Position without DRF/Datums

Hey all,
Wondering how to best measure and report a pattern position without datums. (See Dim labeled 11 on attached print view). The three holes are properly dimensioned to each other with basics and are the primary datum so the GD&T checks out but I'm not sure how to do it properly on PCDMIS. I've used a constructed feature set for that Datum A made from three cylinders, and it seems to be the centerpoint between the three, but I cannot report position with GeoTol as it says datums are required. Do I have to use Legacy? And can MMC be applied in Legacy? Thanks in advance for any advice!

Attached Files

PositionQuestion.pdf

Parents

Neil Challinor over 3 years ago

edw.jack23 You need to measure the three diameters as cylinders making sure they all have the same nominal diameter and length. Next create a geometric tolerance command - position 0.1 (M) - referencing all three as the considered features and be sure to enter the correct tolerance values for the diameters so that the MMC is calculated correctly. Following that, INSERT>DIMENSION>DATUM DEFINITION, select all three cylinders from the feature list and define them as datum A. PC-Dmis will treat all three cylinders as a pattern and apply MMB based on their previously defined size tolerance (from the position command).
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel
edw.jack23 over 3 years ago in reply to Neil Challinor

So that's how you do it. That makes a lot of sense. I was using an alignment to one to get the basics to the the others, sort of a fake datum. It worked but this seems easier and more correct. Thank you!
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel

Reply

edw.jack23 over 3 years ago in reply to Neil Challinor

So that's how you do it. That makes a lot of sense. I was using an alignment to one to get the basics to the the others, sort of a fake datum. It worked but this seems easier and more correct. Thank you!
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel

Children

No Data