.
Improving transmission accuracy is an important measure to prevent mechanical failures. The transmission accuracy can be improved by adjusting the preload of each moving pair, adjusting the loose links, eliminating the transmission gap, shortening the transmission chain, and setting a reduction gear in the transmission chain.
For spindle component failures, first check whether the transmission components are loose or too loose or too tight. If this is found, it is necessary to adjust according to the preload parameters. When the spindle box is noisy or hot, it should be inspected and repaired in time.
Understanding the different components of CNC machines (such as control panels, spindles, axes, tools, etc.) and their functions and importance will help to carry out more targeted preventive maintenance.
Through fault diagnosis and maintenance examples, you can master the maintenance skills and methods of CNC systems, servo systems, programmable controllers and machine tool side faults, and CNC lathe auxiliary device faults.
For common CNC machine faults, such as tool breakage, mechanical parts not moving to the specified position, operation interruption, reduced positioning accuracy, etc., the following measures can be taken to prevent and deal with them:
Improve transmission accuracy, adjust the preload of each moving pair, adjust the loose links, eliminate transmission clearance, shorten the transmission chain and set a reduction gear in the transmission chain.
During high-speed operation, pay attention to tool wear, select appropriate tool materials, and avoid breakage due to excessive tool wear.
Taking a proactive maintenance strategy and arranging maintenance time according to equipment needs can significantly improve the performance and life of the equipment.
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