Calculate runout with form + position

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  • Calculate runout with form + position

    Hey all frends n family

    I got a callout of radiall runout of 0.02mm on a OD Ø32, against datum A (an ID Ø17 with 19mm in lenght)
    I measure the ID as circle and assign it to datum A. ( i tried cylinder too, but it gave same result as circle)
    Measure the OD as circle and go to xact and callout the runout to A.

    The runout shows 0.033mm
    Although i also checked the roundness of both datum A and the OD, and they have an roundness of 0.002mm
    Then i checked concentricity and it showed 0.034.

    From what ive read concentricity only checks position, and roundess controls the form.
    And runout should be kinda like concentricity + roundess: So shouldnt the runout deviation be higher than the concentricity?

    Also, do i have to measure the datum A as cylinder and align to it and then measure the OD circle?
    or will it calculate that automatically in xact.

    Because my alignment was
    plane > level
    measure datum A and another ID as circle > rotate
    orgin on plane, and datum A.

    Can i manually calculate the runout somehow based on the deviation in form/roundness and position/concentricity

    ty all!

  • #2
    Although runout encompasses both form and location, it is not as simple as just adding a concentricity (or position) and a form value together. What runout actually does is define two circular boundaries separated by the tolerance distance (think of it as an O'ring groove where the groove width is your tolerance). All of the points on the surface of your considered feature must lie within these boundaries.

    Datum A is the inner bore and is the only datum referenced in the feature control frame so you should measure it as a cylinder and level to that. You can use the top face as an origin but if you level to it, it could skew the results if it is not perfectly perpendicular to your datum A bore.

    To Manually Calculate.
    The closest you will get to manually calculating it would be to align as I have described above and then measure your OD in circular cross sections. If it is circular runout (single arrow symbol) then for each individual cross section you would need to look at the radial deviation (PR) of each hit and work out the range (max-min). Once you have done this for all cross sections, the one with the largest range would be the value you report. If it is total runout (double arrow symbol) you look at all of the radial hits combined and take the total range of all of the deviations.
    Neil Challinor
    PC-DMIS Product Owner

    T: +44 870 446 2667 (Hexagon UK office)
    E: [email protected]


    • #3
      Measure Datum A as cylinder and use as level and origin. Rotate as before.


      • #4
        In the neil.challinor alignment, assuming inner diam is along Z)
        Measure the OD as some circles, with many points (scan if you can)
        If double arrow, then construct a cylinder on hits.
        Calculate hits polar radii

        You can add a report comment with "RUNOUT of CIRCLE 1 = "+RO_CIRC1+"mm"

        Do it for each circle, or replace CIRC by CYL if double arrow.


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