Fanuc stops welding when crossing Light Curtain

  • Fanuc LR Mate 200ic


    First time posting, not sure if the terms I use are correct, but it’s the terms we use at my job.


    Fanuc robot doesn’t weld the next 2 weld points when a person crosses the safety light curtains. The robot continues the cycle, but skips welding either 1 or 2 weld spots and then continues to weld the next few points. Is that standard or is there a way to fix that?

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  • Missing too much application specific information here. Has it always done this? Is having an operator cross the light curtain part the normal process? Is the light curtain tied into the robots IO/fence/safe circuit directly or is there a PLC involved. Does the robot stop immediately when the curtain is crossed? What do you then do to recover? Are you able to step through the recovery from a light curtain stop?

  • Missing too much application specific information here. Has it always done this? Is having an operator cross the light curtain part the normal process? Is the light curtain tied into the robots IO/fence/safe circuit directly or is there a PLC involved. Does the robot stop immediately when the curtain is crossed? What do you then do to recover? Are you able to step through the recovery from a light curtain stop?

    Yes, we (the company I work for) have multiple fixtures that use the Fanuc robot (as well as Kawasaki) and all the Fanuc robots do this for some reason. The robots arrive preprogrammed from one of our other plants. They all and always do this.


    Having an operator cross the LC is not part of the process, but there are times when an operator accidentally puts an elbow across the LC or leans onto the LC causing the robot to stop.


    There is a PLC involved. We mostly use the omron PLC.


    Yes the robot stops immediately as do all other operations for safety.


    To recover, there are times that the robot continues the cycle once the LC is cleared, other times we would have to press the reset button on the teach pendant. The Fanuc robots that continue the cycle after clearing the LC are the ones not welding the next point or two. The ones we have to manually reset to continue the cycle have no problem welding.

  • Sam,


    Do you have "return to path" enabled? Setup - Weld Syst - Line 7 'Return to Path'. The paused program MUST remain at the same line number where the fault occurred for this feature to work.


    It sounds like when it resumes after the LC is cleared, the robot is getting a fault reset somewhere prior. It must in order to continue. Also, check that your weld is still enabled when you resume next time.

  • Sam,


    Do you have "return to path" enabled? Setup - Weld Syst - Line 7 'Return to Path'. The paused program MUST remain at the same line number where the fault occurred for this feature to work.


    It sounds like when it resumes after the LC is cleared, the robot is getting a fault reset somewhere prior. It must in order to continue. Also, check that your weld is still enabled when you resume next time.

    I cannot find the “weld syst”. How can I check that my weld is still enabled?

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