Operation process, CNC machine tools have the following 8 common faults, master these faults information, help us to maintain their own CNC machine tools.

First, over-travel alarm (5n0 ~ 5nm):

       (1) return to the reference point in the start point is too close to the reference point, or too slow. Through certain methods to move the machine's overtravel axis out of the overtravel area can be.



       (2) Execute the return-to-zero action correctly, manually move the machine tool a certain distance in the opposite direction of return-to-zero, and this position is required to be outside the deceleration zone, and then execute the return-to-zero action.



       (3) If there is still an alarm after the above operation, check the return to zero deceleration signal, check the return to zero gear block, return to zero switch and associated signal circuit is normal.


Second, return to zero action abnormality

       Manual and automatic can not run the reason and processing: when the position display (relative, absolute, mechanical coordinates) are not moving, check the status of the CNC display, emergency stop signal, reset signal, the status of the operating mode.

Third, 90# alarm ALM998 ROM parity alarm

       When the system is in use, all ROMs should be parity-checked during the initialization and operation of the system, and an alarm will be generated when there is an error in the parity-checking, and the ROM number of the error will be pointed out.



       Failure causes and processing methods: memory card ROM error or improper installation, or memory card circuit board abnormalities, when the display screen shows the ROM alarm number, most likely because of memory card failure, first check the display screen prompts the number of locations of the ROM is well installed, such as confirming that there is no error, it is necessary to replace this ROM.

Fourth, AL950 power supply unit within the 24V insurance (F14) fuse

       In the FANUC-0C system in order to prevent short-circuiting of the power supply caused by the DI/DO interface, a separate external 24V fuse is set in the circuit structure.

       Fault cause and treatment method: Turn off the system power when the cable on the machine side is short-circuited to ground, and determine whether there is a +24E short-circuit to ground by measuring the resistance. There are (+24E) and ground (GND) measurement terminals on the motherboard and memory card, and the resistance between them can be measured directly. When the measured value is 0 ohm, unplug each connector on the I/O card and check the resistance value again. If the measured resistance value increases by about 100 ohms after unplugging the I/O connector, you can confirm that there is a short circuit to ground on the I/O load side.

V. SV400#, SV402# (overload alarm)

       Fault cause: 400# for the first and second axis in the overload; 402# for the third and fourth axis in the overload.

This alarm is issued when the overheat switch of the servo motor and the overheat switch of the servo amplifier operate.



       The servo amplifier has an overload check signal, which is a normally closed contact signal. When the servo motor overload switch detects that the motor is overheating or the temperature of the amplifier is rising, it causes the switch to open and generate an alarm. Generally this switch is connected in series with the overheat switch of the transformer and the overheat switch of the external discharge unit, and the signal is a normally closed contact, when the motor is overheated, the signal sends out an alarm, which is transmitted to the NC by the PWM command.



Six, P / S85 ~ 87 serial interface failure

       Failure causes: in the parameters of the machine tool, program input is often used in serial communications, the use of RS232 interface will be connected to the computer or other storage devices and machine tools. When the parameter settings are incorrect, cable or hardware failure will occur when this alarm.

       Fault finding and recovery:

       85 # Alarm: when reading data from external devices, the serial communication number of overflow errors, the data being input does not match or transmission speed mismatch, should check the parameters related to serial communication, if the check parameters are not wrong and still appear in this alarm , check whether the I / O device is damaged.



       Alarm 86#: The motion ready signal (DR) of the I/O device is turned off during data input. Check:

       ① Interfaces at both ends of the serial communication cable (including the system interface)

       ②Check the serial communication parameters of the system and external devices.　

       ③ Check whether the program protection switch of the external device or system is open.



VII. P/S 00# alarm

       Failure reason: After setting important parameters, such as servo parameters, the system enters the protection state, requiring the system to restart and load new parameters.



       Recovery method: After confirming the correct content of the modification, cut off the power supply and restart again.



Eight, P / S 100 # alarm

       Fault Cause: When modifying the system parameters, the system issues the alarm after the write-protect setting PWE=1.



       Recovery method:

       ① After the alarm, you can call the parameter page as usual to modify the parameters.

       ② modify the parameters to confirm the write-protect setting PWE = 0　

       ③ Press RESET to reset the alarm. If important parameters are modified, the system needs to be restarted.