Analysis of Common Fault Diagnosis and Maintenance in CNC Machining Centers

In industrial manufacturing, CNC machining centers have been continuously improved and perfected, and have gradually been widely used, playing a positive role in promoting the development of modern industry. To fully leverage the role of CNC machining centers, it is necessary to ensure that they have good performance. Therefore, it is necessary to diagnose and repair common faults in CNC machining centers. This not only has positive significance for improving industrial production quality, but also is an important link in the development of industrial manufacturing towards modernization and automation.
1. Overview of CNC machining centers
The so-called CNC machining center is a high-efficiency automated machine tool with a tool library and an automatic tool changing device. After completing one clamping treatment of the workpiece, it can perform boring, reaming, milling, drilling and other processes on two or more surfaces, because automatic tool changing operations can also be carried out during processing, effectively improving the degree and efficiency of automated production. In the actual use of CNC machining centers, they are often affected by various factors. In order to ensure their good performance, it is necessary to have skilled operators before using the machining center. It is also necessary to implement precise programming for the machining, fully understand the performance of the machining center used, the machining process and characteristics, and make reasonable choices for the machining object, At the same time, regular maintenance and upkeep of equipment should also be carried out in management.
2. Common types of faults in CNC machining centers
2.1 System malfunction
System failure is a common type of failure in CNC machining centers, mainly caused by their own conditions and related components not meeting the standards for use. If there is leakage in the cooling system, long-term use can cause significant pressure on the cooling system. In high load environments, leakage is prone to occur, leading to heating during the operation of CNC machining centers, resulting in sluggish and slow system response, which can have a significant impact on machining accuracy. If severe, it can also cause alarms and automatic shutdowns in the machining center; During the movement of different axes in the machining center, there may also be situations that exceed the specified range. Under such exceeding conditions, an over travel alarm will occur.
2.2 Random faults
Compared with system failures, random failures do not occur frequently in the operation of CNC machining centers, but they are also relatively common. This type of failure is often accidental and only occurs under corresponding conditions. Faced with this type of fault, CNC machining centers often cannot analyze and judge the cause of the fault in advance during operation, and can only implement some preventive measures. For the occurrence of random faults, it is generally closely related to some important parameter settings, the environmental conditions of the operation, and also to the actual operation process and skills of the operator. During the operation of docking plugins and connecting components, due to negligence and failure to lock, the position and performance of relay contacts and various switch sockets have changed, which does not meet the requirements and leads to malfunctions in the CNC machining center.
2.3 Alarm display failure
For CNC machining centers, they are generally composed of multiple hardware and software components. If there is a malfunction in its software and hardware, an alarm display will appear. Often, both hardware and software devices are equipped with automatic alarm devices. In the event of abnormal faults or exceeding specified values in their hardware and software devices, alarm devices related to their hardware and software devices will be triggered, resulting in warning lights turning on or flashing. If there are errors in the processing program of the system, loss of system parameter settings, and errors in computer calculations, automatic alarm devices will be triggered to provide fault prompts, thereby attracting the attention of relevant personnel. If there is such a type of fault, relevant personnel can handle the fault according to the corresponding alarm prompts. But there is also a type of fault that is often difficult to diagnose, which is the absence of clear indicator lights when the hardware and software equipment of the system malfunctions. To quickly diagnose such faults, it is often necessary to quickly delineate the fault area and combine it with the state before and after the system malfunction to determine the fault location.
3. Diagnosis and maintenance of common faults in CNC machining centers
3.1 Tool magazine malfunction
Common tool magazine malfunctions include inability or inaccurate rotation of the tool magazine, inability of the tool holder to clamp the tool, and inadequate positioning of the tool holder. The inability or inaccurate rotation of the tool magazine may be due to loose couplings used to connect the motor shaft and worm shaft, faulty frequency converters, overly tight mechanical connections, low grid voltage, and errors in the transmission mechanism. This requires a comprehensive inspection and repair; The inability of the tool holder to clamp the tool may be due to insufficient clamping force caused by loosening of the tool holder adjustment screw or excessive spring, which requires performance inspection and fixing and repairing measures to ensure the firmness of the screw and spring; The inadequate positioning of the knife sleeve may be due to improper adjustment of the device, large machining errors, etc., resulting in inaccurate fork position, or it may be due to incorrect installation of the limit switch, leading to feedback signal errors [3].
3.2 Inaccurate spindle positioning affects automatic tool change
After positioning the spindle, it was found that there was a certain deviation in its position. After inspecting the drive system of the spindle, there were no alarms, and the structure of the mechanical part was relatively simple. The positioning of the machine tool was implemented through an encoder, and its positioning action had good accuracy. Therefore, the possibility of its failure caused by electrical problems is very small. Then the mechanical department that caused the malfunction considered that it may be due to a problem with the encoder connection. After inspecting the connection part, it was found that the connecting sleeve screws on the encoder were loose, resulting in a large gap in the area where the encoder and spindle were connected. Therefore, the screws need to be securely fixed according to the requirements.
3.3 CNC machining center has faults with no display
If the fault area is not displayed during the use and debugging of the CNC machining center, the system can continue to operate, but its display fails. After restarting, the fault disappears. In the face of faults in CNC machine tools, relevant maintenance personnel need to make judgments based on experience, inspect the performance of various component contacts, to determine whether the fault is caused by poor contact, and also need to inspect the display board. During the inspection, manual mode can be used to diagnose faults one by one.
3.4 Uneven motion of machining center
The imbalanced motion of the machining center is mainly due to the vibration and crawling of the coordinate axis, which is often closely related to various reasons. This may be due to problems in the mechanical transmission system or improper adjustment and setting of the servo feed system. In diagnosing this fault, it is necessary to first set the operation mode of the airport to manual mode, and control the feed of the Y-axis through a manually operated pulse generator. It is found that there is vibration in the Y-axis, and the speed unit alarm light of the Y-axis lights up after a long period of movement. This indicates that there is an overcurrent alarm in the drive of the Y-axis servo. The analysis suggests that the cause of the fault may be excessive motor load or poor mechanical transmission system The gain of the position loop is too high and there is a malfunction in the servo motor. In troubleshooting, the exchange method can be used to confirm the cause of the fault.
4. Conclusion
In summary, there are many common types of faults in the use of CNC machining centers. In order to ensure their good performance and meet the needs of machining production, effective diagnosis of the fault types should be carried out, and effective maintenance should be carried out according to the fault situation. This is also a necessary way to ensure the good use of CNC machining centers and improve the quality of mechanical processing production.In industrial manufacturing, CNC machining centers have been continuously improved and perfected, and have gradually been widely used, playing a positive role in promoting the development of modern industry. To fully leverage the role of CNC machining centers, it is necessary to ensure that they have good performance. Therefore, it is necessary to diagnose and repair common faults in CNC machining centers. This not only has positive significance for improving industrial production quality, but also is an important link in the development of industrial manufacturing towards modernization and automation.
1. Overview of CNC machining centers
The so-called CNC machining center is a high-efficiency automated machine tool with a tool library and an automatic tool changing device. After completing one clamping treatment of the workpiece, it can perform boring, reaming, milling, drilling and other processes on two or more surfaces, because automatic tool changing operations can also be carried out during processing, effectively improving the degree and efficiency of automated production. In the actual use of CNC machining centers, they are often affected by various factors. In order to ensure their good performance, it is necessary to have skilled operators before using the machining center. It is also necessary to implement precise programming for the machining, fully understand the performance of the machining center used, the machining process and characteristics, and make reasonable choices for the machining object, At the same time, regular maintenance and upkeep of equipment should also be carried out in management.
2. Common types of faults in CNC machining centers
2.1 System malfunction
System failure is a common type of failure in CNC machining centers, mainly caused by their own conditions and related components not meeting the standards for use. If there is leakage in the cooling system, long-term use can cause significant pressure on the cooling system. In high load environments, leakage is prone to occur, leading to heating during the operation of CNC machining centers, resulting in sluggish and slow system response, which can have a significant impact on machining accuracy. If severe, it can also cause alarms and automatic shutdowns in the machining center; During the movement of different axes in the machining center, there may also be situations that exceed the specified range. Under such exceeding conditions, an over travel alarm will occur.
2.2 Random faults
Compared with system failures, random failures do not occur frequently in the operation of CNC machining centers, but they are also relatively common. This type of failure is often accidental and only occurs under corresponding conditions. Faced with this type of fault, CNC machining centers often cannot analyze and judge the cause of the fault in advance during operation, and can only implement some preventive measures. For the occurrence of random faults, it is generally closely related to some important parameter settings, the environmental conditions of the operation, and also to the actual operation process and skills of the operator. During the operation of docking plugins and connecting components, due to negligence and failure to lock, the position and performance of relay contacts and various switch sockets have changed, which does not meet the requirements and leads to malfunctions in the CNC machining center.
2.3 Alarm display failure
For CNC machining centers, they are generally composed of multiple hardware and software components. If there is a malfunction in its software and hardware, an alarm display will appear. Often, both hardware and software devices are equipped with automatic alarm devices. In the event of abnormal faults or exceeding specified values in their hardware and software devices, alarm devices related to their hardware and software devices will be triggered, resulting in warning lights turning on or flashing. If there are errors in the processing program of the system, loss of system parameter settings, and errors in computer calculations, automatic alarm devices will be triggered to provide fault prompts, thereby attracting the attention of relevant personnel. If there is such a type of fault, relevant personnel can handle the fault according to the corresponding alarm prompts. But there is also a type of fault that is often difficult to diagnose, which is the absence of clear indicator lights when the hardware and software equipment of the system malfunctions. To quickly diagnose such faults, it is often necessary to quickly delineate the fault area and combine it with the state before and after the system malfunction to determine the fault location.
3. Diagnosis and maintenance of common faults in CNC machining centers
3.1 Tool magazine malfunction
Common tool magazine malfunctions include inability or inaccurate rotation of the tool magazine, inability of the tool holder to clamp the tool, and inadequate positioning of the tool holder. The inability or inaccurate rotation of the tool magazine may be due to loose couplings used to connect the motor shaft and worm shaft, faulty frequency converters, overly tight mechanical connections, low grid voltage, and errors in the transmission mechanism. This requires a comprehensive inspection and repair; The inability of the tool holder to clamp the tool may be due to insufficient clamping force caused by loosening of the tool holder adjustment screw or excessive spring, which requires performance inspection and fixing and repairing measures to ensure the firmness of the screw and spring; The inadequate positioning of the knife sleeve may be due to improper adjustment of the device, large machining errors, etc., resulting in inaccurate fork position, or it may be due to incorrect installation of the limit switch, leading to feedback signal errors [3].
3.2 Inaccurate spindle positioning affects automatic tool change
After positioning the spindle, it was found that there was a certain deviation in its position. After inspecting the drive system of the spindle, there were no alarms, and the structure of the mechanical part was relatively simple. The positioning of the machine tool was implemented through an encoder, and its positioning action had good accuracy. Therefore, the possibility of its failure caused by electrical problems is very small. Then the mechanical department that caused the malfunction considered that it may be due to a problem with the encoder connection. After inspecting the connection part, it was found that the connecting sleeve screws on the encoder were loose, resulting in a large gap in the area where the encoder and spindle were connected. Therefore, the screws need to be securely fixed according to the requirements.
3.3 CNC machining center has faults with no display
If the fault area is not displayed during the use and debugging of the CNC machining center, the system can continue to operate, but its display fails. After restarting, the fault disappears. In the face of faults in CNC machine tools, relevant maintenance personnel need to make judgments based on experience, inspect the performance of various component contacts, to determine whether the fault is caused by poor contact, and also need to inspect the display board. During the inspection, manual mode can be used to diagnose faults one by one.
3.4 Uneven motion of machining center
The imbalanced motion of the machining center is mainly due to the vibration and crawling of the coordinate axis, which is often closely related to various reasons. This may be due to problems in the mechanical transmission system or improper adjustment and setting of the servo feed system. In diagnosing this fault, it is necessary to first set the operation mode of the airport to manual mode, and control the feed of the Y-axis through a manually operated pulse generator. It is found that there is vibration in the Y-axis, and the speed unit alarm light of the Y-axis lights up after a long period of movement. This indicates that there is an overcurrent alarm in the drive of the Y-axis servo. The analysis suggests that the cause of the fault may be excessive motor load or poor mechanical transmission system The gain of the position loop is too high and there is a malfunction in the servo motor. In troubleshooting, the exchange method can be used to confirm the cause of the fault.
4. Conclusion
In summary, there are many common types of faults in the use of CNC machining centers. In order to ensure their good performance and meet the needs of machining production, effective diagnosis of the fault types should be carried out, and effective maintenance should be carried out according to the fault situation. This is also a necessary way to ensure the good use of CNC machining centers and improve the quality of mechanical processing production.