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Assembly GD&T Callouts referencing Component Datums

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Newbie

Assembly GD&T Callouts referencing Component Datums

Folks,
Have a situation, and wonder if anyone knows how to make this work properly. Have an assembly, where a GD&T callout applies at the assembly level, but needs to reference a datum at the component level. Right now, the only workaround we've found is to re-create the component datum at the assembly level, then link the constraint to that datum. Needless to say, this is a pain. Looking for solutions.

Thanks!

Mike Brattoli
4 REPLIES 4
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RE: Assembly GD&T Callouts referencing Component Datums

This is not supported by Y14.5M so I doubt Pro-E will be able to do it. I have never in my ten years of experience had a situation where I even thought this would be needed. Not to be judgmental but do you really understand GT&T ?

Brian
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RE: Assembly GD&T Callouts referencing Component Datums

I haven't seen the 2001 standard yet, so maybe there is some additional
information in there, but I have never seen any reference to CAD model
structure in Y14.5M-1994. I don't think it's as simple as saying Y14.5M
doesn't support it, because in large part the issue Mike is talking
about is simply an artifact of the software functionality.

Pro/E forces you to stay consistent with the context for your
tolerances, i.e., the datum features and gtols have exist in the same
model. There are plenty of cases for castings/machinings and weldments
where the same geometry is used to define a datum at different levels of
an assembly. In those cases, it would be easiest if Pro/E would allow
you to re-use the part-level datum in an assembly-level gtol, but it
wont. The solution is simple enough, however, you just have to
duplicate the datum feature at the assembly level.

Best Regards,
Highlighted

RE: Assembly GD&T Callouts referencing Component Datums

Are you sure Brian? I think you can do what he is asking.

I have often taken an assembly of a mechanism and applied GD&T to it.
Imagine an automatic floor shifter in an automobile. To measure the
change in cable length as it is shifted from each PRNDL position I need
to establish datum reference frames for the assembly and where the cable
is located. To "lock the shifter" 6 DOF I used the exact same datums as
the individual component (the base of the shifter mimicking
installation), for the cable I would locate a basic point from that DRF
and define linear length requirement tolerance to my cable attachment
points at different positions.

To answer Mike's question... I think your stuck defining new DRF at the
assembly level even though it exactly matches your component DRF.



Erik Peterson
Sr. Product Engineer
Highlighted

RE: Assembly GD&T Callouts referencing Component Datums

Brian is right. Datums and tolerances only apply at the current drawing
level. You cannot reference datums on another drawing. You cannot
reference part datums on an assembly drawing. Pro/E forces compliance to
the standard by disabling your ability reference part datums in assembly
Gtols.

By the way, Y14.5M-1994 is the latest GD&T standard. There is no 2001
standard but it was re-affirmed in 1999 and 2004 (without any changes).

John Suyes
-
ASME GD&T Professional, Senior Level.




"Eric Hill" <->
Sent by: -
08/29/2006 10:54 AM
Please respond to
"Eric Hill" <->


To
"PTC/USER 2D Products Discussion" <->
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Subject
[draft] RE: Assembly GD&T Callouts referencing Component Datums






I haven't seen the 2001 standard yet, so maybe there is some additional
information in there, but I have never seen any reference to CAD model
structure in Y14.5M-1994. I don't think it's as simple as saying Y14.5M
doesn't support it, because in large part the issue Mike is talking
about is simply an artifact of the software functionality.

Pro/E forces you to stay consistent with the context for your
tolerances, i.e., the datum features and gtols have exist in the same
model. There are plenty of cases for castings/machinings and weldments
where the same geometry is used to define a datum at different levels of
an assembly. In those cases, it would be easiest if Pro/E would allow
you to re-use the part-level datum in an assembly-level gtol, but it
wont. The solution is simple enough, however, you just have to
duplicate the datum feature at the assembly level.

Best Regards,
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