Can someone please give me brief steps on how to do MMB on a secondary datum using GeoTol or Legacy (doesn't matter). Right now the secondary datum is two planes and a constructed width. So I am using the constructed width as my DATDEF/in my FCF. I am using GeoTol currently. Do I need to construct a circle from the constructed width? And where would I input the tolerances for that datum? Do I use the Size dimension prior to dimensioning the true position? Sorry I do this type of thing so infrequently
Constructing a width and referencing that width in the DATDEF command is the correct approach. You do not need to construct a circle from the width - that was a work-around for auto-slot features referenced at MMB/LMB when using legacy dimensioning or XactMeasure.
Check your drawing to see if there is any GD&T relating the width at MMC back to the primary datum - there should be a perpendicularity, parallelism or position. This would need to be created first and allows PC-DMIS to calculate the correct material boundary and apply the maximum allowable datum shift. If there is no such tolerance present in the routine ABOVE the point where you insert your position command, then PC-DMIS will only use the size aspect of the width, resulting in a lesser amount of datum shift. You can use the size command to supply this information (again, it must be present prior to any other geometric tolerance command referencing that width as a datum) or you can enter the datum size information on the nominals tab of the geometric tolerance dialog. Obviously, if there is a GD&T callout linking your width back to your primary datum and you add it to your routine as I have described, you would supply the size information for the width within that command.
Constructing a width and referencing that width in the DATDEF command is the correct approach. You do not need to construct a circle from the width - that was a work-around for auto-slot features referenced at MMB/LMB when using legacy dimensioning or XactMeasure.
Check your drawing to see if there is any GD&T relating the width at MMC back to the primary datum - there should be a perpendicularity, parallelism or position. This would need to be created first and allows PC-DMIS to calculate the correct material boundary and apply the maximum allowable datum shift. If there is no such tolerance present in the routine ABOVE the point where you insert your position command, then PC-DMIS will only use the size aspect of the width, resulting in a lesser amount of datum shift. You can use the size command to supply this information (again, it must be present prior to any other geometric tolerance command referencing that width as a datum) or you can enter the datum size information on the nominals tab of the geometric tolerance dialog. Obviously, if there is a GD&T callout linking your width back to your primary datum and you add it to your routine as I have described, you would supply the size information for the width within that command.
