constant touch-up of Fanuc M-10iD after safety gate has been entered

    Let me start off by saying that I received a new M-10iD with a R-30iB PLUS controller 5 months ago. Occasionally we have had a chain fault which required a reset of channel 1 from the pendant. The problem that I am having now is that every time the operator goes into the fence the robot needs to be touched up. even if nothing is moving when he opens the gate. It is usually the X that is a mm or so off, even though the position numbers have not changed. Can anyone explain why this may be happening or give me a clue on how I may be able to fix it? Everything runs fine unless the fence is opened.

    Thanks in advance,
    EMSSTC

    I'll double check on that, but something I failed to mention before is that there are two different trays (and position points) that the robot uses, but it only seems to effect one of them. I'm not 100% sure, but I think it has happened on both trays, just not at the same time. It is only a mm or so, so maybe I'm just not noticing it on the other.

    I checked and everything is bolted to the floor. The operator states that it has been both trays and it is always the very next tray it uses after entry. As I said before it is only a mm or so, but it causes big problems for our process. I just don't understand how the fence could affect it or why it would only be the next tray and not both.

    Trays, hmmm. So what if you open the gate, no one goes in, then lock gate and resume? Also, I have to ask if the is some type of pneumatic or otherwise a device that locates or "crowds" your trays? Are they de-energized because the gate is opened and then re-energized upon resuming auto? Could there be a sequence to locating these trays?

    Lemster68 has a very valid point. Pulling a gate key will de-energize the line and things will often "shift" around a bit. Something else that sticks out to me is that you were dealing with "chain Faults" which are safety faults regarding the TP deadman, safety gates, e-stops ect. Did you do anything to fix that issue? It's possible that the two are related in some way though I don't exactly know how??

    "I could tell that my parents hated me. My bath toys were a toaster and a radio."

    We don't have anything that affects the trays. They are placed on hooks with no centering mechanism. The problem started on 2nd shift Tuesday and I fought it all day Wednesday, but I haven't had much trouble so far today. I wish I could find the cause because it will probably come back. I was wondering if it had something to do with the occasional chain/fence fault. Our best guess on that one is that the gate may have shaken and quickly unlatched and latched back. As of now everything is looking good, but if anyone could give some insight on what it might have been, I would be grateful. As I said, I'm afraid that it will come back.

    Thank you,
    EMSSTC

    Do not blame the robot, check your process

    Since the first time I read your post I couldn't stopped thinking how can you be so sure the robot "moved"?
    The only way to be positive is to program a verification posture and check robot's repeatability.

    In arc welding for example we verify the torch regularly by replacing the conic torch nozzle with a straight nozzle
    the robot moves to a verification station that has a sliding tube. If torch is perfectly aligned the tube slides over the nozzle as a sleeve, otherwise any deviation would prevent it.

    If the robot does not repeat after opening the gate, I think is just a mere coincidence and I bet the variation is in other elements of the cell.

    If the robot is not properly anchored, it would start shifting.

    Quote from robotero


    Since the first time I read your post I couldn't stopped thinking how can you be so sure the robot "moved"?
    The only way to be positive is to program a verification posture and check robot's repeatability.

    In arc welding for example we verify the torch regularly by replacing the conic torch nozzle with a straight nozzle
    the robot moves to a verification station that has a sliding tube. If torch is perfectly aligned the tube slides over the nozzle as a sleeve, otherwise any deviation would prevent it.

    I've seen similar issues when there is slight movement in the tooling. As suggested by Robotero, you should setup a position where you can verify a known position point on the tooling to a fixed position in the cell.
    Make sure there are properly sized dowel pins used at the mounting flange and any adapting plates on the tooling. A very slight movement may be causing this.

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