[Cl...] Posted May 10, 2021 Share Posted May 10, 2021 This partial cylinder is Datum -A-. perpendicular wall of the larger cylinder on the right is Datum -B-. There is a .050 perp callout for -A- to -B-. The repeatability of the type 1 is terrible. Any suggestions as to how I can improve it? Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/ Share on other sites More sharing options...
[Ün...] Posted May 10, 2021 Share Posted May 10, 2021 Are these two references processed in the same operation. If yes, this deviation is not normal. I check the cylindrical diameters of ref A, the diameter differences of 3 circles, and the flatness of reference B. Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65408 Share on other sites More sharing options...
[Cl...] Posted May 10, 2021 Author Share Posted May 10, 2021 Yes to your first question. Each of the tree diameters are within couple of tenths. Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65410 Share on other sites More sharing options...
[Pe...] Posted May 10, 2021 Share Posted May 10, 2021 I would check the flatness of -B- as Ünal Kırat suggested. Even if your features are processed at the same time, I doubt it would be the same tool for all the features. I would expect a lathe to turn the diameters and also the datum -B- surface, and then come in with an endmill to cut the flat on -A-, meaning there might be a mismatch between the lathe cut -B-, and the area that an endmill cleans it up. Looking at the -B- flatness would tell you that. That is also an odd callout. I think Perp -B- to -A- is more normal. Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65412 Share on other sites More sharing options...
[SH...] Posted May 10, 2021 Share Posted May 10, 2021 Please sign in to view this quote. What is your evaluation LSQ or OTE? Is there is any probe shanking? Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65414 Share on other sites More sharing options...
[Da...] Posted May 10, 2021 Share Posted May 10, 2021 Any chance you're shanking ? Tight fixture ? Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65416 Share on other sites More sharing options...
[Jo...] Posted May 10, 2021 Share Posted May 10, 2021 Please sign in to view this quote. Still could be banana shaped from milling flat Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65418 Share on other sites More sharing options...
[Cl...] Posted May 10, 2021 Author Share Posted May 10, 2021 Please sign in to view this quote. Scanning the three circles, no shanking. I'm re-designing the fixture to start with and then doing another type 1. I think part of the problem is the fixture constraining/stressing the part too much. Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65420 Share on other sites More sharing options...
[Er...] Posted May 10, 2021 Share Posted May 10, 2021 Have you tried scanning line paths along the cylinder? I have had some great success using lines, especially on short cylinders. Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65422 Share on other sites More sharing options...
[Cl...] Posted May 10, 2021 Author Share Posted May 10, 2021 Please sign in to view this quote. Haven't tried that. It is short and is an interrupted surface (the flat) so I can only scan 300 degrees on each circle path. I'll give that a try Eric. My holding fixture is a little suspect as well. Good stuff, thanks for the input! Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65424 Share on other sites More sharing options...
[Cl...] Posted May 11, 2021 Author Share Posted May 11, 2021 Turns out the holding fixture I was using was distorting the part. The datum cylinder is working fine. I re-designed the fixture and now I pass the type 1. Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65426 Share on other sites More sharing options...
[SH...] Posted May 12, 2021 Share Posted May 12, 2021 Please sign in to view this quote. Can I ask what you mean by type 1?? Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65428 Share on other sites More sharing options...
[Cl...] Posted May 12, 2021 Author Share Posted May 12, 2021 Please sign in to view this quote. A type 1 Gage R&R. One part cycled 10x, on/off fixture. Link to comment https://qualityforum.zeiss.com/topic/12940-poor-datum/#findComment-65430 Share on other sites More sharing options...
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