Fanuc RO output problems

  • Hello, Recently when testing out a new program my fanuc robot has been giving me some problems. Usually whenever i run a program and I want to use the air drill on the robot all I have to do is turn RO[1] to "on" I have never had a problem until yesterday. Now when I go to test a program I can turn the air drill on just fine with no problems at all. But as soon as the robot starts making movements the drill turns off. When i look at the input monitor RO[1] is still showing a "on" but the drill is completely off. I am pretty new to fanuc robots and am at a loss right now as to what my next move should be. Any help would be greatly appreciated. If any further info is needed i can gladly supply it. Thanks in advance.

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  • I think that the relay has to be shorting out somehow. Which would explain why the output on the I/O monitor is still showing as "on" even after it kicks off. I'm a programmer honestly and not an electrician so this might be interesting. I mean I completely understand the basics and I'm sure I could trace down the problem if the person who wired it before me didn't wire it like a rats nest.

  • Maybe something is coming loose when the robot moves. You should check all the connections and make sure you understand how it is wired and plumbed.

    Absolutely agree.

    You have local control of the output which prove it's working in the current position.

    Upon motion, this signal is being lost (not from the Fanuc side, the output status is clearly staying on).

    So check the harness from RO[1] connection to the drill, check for 'cable flexing', 'stretching', 'compression' and 'dvm continuity'.

    Also check the supply to the drill is not being lost instead, and it is still receiving the physical output from the Fanuc.

    It could be the supply lines, common line or just the output signal line that is the problem or a combination of all 3 conductors being loose.


    like a rats nest.

    Sadly this situation is common place, especially if people have been troubleshooting previously and not returned the harness and connections to a neat condition, you may find just by 'disturbing' the rats nest suddenly cures it.

    Also note, it could go the other way.......touching the rats nest can also introduce further problems.


    In situations like this, I rip it all out and re-wire it (if there's not too much) and check each io line has enough flex on it to not get 'pulled', 'twisted'.

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