Iterative alignment and using XactMeasure

Alright here is my problem/question.
I have a part where Datum -A- (Z axis) is not prismatic, however datum -B- (X axis) and -C- (Y axis) are.

I do not have much experience with Iterative alignments other than that I have been to the Level 2 Hexagon class (Just don't use them or have the need too).

My thoughts were, this is a good time, to try an Iterative alignment.
I believe I have that part of the program correct:
I created 6 auto vector points on top (Datum -A-),
then 5 auto vector points on left side (Datum -B-)
then finally 5 auto vector points on the front of the part (Datum -C-).

When I create the Iterative alignment I pick top 6 points as level (Datum -A-),
5 points on left rotate (Datum -B-),
then 5 points on front as origin (Datum -C-).

After completing this Iterative alignment my trihedron doesn't move from before the alignment.
So I constructed planes out of the five points for datum -B- and -C- respectively.
I then origin my "X" to Datum -B- and my "Y" to datum -C-.
How do I origin my "Z", and how do I assign my datum -A- for exact measure? Where did I go wrong? Please any help would be greatly appreciated.

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NinjaBadger over 9 years ago

It is NOT ok of for me to leave it in body position! My customer requirements are to have the dimensions report out from the Datums, not the CAD origin. My report would need to say 1 inch from "X" and 1 inch from "Y". I have no way of measuring Datum "A" to my CAD origin due to it being an irregular surface.

How can you report out from datum A when it's not a prismatic feature? Where about on this irregular feature do you want your zero/origin to be exactly?

Iterative is the only way to align a part like this.

Now once you've aligned using iterative you could translate your origin by a given value so the zero moves where you want it. i.e. if your two holes are perpendicular to datum A (or should I say they are square to the axis controlled by Datum A) then you could move it by the theo values of datum B so you're origined over this hole, but how much you move it up or down to the datum A surface is anyone's guess!

Not sure if that's clear, but it would be like aligning to the corner of a 1-2-3- block, then measuring a hole and reporting the deviations. Your nominals would come from the corner.

You could then offset the alignment by the nominal values so the hole's theoretical location would be 0,0. If you report the location again the deviations would be identical, but the Noms would be 0,0. The edges you aligned to are still the datums (i.e. They are right/have zero deviation) even though their nominal values are no longer zero!
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NinjaBadger over 9 years ago

It is NOT ok of for me to leave it in body position! My customer requirements are to have the dimensions report out from the Datums, not the CAD origin. My report would need to say 1 inch from "X" and 1 inch from "Y". I have no way of measuring Datum "A" to my CAD origin due to it being an irregular surface.

How can you report out from datum A when it's not a prismatic feature? Where about on this irregular feature do you want your zero/origin to be exactly?

Iterative is the only way to align a part like this.

Now once you've aligned using iterative you could translate your origin by a given value so the zero moves where you want it. i.e. if your two holes are perpendicular to datum A (or should I say they are square to the axis controlled by Datum A) then you could move it by the theo values of datum B so you're origined over this hole, but how much you move it up or down to the datum A surface is anyone's guess!

Not sure if that's clear, but it would be like aligning to the corner of a 1-2-3- block, then measuring a hole and reporting the deviations. Your nominals would come from the corner.

You could then offset the alignment by the nominal values so the hole's theoretical location would be 0,0. If you report the location again the deviations would be identical, but the Noms would be 0,0. The edges you aligned to are still the datums (i.e. They are right/have zero deviation) even though their nominal values are no longer zero!
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