[Ky...] Posted January 13, 2020 Share Posted January 13, 2020 We have a part that has a key in it with .001 TP called out with MMC. I programed it like I program a slot with MMC. 2 Planes, Create a line perpendicular to the planes, place a point on the center of the line, Create a theoretic circle and have the length of the line control the diameter of the circle. This controls the MMC tolerancing. As shown on the print the key is .471 +0 -.004. But Saturday we had a key that was the smallest it has ever been .4679 , the True position is .002, The key is .001 from center. But the CMM say tolerance is .0019 with MMC and show the key True position out of tolerance. But shouldn't the tolerance be .0031 because you start from the top and work down on a outside dimension?? HELP!!! My brain has been thinking about this all weekend and its tired. KyleMMC on Key.png Link to comment https://qualityforum.zeiss.com/topic/16836-mmc-on-a-key/ Share on other sites More sharing options...
[Wi...] Posted January 13, 2020 Share Posted January 13, 2020 .471"-.004" =.467" the smallest size the slot is allowed to be. Thats the MMC... Your actual is .4679. So .4679"-.467"=.0009" plus stated tolerance of .001 is .0019... Hope that helped Link to comment https://qualityforum.zeiss.com/topic/16836-mmc-on-a-key/#findComment-94174 Share on other sites More sharing options...
[Ky...] Posted January 13, 2020 Author Share Posted January 13, 2020 The .471 +.000/-.004 is the tolerance of the key. Link to comment https://qualityforum.zeiss.com/topic/16836-mmc-on-a-key/#findComment-94176 Share on other sites More sharing options...
[Ja...] Posted January 13, 2020 Share Posted January 13, 2020 Ignoring the MMB on datum A - Your O.D. Width will be at MMC size at the largest allowable size, namely .471. You are measuring it at .4679, so the difference of .471 - .4679 = .0031 will be added to your .001 Position tolerance. You will have a Position tolerance of .0041. Check that the size is being computed correctly and you are in the correct workplane. I personally don't create the perpendicular lines and circle for MMC purposes, I just position the midplane and I use a formula for the tolerance that takes into consideration the width size when aligned correctly to the DRF. Link to comment https://qualityforum.zeiss.com/topic/16836-mmc-on-a-key/#findComment-94178 Share on other sites More sharing options...
[Cl...] Posted January 13, 2020 Share Posted January 13, 2020 You can construct a symmetry plane (Features - Special Geometry - Symmetry Plane), which you can then use for MMC. Link to comment https://qualityforum.zeiss.com/topic/16836-mmc-on-a-key/#findComment-94180 Share on other sites More sharing options...
[Ri...] Posted January 13, 2020 Share Posted January 13, 2020 This is an OD Key? If you are using theoretical features, make sure that it is properly set as an OD instead of an ID. Link to comment https://qualityforum.zeiss.com/topic/16836-mmc-on-a-key/#findComment-94182 Share on other sites More sharing options...
[Ja...] Posted January 13, 2020 Share Posted January 13, 2020 Please sign in to view this quote. This must be the solution, you were granted .0009 additional tolerance instead of .0031. Link to comment https://qualityforum.zeiss.com/topic/16836-mmc-on-a-key/#findComment-94184 Share on other sites More sharing options...
[Ky...] Posted January 13, 2020 Author Share Posted January 13, 2020 Was just fixing to call you Richard. Will look at that. Link to comment https://qualityforum.zeiss.com/topic/16836-mmc-on-a-key/#findComment-94186 Share on other sites More sharing options...
[Ky...] Posted January 13, 2020 Author Share Posted January 13, 2020 Yes Richard you were right. I had the circle as a hole not a boss. Changed that and it fixed my problem. Thanks to everyone for helping me fix MY error. Kyle Link to comment https://qualityforum.zeiss.com/topic/16836-mmc-on-a-key/#findComment-94188 Share on other sites More sharing options...
[Wi...] Posted January 13, 2020 Share Posted January 13, 2020 Oops... thought it was an id Link to comment https://qualityforum.zeiss.com/topic/16836-mmc-on-a-key/#findComment-94190 Share on other sites More sharing options...
[Ky...] Posted January 13, 2020 Author Share Posted January 13, 2020 No worries William, Thanks for trying to help. Kyle Link to comment https://qualityforum.zeiss.com/topic/16836-mmc-on-a-key/#findComment-94192 Share on other sites More sharing options...
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