Profile without a Datum

[[Li...]]

I attached a file for you guys to look at.  Am I correct in the thought that Profile without reference to a datum is Flatness.  The attachment are screenshots of the part and the callout in question.   Profile .001 (no datum) and Profile .004|A|

Below is what an engineer in charge of the program sent me.  

Hey Lincoln,

 

Thanks for doing that, that’s great that all of the retested items were in tolerance. The only issue now is items 49 and 50…. It looks like none of the housings meet the profile of .001”. To clarify, the requirement for the .001 profile (Item 49) was that all 14 surfaces are within .001” with respect to each other, whereas it looks like you inspected item 49 as a flatness. The old LR60121 drawing called out a flatness so it makes sense that we inspected it like that, but in the future, this should be a profile of all 14 surfaces with respect to each other. I’ll forward you an email with more information on this deviation.

 

-Sean

My response back to him....

To me, this 49 and 50 call out is

1. Profile without a datum is simply flatness, meaning it only has to be flat.
2. Profile .004 to Datum A is called out and reported how it should be.  
3. In my programming software I cant have a surface checked for “profile” without it being constrained back to a datum except for flatness.

 

Please send me some feedback on this. Not sure what he means with the statement I underlined above. How would I build that in the program? I also attached the report for KC inspection we had to do on all parts. 

profile vs. flatness.xlsx 20LR60121-1_9336802024-12-149.pdf

[[Ma...]]

I think you will get same numbers from flatness and profile - there will be 14 evaluations of profile/flatness. I am not sure how you are common wiht profiles in ASME, but on ISO you will get usually one result which is doubled worst deviation ( here it would give twice same number ) - on ASME you are printing both numbers on report as far as i know.

For reporting profile on plane feature you would need to use freeform to use no reference datums, or fillout all datums as that plane with correct evaulatuion method ( not tangent but minimum i believe )

[[Li...]]

In the report I attached, Item 49-1 has the same feature as 50-1. 50-1 is profile back to datum -A- so size/form/location now affects the result.  If the surface checked is not at

4.930"(Item 51 in attachment) that deviation will affect the results.  Can you use free-form on top of a surface(s)? Wouldn't free-form make a slice/cross-section through the CAD model?

Edited December 17, 2024

[[Je...]]

redacted.

Zeiss, allow deletes and remove the time constraint.  The present parameters are dated and ineffective.

Edited December 17, 2024

[[Li...]]

Thanks let me fix that.

[[Li...]]

I cant seem to do anything with.

[[Je...]]

Lincoln,

Great questions about this profile characteristic.

A refinement in the wording would be that profile with no datum constraint controls form.  As you mentioned, this equates to flatness for planar features, but it could be applied to other types of features to control form.

According to ASME Y14.5, the "14 surfaces" note means that the controlled feature is a constructed plane made from 14 coplanar surfaces.  I would recommend recalling the measured points from all 14 surfaces into one plane feature.  Important: make sure that when you initially recall the 14 surfaces into one "blank" plane feature that the 14 surfaces do not have actual data populated, because the nominals for the constructed plane will reflect the measured data rather than the nominal data.  This can be manually correct by typing in the correct nominal values, but it's easier to avoid needing to do so.





At this point, yes, you could create a flatness characteristic and recall the constructed plane feature.  However, to go the extra mile and please your customer, I would recommend the following:

1.  Create a "Geometry Best Fit" alignment.

2. Click on "Select Elements" and choose the constructed plane.

3.  Click on "Evaluation Constraints" and make sure that all six degrees of freedom are selected (they already will be).

4. Then, create a profile characteristic and choose your constructed plane.  Then, use the drop-down menu to choose the Geometry Best Fit alignment you just created.

Enter the tolerance as specified on the print, but understand that the result will compute based on twice the largest deviation from the nominal profile (an oft-argued behavior throughout manufacturing 🤣).





Good luck.  Let us know how this turns out for you!

[[Li...]]

Thanks Jeff. 

The engineer talked with his other team members along with doing some research on their end and came to an agreement that they didn't correctly define this at least the way they wanted to. 

 

[[Je...]]

Please sign in to view this quote.

Lincoln, that's an interesting development.  Is there more you can share about this?  How did they intend to define the characteristic?

[[Ja...]]

Please sign in to view this quote.

Use the same surface as the datum in the profile characteristic. If the evaluation methods (LSQ, Min Feature, Max Inscribed, etc.) for the features are the same then the results for profile and flatness should match. 

Flatness defaults to Minimum Feature, older versions of Calypso will let you change the dropdown but it would still evaluate the plane with minimum feature regardless of what you chose. In 7.2, and later versions I assume, it will evaluate flatness with whatever evaluation method you choose.