Dimensioning Datums for MMB

Question

As I understand it, if you want to apply a MMB modifier to a datum in a FCF, you must first ensure that said datum has already been dimensioned with tolerances to determine its MMC and LMC. So my question is, does it need to be dimensioned with a size dimension and default math, or will a location dimension with LSQ math also work? And if you happen to have both in your routine (with the same tolerances applied), will that mess up the position calculation?

Neil Challinor · Accepted Answer

This is explained in the help file : PC-DMIS Help Center - 2023.2 (hexagonmi.com) 
 The easiest thing to do is to include the size in your Geometric tolerance commands for the datums. If you need to do the sizes separately then you should use a size command, the geometric tolerance command does not recognise location dimensions.

Neil Challinor · Answer

ESchertz I took a look at the routine you sent me and think I can explain. The problem is that you're editing existing commands so the tolerances don't automatically ripple through the rest of the program when you change them. If you were creating a fresh routine, each command would read up and grab the information as they are being created. To get that same behaviour in existing commands, you need to force them to update by removing and then re-adding the feature. You would need to do this in the edit window, not the dialog, because the dialog "remembers" what tolerances were previously set. To do it through the dialog, you would have to edit (F9), remove the feature and replace with something else, then create, then edit (F9) again, restore your original feature and create. 
 I also noticed a lot of spaces in your feature and dimension names which can also cause problems, especially when (as you have) there are several names that all begin with the same string (DATUM C ...... in your case). When you have this type of scenario, PC-DMIS can get in a state where it only reads up to the first space and then doesn't know which item it is supposed to be referencing because, as far as PC-DMIS is concerned, it sees multiple items with the same name.