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Cylinder to Cylinder Plus Radius

acgarcia
Good Morning,

I am measuring how far apart 2 the centers of 2 cylinders are plus their radi. This is to see how wide this cavity is. So I selected distance measurement, clicked my 2 cylinders across an axis and then selected add radi. Is that calculation taking into effect the size of the cylinder? So if 1 diameter is larger than the other, that distance will be longer? That tolerance is huge with +/-0.020". I am also measuring the location of the centers of the cylinders with a +/-0.0025" tolerance which is failing. I'm having a hard time explain this to the designer who says the CMM isn't correct.





Parents
  • You are correct. The software will take the center to center distance between the cylinders and add the measured radius of each cylinder.

    I can understand why the designer may be concerned about measuring it that way. That measuring method would not account for any form errors on the cylinder diameters or parallelism deviations between the cylinders. The measurement would just use the centroids of the cylinders and the average radii.

    A step up may be to measure the cylinders as circles at different depths and report the distances at several depths. That would help to remove any parallelism or taper form error in the reporting, but it would still have error from assuming the circles are true round.

    It may be most accurate to align to one cylinder and rotate to the other. Then measure points at different depths where the dimension indicates, and report point to point distances. You could also get really involved with scans and variables and formulas to find the furthest point to point distance, but that is a personal preference sort of thing.
Reply
  • You are correct. The software will take the center to center distance between the cylinders and add the measured radius of each cylinder.

    I can understand why the designer may be concerned about measuring it that way. That measuring method would not account for any form errors on the cylinder diameters or parallelism deviations between the cylinders. The measurement would just use the centroids of the cylinders and the average radii.

    A step up may be to measure the cylinders as circles at different depths and report the distances at several depths. That would help to remove any parallelism or taper form error in the reporting, but it would still have error from assuming the circles are true round.

    It may be most accurate to align to one cylinder and rotate to the other. Then measure points at different depths where the dimension indicates, and report point to point distances. You could also get really involved with scans and variables and formulas to find the furthest point to point distance, but that is a personal preference sort of thing.
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