[To...] Posted May 23, 2023 Share Posted May 23, 2023 I'm sure this has been hashed in the past but I need to ask again. Drawing calls for Flatness of a Plane and Surface Profile with No DRF on the same plane. The Profile uses LSQ and can't be changed so I change the Flatness to LSQ. I turned off all filters and outlier elimination. Why would the result not be the same? Link to comment https://qualityforum.zeiss.com/topic/7828-profile-vs-flatness/ Share on other sites More sharing options...
[Th...] Posted May 23, 2023 Share Posted May 23, 2023 Result calculation method? If both are LSQ they might have the same deviations from the nominal plane, but flatness is a simple range between extremes and profile is effectively double the greatest deviation. If your LSQ evaluation leaves you with, say, one localized deviation that's .003" plus material and one localized deviation that's .001" minus material, your flatness would be .004" but your profile would be .006". Link to comment https://qualityforum.zeiss.com/topic/7828-profile-vs-flatness/#findComment-33884 Share on other sites More sharing options...
[Ri...] Posted May 23, 2023 Share Posted May 23, 2023 Please sign in to view this quote. Flatness uses the Minimum Zone calculation by default. Profile is using a Best Fit algorithm. You can get the same exact result if you use a Free-Form Surface and allow a Tschebyscheff fitting for the best fit. Link to comment https://qualityforum.zeiss.com/topic/7828-profile-vs-flatness/#findComment-33886 Share on other sites More sharing options...
[Ri...] Posted May 23, 2023 Share Posted May 23, 2023 Please sign in to view this quote. Yes. Minimum Zone should leave you with Min/Max points that are the exact values, but on opposite sides of nominal. Profile can have data to one side or the other, and the range from the min/max doesn't equal the Profile as you stated. Link to comment https://qualityforum.zeiss.com/topic/7828-profile-vs-flatness/#findComment-33888 Share on other sites More sharing options...
[To...] Posted May 23, 2023 Author Share Posted May 23, 2023 I was not able to get the same results with the Tschebyscheff.. Honesty, I really wasn't looking for the same result but on many occasions, I've heard people say "just use a Flatness if you need profile without a DRF, for people who didn't have Free Form. So, I was surprised when I saw the difference. Mr. Gorman reminded me how Profile was calculated. DOH You reminded me that it used a best fit algorithm, Double DOH It's tough getting old. Link to comment https://qualityforum.zeiss.com/topic/7828-profile-vs-flatness/#findComment-33890 Share on other sites More sharing options...
[Ri...] Posted May 23, 2023 Share Posted May 23, 2023 Please sign in to view this quote. This only works though without filters/outlier. I think 2023 allows for filtering inside of a FFS now. This was in 2019 that I was doing the testing. Link to comment https://qualityforum.zeiss.com/topic/7828-profile-vs-flatness/#findComment-33892 Share on other sites More sharing options...
[Ph...] Posted May 23, 2023 Share Posted May 23, 2023 Works just fine if setup properly..... Link to comment https://qualityforum.zeiss.com/topic/7828-profile-vs-flatness/#findComment-33894 Share on other sites More sharing options...
[Ri...] Posted May 23, 2023 Share Posted May 23, 2023 Please sign in to view this quote. I couldn't get it to work earlier in the Profile with the 3 Planes. I think I just had something unchecked wrong as it shows correctly now. Link to comment https://qualityforum.zeiss.com/topic/7828-profile-vs-flatness/#findComment-33896 Share on other sites More sharing options...
[Ri...] Posted June 2, 2023 Share Posted June 2, 2023 Shouldn't Flatness report different than Profile (with or without a DRF)? Flatness is not a result of A1 and A2 values while Profile is a result including A1 and A2 values. Your Plane has A1 and A2 values as defined by your nominals (Assuming A1 and A2 are 0.0 respectively). The spatial existence of the plane shouldn't affect Flatness but should affect a Profile. Link to comment https://qualityforum.zeiss.com/topic/7828-profile-vs-flatness/#findComment-33898 Share on other sites More sharing options...
[To...] Posted June 2, 2023 Author Share Posted June 2, 2023 Please sign in to view this quote. I don't believe the projection angles of the plane have any affect though. No DRF means the plane can rotate or translate in any direction it wants. However, as Richard pointed out, the best fit algorithm on the profile does behave differently than the minimum feature evaluation on the flatness, so the results will be different. Link to comment https://qualityforum.zeiss.com/topic/7828-profile-vs-flatness/#findComment-33900 Share on other sites More sharing options...
[Je...] Posted June 2, 2023 Share Posted June 2, 2023 A few thoughts that don't directly answer the question but dance around it like a politician on a podium: - A profile requirement with no DRF will behave like flatness, but the keyword is behave. -Besides understanding how a GD&T callout functions on a print, we also have to understand how Calypso will simulate it. Pre-2021, Zeiss had particular trouble mimicking profile but seems to have turned the corner. -The strategy of inputting the same feature in the characteristic window for primary, secondary and tertiary datums is a workaround. It was not an intended solution but seems to work in some cases. -In Calypso, the nominal geometry for freeform surfaces is defined wholly by the CAD model. This doesn't really present a challenge for planes as long as the CAD model is drawn correctly. -I prefer to use Geometry Best Fit alignments in Calypso for profile characteristics that are meant to evaluate planes. Link to comment https://qualityforum.zeiss.com/topic/7828-profile-vs-flatness/#findComment-33902 Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in