What is wrong here? #ISO 5459 #ASME Y14.5 #Datum Reference Frame #Degree of Freedom #Profile #Freeform #2D curve #point

[[Ap...]]

8/9/2023 update:
Aukom content:
although it says "hole" but B and C are constructed as inscribed cylinders vertical to datum A.

8/1/2023 update:
Just a follow up.
I see there is the same setting for datum in 2023 demo video.
If there are changes in datum system for 2023, then all the previous version with bugs?
If there are NO changes in datum system for 2023, then why is it applicable for True position but not Profile with freeform?


==
The test versions are from 5.6~7.4, all with the same issue.
This issue had led us to false judgment of part quality.
This issue had been raised to local ZEISS but no response yet. (not closed yet)

==
There is an issue when I assigned a freeform feature for surface profile. After some tests, it seems different features (freeform, 2d curve, point) behave differently with the same given datum features.

The part is similar to the photo below,
Primary datum A: Plane
Secondary datum B: Cylinder (continuous feature)
Tertiary datum C: Cylinder (continuous feature)
At the end portion I have created freeform, 2d curve and points

Based on the ISO 5459 and ASME Y14.5.1 (case 2.18, 3.9 and 3.11), the datum A|B|C is supposed to control all degree of freedom and best-fit is not allowed.
It is also very clear, when assembly with a plane and 2 cylinder holes, it is not supposed to move anymore.


However, the results I got as below, (The measured sample was made really BAD)
It is correct only when datum C is a circle, or intersected point, or a parallel cylinders of B-C.

It shows clearly a best-fit is performed and the result is just like A|B.

However it is normal when B|C is replaced by Parallel cylinder as mentioned above, or when the feature is a point with datum A|B|C.

The 2D curve with profile of line, also give me a best-fitted result just like A|B.

The GOM 2022 and PC-DMIS, can directly judge it is a bad part with the same datum A|B|C.

I don't know if there's a clear statement that Calypso cannot fullfill this basic datum settings or do I need to have some more trainings regarding to this?

Thanks.

2023-TP demo.pngISO5459 Case.png

[[Da...]]

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More training would always help, but I believe you are already on the right path with using circle as a tertiary datum feature (possibly with multiple scanning paths at different heights).

If you can, test Calypso 2023 I think there is more intuitive way.

[[Gu...]]

Hello,

Datum B (and C) is the same direction than datum A, so make sure to use a point (circle or intersection of plane A and cylinder B) in your reference system.

I would proceed like this :

Primary datum : A (plane) for the Z+ direction
Secondary datum : C (intersection of plane A and cylinder C) for the Y+ direction
Origin X : B (intersection of plane A and cylinder B)
Origin Y : B (intersection of plane A and cylinder B)
Origin Z : A (plane)

[[Ap...]]

That'll be an alternative methods temporarily and cannot explain why a point is able to get correct result with the same A|B|C. Shouldn't it be easier to fit to the cad model?

With these results I am worried about the 2023, but I haven't have that yet.

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[[Ap...]]

It is possible Calypso is not working like GOM or other CMM software...Which means we have to be trained well and cannot just select those datun features directly from the drawing.

However I don't remember if any training materials requires us to do that (or it does?) and the best-fit just violates the standards as it shouldn't.

To use intersected point or circle would be the way to get the correct result. With newer version I'll probably use the parallel cylinder.

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[[Da...]]

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Beware that parallel cylinder feature will not follow the |A|B|C| DRF, but |A|B-C| instead. Which is different and probably doesn't reflect the actual mating of the part at all.

[[To...]]

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X and Y origin are already calculated as the intersection of Cylinder B to Plane A. Creation of an intersection is not necessary.

To prove my statement, create an intersection after using cylinder B as X and Y origin in the BA, and you will see the nominal and actuals are X0, Y0 and Z0

[[No...]]

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not "possible"......CERTAIN !
GOM calculates most GD&T tolerances according to the standard by default. It does it "in the background", so even if you use, say, a least squares element where a tangential is required, GOM recalculates everything auomatically.
Calypso does not always do that. The whole GD&T part was designed when the old standards were still in effect. You need to take care of a lot of things yourself in Calypso.

[[Ap...]]

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I assume that is the two parallel cylinders (C.2.4 of ISO 5459:2011). Compared with ISO case in my context, these 2 scenarios both need to create a plane which containing these axes. To me that is the orientation control and no best-fit is allowed. It just makes no sense to me that it performed a best-fit when tertiary datum is a cylinder.

But yes, they are different, thanks for reminding.

C.2.4, origin at median straight line and a plane for orientation control.
Example 3, origin at cylinder B and an intersected straight line from the associated primary datum plane and the plane containing these two axes for orientation control.

Since the associated features of secondary and tertiary datum should perpendicular to the primary datum, I think the "plane" is almost identical and the major difference would be the origin. Is this the same understanding?

[[Ap...]]

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The oldest related standards I've read is ISO 5459:2011 and Y14.5-1994, I think there's no major changes regarding to datum reference frame and the degree of freedom. I knew we probably need to take care something, for example to shift the chebyshev plane by half of the form for tangential element, but I do not expect ZEISS as the leading company (in my mind) leaves all the details (use circle or intersection point or parallel cylinders, instead of using cylinder directly) to users and potentially cause failures. (if they do have training materials related to this topic then it is my careless)

[[Ap...]]

Just a follow up.
I see there is the same setting for datum in 2023 demo video.

If there are changes in datum system for 2023, then all the previous version with bugs?
If there are NO changes in datum system for 2023, then why is it applicable for True position but not Profile with freeform?