TL;DR
FANUC servo joint alarms are usually caused by overload from incorrect payload settings, brake failure, or pulse coder errors. Read the alarm number on the Teach Pendant first before touching hardware.
What you might see
- SRVO alarm number displayed on the FANUC Teach Pendant
- robot stops mid-cycle at one specific joint
- axis joint overload alarm repeating on the same joint
- robot difficult to lead-through in manual mode on one axis
Likely causes
Payload parameter set incorrectly in the FANUC system causing overload
Joint brake failing to release causing the servo to overload trying to move
Pulse coder feedback error from contamination or coder failure
Mechanical interference or fixture collision stalling the joint
Required tools
- Multimeter for brake voltage check
- FANUC alarm code reference for R-2000iC / R-1000iA
- LOTO kit
Safety first
- Lock out the robot controller before reaching near the robot arm. Robot arms can move with significant force at speeds exceeding 2 m/s without warning.
- Heavy fixturing and tooling on automotive spot welding robots represent crush hazards. Ensure all personnel are outside the robot working envelope before any power-on test.
- Robot brakes prevent the arm from falling when power is removed. Do not manually release joint brakes without supporting the robot arm with a safety crane or fixture.
Procedure
- 1
Read and record the SRVO alarm number on the Teach Pendant. Each alarm number corresponds to a specific fault in the FANUC alarm code list.[1]
- 2
Check the payload and payload offset settings in the FANUC system configuration. A misconfigured payload causes the servo to over-torque on inertia moves.[1]
- 3
If the alarm is a brake-related fault, lock out the robot controller and check the brake release voltage at the motor connector with a multimeter.
- 4
Inspect the joint for any mechanical interference. Confirm there is no fixture misalignment or obstruction preventing free joint movement.
Warning: Lock out the robot controller before reaching near the robot arm. FANUC robots move without warning when a program is resumed. Heavy robot arms create crush hazards. - 5
If the alarm includes a pulse coder error, inspect the pulse coder cable at the motor for contamination or damage. Re-seat the connector.
- 6
After correcting the identified fault, clear the alarm and verify normal motion with a low-speed test before resuming production speed.
Sources
FANUC FANUC R-2000iC / R-1000iA Body-in-White Spot Welding Robot Cell general technical documentation, FANUC
FANUC R-2000iC / R-1000iA robot operator and maintenance manual, servo alarm diagnosis procedures (general)
More guides for FANUC FANUC R-2000iC / R-1000iA
How to diagnose position deviation alarms on a FANUC R-2000iC / R-1000iA robot
Position deviation alarms indicate the robot arm is not reaching the commanded position. Check for mechanical interference, verify the zero position mastering, and inspect the speed reducer before calling FANUC service.
How to manage spot welding electrode wear on a FANUC R-2000iC / R-1000iA robot cell
Worn spot welding electrodes cause weld splash, small nugget size, and surface indentation on the visible side of the car body. Dress electrodes on a schedule rather than waiting for weld quality to degrade.
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