E-stop delay

    I'm new to this type of work (programming robots and programming in general) so if my questions seem obvious I'm sorry.


    We are going to be programming a new robot cell we're building for a customer. We are using M-20iA robots with R-30iB controllers. We are still kinda in the planning phase so I can't really test anything yet but the customer threw a bit of a curveball at us already. On top of the 6 axis for the robot itself one of the two robots will also be controlling a load table on axis 7 and 8. But they want us to set it up so if an e-stop is pressed, the robot stops immediately but the table continues moving for 5-10 seconds after the e-stop. Is this possible and if so how do I do it?


    Any advise is appreciated. Thank you.

    I would say that it will be really hard from the standard compliance and risk assessment point of view. What safety systems you're planning to use?
    Look into fanuc manuals regarding "Auxilary axis servo off (local stop) function" in operation manual and DCS manual. From a quick glimpse maximum delay is 2s.

    First of all, what is the reason they want this? And like macru said, this causes a huge safety risk.
    Second, if the robots are interacting with axis 7 and 8 at the moment of pressing the E-stop, and axis 7 and 8 have a delay, this can cause a crash?

    I didn't get a whole lot of info but from what I'm being told I think they are just trying to come to a slow stop rather then an abrupt stop on e-stop for axis 7 and 8. They are worried about damaging the gear assembly. Is there a way to safely add a slow down timer to those 2 axis when e-stop is pressed without applying the delay to the whole robot?

    I would suggest you look into adding a special button for controlled start, and using that for this application. It seems like what they are asking for would be a major safety violation. E-Stop should not be used for every instances of wanting to stop the line, it should generally be reserved for emergencies because it IS hard on the hardware. Repeated E-Stops will eventually take a toll on the robot as well as external axis. Fanuc robots, and i am assuming external axis, have a controlled stop option for all other instances, which will bring motors to a more gradual stop to keep damage from occurring.

    Exactly what Robo_Eng_13 is saying then. For reason of non-emergency stops you have the hold, pause and controlled stop procedures. And it is not a delay issue but a graduate slowdown. You can use controlled stop for emergency stop (option), but that increases overall stop time and distances of the system.
    Other thing is that the system needs to be engineered to withstand estop torques and forces.
    What are the external axes used for? As long as sudden stop is not going to spill liquid hot metal out of foundry bucket I wound't ever consider doing a 10s long emergency stop!

    Edited once, last by macru ().

    I have already met such a request from the customer. But it makes no sense actually. The robot is supposed to stop immediately, and the table with a delay - but exactly in the same manner, with immediate power cut-off. This means, that the table still stops harshly and quickly, it doesn't make life easier for the mechanics.

    Well, Controlled Stop as estop will make it slightly less harsh as it won't engage the brakes but it will slow the system down using servos, but it still be full torque for tables. Which so instead of being hard on mechanics it'll be hard on servos.

    I had all but abandon this idea because it didn't seem like a safe choice but in testing we've discovered a new problem. If an e-stop is hit while the table is traveling it slams to a stop, hard enough to throw the calibration for that group off. I had to jog it to zero and recalibrate from scratch. How do I set that group up as a controlled stop? I can try it that way and see how it works. And/or does anyone have another solution to this problem?

    The long and short of it is that E Stops are meant for emergencies, and in an emergency, the life of the operator is more important than the calibration of the positioner. Using a separate button for controlled stop is the best possible option. Making an E Stop perform a gradual stop is almost certainly a major safety violation.


    As for solutions to the root problem, it is very odd that it would mess with the calibration, at least if you are using a Fanuc motor. They have a built in pulse coder that is tied directly to the drive output of the coils. In order to mess up your calibration, it would have to make the pulse coder wheel slip on its axis, make some internal gears skip teeth, or make your fixture slip on its axis. The first is unlikely, and the second would be damaging, so it is probably the third.


    If your momentum is causing your positioner to slip on the suddenly stopped drive shaft, you need to more firmly fix it to the shaft, lighten the weight, or slow it down. I imagine if you suggest slowing a machine down, you will get laughed at, and the weight is probably non-optional. Fixing the current positioner more firmly to the shaft will likely move the issue elsewhere, and you may get a stop position error, but that does not require recalibration.

    "The long and short of it is that E Stops are meant for emergencies, and in an emergency, the life of the operator is more important than the calibration of the positioner."


    Excellent comment. It is a big problem that people in the industry uses the e-stop for any reason
    E-stop are for emergencies and not for process control

    Retired but still helping

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