[Je...] Posted January 14, 2021 Share Posted January 14, 2021 I have two suppliers of the part attached . One uses a tri lobe chuck and datum B is distorted but while the part measures in print ..it will not function. The other supplier uses pie jaw chucks measures in print and no issues. I ask engineering for a simple cylindricity call out on datum B. and was told it was not needed as the part is NOT to print ? I have attached the section of the drawing and the response ..What is the correct methodology here ? Thanks in advance ! Link to comment Share on other sites More sharing options...
[To...] Posted January 14, 2021 Share Posted January 14, 2021 If the drawing states "Per ASME Y14.5" then the engineer would be correct. Link to comment Share on other sites More sharing options...
[Ri...] Posted January 14, 2021 Share Posted January 14, 2021 As Tom said, per ASME, the envelope rule is invoked by default. In ISO it would have to be specified. Link to comment Share on other sites More sharing options...
[Ke...] Posted January 14, 2021 Share Posted January 14, 2021 Please sign in to view this quote. I'm getting hung up where you say that both supplied parts "measures in print", but engineering says "the part is NOT to print" ...seems like a riddle. While the Envelope Principle controls the form in ASME by default, and is not *necessarily* a requirement to put it on the print, if the form of Datum B is found to be a root cause of fit/function, then it may be time for a print update. Personally, if I am investigating a part issue, I have no problem putting in a cylindricity result as "REFERENCE ONLY", to highlight the suspect conditions (of course you may want to present it in a separate report) Link to comment Share on other sites More sharing options...
[Ri...] Posted January 14, 2021 Share Posted January 14, 2021 Please sign in to view this quote. His post talks about how they are held differently. Supplier A is holding the parts in a way that produces a tri-lobe effect. The part measures in specification (most likely with LSQ). Supplier B is holding the parts in a way that doesn't produce a tri-lob effect. The part measures in specification as well. Engineer is saying they do not measure in specification (most likely referring to a fit-function OTE). This is kind of my reading between the lines interpretation. A plug gage is always a great tool to have for cases like this. Link to comment Share on other sites More sharing options...
[Me...] Posted January 14, 2021 Share Posted January 14, 2021 Here's a good article on this subject..... https://iigdt.com/Content/Articles/are ... ectly.htm Link to comment Share on other sites More sharing options...
[To...] Posted January 14, 2021 Share Posted January 14, 2021 Please sign in to view this quote. Sometimes a drawing revision is not a reality. Link to comment Share on other sites More sharing options...
[Je...] Posted January 14, 2021 Author Share Posted January 14, 2021 Thanks Tom, I ran a full print report with everything in specification. They complained that the part would not fit so I re checked and added the cylindricity report. Link to comment Share on other sites More sharing options...
[Je...] Posted January 14, 2021 Author Share Posted January 14, 2021 Thanks to ALL for the replies Jerry Link to comment Share on other sites More sharing options...
[Ri...] Posted January 14, 2021 Share Posted January 14, 2021 Add a second diameter check, and change the evaluation to Outer Tangential. That will simulate fit/function for you. Link to comment Share on other sites More sharing options...
[Ke...] Posted January 14, 2021 Share Posted January 14, 2021 Please sign in to view this quote. Yeah, my 20+ years in metrology has definitely found this to be true, but it all depends on the circumstances. I have found more willingness to engage the customer on print revisions during product development, and initial PPAP, than *after* product launch. Whether the company one works at is on the supply side, or the end item customer, also makes a difference. ...I guess I'm an optimist 🤣 Link to comment Share on other sites More sharing options...
[Ri...] Posted January 14, 2021 Share Posted January 14, 2021 Depending on the customer, it can be a huge ordeal for a drawing change. An example of a nightmare is in the automotive world where a lot of times you are Tier-3, and Tier-2 is the designer - it still has to be approved by Tier-1. I took the initiative to be more active in the bidding process to try and catch things early on. It made life so much simpler down the road. Link to comment Share on other sites More sharing options...
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