[Ri...] Posted October 13, 2022 Share Posted October 13, 2022 Why does the same feature report what appears to be two greatly deferent results for the following methods: (All numeric values are in inches). Bilateral with unequal distribution - one result. Bilateral with unequal distribution - two results. It seems to me that "Bilateral with unequal distribution - two results." ignores the size of the feature. (Feature nominal: Ø1.28150, Feature actual: Ø1.25938, deviation: 0.02212) See the attached JPG files. Why are these results so different?Profile_Unequal Dist with 2 results.JPGProfile_Unequal Dist with 1 result.JPG Link to comment Share on other sites More sharing options...
[SH...] Posted October 13, 2022 Share Posted October 13, 2022 Profile tolerance is being calculated by determining the maximum dviation from tolerance zone symmetry line, I think in that 2 cases symmetry line is different. Can I ask under what circumstance we should use bilateral tolerance zone with unequal distribution having two result?? What is the significance of the xyz value(additional report)??, I think it is being calculated from the maximum point and minimum point.. Link to comment Share on other sites More sharing options...
[Th...] Posted October 13, 2022 Share Posted October 13, 2022 Funny, I just finished typing up something on almost the same topic. So as far as I can tell unequal 2 does the same thing as equal 2, where it just reports the greatest plus and minus deviations from the true profile. As reported, those appear to be +0.00413" and -0.00759". The only difference from equal distribution is the reported + and - edges of the tolerance zone. Unequal 1 follows a formula shown in ASME Y14.45 or is coincidentally matching it. This is P=T+2g. P is the profile result, T is the total width of the zone, and g is the shortest distance from a measured point to the zone boundary. g is a negative value within the zone, and positive without. In this case, with a bias of +0.03" and -0.01", your shortest distance is from the -0.00759" point to the -0.01" zone boundary, where g = -0.00241. Thus, P=0.04+2(-0.00241) = 0.04-0.00482 = 0.03518". With your report showing just 10 millionths off, I would say Calypso is rounding the displayed values. Link to comment Share on other sites More sharing options...
[Ro...] Posted October 13, 2022 Share Posted October 13, 2022 The tolerances are different in the 2 examples. And what Thomas said. Link to comment Share on other sites More sharing options...
[Ch...] Posted October 13, 2022 Share Posted October 13, 2022 This is a great catch , I just caught this recently as well.. See attached and my other posts .. https://portal.zeiss.com/my-voice/softw ... 26866162b2GDT Differences ASME and ISO.pdf Link to comment Share on other sites More sharing options...
[Ri...] Posted October 13, 2022 Share Posted October 13, 2022 My monkey brain doesn't allow for the comprehension as to why you would ever have the need for an unequal distribution or even a unilateral tolerance zone. Most of the machinists that I'm encountering now just make everything to the nominal of the model, so just sounds like a recipe for disaster. Link to comment Share on other sites More sharing options...
[Ri...] Posted October 13, 2022 Author Share Posted October 13, 2022 Please sign in to view this quote. I can assure you the tolerance in the Profile dialog is the same, why it displays differently I do not know, never really noticed it before. Link to comment Share on other sites More sharing options...
[Th...] Posted October 13, 2022 Share Posted October 13, 2022 Please sign in to view this quote. We make heavy use of unequal distribution for areas of parts that get hand finished. Allowance for the inherent variation between people when removing material from a surface, while maintaining limits for our cosmetic criteria. Link to comment Share on other sites More sharing options...
[Ch...] Posted October 13, 2022 Share Posted October 13, 2022 I see ISO seems to offset the nominal profile - to keep the band 'equal' ; however I'm not a fan of it. EDIT : After further review Y14.45, I still need to read it in detail, it seems this is allowing for some 'offset' of the band. - which is news to me and differs from Y14.5-2009 I believe. EDIT2 : Yep, it seem per Y14.45 they are using the T + 2g calculation and shifting the profile, However per Y14.5-2018, I believe it clearly still states the bands apply from the TRUE PROFILE. Sec 11.3.1.1 + 11.3.1.2 (a) thru (d). - which is similar but still differs from ISO. Is there a Y14.5 version newer the 14.45 that correlates with this ? Yikes. Adding a 'growth factor' "g" to the calculation ? Jeesh, wish they could have left it simple enough as deviation from true profile (even though the doubling was over many peoples heads). More research to do before I try to comprehend this .. I'm sure Calypso clearly spells out how they report per which spec, etc.. and is easy for us to find .. 🤣 Link to comment Share on other sites More sharing options...
[Th...] Posted October 13, 2022 Share Posted October 13, 2022 I don't have a copy of 2018 to check, but I don't think the section on profile in 2009 actually specifies anything about result reporting at all. Presumably this is why 14.45 exists, additionally covering other measurements. At any rate, Y14.5-2018 is still the newest revision, and it is not currently being reviewed or revised. I believe the scope paragraph of 14.45 specifies 14.5-2018 as the version of note. Link to comment Share on other sites More sharing options...
[Er...] Posted October 15, 2022 Share Posted October 15, 2022 ASME Y14.5.1M section 6.5(c) says that there is "no single value" except for unilateral tolerances. In other words the committee could not agree 🤣 Link to comment Share on other sites More sharing options...
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