Iterative alignment and using XactMeasure

I'm looking for a way to get my nominals to come from the datums, not from my trihedron. Iterative alignment will align to trihedron not the datums. I guess my problem is making Datum "A" an origin more than the Iterative alignment. The Iterative alignment part of the problem is just what I thought would fix the problem, and apparently it will not. All of the information on Iterative alignments is great, but is not the answer I'm looking for. I guess all I really want to know is how do you orgin on an irregular CAD surface?

Iterative alignments are great for measuring parts in aircraft/car body coordinates, but that seems to be about it. When you need your report to measure from the datums and not the trihedron, its not effective alone.

Ignore the trihedron. Iterative alignment is a CAD alignment, or PART alignment.

A 3-2-1 alignment uses features to align, and YOU tell Pcdmis what those features need to be, nominal-wise.
An Iterative alignment uses features to align, but the CAD data tells Pcdmis what those features need to be, nominal-wise.

The ONLY way to "level" to a non-planar, non-flat surface is ITERATIVE alignment. EVERY PART has datums, even car position parts. There are "A" datums, "B" datums, "C" datums, as many datums as you want, just like for every other part out there.

DATUM does NOT EQUAL ZERO. It never has, it never will. A datum CAN BE zero, but it does not have to be zero. Datums are the "START POINTS" for inspection.

The top of a flat, square 123 block that is the "A" datum can be Z0, Z1.0, Z523.984. It makes NO DIFFERENCE. DATUM <> 0, it never has. The trihedron is nothing more than a visual aid for you to see which way each axis is pointing in the current alignment, NOTHING more. The trihedron <> 0 anymore than DATUM.

'top, curvy, non-flat' surface = "A Datum". Pick 3, 4, 5,000 points on that surface, from the CAD DATA (and the "B" and "C" datums as well). BEFORE you measure them, OPEN the alignment utility, go to iterative alignment, select all those points on the "A DATUM" surface for the "LEVEL" features, pick the "B" feature for the rotate, pick the "C" features for the origin.

Pcdmis will then "level" and "origin" to those "A" features. It will 'rotate' and 'origin' to the "B" features. It will origin to the "C" feature. And guess what? You are NOW origined to ALL your datums, no matter what their numerical value is, be it Z127.398 or Z-1928.392. Pcdmis will have them as close as possible to the nominal values as can be done.

I guess if you don't get it after all this, you either need to find some other calling or go to Pcdmis classes.

I'm looking for a way to get my nominals to come from the datums, not from my trihedron. Iterative alignment will align to trihedron not the datums. I guess my problem is making Datum "A" an origin more than the Iterative alignment. The Iterative alignment part of the problem is just what I thought would fix the problem, and apparently it will not. All of the information on Iterative alignments is great, but is not the answer I'm looking for. I guess all I really want to know is how do you orgin on an irregular CAD surface?

Iterative alignments are great for measuring parts in aircraft/car body coordinates, but that seems to be about it. When you need your report to measure from the datums and not the trihedron, its not effective alone.

Ignore the trihedron. Iterative alignment is a CAD alignment, or PART alignment.

A 3-2-1 alignment uses features to align, and YOU tell Pcdmis what those features need to be, nominal-wise.
An Iterative alignment uses features to align, but the CAD data tells Pcdmis what those features need to be, nominal-wise.

The ONLY way to "level" to a non-planar, non-flat surface is ITERATIVE alignment. EVERY PART has datums, even car position parts. There are "A" datums, "B" datums, "C" datums, as many datums as you want, just like for every other part out there.

DATUM does NOT EQUAL ZERO. It never has, it never will. A datum CAN BE zero, but it does not have to be zero. Datums are the "START POINTS" for inspection.

The top of a flat, square 123 block that is the "A" datum can be Z0, Z1.0, Z523.984. It makes NO DIFFERENCE. DATUM <> 0, it never has. The trihedron is nothing more than a visual aid for you to see which way each axis is pointing in the current alignment, NOTHING more. The trihedron <> 0 anymore than DATUM.

'top, curvy, non-flat' surface = "A Datum". Pick 3, 4, 5,000 points on that surface, from the CAD DATA (and the "B" and "C" datums as well). BEFORE you measure them, OPEN the alignment utility, go to iterative alignment, select all those points on the "A DATUM" surface for the "LEVEL" features, pick the "B" feature for the rotate, pick the "C" features for the origin.

Pcdmis will then "level" and "origin" to those "A" features. It will 'rotate' and 'origin' to the "B" features. It will origin to the "C" feature. And guess what? You are NOW origined to ALL your datums, no matter what their numerical value is, be it Z127.398 or Z-1928.392. Pcdmis will have them as close as possible to the nominal values as can be done.

I guess if you don't get it after all this, you either need to find some other calling or go to Pcdmis classes.