Motoman MRC with Motoarc 500i intermittently welding cold

  • Hello all, we have a single Motoman MRC robot that will weld fine for an unspecified amount of time then will start welding cold with undersized welds. We changed the tip, cleaned the nozzle, checked for gas leaks and tweaked weld settings but it always comes back. I watched volts and amps on the Motoarc 500i digital display while welding and they stay constant. I understand that is just the output of the power supply, I don't know how I would measure the actual V and A at the tip while welding.

    I fabricated a temporary ground cable going from the welding fixture to ground to eliminate the positioner grounds, there was no change.

    Is there some way I can check the 500i power supply for faults? I have looked all over the internet for diagrams or info but there is practically nothing. If anyone has a diagram or some troubleshooting tips it would be awesome.

    Thank you

  • This can be anything from the weld torch (known as the whip) to the power source going bad.

    One thing to check is the wire spool. There will be a conduit that runs from the wire spool to the feeder. Make sure this is not grounding on anything (Fence, fixture, robot arm...)


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