I'm dealing with an older program that I'm questioning the validity of and want to make sure I understand this correctly. Say I have a hole pattern that has a position callout to AXY, all of which are planes. The holes have basic dimensions that originate from one of the holes, but that hole is not a datum. It's just an origin point for the basic dimensions. So the basic dimension for that hole is actually 0,0. By creating an alignment to that hole, I can then select "Report to current alignment" so the nominals on the report match the basic dimensions on the print. As I understand it, PC DMIS creates a hidden alignment in the background to match the FCF, so the results are still valid. They're just being reported differently. Now here's where I think this old program is not correct. The program defines that origin hole as Datum B, even though the print does not, and the FCF in the position dimension is AB. So, the reported nominals match the basic dimensions on the print and everything appears to be in-tolerance. But the DRF is not the same as the print. Now correct me if I'm wrong, but this will give a different (and potentially incorrect) result than the previous method because it's being held to a completely different DRF than the print calls out. My assumption is that the programmer at the time either did not understand that you can report to the current alignment or he did not understand that the hole was just an origin point, not a Datum. Or am I the one who doesn't understand? Does this give a different result than aligning to the origin hole and reporting to that alignment? Or would the two results actually be the same? I hope all that was clear.
