When you get an alarm on your CNC machine please note the following points to enable our service staff to quickly identify the causes. This will enable us to make your CNC machine tool repairs better.
When did the failure occur?
Note the Date and time?
Did it occur during operation? (How long was the operation?)
Did it occur when the power was turned on?
Was there any lightening surge, power failure, or other disturbances to the power supply?
How many times has it occurred?
Only once? Or occurred lots of times? (How many times per hour, per day, or per
With what operation did it occur?
What was the NC mode when the failure occurred?
Jog mode / Mem mode /Mdi /Zrn
If during program operation,
Where exactly in the program?, Which program Number, and sequence Number?
Did it occur during the axis movement?
Did it occur during the execution of an M/S/T code?
Is the Failure specific to the program?
Does the same operation cause the same failure? Check the repeatability of the failure.
Did it occur during data input/output?
(Axes and spindles)
For a failure related to feed axis servo
Occurred at both low feed rate and high feed rate?
Occurred only for a certain axis?
For a failure related to spindles
When did the failure occur? (During power–on, acceleration, deceleration, or constant rotation)
What failure occurred?
Which alarm was displayed on the alarm display screen?
(Check the axis along which an alarm has occurred for alarms 300
For alarm 350: Examine diagnostic 202
For alarm 351: Examine diagnostic 203
For alarm 414: What does diagnostic display 200,201,204
For alarm 751 or 761: Which spindle alarm is indicated?
Is the screen correct?
If machining dimensions are incorrect
a) How large is the error?
b) Is the position display on the CRT correct?
c) Are the offsets correct?
d) Other information
Is there noise source near the machine?
If the failure has not occurred frequently, the cause may be external electrical
Noise to the power supply or inductive noise on machinery cables.
Operate other machines connected to the same power line and see
If electrical noise come from the relays or compressors.
Does the machine have any countermeasure for electrical noise (i.e.: emi filter)?
Check the following for the input power supply voltage:
a) Is there variation in the voltage?
b) Are the voltages different depending on the phase?
c) Is the standard voltage supplied?
How high is the ambient temperature of the control unit?
(0 to 45 degrees Celsius during operation)
Has excessive vibration been applied to the control unit?
When you contact our service centre, specify the following items:
a) Name of the NC unit
b) Name of the machine tool builder and type of machine
c) Software series/version of the NC
d) Specifications of the servo amplifier and motor (for a failure related to the servo)
e) Specifications of the spindle amplifier and spindle motor (for a failure related to a spindle)
Fanuc Alpha Servo drive alarms
Fanuc Servo amplifier Alarms
These alarms are found on the Fanuc Alpha servo drives, please check these alarms to enable us to complete a CNC repair to your machine tool quickly.
Alarm LED display Likely Cause, (for further information about these alarms please call or email us )
1 Inverter: internal cooling fan stopped
2 Inverter: control power supply under voltage
5 Inverter: DC link under voltage
6 Inverter: overheat
F Inverter: cooling fan stopped of the radiator
P Communication error between amplifier and module
8 Inverter: IPM alarm (L axis)
9 Inverter: IPM alarm (M axis)
A Inverter: IPM alarm (N axis)
8 Inverter: IPM alarm (OH) (L axis)
9 Inverter: IPM alarm (OH) (M axis)
a Inverter: IPM alarm (OH) (N axis)
b Inverter: DC link current alarm (L axis)
c Inverter: DC link current alarm (M axis)
D Inverter: DC link current alarm (N axis)
For the older ac servo drives the alarm led lights on the servo PCB when in trouble. These alarms usually follow a 401 or 403 alarm on Fanuc system 0 controls and have the following meanings.
These alarms can also be checked in diagnostic 720-724 on system 0.
(The bits are referenced as 76543210)
OVL Overload alarm 720-724 bit 7
LVAL Low voltage alarm 720-724 bit 6
OVC Over current alarm 720-724 bit 5
HCAL high current alarm 720-724 bit 4
HVAL High voltage alarm 720-724 bit 3
DCAL DC alarm 720-724 bit 2
FBAL A wire disconnection alarm 720-724 bit 1
OFAL Overflow alarm 720-724 bit 0
These are some of the common Fanuc alarms which are used to enable us to make CNC repairs quickly.
ALARM 85 TO 87 (READER/PUNCHER INTERFACE ALARM)
ALARM 90 (REFERENCE POSITION RETURN IS ABNORMAL)
ALARM 300 (REQUEST FOR REFERENCE POSITION RETURN)
ALARM 301 TO 305 (ABSOLUTE PULSE CODER IS FAULTY)
ALARM 306 TO 308 (ABSOLUTE PULSE CODER BATTERY IS LOW)
ALARM 350 (SERIAL PULSE CODER IS ABNORMAL)
ALARM 351 (SERIAL PULSE CODER COMMUNICATION IS ABNORMAL)
ALARM 400 (OVERLOAD)
ALARM 401 (*DRDY SIGNAL TURNED OFF)
ALARM 404 (*DRDY SIGNAL TURNED ON)
ALARM 410 (EXCESSIVE POSITION ERROR AMOUNT DURING STOP)
ALARM 411 (EXCESSIVE POSITION ERROR DURING MOVE)
ALARM 414 (DIGITAL SERVO SYSTEM IS ABNORMAL)
ALARM 416 (DISCONNECTION ALARM)
ALARM 417 (DIGITAL SERVO SYSTEM IS ABNORMAL)
ALARM 700 (OVERHEAT AT CONTROL SIDE)
ALARM 704 (SPINDLE SPEED FLUCTUATION DETECTION ALARM)
ALARM 749 (SERIAL SPINDLE COMMUNICATION ERROR)
ALARM 750 (SPINDLE SERIAL LINK CANNOT BE STARTED)
ALARM 751,761 (SPINDLE ALARM)
ALARM 900 (ROM PARITY ERROR)
ALARM 910 AND 911 (DRAM PARITY ERROR)
ALARM 912 AND 913 (SRAM PARITY ERROR)
ALARM 920 AND 921 (WATCH DOG OR RAM PARITY)
ALARM 924 (SERVO MODULE MOUNTING ERROR)
ALARM 930 (CPU ERROR)
ALARM 950 (PMC SYSTEM ALARM)
ALARM 960 (ABNORMAL 24 V INPUT POWER)
ALARM 970 (NMI ALARM IN PMC CONTROL MODULE)
ALARM 971 (NMI ALARM IN SLC)