tool calibrating error

    • Hi,

      I have a big problem with calibrating the tool of Kuka KR210. I use a manual dial gauge for mastering the axis. There is also an external axis ( a turntable). However, after calibrating the tool using the 4points method, I got a maximum error of 5mm. we have an HSD spindle on the flange.

      The error shows itself when I want to cut an object from the top of the block and its sides, For example, I want to cut a block from two sides with a rotation of 90 degrees. I can cut the objects precisely when the robot cuts them from one direction. but when I change the planes for the rest of the cut the TCP has a deviation of up to 1cm.

      or another example is when I want to reach a point (XYZ) with the z-axis of the TCP, and the same point with the TCP rotated 90 degrees around x or y, the robot doesn't go in the same coordinate.

      I would be grateful if you can guide me on what did I do wrong? is it possible that there might be sth wrong with the gears?

      Btw, is it necessary to use apply load data for the tool? does it have any effect on a big robot of 210kg payload?

  • Hi farzaneh.eskandari,

    It sounds like you might have just taught your tool inaccurately. A 5mm error is fairly large. When you teach tools with 4 points, it might take more than one try to get the tool taught correctly. When you're done teaching it, always verify by rotating A, B, and C with respect to the tool you just taught. If it was taught correctly, the point will stay static, and the robot will move the axes to accommodate the new positions.

    Make sure, when you're teaching that you're using very sharp, very precise pointers, and that the surface you're putting you're pointers on is completely static. Make sure you're not leaning on the pointers or the robot while you teach it, since it might move the reference pointer a little. It's okay to try to get the best result and teach your tool more than once. But remember that if you reteach your tool, you need to check all the points you've taught in any programs.

    Lastly, it is important to apply the load data, definitely! The robot will move way more accurately when it applies the correct load data, specially with heavier loads. Your payload is 210kg max. so the robot will definitely compensate when moving with a heavy load.

    Hope that helps.

  • Well, I do use a very sharp and static point for the calibration. It's actually a very sharp metal on the turntable which is absolutely static and doesn't have any movement.

    I will add the load data for the spindle to see the difference.

    Is there also any possibility that one of the gears might cause the problem?

  • You use that instead of an EMT/EMD, correct? Or are you using the dial gauge during the 4-point TCP process?

    Payload data is important, even for a larger robot, although it generally has little effect during TCP calibration.

    Is this an Absolute Accuracy robot?

    I use the dial gauge instead of the EMD, For mastering the axis, not for the TCP process.

    About the second question, I'm not sure whether it's an absolute accuracy robot or not. We have bought that as a second-hand robot from Turkey. How should I check if it`s an absolute accuracy robot?

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