Run-Out out of tolerance?

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  • Run-Out out of tolerance?

    I need to measure run-out on the outer diameter of a round part at two different heights. The datum A-B is at the center of the part. I constructed a cylinder at the center out of two separate cylinders (one is located on one side and the other one is located on the other side of the part). and that's my A-B datum. Now for the outer diameter, the part is not continuous on the outside, so I created a basic circle scan on the 12 segments of the part at the two different heights. After that, I construct two circles using those scans and a cylinder out of those two circles. I then use this cylinder to dimension the Total axial run-out.

    The problem is that the run-out is too out of tolerance, but the scans are completely fine and the independent circles' diameters are fine too (within tolerance), so I don't know whats going on.

  • #2
    Are you using total runout or circular runout?

    Circular runout checks the runout of the specified feature at different heights and evaluates the runout at each height INDIVIDUALLY (the largest runout value at any height is the reported value), whereas total runout checks the runout over the entire length of the feature (so that the reported value is the difference between the highest deviation at any height and lowest deviation at any height). If your top and bottom circle are both very round and very concentric, but different sizes (when they should be the same size), then you can have a situation where checking each one individually they are good, but when checked as a cylinder with total runout, it can measure bad, because the cylinder is tapered due the diameters at the top and bottom being different.

    HTH

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    • #3
      I'm not sure how PC-DMIS will handle constructing a cylinder from 2 constructed circles. Have you tried constructing the cylinder directly from all the scans?

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      • #4
        Originally posted by Cris_C View Post
        I'm not sure how PC-DMIS will handle constructing a cylinder from 2 constructed circles. Have you tried constructing the cylinder directly from all the scans?
        I construct circles from Auto Points, and construct cylinders from those constructed circles and it analyzes the form of the cylinder using the points. I haven't personally done it with scans, but since it works with points, I would hope that scans also work!

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        • #5
          Originally posted by Mike Ruff View Post

          I construct circles from Auto Points, and construct cylinders from those constructed circles and it analyzes the form of the cylinder using the points. I haven't personally done it with scans, but since it works with points, I would hope that scans also work!
          Oh, that's good to know. Well, if it works with points I bet it works just fine with scans.

          Also, I really think you're on to something with the taper. With that, I think graphing the runout may reveal a lot.

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