[Za...] Posted February 9, 2023 Share Posted February 9, 2023 Hello everyone, I just wanted to see how you might handle this concentricity callout in this cavity: It says that each diameter much be concentric with each other and I was trying to avoid having 4 concentricity callouts for each diameter if at all possible. I know concentricity is obsolete, but I'm curious how you guys would handle this. I've tried a 3d line that recalls all of the diameters and using that as my comparison, but the results are less than desirable. Any and all help is appreciated! Thanks, Zach Link to comment Share on other sites More sharing options...
[Ma...] Posted February 9, 2023 Share Posted February 9, 2023 What about recalling all centers into 3d line and report straightness? Link to comment Share on other sites More sharing options...
[Ro...] Posted February 9, 2023 Share Posted February 9, 2023 Similar to Martin's response. Theoretical Cylinder created from "recall Feature points" of all your circles to create an "Average Cylinder" Then you can do a Concentricity from each individual circle to the constructed Cylinder. Circle must be selected first, then Cylinder second. Then use that Cylinder as Perpendicular to top Spot face. Link to comment Share on other sites More sharing options...
[Za...] Posted February 9, 2023 Author Share Posted February 9, 2023 Please sign in to view this quote. Thank you for the responses. The way we're building our inspection sheets, they're going to want the concentricity callouts rather than the straightness, but that's a good way to verify that the cavity is good so I might add that in as an extra check. How is creating a Cylinder with recall feature points different from the 3d line with the recall feature points? I'm still getting results that are way over .001" so I don't know. This is an aluminum part with form tooling, so I'm pretty confident the cavity is good. Link to comment Share on other sites More sharing options...
[Ma...] Posted February 9, 2023 Share Posted February 9, 2023 How do you measure it? That's pretty deep. 2 circles per cylinder? Roberto pointed better than me. You create common cylinder using recalled points to have best axis - 3d line with recalled measured points is not doog approach. After you create common cylinder, then report each seperate cylinder to common one. Straightness should give you concentricity-like number from all circles - having common axis and reported all at once ( maybe you will need to double the result from straightness to have same number - you can test it with theoretical circles with changed nominals ) Link to comment Share on other sites More sharing options...
[Ro...] Posted February 9, 2023 Share Posted February 9, 2023 Please sign in to view this quote. Link to comment Share on other sites More sharing options...
[Ri...] Posted February 10, 2023 Share Posted February 10, 2023 Please sign in to view this quote. What is the Form/Roundness of each cylinder? This will affect your results. Link to comment Share on other sites More sharing options...
[Ma...] Posted February 10, 2023 Share Posted February 10, 2023 Please sign in to view this quote. I don't understand your quote ( or question ), but how is evaluated feature for concentricity - i would doubt same evaluation as feature - Form/Roundness would apply for roundness, for concentricity it's axis deviation. Link to comment Share on other sites More sharing options...
[Ri...] Posted February 10, 2023 Share Posted February 10, 2023 Please sign in to view this quote. Pretend one cylinder has .005" roundness Another has .001" You axis can change based on where the center is found per roundness/form condition. If you look at the A1 and A2 values for either the Cylinder as a whole or a 3d Line any deviation can affect the center line of the axis. Roundess/Form can affect A1 and or A2 values. Similar to the attached image.Capture.JPG Link to comment Share on other sites More sharing options...
[Ma...] Posted February 10, 2023 Share Posted February 10, 2023 Please sign in to view this quote. I agree that A1,A2 will affect results when you have different lengths of cylinders. I don't agree that form will affect results - once it's evaluated it stays - only roundness is evaluate as minimum no matter what. Author can do all concentricity callouts for each cylinder ( which will be time consuming ), but over all they just need to have one common axis. Tolerance ,001" ( which is 0,0254 mm ) for those lengths of cylinders it's negligible. But if he want's to fully go with drawings, he needs to place all concentricity callouts as drawing says. Link to comment Share on other sites More sharing options...
[Er...] Posted February 10, 2023 Share Posted February 10, 2023 For cylinders I have found scanning 4 circles gives more consistent and accurate results. Sometimes I can get away with only three. Link to comment Share on other sites More sharing options...
[Jo...] Posted February 10, 2023 Share Posted February 10, 2023 Please sign in to view this quote. Concentricity is similar to derived median line straightness.. form will affect it. It is not "center" of a constructed circle.. It is the aggregate of multiple 2 point measurements into a diametrical zone, then extruded to a cylinder. There are several challenges to report this, one is that a 2d circle is alignment dependant. Link to comment Share on other sites More sharing options...
[Jo...] Posted February 10, 2023 Share Posted February 10, 2023 Please sign in to view this quote. ASME Y14.5-2009 is the last citation of concentricity. 7.6.4 Fig 7-60, also see ASME Y14.5.1-2019 Fig. 7-3 I'm not trying to be smart , I'm just trying to convey, the machine shop floor understanding of concentricity and the mathematical definition are totally different things. You need to understand which one you're talking about. Link to comment Share on other sites More sharing options...
[Ma...] Posted February 10, 2023 Share Posted February 10, 2023 Please sign in to view this quote. ASME Y14.5-2009 is the last citation of concentricity. 7.6.4 Fig 7-60, also see ASME Y14.5.1-2019 Fig. 7-3 I'm not trying to be smart , I'm just trying to convey, the machine shop floor understanding of concentricity and the mathematical definition are totally different things. You need to understand which one you're talking about. [/quote] Well I don't know and I don't have access to ASME, so clearly i don't know what you want to tell me. My guess was, that it doesn't matter if i'll use cylinder or 3D line when start point and A1,A2 angles are same. Or does concentricity something else then reporting the most deviation from center of main feature axis? I am not trying to be dificult - i just want to understand it clearly Link to comment Share on other sites More sharing options...
[Jo...] Posted February 10, 2023 Share Posted February 10, 2023 I assumed ASME because of the obsolete comment. I can't find a better example and I don't have an electronic copy of the old standard. Here are some picsMedian_Points.jpgconcentricity-median-line-l.jpgconcentricity-and-symmetry-l.jpg Link to comment Share on other sites More sharing options...
[Ma...] Posted February 10, 2023 Share Posted February 10, 2023 Please sign in to view this quote. Thanks for clearing - just looked up for ISO https://www.gdandtbasics.com/concentricity Anyway - recalling circle centers into 3d line should work same way - not? Link to comment Share on other sites More sharing options...
[Jo...] Posted February 10, 2023 Share Posted February 10, 2023 Please sign in to view this quote. No The 2009 version of the Y14.5 GD&T standard defines concentricity as “the condition where the median points of all diametrically opposed elements of a surface of revolution (or the median points of correspondingly located elements of two or more radially disposed features) are congruent with a datum axis (or center point).” It further recommends using concentricity tolerance only where “the relationship between the derived median points of the controlled feature and the datum axis is a primary design concern, or where the coaxial control of noncircular features is a design requirement.” This complicated definition and application criteria along with the confusion that they create are the main reasons that the constraint has been removed from the latest standard. Note that ASME’s definition of concentricity is very different from the common English definition according to Meriam-Webster: “concentric: (1) having a common center (2) having a common axis.” Link to comment Share on other sites More sharing options...
[Jo...] Posted February 10, 2023 Share Posted February 10, 2023 It is so misunderstood, that it appears on the 2009 GDTP exam and finally removed it altogether from the 2018 standard. The designer may not even understand what they are invoking. A T.I.R , roundness or some other controls have replaced it. Link to comment Share on other sites More sharing options...
[Ri...] Posted February 11, 2023 Share Posted February 11, 2023 I was told long ago, in a land far far away, when I have a cylindrical feature, create the scanned/trigger points so all points will have an opposing point. Never use an odd number of points if you have to use Concentricity. I'm not sure if that still applies, or if outliers, filters or the concentricity routine can alleviate that, but I still use this method. Link to comment Share on other sites More sharing options...
[Ow...] Posted February 13, 2023 Share Posted February 13, 2023 The attached come from a Zeiss provided GD&T training session back in 2011, before ASME Y14.5 changed their flavor in 2018. It's 82 pages but, does a good job explaining how concentricity is calculated/not-calculated in Calypso per the ASME 14.5 2009 STD. Essentially, a piece of angle-iron could have good concentricity by that standard that 1/2 the world still uses 🙄Concentricity_by _Mark-Foster-CALYPSO .pdf Link to comment Share on other sites More sharing options...
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