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same piece varying concentricity

ketlin
hey guys! I'm having trouble validating a measurement method. I am finding different values ​​of concentricity between two diameters. We have already tested leveling in different work planes and positions and the values ​​do not match when compared. in DCC mode I am always creating a plane and a cylinder, where I level and give origin to the cylinder and the plane is my height reference. In this cylinder that I level, I measure three diameters and after measuring them, I measure another larger diameter that is about 20mm away from them and I make the concentricity between them.depending on whether I place the piece lying down or standing up, changing my work plane, my concentricity varies from 0.070mm to 0.200mm. what do you think it could be?
  • can you please post your code so we can visualize it better?
  • What is the size of the cylinder ? (diameter ; length) How many hits ?
    Do you measure the larger diameter as a circle or as a cylinder ? If the datum is the cylinder axis, then you should measure the larger diameter as a cylinder (coaxiality).
    You measure 3 diameters in the cylinder : are they concentric to the cylinder axis at the same height ?
    As said, post the code...
  • I would:

    At top of program with STARTUP alignment recalled, construct a plane and force the vector to be X+, lets call it PLN_THEO_XP

    Then, probe your plane and datum cylinder. For the datum cylinder I would use a logical amount of hits for the size & use AT LEAST 4 levels of hits so you can cover as much of the surface as possible. For concentricity checks I usually use 5 or 7 levels depending on the length of the datum surface.

    Then, INSERT/ALIGNMENT/NEW: Level to datum CYL, rotate to PLN_THEO_XP, CYL = XY origin and PLN = Z origin

    Then, measure the features you'd like to check the concentricity of as CYLINDERS

    Remember, concentricity is the evaluation of derived median center points along a CYLINDRICAL AXIS so you need to be measuring the features you're evaluating as cylinders...NOT circles...in order to be geometrically correct here.

    Hope this helped
  • [...]Remember, concentricity is the evaluation of derived median center points along a CYLINDRICAL AXIS so you need to be measuring the features you're evaluating as cylinders...NOT circles...in order to be geometrically correct here.

    Concentricity is the evaluation of a point or center point (of a circle) to a datum. The derived median points along an axis would be Coaxiality. The datum of both is always an axis, although the datum of a concentricity can be simplified to a projected point.

  • Concentricity is the evaluation of a point or center point (of a circle) to a datum. The derived median points along an axis would be Coaxiality. The datum of both is always an axis, although the datum of a concentricity can be simplified to a projected point.


    you do you

    cheers Sunglasses

  • Concentricity is the evaluation of a point or center point (of a circle) to a datum. The derived median points along an axis would be Coaxiality. The datum of both is always an axis, although the datum of a concentricity can be simplified to a projected point.


    In addition, in the ISO world, the dimensioned circle and the datum must be coplanar for concentricity (see ISO 1101).
    One of the problems for designers and metrologists is that concentricity and coaxiality have the same graphical representation.​


  • In addition, in the ISO world, the dimensioned circle and the datum must be coplanar for concentricity (see ISO 1101).
    One of the problems for designers and metrologists is that concentricity and coaxiality have the same graphical representation.​

    Yes, but the ASME standard got rid of concentricity. There is a tendency for the standards to take over certain developments from each other (not all, of course), and from what I've heard, it can be expected that ISO will follow the elimination of concentricity.
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