Measuring precise position of a part without touch sensor.

    Grettings !

    We have a problem with a production of one type of parts. We cannot guarantee repeatability of produced part and problems occour when the parts need to be Arc welded with robots - The seam doesnt always come in the programmed position.
    The company wants to avoid investing in laser sensors becouse of related problems with reflection, they were thinking about getting a camera for robot vision.

    I was thinking, is there any possibility of solving this problem with a program for measuring where the Seam is.

    With the help of $PX50 - Torque Values, the robot would touch the position where the seam is and if it measures that the seam isnt in the " correct " location, it would then call a shifted program.

    is something like this possible with the use of Torque values of axis or do we need to invest into either an optical sensor or camera ?

    Ty for all help and suggestions im still learning stuff !

    Thank you for all your information.

    My initial plan was as someone mentioned to do Touch sensing by using the weld wire.

    The problem with this is, as someone also mentioned, the wire bends easly and im not sure that the axis would register any proper torque change before the wire bends. i guess i would have to test that somehow.

    Another idea would be using the gooseneck of the welder but the problem with that is if it bends from too much force it needs to be changed - expenses.

    As far as i know ( ive been at this position for 2 month now) the problem is becouse we work with cold rolled steel which has high reflectivity. I mentioned a possible solution would be getting laser sensor for locating seams ( it could probably also be used for getting exact position of the working part), but Bossman said the reflectivity would be a problem and that he would rather buy a camera - but isnt sure himself the cost vs benifit would be worth it for us.

    That is why im trying to find an alternative to using expensive sensors.

    You are not going to measure any torque using the wire no matter how slow the robot goes. Touch sense uses a voltage in the wire and detects the part when the wire grounds on the part. I think there is some confusion on what you were planning to do. Touch sense is pretty reliable. We have it on all our robots. Yaskawa, ABB doing exactly what you want your robot to do..price it out. It will save you headaches for sure.

    Our last robot came with touch thru the wire and a little spot laser. I only use the spot laser. I have had reflective issues a few times but that was mostly from measuring at too much angle to the part. If you measure directly adjacent, i've never had an issue. It's a lot faster than using the wire too. Everything we weld is mild steel btw

    Edited 3 times, last by jarm (December 9, 2024 at 2:12 PM).

    Quote from jarm

    You are not going to measure any torque using the wire no matter how slow the robot goes. Touch sense uses a voltage in the wire and detects the part when the wire grounds on the part. I think there is some confusion on what you were planning to do. Touch sense is pretty reliable. We have it on all our robots. Yaskawa, ABB doing exactly what you want your robot to do..price it out. It will save you headaches for sure.

    Our last robot came with touch thru the wire and a little spot laser. I only use the spot laser. I have had reflective issues a few times but that was mostly from measuring at too much angle to the part. If you measure directly adjacent, i've never had an issue. It's a lot faster than using the wire too. Everything we weld is mild steel btw

    Cheers for the detailed answer!

    Yes it seems i didnt quite get out what I wanted to do, hence some people thought we have a touch sensor ( we do not).

    Im going to do some research then with prices of touch sensors and laser sensors. I assume touch sense can be usefull in practically any application, where as Laser sensors would have a problem with high reflectivity, but even that can be managed with angles.

    Do/did you have any problems with metal dust covering the laser ( causing interferance) - requiring extra cleaning etc?

    Thank you for sharing your knowledge, really appreciate it !

    Quote from YakawFaBB

    Hi darth0 ,

    I use often the touch sensor on aluminum and steel, it's works perfectly on dust covering.

    As long as the electrical contact works the touch wire sensor works.

    YakawFaBB Hey cheers for the answer !

    I looked a bit into touch sensors and that seems like the perfect solution for us, as they can be used in the wides variety of applications and speed/cycle time isnt an important factor for us, where a laser/camera sensor would make more sense.

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