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Line Profile with No DRF


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I am working on a compressor fan blade that has a Surface Profile of .010" but on the leading and trailing edges, .040" from the tips, they call out Line Profiles of .004" .  The entire blade (PIC 1), including the points from the curves, measures around .008" Surface Profile but the Line Profiles of the curves (PIC 2) with No DRF are reporting as high as .033".  I created a best fit of multiple curves alignment (PIC 3) and applied it to line profiles and thing improved drastically, but is this legit?  There is something going on with the No DRF best fit that I don't understand.   Any thoughts?

FFS Surface Profile_fully constrained.jpg

Curves Line Profile_No DRF.jpg

Curves Line Profile_best fit to multiple curves.jpg

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If there are no datums then you can use bestfit - i would use both curves to make one alignment.

Don't forget to change evaluation to spline instead of gauss ( it's open curve ), or mask at least 0.5second from start and end ( if you didn't already )

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The best fit of multiple curves consists of 6 curves.  I only showed 2 for clarity.   I have .01" of pre- and post-travel active on my scans.

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If those curves are on one blade, then ok - if there can be possible blade deformation, then i would make more alignments with just two which are next to each other to avoid middle curve to be affected.

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My question was really more about why can't I assign a curve to a line profile with No Datum Reference Frame and get the desired results.  Why do I need to do anything else? 

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 These are 3d curves?

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 They should be. But even 3D curve can not set no datum ref.

But possibly you are aiming to bestfit within feature to create it's own alignment? I would need to see it in Calypso - i know this can be done in FF but i am not sure for curves.

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 I recently built a program to measure 3d curves and only evaluated the form (no datums) using line profile. This is with 2019. In the characteristic drop down, just select No Datum Reference Frame.

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I create the best-fit alignment ticking all translations and rotations from the 3d curves.

Then evaluate each curve profile back to the alignment I created from said curve. Instead of No Datum Reference Frame.

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So they could possibly changed that. I think in 2018 you can select that, but it's not saved like that.

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I will test this in the morning, but my understanding is I will get the same results.

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I am using No DRF on Line Profiles of 3d Curves in 2023

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Been in meetings all morning but been meaning to get to this one.  

On compressor wheels, I don't do many evaluations of profile using no datums.  But I know what is probably causing your issue with using no DRF.   There is almost always blade deformation as you move up or down/inside to outside of the blade.  This makes it difficult for Calypso to properly fit the points back to the cad model.   If you could 3d scan the part and get a color map, then it would be easier to see what I'm talking about. 

 

Aligning it to a best fit alignment made from 1 or more curves is much better in my opinion.  Just like you have been doing.  

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