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I need help with measuring TP

Good morning All,
I have a problem with TP. The position of the cylinders on the cone is at an angle. I need to understand why TP is out of tolerance if the diameter and position of these cylinders are correct.
Every tip is valuable.

-A- -> TOP PLN ( Z+ )
-B- ->ID CYL in center ( Z+ )
-C- -> cylinder on the side ( Y-)​

Attached Files
Parents
  • measure datum 'A' plane
    measure datum 'B' circle
    measure datum 'C' circle

    create a line between circle 'B' and circle 'C'

    align datum 'A' in Z and datum
    align the created line in 'Y' axis
    datum circle 'B' in X and Y axis

    Do the same thing again in auto, When you do datum 'C' use a sample hit inline with the hole ( ie 12 clock )

    when you measure the angle holes use a sample hit on the angled surface or even better measure the angled hole as a cylinder and measure a line on the angled surface at the center of the hole and intersect the 2 features.

    As the angled holes are 10' apart you should be able to do a paste with pattern.

    Hope this helps.
Reply
  • measure datum 'A' plane
    measure datum 'B' circle
    measure datum 'C' circle

    create a line between circle 'B' and circle 'C'

    align datum 'A' in Z and datum
    align the created line in 'Y' axis
    datum circle 'B' in X and Y axis

    Do the same thing again in auto, When you do datum 'C' use a sample hit inline with the hole ( ie 12 clock )

    when you measure the angle holes use a sample hit on the angled surface or even better measure the angled hole as a cylinder and measure a line on the angled surface at the center of the hole and intersect the 2 features.

    As the angled holes are 10' apart you should be able to do a paste with pattern.

    Hope this helps.
Children
  • There is one problem...

    DATUM A - PLANE - Z
    DATUM B - CYLINDER - facing up - can controls X and Y
    DATUM C - on the side - can controls Z and X
  • What you said is TECHNICALLY true, but not possible given what you are told to do by the FCF.

    -A- plane, controls rotation about X and rotation about Y (two rotaions) and it controls translation in Z. Because it CAN and the engineer called it first (primary) so it DOES.
    That leaves rotation about Z, translation in X and translation in Y.
    Doesn't matter what the following things CAN do, they are only allowed to control that which is still available after the primary datum takes its chunk.

    -Y- cylinder, can control rotation about X, but that is not available, so it doesn't.
    Can control rotation about Y, but that is not available, so it doesn't.
    Can control translation in X and Y, those are both available so it does.

    That only leaves rotation about Z.
    That is all.
    Whatever comes next, it doesn't matter what it CAN do, only what it has left and is allowed to do.

    -C-, cylinder can control rotation about Z, this is available, so it does.
    Can control translation in Z, but that isn't available, so it does NOT.
    Once rotated, can control translation sideways (you said X), but that is not available, so it does NOT.

    Primary takes what it can.
    Secondary and tertiary take whatever is left over to them.
    Every time.

    There is a method an engineer can employ to over-ride this, I've never seen it on a print, you would KNOW it if you saw it.

    It is not in the snips of print you posted.

    I'd also make the line from B to C as it will provide better rotation, but, in the instance -C- is not on center (and the more off center it is the worse this gets), it is the axis of C that rotates about Z, not a line from B to C. That would look like | A | B | B-C |
    So long as -C- is sufficiently close to the center-line of -B-, a line will work and be representative of reality.
    "Sufficiently" is dependant on your tolerances, actual product and how risk averse you are.

    Using an axis that is .5" long (or however thick your wall is with -C- in is) to rotate a 33" diameter is going to carry it's own risk.