“Detailed Explanation of Basic Methods for Fault Analysis of CNC Machine Tools”
As a key equipment in modern manufacturing, the efficient and accurate operation of CNC machine tools is crucial for production. However, during use, various faults may occur in CNC machine tools, affecting production progress and product quality. Therefore, mastering effective fault analysis methods is of great importance for the repair and maintenance of CNC machine tools. The following is a detailed introduction to the basic methods for fault analysis of CNC machine tools.
I. Conventional Analysis Method
The conventional analysis method is the basic method for fault analysis of CNC machine tools. By conducting routine inspections on the mechanical, electrical, and hydraulic parts of the machine tool, the cause of the fault can be determined.
Check power supply specifications
Voltage: Ensure that the voltage of the power supply meets the requirements of the CNC machine tool. Too high or too low voltage may cause faults in the machine tool, such as damage to electrical components and instability of the control system.
Frequency: The frequency of the power supply also needs to meet the requirements of the machine tool. Different CNC machine tools may have different requirements for frequency, generally 50Hz or 60Hz.
Phase sequence: The phase sequence of the three-phase power supply must be correct; otherwise, it may cause the motor to reverse or fail to start.
Capacity: The capacity of the power supply should be sufficient to meet the power requirements of the CNC machine tool. If the power supply capacity is insufficient, it may lead to voltage drop, motor overload and other problems.
Check connection status
The connections of CNC servo drive, spindle drive, motor, input/output signals must be correct and reliable. Check whether the connection plugs are loose or have poor contact, and whether the cables are damaged or short-circuited.
Ensuring the correctness of the connection is crucial for the normal operation of the machine tool. Incorrect connections may lead to signal transmission errors and motor out of control.
Check printed circuit boards
The printed circuit boards in devices such as CNC servo drive should be firmly installed, and there should be no looseness at the plug-in parts. Loose printed circuit boards may lead to signal interruption and electrical faults.
Regularly checking the installation status of printed circuit boards and finding and solving problems in time can avoid the occurrence of faults.
Check setting terminals and potentiometers
Check whether the settings and adjustments of the setting terminals and potentiometers of CNC servo drive, spindle drive and other parts are correct. Incorrect settings may lead to decreased machine tool performance and reduced machining accuracy.
When making settings and adjustments, it should be carried out in strict accordance with the machine tool’s operation manual to ensure the accuracy of parameters.
Check hydraulic, pneumatic, and lubrication components
Check whether the oil pressure, air pressure, etc. of hydraulic, pneumatic, and lubrication components meet the requirements of the machine tool. Inappropriate oil pressure and air pressure may lead to unstable machine tool movement and reduced accuracy.
Regularly inspecting and maintaining hydraulic, pneumatic, and lubrication systems to ensure their normal operation can extend the service life of the machine tool.
Check electrical components and mechanical parts
Check whether there is obvious damage to electrical components and mechanical parts. For example, burning or cracking of electrical components, wear and deformation of mechanical parts, etc.
For damaged parts, they should be replaced in time to avoid the expansion of faults.
The conventional analysis method is the basic method for fault analysis of CNC machine tools. By conducting routine inspections on the mechanical, electrical, and hydraulic parts of the machine tool, the cause of the fault can be determined.
Check power supply specifications
Voltage: Ensure that the voltage of the power supply meets the requirements of the CNC machine tool. Too high or too low voltage may cause faults in the machine tool, such as damage to electrical components and instability of the control system.
Frequency: The frequency of the power supply also needs to meet the requirements of the machine tool. Different CNC machine tools may have different requirements for frequency, generally 50Hz or 60Hz.
Phase sequence: The phase sequence of the three-phase power supply must be correct; otherwise, it may cause the motor to reverse or fail to start.
Capacity: The capacity of the power supply should be sufficient to meet the power requirements of the CNC machine tool. If the power supply capacity is insufficient, it may lead to voltage drop, motor overload and other problems.
Check connection status
The connections of CNC servo drive, spindle drive, motor, input/output signals must be correct and reliable. Check whether the connection plugs are loose or have poor contact, and whether the cables are damaged or short-circuited.
Ensuring the correctness of the connection is crucial for the normal operation of the machine tool. Incorrect connections may lead to signal transmission errors and motor out of control.
Check printed circuit boards
The printed circuit boards in devices such as CNC servo drive should be firmly installed, and there should be no looseness at the plug-in parts. Loose printed circuit boards may lead to signal interruption and electrical faults.
Regularly checking the installation status of printed circuit boards and finding and solving problems in time can avoid the occurrence of faults.
Check setting terminals and potentiometers
Check whether the settings and adjustments of the setting terminals and potentiometers of CNC servo drive, spindle drive and other parts are correct. Incorrect settings may lead to decreased machine tool performance and reduced machining accuracy.
When making settings and adjustments, it should be carried out in strict accordance with the machine tool’s operation manual to ensure the accuracy of parameters.
Check hydraulic, pneumatic, and lubrication components
Check whether the oil pressure, air pressure, etc. of hydraulic, pneumatic, and lubrication components meet the requirements of the machine tool. Inappropriate oil pressure and air pressure may lead to unstable machine tool movement and reduced accuracy.
Regularly inspecting and maintaining hydraulic, pneumatic, and lubrication systems to ensure their normal operation can extend the service life of the machine tool.
Check electrical components and mechanical parts
Check whether there is obvious damage to electrical components and mechanical parts. For example, burning or cracking of electrical components, wear and deformation of mechanical parts, etc.
For damaged parts, they should be replaced in time to avoid the expansion of faults.
II. Action Analysis Method
The action analysis method is a method for determining the faulty parts with poor actions and tracing the root cause of the fault by observing and monitoring the actual actions of the machine tool.
Fault diagnosis of hydraulic and pneumatic control parts
Parts controlled by hydraulic and pneumatic systems such as automatic tool changer, exchange worktable device, fixture and transmission device can determine the cause of the fault through action diagnosis.
Observe whether the actions of these devices are smooth and accurate, and whether there are abnormal sounds, vibrations, etc. If poor actions are found, the pressure, flow, valves and other components of the hydraulic and pneumatic systems can be further inspected to determine the specific location of the fault.
Steps of action diagnosis
First, observe the overall action of the machine tool to determine whether there are obvious abnormalities.
Then, for specific faulty parts, gradually narrow the inspection range and observe the actions of each component.
Finally, by analyzing the reasons for poor actions, determine the root cause of the fault.
The action analysis method is a method for determining the faulty parts with poor actions and tracing the root cause of the fault by observing and monitoring the actual actions of the machine tool.
Fault diagnosis of hydraulic and pneumatic control parts
Parts controlled by hydraulic and pneumatic systems such as automatic tool changer, exchange worktable device, fixture and transmission device can determine the cause of the fault through action diagnosis.
Observe whether the actions of these devices are smooth and accurate, and whether there are abnormal sounds, vibrations, etc. If poor actions are found, the pressure, flow, valves and other components of the hydraulic and pneumatic systems can be further inspected to determine the specific location of the fault.
Steps of action diagnosis
First, observe the overall action of the machine tool to determine whether there are obvious abnormalities.
Then, for specific faulty parts, gradually narrow the inspection range and observe the actions of each component.
Finally, by analyzing the reasons for poor actions, determine the root cause of the fault.
III. State Analysis Method
The state analysis method is a method for determining the cause of the fault by monitoring the working state of the actuating elements. It is the most widely used in the repair of CNC machine tools.
Monitoring of main parameters
In modern CNC systems, the main parameters of components such as servo feed system, spindle drive system, and power module can be detected dynamically and statically.
These parameters include input/output voltage, input/output current, given/actual speed, actual load condition at the position, etc. By monitoring these parameters, the operating state of the machine tool can be understood, and faults can be found in time.
Inspection of internal signals
All input/output signals of the CNC system, including the status of internal relays, timers, etc., can also be checked through the diagnostic parameters of the CNC system.
Checking the status of internal signals can help determine the specific location of the fault. For example, if a relay does not work properly, a certain function may not be realized.
Advantages of state analysis method
The state analysis method can quickly find the cause of the fault based on the internal state of the system without instruments and equipment.
Maintenance personnel must be proficient in the state analysis method so that they can quickly and accurately judge the cause of the fault when a fault occurs.
The state analysis method is a method for determining the cause of the fault by monitoring the working state of the actuating elements. It is the most widely used in the repair of CNC machine tools.
Monitoring of main parameters
In modern CNC systems, the main parameters of components such as servo feed system, spindle drive system, and power module can be detected dynamically and statically.
These parameters include input/output voltage, input/output current, given/actual speed, actual load condition at the position, etc. By monitoring these parameters, the operating state of the machine tool can be understood, and faults can be found in time.
Inspection of internal signals
All input/output signals of the CNC system, including the status of internal relays, timers, etc., can also be checked through the diagnostic parameters of the CNC system.
Checking the status of internal signals can help determine the specific location of the fault. For example, if a relay does not work properly, a certain function may not be realized.
Advantages of state analysis method
The state analysis method can quickly find the cause of the fault based on the internal state of the system without instruments and equipment.
Maintenance personnel must be proficient in the state analysis method so that they can quickly and accurately judge the cause of the fault when a fault occurs.
IV. Operation and Programming Analysis Method
The operation and programming analysis method is a method for confirming the cause of the fault by performing certain special operations or compiling special test program segments.
Detection of actions and functions
Detect actions and functions by methods such as manually performing single-step execution of automatic tool change and automatic worktable exchange actions, and executing processing instructions with a single function.
These operations can help determine the specific location and cause of the fault. For example, if the automatic tool changer does not work properly, the tool change action can be performed manually step by step to check whether it is a mechanical or electrical problem.
Checking the correctness of program compilation
Checking the correctness of program compilation is also an important content of the operation and programming analysis method. Incorrect program compilation may lead to various faults in the machine tool, such as incorrect machining dimensions and tool damage.
By checking the grammar and logic of the program, errors in the program can be found and corrected in time.
The operation and programming analysis method is a method for confirming the cause of the fault by performing certain special operations or compiling special test program segments.
Detection of actions and functions
Detect actions and functions by methods such as manually performing single-step execution of automatic tool change and automatic worktable exchange actions, and executing processing instructions with a single function.
These operations can help determine the specific location and cause of the fault. For example, if the automatic tool changer does not work properly, the tool change action can be performed manually step by step to check whether it is a mechanical or electrical problem.
Checking the correctness of program compilation
Checking the correctness of program compilation is also an important content of the operation and programming analysis method. Incorrect program compilation may lead to various faults in the machine tool, such as incorrect machining dimensions and tool damage.
By checking the grammar and logic of the program, errors in the program can be found and corrected in time.
V. System Self-Diagnosis Method
The self-diagnosis of the CNC system is a diagnostic method that uses the system’s internal self-diagnosis program or special diagnostic software to perform self-diagnosis and testing on the key hardware and control software inside the system.
Power-on self-diagnosis
Power-on self-diagnosis is the diagnostic process automatically performed by the CNC system after the machine tool is powered on.
Power-on self-diagnosis mainly checks whether the hardware equipment of the system is normal, such as CPU, memory, I/O interface, etc. If a hardware fault is found, the system will display the corresponding fault code so that maintenance personnel can troubleshoot.
Online monitoring
Online monitoring is the process in which the CNC system monitors key parameters in real time during the operation of the machine tool.
Online monitoring can detect abnormal conditions in the operation of the machine tool in time, such as motor overload, excessive temperature, and excessive position deviation. Once an abnormality is found, the system will issue an alarm to remind maintenance personnel to handle it.
Offline testing
Offline testing is the testing process of the CNC system using special diagnostic software when the machine tool is shut down.
Offline testing can comprehensively detect the hardware and software of the system, including CPU performance testing, memory testing, communication interface testing, etc. Through offline testing, some faults that cannot be detected in power-on self-diagnosis and online monitoring can be found.
The self-diagnosis of the CNC system is a diagnostic method that uses the system’s internal self-diagnosis program or special diagnostic software to perform self-diagnosis and testing on the key hardware and control software inside the system.
Power-on self-diagnosis
Power-on self-diagnosis is the diagnostic process automatically performed by the CNC system after the machine tool is powered on.
Power-on self-diagnosis mainly checks whether the hardware equipment of the system is normal, such as CPU, memory, I/O interface, etc. If a hardware fault is found, the system will display the corresponding fault code so that maintenance personnel can troubleshoot.
Online monitoring
Online monitoring is the process in which the CNC system monitors key parameters in real time during the operation of the machine tool.
Online monitoring can detect abnormal conditions in the operation of the machine tool in time, such as motor overload, excessive temperature, and excessive position deviation. Once an abnormality is found, the system will issue an alarm to remind maintenance personnel to handle it.
Offline testing
Offline testing is the testing process of the CNC system using special diagnostic software when the machine tool is shut down.
Offline testing can comprehensively detect the hardware and software of the system, including CPU performance testing, memory testing, communication interface testing, etc. Through offline testing, some faults that cannot be detected in power-on self-diagnosis and online monitoring can be found.
In conclusion, the basic methods for fault analysis of CNC machine tools include the conventional analysis method, action analysis method, state analysis method, operation and programming analysis method, and system self-diagnosis method. In the actual repair process, maintenance personnel should comprehensively apply these methods according to specific situations to quickly and accurately judge the cause of the fault, eliminate the fault, and ensure the normal operation of the CNC machine tool. At the same time, regularly maintaining and servicing the CNC machine tool can also effectively reduce the occurrence of faults and extend the service life of the machine tool.