Position not reachable in automatic mode

  • Hello everybody,


    I am pretty new to Industrial Robots (6 months working in this field) and I am currently working on a Robotic Milling plant for Foundry with a Fanuc M900iB400L.
    We build complex processes by using small TPP as building blocks and combining them with KAREL programs; we got this problem where, in automatic mode, one of those TPP stops and gives error MOTN-018 Position not reachable.


    We checked most common causes like changes in configuration or outside of robot envelope, but everything seems ok.
    When we try to reach the same point in manual (starting in the same settings) the robot moves normally to the point and gives no alarm.
    The same happens if we try to execute the same TPP in automatic mode but with reduced override speed.


    Anyone has any idea?
    Thanks in advance!

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  • It is not moving through singularity of the wrist and the wrist center is far from axis of joint 1 (this is a common case described in the Alarm Codes manual I have).
    As for what concern the base of the robot I am not sure to fully understand what you mean.


  • Is the position a PR?


    Yes, the position is a PR



    Could the wrong frame be active when you attempt the move?


    I don't think so, since the frame is assigned by the TPP when it starts


    This is pretty much the code of the TPP when the alarm pops up
    MOTN-018 Position not reachable at Line 11
    ...11: L @PR[26] FINE...12: L PR[27] FINE...
    Another strange thing is the '@' at line 11, suggesting that the motion to PR[26] has completed

  • Also converting the problem point to a joint representation may solve the issue. That way the robot doesn't have to call up the IK solver and have it spit out the position unreachable alarm.

    Check out the Fanuc position converter I wrote here! Now open source!

    Check out my example Fanuc Ethernet/IP Explicit Messaging program here!


  • Hi
    Is this a brand new program, was PR[26] working before ?
    Could you post the values (all of them, x,y, config, etc) of point 25,26 and 27 ? Three pictures will be ideal


    The program is not new and we used it a lot of times without having issues like this; in fact, the 'sequence' we are running launches this program multiple times (~ 10 times)
    I cannot give the pictures right now or exact points because I am not anywhere near the plant, but the situation is:
    point 25 -> same as 26 but with CNT100
    point 26 -> L PR[26] FINE
    point 27 -> moves with a linear motion in FINE along Ztool of 50mm
    point 28 -> get back to point 26 with a LIN and CNT100


    You can imagine the program performing a finger touch



    Also converting the problem point to a joint representation may solve the issue. That way the robot doesn't have to call up the IK solver and have it spit out the position unreachable alarm.


    We tried that and it doesn't pop up the alarm, but we need to perform this motion in LIN and with FINE since the tool is really close to the product and we must avoid damage to boht the tool and the product.


  • We tried that and it doesn't pop up the alarm, but we need to perform this motion in LIN and with FINE since the tool is really close to the product and we must avoid damage to boht the tool and the product.


    You can still use a linear interpolation to get to the PR. Its just inside of the PR it will be joint values instead of linear values.

    Check out the Fanuc position converter I wrote here! Now open source!

    Check out my example Fanuc Ethernet/IP Explicit Messaging program here!

  • I probably misunderstood what you meant; sadly when we pack up the TPP program (by setting proper PRs) the information we have is points in cartesian space and not joints, computing joints would mean a big change in our software, but I guess I'll give it a try.

  • 1. manual check motion with STEP On condition.
    2. When MOTN-018 appear again with STEP off condition, maybe calculate next position out of actual Stroke. becuz robot Precedence calculate next Motion data.


    MOTN-018 is meaning out of stroke. Not undefined position data.
    so, you have to check XYZWPR value.

    ABB<br />FANUC<br />KAWASAKI<br />HHIR<br /><br />I Can handle it!

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