Confusing Position measurement

[[Ja...]]

I have attached images of my situation. Primary datum is a cylinder along Z+, Secondary is a plane with normal along Z+. The tolerance zones are diametral, located a basic distance from the origin (along X), and rotated at a basic angle (Z/X). Let's say the radial deviation from basic is "dr" and the angular deviation of the feature axis from the basic angle is "dA". A geometric analysis shows that the Position can be calculated as P = sqrt(4 * (dr)^2 + h^2 * (tan(dA))^2) where "h" is the height of the thru bore.

Everything works OK and simulation in Calypso agrees with the mathematics. The problem, with Calypso I believe, lies when you ask for the Position to A and C but you have a deviation in X between the feature and primary datum. Since the coordinate system is unclocked, it clocks to the machine axes and determines the Position value accordingly. This is incorrect.

Is the only solution to create an alternate alignment that is clocked to each hole and then report Position to that alignment?

[[Me...]]

They have simultaneous requirements. Do a BF Bore Pattern, choose A Primary, C secondary, and allow rotation around A.

C essentially does nothing, as it controls the Z height only. I suspect that they may want to level to C instead of A but just responding to what the print shows.

[[Ke...]]

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Is it defaulting to the machine axis, or the Base Alignment orientation? (which could also be wrong)

I would question the designers intent. I would presume (but require confirmation) that the sides of the slot (that flank the Datum A cylindrical feature) would restrict the permissible rotation of "A", and would be a prime candidate for clocking the rotation of the part.

[[Br...]]

Sometimes Calypso does funny things when you don't have a primary secondary and tertiary datum all filled out. You can always do a best fit bore pattern at let the rotation best fit the bores. Otherwise, yes, you might have to create a secondary alignment.

[[Ja...]]

The problem does not go away when I try a BF of Bore pattern, which I agree that I should do to meet the simultaneity.

I set up my alignment as follows - Spatial Rotation to A, Planar Rotation to any repeatable feature to allow clocking, Ox to A, Oy to A, and Oz to C with Ox representing X-Origin and so on.
The coordinate system formed is centered on A, sitting on C. Since C is not coincident with the center of the thru bore, a rotation by the basic angle puts the bore axis "off in X". I manually translate the coordinate system by a calculated amount (L*sin(A) where L is the distance from C to the bore center and A is the basic angle) in X to fall along the axis of the thru bore in a secondary alignment. Now the error in Position should be tied to deviation from the basic angle and linear deviation to A.

The BF of Bore Pattern seems to not capture the basic angle. It reports a deviation in X even from the CAD that is (h/2) * sin(A).

[[Ja...]]

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And they control A to C as primary...

[[Ja...]]

Here's something more - I started over. New program, new CAD. Set up my alignment to A, C (clocked to a line between A and a thru hole). Asked for the Position of the small hole with respect to A, C. I also opened the special functions window to rotate my coordinate system by my basic angle and I performed the translation required to get me back on the feature axis. Obviously it is offline so I get a result of 0, no deviation in X or Y.


Now I try BF of bore pattern for simultaneity. I open the Bore Pattern window, select my features, define their coordinates, tolerance them, select the BF method - [Calculate now] does nothing. Make sure my DRF is correct and using the Special Functions window, again, I rotate and translate my coordinate system. Now it is telling me that the evaluation of the characteristic is not possible.

[[Ja...]]

I got it figured out. I wasn't rotating/translating the coordinate system correctly through the Special Functions window in the BF Bore Pattern window itself. And I had to run the program through for the evaluation to occur. Thank you everybody.

[[Ri...]]

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I do believe that this has changed in 2018/2019 as it will automatically convert it into a BF if there isn't a fully locked DRF.

[[An...]]

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I don't think so.
See attached.

Contribution_28_01_2020_a.pdf

[[Ja...]]

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Andreas,

Take a careful look at the right side view that I had posted. When I set my alignment up per my DRF A|C, my coordinate system is on the axis of A and lying on C. Look closely, and you will see that this is not on the axis of the thru holes. Rotation about the X axis by my basic angle will put the system parallel to, but not coincident with, the feature axis. In the rotated system, a translation will put the origin on the feature axis.

I think that you are mistaking my Special Functions operations as a way to clock the system. The system doesn’t need to be clocked if the Position is evaluated as a polar Position.

[[An...]]

Thoughts about a Cylinder/Plane - DRF.
See attached.

Contribution_03_02_2020.pdf

[[Ja...]]

Andreas,

I am not exactly sure what message you are trying to get across. It might be easier if you provide some context, rather than a rapid succession of images. You seem to have generalized my case by allowing the bores to be at an angle in the XY plane and you do not have the three holes collinear as is the case on my drawing.

After you align to the symmetry point you rotate about the X-axis by your basic angle. That is what I had decided on doing in my case, the only problem was an additional translation because the secondary datum is not on the center of the angled bores so rotation about X puts you off the axis of the bores. Hence the translation to return to the axis and report Position relative to the rotation angle of the bore.

Is there something that I am doing wrong that you are calling out, or are you just coming up with general examples and solving them?