[Ma...] Posted January 22 Share Posted January 22 Howdy, Im confused on if what im doing is correct. Datum B is called out as the profile of a surface (it happens to be a cylinder) And B is called out for finding True Position of a bolt pattern, obviously there's no option to select a profile as the secondary datum. At the moment I have created a cylinder and recalled feature points from multiple scans that follow the desired surface and using that as Datum B. I am just looking for some clarification on if this is an accurate way of going about it. Thanks for the help! -Max Link to comment Share on other sites More sharing options...
[Da...] Posted January 22 Share Posted January 22 (edited) It's the radius that is the datum, not the profile. The profile is called out on the datum B surface. The profile looks to be redundant, because the radius tolerance is the same. Edited January 22 Link to comment Share on other sites More sharing options...
[Cl...] Posted January 22 Share Posted January 22 Also, not a very stable datum. Link to comment Share on other sites More sharing options...
[Ma...] Posted January 22 Author Share Posted January 22 Please sign in to view this quote. lol. Link to comment Share on other sites More sharing options...
[Ma...] Posted January 22 Author Share Posted January 22 Please sign in to view this quote. sounds about right, thats kind of what i figured, Thank! Link to comment Share on other sites More sharing options...
[Da...] Posted January 23 Share Posted January 23 (edited) I'm assuming this is in inches. Still, using a 30° radius sector as a datum seems a bit foolhardy, even with a tolerance zone of +0.025"/-0.000". My experience with zeroing on a radius of anything less than a 60° sector have been mostly futile. That radius has to be REALLY carefully machined! I guess the profile was added as if to say "this surface MUST have a +0.025"/-0.000" EVERYWHERE". Not really necessary, IMO.... BTW, what is dimensioned off this datum, and what are the tolerances like for them? Edited January 23 Link to comment Share on other sites More sharing options...
[Ma...] Posted January 23 Share Posted January 23 I would say that for surface profile is missing basic dimension for radius/diameter. It's in MM and even with that tolerance it would be 80,75 +/- 0,125. Is this whole part or is that 1 of x? Link to comment Share on other sites More sharing options...
[Da...] Posted January 27 Share Posted January 27 I'm also assuming that there are at least 2 other 'sector elements' of the same radius not shown on the print? Link to comment Share on other sites More sharing options...
[Ma...] Posted February 6 Author Share Posted February 6 Please sign in to view this quote. Most of the features that use datum B have a tolerance of 0.05mm, position, and profiles mostly. I have brought that up to the engineers with this not being a reliable datum, but went in one ear and out the other... Got some time to revisit this project today and realized the profile measurement is coming out to about 0.40mm. The shop that made these did an inspection and had values around 0.06-0.07mm. I'm in my first year of Calypso programing and I have not encountered this issue yet, if you have any ideas as to why my profile is so high id like to hear them. I noticed if I use a Best Fit from a bore position as an alignment for my Datum B profile my values get substantially smaller(0.07mm) but I don't believe this is stable. Right now the profile of B is using the part BA. Thanks for the help. Link to comment Share on other sites More sharing options...
[Ma...] Posted February 6 Author Share Posted February 6 Please sign in to view this quote. 1 of 8 Link to comment Share on other sites More sharing options...
[Da...] Posted February 7 Share Posted February 7 Avoid edges...... Link to comment Share on other sites More sharing options...
[Ma...] Posted February 7 Share Posted February 7 I would rather use FF for surface profile, because of no alignment. If you use cylinder, then you have to assure that nominals for origin and vector matches actuals. Only radius has to be same as drawing. What numbers it's giving you with only cylindricity? It should be roughly the same as profile if shape is good. Is there number of segments anywhere near the definition of radius R80.75 ( you wrote 8 segments )? This would apply as one cylinder as datum B from eight surfaces. That should correct TP. Link to comment Share on other sites More sharing options...
[Ma...] Posted February 7 Author Share Posted February 7 Please sign in to view this quote. Much obliged.......... Link to comment Share on other sites More sharing options...
[Ma...] Posted February 7 Author Share Posted February 7 Please sign in to view this quote. Boy do I owe you a beer! The FF surface (recall points from cylinder B) allowed me to use no datum and that's exactly what I was looking for. Reading 0.035mm for profile now. Seems much more trustworthy. Link to comment Share on other sites More sharing options...
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