Flatness measurement with laser scanner RS4

Hello-
I'm looking to take a flatness measurement. Equipment is a Romer RA-7525 (7 series) and RS4 red laser scanner. Part is aligned, and I'm using the CAD. I believe I should be able to do a flatness measurement using the laser scanner but have had no luck. I've attempted point clouds, cleaned clouds, surface colormaps, pointcloud color maps, and even to check my sanity went back to using a hard probe and taking a physical scan. Nothing seems to pull in to the flatness callout except for planes. And last I checked, planes are flat by definition, yes?? I've tried both with Legacy Dimensions and Xact Measure. What am I missing??? Apologies if this has been covered. I searched the forum with no luck but I'm relatively new here. Thanks in advance.

Aaron

vpt.se over 3 years ago

You must construct a plane from your point cloud, then do a flatness evaluation on that plane.
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Neil Challinor over 3 years ago in reply to vpt.se

+1
Flatness is the form deviation of a plane. If your surface is not planar then you need to use surface profile. It is also worth taking into account the tolerance being asked for since the laser may not be accurate enough.
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abeyersdorff over 3 years ago

To follow up, vpt.se had the answer I needed and this worked out fine. In my mind, a plane is, by definition, mathematically flat. But in PC DMIS I guess a plane will have all the points that created it still tied to it.
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JEFMAN over 3 years ago

On a cmm, or with an arm, you take hits, and construc from them a perfect feature (plane, circle, cylinder...).
This feature is mathematically perfect (if you intersect two features between them, the intersection is calculated between perfect surfaces), but COP are not perfects, so the association uses an algorithm to fit a perfect surface to the COP, and the form (flatness, circularity...) shows how the fit is "unperfect".

Depends on the material and the tolerance, but I'm not sure using a laser to measure a flatness is the right tool.
Maybe you should look at filters to get a "accurate" value.

Just my thoughts...
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Douglas over 3 years ago in reply to JEFMAN

filtering noise was my first thought, maybe on a large section of plate and a .030" tolerance it would be ok, checking raw materials to see which side of a plate is better. I could see it in a fabrication shop with large surfaces and variations
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