CNC machine tools; Fault; diagnose
As we know, CNC machine tools are electromechanical integration equipment with high precision, high added value and high automation. Although it also has high reliability and stability, in actual production projects, due to the complex environment and many interferences, the normal work of the real-time control system of CNC machine tools will be greatly affected, and failures will occur at any time due to human factors and changes in component characteristics. Therefore, the rapid diagnosis and maintenance of common electronic control faults is particularly important. The following will explain the diagnosis and analysis methods according to the specific faults of FANUC CNC machine tools.
1.FANUC 0i-MC NC machine tool starts the emergency stop alarm.
Analysis idea: From the schematic diagram, it can be seen that the emergency stop fault is the emergency stop loop that causes the system to stop working. It can be seen from the circuit analysis that X8.4 inputs the emergency stop signal of the numerical control system to the external circuit, which is 1 (high level 24V) in normal operation. When giving an emergency stop alarm, X8.4 must be 0 (low level 0V), mainly the emergency stop button X/Y/Z Y/.
Diagnostic process: firstly, enter the PMC status list, check that the status of X8.4 is 0, then check the 24V voltage and relay coil contacts, cut off the power supply and measure the switches of the emergency stop circuit in turn, and after troubleshooting one by one, replace the corresponding devices to troubleshoot the startup failure.
Return to zero failure
Analysis thinking: Returning to zero failure can be divided into returning to zero failure and X, or the feed shaft can't find the intersection point and overtravel.
1) returns to zero. According to the system schematic diagram, the address signal of the mode switch input system is X3.0-X3.3.
Under normal circumstances, there will be a 24V change when changing the mode. Without change, there is no correct working mode, and the key point is the state of X3.2x3.3.
Diagnostic process: enter the PMC status list of the system, check the status of X3.0-X3.3, turn the mode switch and observe their status changes, then enter the CB 105 connection, and measure the voltages of X3.2.X3.2 and 0V with a multimeter. Under normal circumstances, if the switch is changed, there will be 24V voltage to troubleshoot.
2) No zero return point can be found on the X axis. The address of the X-axis zero return deceleration switch input to the system is X9.0, which is 0 under normal circumstances. When it returns to zero and presses SQ, X9.0 becomes 1. Diagnostic process: First, enter the PMC status list interface of the system, check the state change of X9.0 (by moving the X axis), and further check the deceleration when it reaches the deceleration switch.
3. Handwheel failure
Analysis: The handwheel only works in its mode.
Analysis process: In addition to software parameters, it is caused by line failure. According to the schematic diagram, the first round is connected to the system through I/O interface, with four lines, 5V power supply and two signal lines, A and B. First, check the on-off of the lines, and then check the 5V power supply one by one, and the problem will be solved.
4. The spindle cannot be started.
Analysis; Spindle cannot be started. From the hardware analysis, there are two problems: 1 spindle button failure, and 2 inverter wiring failure.
1) key failure: stop the key address X3.0, the normal state is 0, and the disconnected state is 1. Enter the PMC state list interface, check the state of X3.0, then check the wiring of CB 104, and check the voltage of X3.0 and 0v. If it is 24V, it can't be started. Check the switch, line and.
2) Wiring failure of frequency converter: check incoming and outgoing lines and power supply of contactor KM2 powered by spindle frequency converter, and check contactor coil and power supply. Secondly, check the normally open contacts of KM2 coil circuit KA 10, and check them one by one. Problem solved.
5. Tool rest failure
Analysis process: The main manifestations of tool rest failure are: the electric tool rest is not locked, and the tool rest cannot find any tool position to continue rotating.
1) The electric tool holder is not locked, and the position of the letter board is incorrect: disassemble the top cover of the tool holder, rotate and adjust the position of the letter board, so that the Hall element of the tool holder is aligned with the magnetic steel, and the tool position is stopped at an accurate position.
2) The electric tool holder can't find a certain position, and the Hall element corresponding to the tool position is damaged or broken: confirm which tool position keeps the tool holder rotating, input the instruction to rotate the tool position on the system, and measure whether the voltage of the tool position signal contact changes to the +24V contact with a multimeter. If there is no change, it can be judged that the Hall element of the tool position is damaged.
3) When the cutter position keeps rotating, check the power supply and circuit of letter board and Hall sensor.
In a word, there are many fault types of CNC machine tools, including mechanical fault, electrical fault and software fault. No matter what kind of fault, to diagnose and maintain correctly and quickly, we must first understand the structure, working process and technological process of CNC machine tools, master general operating skills, and then be extremely familiar with the schematic diagram and actual distribution of the system, and at the same time be clear about the composition and connection of the system. The key is to master system parameters and PMC programs, especially important parameters and programs, and then use them correctly. At the same time, pay attention to collect the technical data of CNC machine tools for ready use. These knowledge and skills are necessary for the maintenance of CNC machine tools.
The principle of diagnosis and maintenance basically follows the process from simple to complex, from surface to inside, from shallow to deep, step by step, bold and cautious. First, visible and tangible devices, then line power supply, second, external wiring and status indication of system part, third, PCB board level, and finally, software and parameters. At the same time, the principle is to follow the technical requirements of the original system, not to change the system requirements at will, and not to expand the fault range; Make maintenance records and analyze the cause of failure.
With the above conditions, we must have correct methods and skills. Methods and techniques are not dogmatic words, but the product of long-term combination of theory and practice. In a word, practice makes perfect, and if you are perfect, you can be comfortable and invincible.
refer to
[1] Guo Shiyi. Fault diagnosis and maintenance of CNC machine tools. Machinery Industry Press, May 2005.
[2] Huang Wenguang. Connection and debugging of FANUC numerical control system. Higher Education Press, 20 1 1.5.