Individual feature control in a pattern

[bxbzq]

Hi,
In attached drawing, I want to control the two welded pieces. Look at the two surfaces connected by dash line in upper left view. The perpendicularity tolerance of each surface relative to datum A and B is important. The coplanarity tolerance between them can be larger. It means the two surfaces can be stepped 2mm but each of them needs to be perpendicular to datum A and B within 0.1mm. Because the two surfaces will serve datum feature in next level of assembly, I would like it to be datum feature C in this drawing.
In this case, which callout in the three sheets makes more sense? Or do you have better ways?

 

[CheckerHater]

To me it looks more like fourth option - composite profile.

PLTZF wrt A|B|C will locate two surfaces within 2 mm and FRTZF wrt A will control perpendicularity to A

See Y14.5 Para 8.6 in 2009 or 6.5.9 in 1994


"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[bxbzq]

CheckerHater, your method can do the work, I think. But it narrows down the coplanarity tolerance unnecessarily. I would leave more tolerance for manufacturing while meeting functional requirements, which in this case is the tighter perpendicularity tolerance.

 

[CheckerHater]

The way I see it, if you only specify datum A in your FRTZF it will only control perpendicularity.
Location and orientation will still be controlled by larger tolerance in PLTZF.
See Fig. 8-21 in 2009

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[bxbzq]

CH, you got me.
If I understand the standard correctly, using your method, the FRTZF in composite profile control still controls the two surfaces as a pattern. It means it controls perpendicularity, form AND coplanirity.

By the way, I want the two surfaces to be perpendicular to datum A and B, independently.

 

[CheckerHater]

On composite profile - I still believe it will only control perpendicularity. Compare Fig. 8-21 and Fig. 8-22

On perpendicularity to A and B I will have to dig deeper, and since I am still at work, it may take time

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[pmarc]

To me it also looks more like fourth option - but it is not composite profile, because, like bxbzq said, the FRTZF would control perpendicularity to A|B and coplanarity of surfaces [refer to second sentence in 8.6.1.3(b)].

I would go with profile callout 2 wrt A|B and refine it with perpendicularity 0.1 wrt A|B. Having said that, I think option #1 is ok, but in my opinion profile and perpendicularity combo is more straightforward.

 

[bxbzq]

Makes sense to me.

 

[CheckerHater]

To bxbzq: agree that composite will control everything, not just perpendicularity.
To pmarc: agree that specifying perpendicularity to control perpendicularity will cause less confusion.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future