Help needed, for seat back frame free state coordinate system

I wrote this earlier and deleted it, because I don't want to mislead you, given we are in VERY different industries.
No one else has said anything, so I'm posting this with my concerns.
Please take it with a grain of salt, as your industry could be absolutely OK with what you have done and actually prefer and expect it as compared to what I'm about to say.



I would personally prefer you had made CYL_TA2 from circles A1 and A2. You are leveling, and leveling should be done to 3D features. Cylinders are three dimensional features and lines are not (I understand there are 3D lines in CMM software). I'm also making the assumption they are in a way ( you said a tube, but it could be bent) that could make a cylinder.
I'm in aerospace, not making seats for cars.
What you did could be the way it is done and I sound crazy. If the industry is doing it like you have done it, stick with that.

If the B1 and B2 holes can form a cylinder, I'd make a cylinder there as well. If intersecting, two cylinders will constrain all six degrees of freedom, the plane for C is unnecessary, but that doesn't mean an engineer couldn't use it for assembly purposes to make product definition.

If B1 and B2 can't make a cylinder (they are offset to each other), then a line between them for rotation would work.
If B1 and B2 are parallel to -A-, then I don't know how a line between them constrains rotation, which is what you say the engineer said. But you didn't do that, you spun rotation from A to B1, not a line from B1 to B2.

You set Z not to C, but to A1. In fact, you have all three axes zeroed to A1, a circle, which is not permitted in the portion of aerospace I'm in. Again, if this is the norm for your industry, stick with it.

I think it should be more:
Level YPLUS CYL_TA2
Trans X CYL_TA2
Trans Z CYL_TA2
Rotate XPLUS to cir_B1 and Cir_B2 about YPLUS
Trans Z PLN_C

Axes don't matter that much, I'm guessing you used YPLUS because the seat is laying down on the bed of the CMM.

Hi Rob,

I used to work for a company which manufactured seat frames here in the UK.

Normally, the seat back was aligned by creating a 3D line between either the recline mechanism holes or the 'H' point. The 'H' point being the theoretical hip. Or it could be datum holes on both side-members. Your B1/2?
Level the 3D line
create a midpoint between the side-member datums measured with sample hits, again B1/2? This may then be your Datum XYZ.
Measure a circle on the top tube and rotate from the datum to this circle. (the upper datum could be the symmetry of the headrest support tubes instead?). rotate to the required angle.

It would be unusual if your main datum was at the top of the seat rather than the bottom.

Maybe you could sketch out the drawing alignment?

HTH.

Neil