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Perpendicular Help

xbigfatgoat
Hello Everyone,

I'm having issues getting good results with the perpendicularity on this part that I'm checking. The drawing is posted.

Reading here on the forum I see that small cylinders could cause issues with perpendicularity. The parallel and concentricity come out great.

I've tried leveling to the datum B plane and the Datum A cylinder without any success.

Basically, if I report the perpendicularity of the cylinder with respect to Datum B I get extremely small numbers such as .00001.

If I report the perpendicularity of the plane with respect to the Datum A cylinder I'm getting measurements ranging from .003-.005.

The range comes from checking different parts but the measurements are consistent for each individual part.

I'm measuring cylinder A with two constructed circles using a 3mm dia stylus. Im using PCDMIS 2022.1.

Any help would be much appreciated. Thanks.

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  • Hi,

    this problem is quite common. This is neither a measurement error nor a machine error. The computer does everything right.
    The problem lies more with the engineer who thinks that the large plane has a secondary meaning.
    in reality, the cylinder A is much too short to represent the main axis (specify the vector)

    imagine you are trying to check the problem with a hand measuring device (e.g. a steel angle). I doubt you see a slit of light within the .25 height.
    (datum A is only to centering in 99% of these cases​)


    you can get around the problem by evaluating the concentricity to B|A instead of just to A

    I've already experienced that the "designer" can be very stubborn and doesn't see it, but it might be useful if you ask him if you're allowed to do it that way.​
  • in reply to Henniger123
    Ok so it is because the cylinder is too short. Thanks for the reply.
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