TL;DR
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.
What you might see
- weld quality inspection shows nugget size below specification
- excessive weld splash on body panels
- electrode face mushroomed visually
- weld current increasing to maintain nugget size
Likely causes
Electrode tip mushroomed from cumulative spot weld cycles increasing contact area
Electrode tip alloyed with zinc from coated steel reducing conductivity
Electrode water cooling reduced from blocked cooling circuit
Gun alignment shifted causing off-center electrode contact
Required tools
- Tip dresser (integrated in the cell or hand-held)
- Electrode cap replacement set
- Coolant flow meter
- Tip diameter gauge
Safety first
- Lock out the robot and weld controller before manually reaching into the weld gun area.
- Weld guns close with several thousand Newtons of force. Never reach between the electrodes without a physical spacer block confirming the gun is open and locked out.
Procedure
- 1
Check the electrode dressing counter on the robot controller. Initiate the automatic tip dresser cycle at the scheduled dressing interval.[1]
- 2
After dressing, inspect both electrode tips for concentric face geometry. A visually off-center face indicates gun misalignment.[1]
- 3
Measure the electrode tip face diameter after dressing. Replace the electrode cap when the face diameter exceeds the specified maximum.
- 4
Check the electrode water cooling circuit by measuring the coolant flow rate at the weld gun inlet. Low flow causes rapid tip degradation.
- 5
Inspect the gun alignment by running a manual tip-touch-to-center position and comparing the position data on the Teach Pendant to the nominal value.
- 6
Document the electrode replacement and dressing cycles in the tooling log to track electrode life and adjust the dressing interval if needed.
Sources
FANUC FANUC R-2000iC / R-1000iA Body-in-White Spot Welding Robot Cell general technical documentation, FANUC
FANUC R-2000iC / R-1000iA robot cell and spot welding equipment maintenance documentation (general)
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