The basic steps for repairing CNC machine tools are too comprehensive!

Theory guides practice, and when repairing a machine tool, the first step is to diagnose the machine tool fault. So how to determine the problem fault? The following are the general steps for repairing machine tools.
1, Fault records
When a CNC machine tool malfunctions, the operator should first stop the machine tool, protect the site, and then record the fault as detailed as possible, and promptly notify the maintenance personnel. The recording of faults can provide first-hand materials for maintenance personnel to troubleshoot, and should be recorded as detailed as possible.
The content should preferably include the following aspects:
1. Record of the situation when the malfunction occurred
1) The model of the malfunctioning machine tool, the control system model used, and the software version number of the system.
2) The phenomenon of the malfunction, the location of the malfunction, and the phenomenon of the machine tool and control system at the time of the malfunction, such as whether there are abnormal sounds, smoke, odors, etc.
3) The operating mode of the system when a malfunction occurs, such as AUTO (automatic mode), MDI (manual data input mode), EDIT (editing), HANDLE (handwheel mode), JOG (manual mode), etc.
4) If the fault occurs in automatic mode, the machining program number at the time of the fault, the program segment number where the fault occurred, and the tool number used during machining should be recorded.
5) If there are faults such as machining accuracy exceeding the tolerance or contour error being too large, the number of the workpiece being processed should be recorded, and the unqualified workpiece should be retained.
6) When a malfunction occurs, if the system displays an alarm, record the system's alarm display and alarm number.
7) Record the working status of the machine tool when it malfunctions through the diagnostic screen. For example, is the system running M S T and other functions? Is the system in a paused or emergency stop state? Is the system coordinate axis in an "interlocked" state? Is the feed rate 0? Wait a minute.
8) Record the value of the position following error of each coordinate axis when a fault occurs.
9) Record the movement speed and direction of each coordinate axis, spindle speed, steering, and so on when a malfunction occurs.
2. Record of the frequency of faults occurring
1) The time and cycle of the malfunction, such as whether the machine tool has been experiencing a continuous malfunction? If it is a random fault, how many times does it occur? Does it happen frequently?
2) The environmental conditions at the time of the malfunction, such as whether it always occurs during peak electricity usage? Is the other mechanical equipment next to the CNC machine tool working properly when the malfunction occurs?
3) If the fault occurs during the processing of parts, the probability of the fault occurring during the processing of similar workpieces should be recorded.
4) Check if the fault is related to special actions such as "feed rate", "tool change method", or "thread cutting".
3. Regular record of faults
1) Can the fault phenomenon be reproduced without endangering personal and equipment safety?
2) Is the malfunction related to external factors of the machine tool?
3) If the fault occurs during the execution of a fixed program segment, MDI can be used to execute the program segment separately and check if the same fault still exists?
4) If the machine tool malfunction is related to the machine tool action, if possible, it should be checked whether the same malfunction occurs when the action is executed manually?
5) Has the machine tool ever experienced the same malfunction? Does the surrounding CNC machine tool also experience the same malfunction? Wait a minute.
4. Record of external conditions during malfunction
1) Does the ambient temperature during the malfunction exceed the allowable temperature? Is there any localized high temperature present?
2) Is there a strong source of vibration around when the fault occurs?
3) When a malfunction occurs, is the system exposed to direct sunlight?
4) Check when the fault occurs. Is there any cutting fluid, lubricating oil, or water entering the electrical cabinet?
5) When the fault occurs, does the input voltage exceed the allowable fluctuation range of the system?
6) Is there a device using high current in the workshop or on the circuit that is starting and braking when the fault occurs?
7) Is there a strong electromagnetic interference source such as a crane, high-frequency machinery, welding machine, or electric machining machine near the machine tool when the malfunction occurs?
8) When the malfunction occurred, was the machine tool being installed, repaired, or debugged nearby? Are you currently repairing and debugging electrical and CNC devices?
2, Inspection before maintenance
Before repairing a malfunction, maintenance personnel should carefully check the system and machine tool user manual based on the symptoms and records of the malfunction, in order to confirm the cause of the malfunction. These checks include:
1. Inspection of the working condition of the machine tool
1) How is the adjustment status of the machine tool? Does the working conditions of the machine tool meet the requirements?
2) Does the tool used during processing meet the requirements? Is the selection of cutting parameters reasonable and correct?
3) Has the coordinate axis reached the tool change position during automatic tool change? Is the tool offset set in the program?
4) Is the parameter settings for tool compensation in the system correct?
5) Is the gap compensation amount for the coordinate axis of the system correct?
6) Are the system's setting parameters (including coordinate rotation, scaling factor, mirror axis, programming dimension unit selection, etc.) correct?
7) Is the setting of the "zero offset value" for the position of the workpiece coordinate system in the system correct?
8) Is the installation of the workpiece reasonable? Is the measurement method correct and reasonable?
9) Is there any deformation of mechanical parts due to temperature and processing? Wait a minute.
2. Inspection of machine tool operation
1) Has the operation mode been changed or adjusted during the automatic operation of the machine tool? Is manual operation inserted?
2) Is the machine tool side in a normal processing state? Are the workbenches, fixtures, and other devices in their normal working positions?
3) Is the position of the buttons and switches on the machine tool operation panel correct? Is the machine tool in a locked state? Is the multiplier switch set to "&"?
4) Is the "emergency stop" button on each operation panel of the machine tool and on the CNC system in an emergency stop state?
5) Is the fuse inside the electrical cabinet blown? Does the automatic switch and circuit breaker trip?
6) Is the position of the mode selection switch on the machine tool operation panel correct? Is the feed hold button pressed?
3. Inspection of the connection between the machine tool and the system
1) Check if there is any damage to the cable, and if there is any breakage or damage at the cable bend?
2) Is the arrangement of power and signal lines reasonable? Is the cable connection correct and reliable?
3) Is the power supply line of the machine tool reliably grounded? Does the specification of the grounding wire meet the requirements?
4) Is the grounding of the signal shielding wire correct? Is the wiring on the terminal board firm and reliable? Is the system grounding wire connected reliably?
5) Are electromagnetic components such as relays, electromagnets, and motors equipped with noise suppressors? Wait a minute.
4. Appearance inspection of CNC device
1) Is the CNC system running with the electrical cabinet door open? Is there any cutting fluid or cutting powder entering the cabinet? Is the cleanliness of the air filter in good condition?
2) Is the fan, heat exchanger, and other components inside the electrical cabinet working properly?
3) Are there any dust, metal powder, or other contaminants in the internal systems, driver modules, and printed circuit boards of the electrical cabinet?
4) When using a paper tape reader, check if there is any dirt on the paper tape reader? Is the brake solenoid on the reader working properly?
5) Is the fuse of the power unit blown?
6) Is the cable connector plug fully inserted and tightened?
7) Is the number of system modules and circuit boards complete? Is the installation of modules and circuit boards firm and reliable?
8) Is there any damage to the buttons on the MDI/CRT unit of the machine tool operation panel, and is their position correct?
9) Is the bus setting of the system and the position of the module setting end correct?
5. The early system for checking perforated paper tapes, the processing program is usually read in using paper tapes. If it is found that the fault is caused by incorrect information read into the perforated paper tape, the following content needs to be checked and recorded:
1) Is the switch of the paper tape reader normal?
2) Is the setting for paper tape operation correct and is there any error in the operation?
3) Is there any folding or wrinkling of the paper tape?
4) Is there any damage to the holes on the paper tape?
5) Is the joint on the paper tape connected smoothly?
6) Has the paper tape been used before?
7) Are you using black paper tape or other colored paper tape?
In short, during maintenance, there should be more original data and status to be recorded and checked. The more detailed the records, the more convenient the maintenance will be. It is best for users to prepare a fault maintenance record table based on the actual situation of the factory. In the event of a system malfunction, the operator can promptly fill in various raw materials according to the requirements of the table for reference during maintenance
Only by understanding the problem can we solve it step by step.