Interpretation of General Profile Tolerance Note

[dqehornback]

Company uses a datasheet, with standard notes built in, along with an annotated model to completely define MBD parts. One of the notes is a general profile tolerance to datums A, B, C. My question is this: What happens if the model has no datum callouts on the part? I would think the interpretation would be that produced parts can be best fit into the general profile tolerance zone since there are no datums specified on the part. Looking for anything concrete on this one way or the other.

 

[Garland23]

Seems to be an oversight that should really be fixed.
Having a feature control frame on a drawing (even if by way of a note) that references certain datums means that those datum features should be identified somehow.

 

[3DDave]

"What happens if the model has no datum callouts on the part?"

You fire the head of QA.

 

[ctopher]

If the MBD model has no datums, it's not completely defined.

 

[ewh]

The default note should not have datums in the FCF unless those datums are identified. If they are not identified, the model would should be considered basic (should state such in same note as default FCF) and the profile would be controlled to the basic model.

 

[3DDave]

Y'all missing that if this company allowed this discrepancy to happen, that is a failure of the QA department.

The QA department is responsible for defining a fix.

That there is a question about it suggests there is an existing failure in the QA department to establish a clear standard.

 

[Garland23]

If they are not identified, the model should be considered basic (should state such in same note as default FCF) and the profile would be controlled to the basic model.

Not sure about that. You're saying that, without datum features being identified, it should be treated as an all-over profile (that doesn't need datums)?
I would be inclined to say that the designer didn't intend that, and the callout is an oversight simply because there are datums referenced, yet not ID'd.

 

[ewh]

Yes, the FCF would apply all-over, and unless the parts are full MBD the designer probably didn't intend that. My remark was more to clarify that you can use a FCF with no datums referenced.
As for the OPs problem, I agree it is ultimately QAs responsibility to raise the issue before parts are made.

 

[3DDave]

It should be raised before the drawing is released.

 

[Burunduk]

Does the product definition data set include a 2D drawing graphic sheet or just the annotated model? If a 2D graphic sheet is included the datum features could be identified in it.

 

[Garland23]

Burunduk,
The OP stated at the start, "Company uses a datasheet, with standard notes built in, along with an annotated model to completely define MBD parts."
I presume that is the same as a "product definition data sheet" that you're referring to?

 

[jassco]

Hi, dgehornback:

What is "a datasheet"? I assume it is a print. When you have multiple documents (in your case, you have a datasheet and an MBD model), you must define which is a primary document to define the part. I assume your datasheet is primary and your MBD model is referenced on your datasheet.​

Best regards,

Alex

 

[Burunduk]

Burunduk,
The OP stated at the start, "Company uses a datasheet, with standard notes built in, along with an annotated model to completely define MBD parts."
I presume that is the same as a "product definition data sheet" that you're referring to?

I'm not sure what is a datasheet. My wording was "data set" which could be a model and a 2D drawing or just the annotated model.

 

[greenimi]

I would "read" the model as nominal - basic - and the profile tolerance applied in the same way "all over" is defined.
So each of the "as made" part's feature shall be within the specified general profile and their relationship being defined by basic dimensions.
You don't even need an annotated model. Everything (all features of the as made actual part) shall fit between two boundaries-outside boundary and inside boundary which boundaries are offseted from each other with the general profile tolerance.

 

[greenimi]

Per ASME Y14.41-2019 on 12.2.3 Profile Tolerances
(g) All-Over Application. When the all-over symbol is used, all of the appropriate portions of the annotated model should be designated as associated objects for the profile tolerance.

 

[Burunduk]

greenimi,
Profile all over does not act the same as profile relative to a datum reference frame. Profile relative to a datum reference frame is stricter, but the the OP says it's not clear what the datum features are. The problem with your suggestion is that you can't really proove the part is conforming to the profile relative to A,B,C by showing it's good per the "all-over" measurement.