[Th...] Posted August 8 Share Posted August 8 I have a plate with call out for flat and parallel on same surface. Is it possible for flatness to be worse than parallel?1.PNG Link to comment Share on other sites More sharing options...
[Ow...] Posted August 8 Share Posted August 8 Yes, I think it is possible. 🙄 Link to comment Share on other sites More sharing options...
[Ri...] Posted August 8 Share Posted August 8 Please sign in to view this quote. Wouldn't this only be applicable for ASME and not ISO? Link to comment Share on other sites More sharing options...
[Th...] Posted August 8 Author Share Posted August 8 Thanks Owen but for the same part and on the same surface can flat be worse? I can't see how it can be. Link to comment Share on other sites More sharing options...
[To...] Posted August 8 Share Posted August 8 Please sign in to view this quote. Thanks Owen, but I don't believe this one is mine. 🙂 Link to comment Share on other sites More sharing options...
[Ma...] Posted August 8 Share Posted August 8 Please sign in to view this quote. Since you can not use parallel on same plane as base plane here comes different thickness and surface form. So since flatness gives you distance from min - max point after calculated plane ( i believe it's used minimum ) Parallelism gives you worst deviation from calculated plane of base feature. Link to comment Share on other sites More sharing options...
[Ri...] Posted August 8 Share Posted August 8 If we are talking Orientation Parallelism only, then yes it's possible to have a worse Flatness than Parallelism result, but if it's a TIR style measurement, then I don't see how it's possible to have a Flatness worse than Parallelism result. Link to comment Share on other sites More sharing options...
[Je...] Posted August 9 Share Posted August 9 In ASME this is not possible. Parallelism IS Flatness with orientation. Parallelism controls flatness so that flatness callout is redundant or the parallelism control is excessive if this is ASME (I am not as well verse in ISO). If this is ASME, this is poor design. Flatness controls form. Parallelism controls form + orientation. Link to comment Share on other sites More sharing options...
[Da...] Posted August 9 Share Posted August 9 My guess is that Calypso is using the average of all points for parallelism and min/max points for flatness. Link to comment Share on other sites More sharing options...
[Je...] Posted August 9 Share Posted August 9 Please sign in to view this quote. You don't have to "guess". Evaluation methods should be understood when applied and factored for proper standards. https://portal.zeiss.com/knowledge-base?id=420544 Link to comment Share on other sites More sharing options...
[Ky...] Posted August 9 Share Posted August 9 I believe this document covers the definition of parallelism in ISO. As far as I can tell from the part I read, it still seems to be making sure all the points are within that tolerance zone, so I don't think it's an ISO thing either: https://www.researchgate.net/figure/SO- ... _238837369 My initial guess is some sort of evaluation settings (fitlers/outliers, etc), but like Jeff said, those callouts do seem like the department of redundancy department had a hand in it... Link to comment Share on other sites More sharing options...
[Ch...] Posted August 9 Share Posted August 9 Only thing I can think of : standard Calypso (non GDT Beta) allows to report Parallelism of a plane and it appears LSQ is default eval. Well I think we all know what can be done with LSQ and Averaging points. We could have a set of point that are +.003 and -.003 which puts flatness technically over .005 and parallel LSQ 'could' theoretically be good ... Should Calypso be evaluating minimum zone or OTE by default ?? .. thats another topic ... Also original dwg shared appears to be hand sketch, One example here : parallel not flat... tough to machine metal like this ? definetly. Impossible?? I've seen stranger things ... Link to comment Share on other sites More sharing options...
[Mi...] Posted August 12 Share Posted August 12 Please sign in to view this quote. *Below is talking about old Calypso, I have no idea how the new beta works* Talking ASME.... In your example, it doesn't matter what evaluation mode is used since it's an indirect Form control, Calypso uses the actual points regardless, this means your filter/outlier better be correct To prove it, Take a program with real data and a Plane to Plane Parallelism callout, ONLY change the toleranced feature from LSQ to anything else... the result should not change. If you change the evaluation mode of the datum plane...then yes your result will change. Same is true for other GD&T Characteristics like Flatness, Perpendicularity that Directly or Indirectly control form. It is NOT true for Position... Flatness cannot be worse than Parallelism in ASME. Flatness is indirectly controlled by Parallelism. Link to comment Share on other sites More sharing options...
[Da...] Posted August 12 Share Posted August 12 Not explicitly discussed here, but: thickness variation and parallelism are also different things, right? Link to comment Share on other sites More sharing options...
[Ri...] Posted August 13 Share Posted August 13 Please sign in to view this quote. From an ISO GPS perspective the parallelism requirement will control both form and orientation with its tolerance zone, so the flatness requirement is redundant in your example. Link to comment Share on other sites More sharing options...
[To...] Posted August 13 Share Posted August 13 From a designer's prospective, the primary datum feature should have form control on it. So, in the OP's example, Datum A should have a flatness and a parallelism to A, as shown. To add to my first first line, the secondary and tertiary datum features should have form and location/orientation controls related to the primary datum feature. Link to comment Share on other sites More sharing options...
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