Position with no datum

[[Hu...]]

Hi
Calypso Version 6.6
Appreciate if someone can teach me on how to call out position with no datum as per the attached.
It'll be perfect if you can provide the screenshot from Calypso.
Thank you.

draw.pdf

[[Da...]]

This call-out does not make sense. A position call-out without a datum is only good for a pattern of features.

Think about it: A position call-out controls the position of a feature, and for that you need a reference, a datum. In this case, I would assume, that the datum should be the center hole, because the position call-out has an (L) symbol, which stands for Least Material Condition. Least Material Condition modifiers are usually used to control a minimum wall thickness. I would measure the center hole as a cylinder, the outer diameter also as a cylinder, and then use a position evaluation with the hole as the datum. That will ensure, that if the outer diameter is at the minimum diameter, the allowed position tolerance zone is 0.14 mm. If the outer diameter gets larger, the allowed position tolerance can be up to 0.3 mm larger (0.14 + 0.3 = 0.44), because the larger diameter is added as a bonus.

[[Hu...]]

Hi Daniel

Thank you for your sharing.
We told our Customer it cannot be measured without a datum and proposed to add datum and their reply was "it would compare to true model, Zeiss machine able to program this measurement."

[[Iv...]]

Is this ASME? ASME does not allow for datumless true position but only in the case of coaxial features. I can not determine that based on the image you shared, but it is unlikely given there is not a 2x on the diameter size.
Based on their response, I believe they are looking for a profile relative to itself. That would have a better representation of what they are asking for.

[[An...]]

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[[To...]]

You have to make 2 assumptions. 1) The drawing specifies that an ASME Y14.5 standard is to be followed. 2) If so, which version of the ASME (or ANSI) Y14.5 standard. Back in the day (mid 80's), I recall seeing many drawings with datum-less true positions. Then, they evolved to 2 datums for location. Then, they incorporated 3 datums, as they do now.

Based on the OP's drawing, one would have to assume this is a more recent vintage. It's good that you're having discussion with customer.

[[Hu...]]

Thank you for sharing.

The drawing stated per ASME Y14.5-2009.
We start to see drawings that only called out for Profiles and no linear dimensions.
The young designers are based on 3D scan to draft out the drawing. It's not easy to get customer to change/revise its drawing.

[[Ma...]]

unfortunately in German
🙄

viewtopic.php?t=12370

[[Ri...]]

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In this example, in Calypso, would you actually apply MMB to the Datum Cylinder (outer tangential cylinder constructed from the 2x Ø35 cylinders) or would you apply MMC to each Ø35 cylinder? I'm leaning towards MMB on the outer tangential cylinder constructed from the two cylinders, but I wanted to hear someone else's opinion/interpretation.

Thanks.

[[Ri...]]

Just bumping this back up. Wondering if someone had insight to my question above.

Thank you.

[[Ke...]]

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MMB due to presumed fit/function (IMO)

[[Ri...]]

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OK. That's what I was leaning towards as well.