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How is concentricity calculated on pc-dmis?

MelissaM10

So I've read multiple post on this same question, but nothing really explains what PC-Dmis is doing that i saw.

I have a print for basically a cup. Its calling out concentricity of the outside of the part to a cylinder on the inside of the part( datum a is a larger cylinder at the top of the part on the inside)

The outside the diameters check out of location from 0 but its not matching the concentricity. (is the deviation still x2 as radial distance from center?)

Datum A is X = 0.00 Y= 0.00

OD is  X= 0.0004  Y= -0.0013

Concentricity to A = 0.0218

Where did the 0.0218 come from?

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    Current revision of Y14.5 (starting at 2018) has removed concentricity as a control, entirely, as it is the least effective means of controlling definition of a feature of size.

    If the part is shaped like a banana, your OD's output origin is just a small factor of the concentricity output.

    Concentricity is the delta from datum axis center, to the measured feature's axis, across/along that measured feature's entire axis line. 

    the feature's circular "Form" error is NOT a measured value of Concentricity.  it's ONLY looking at/comparing the centroids of the features.

    So if both your datum and the OD are warped, or if just your datum, or just your OD are warped, you will have to construe that datum as a perfect straight axis line someplace.  All of that warping will be picked up eventually as the axis's straightness projects away from the datum's pefect axis line.

    I recommend taking individual circular diameters, and extracting centroids of each circle.  then construct a 3d line for all those circle center points.  measure straightness of that line, and you will better understand why your concentricity is 0.0218"

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  • 0

    Current revision of Y14.5 (starting at 2018) has removed concentricity as a control, entirely, as it is the least effective means of controlling definition of a feature of size.

    If the part is shaped like a banana, your OD's output origin is just a small factor of the concentricity output.

    Concentricity is the delta from datum axis center, to the measured feature's axis, across/along that measured feature's entire axis line. 

    the feature's circular "Form" error is NOT a measured value of Concentricity.  it's ONLY looking at/comparing the centroids of the features.

    So if both your datum and the OD are warped, or if just your datum, or just your OD are warped, you will have to construe that datum as a perfect straight axis line someplace.  All of that warping will be picked up eventually as the axis's straightness projects away from the datum's pefect axis line.

    I recommend taking individual circular diameters, and extracting centroids of each circle.  then construct a 3d line for all those circle center points.  measure straightness of that line, and you will better understand why your concentricity is 0.0218"

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