Profile of a line

[Andera]

Fig 8-7 /2009:
If a profile of a line witin 0.1 to datum feature A (primary datum feature only) is added below the shown profile of a surface, then what will control de size, orientation, form and location of the depicted surface?
Still the profile of the surface?

Otherwise I am asking what kind of refinement profile of a line is capable of providing?

Size+form
Size+form+orientation
Form+orientation
Size+form+orientation+location
Size+orientation

Any other combination?

 

[Belanger]

Profile of a line as added by your description would refine only form, and only in a 2-D (cross-sectional) manner.
Look at the "means this" portion of the graphic: Profile of a line would refine the form of the curve in the main view, as taken at individual depths, but profile of a surface would still control the form in the right-side view (straightness).
Orientation of the curve in all directions would be controlled by profile of a surface. But it's still good to reference datum A in your profile of a line callout, because that dictates how to take the cross-sectional slices.
Location would also be controlled only by profile of a surface, because the only datum in your profile of a line callout is A, which is not addressing location.
And the size of the part across that top surface would also be controlled only by profile of a surface.

Again, that's for the specific case you proposed. The addition of other datum references might then get into the other combinations that you asked about.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[Andera]

Again, that's for the specific case you proposed. The addition of other datum references might then get into the other combinations that you asked about.

Am I correct in my assessment that if a secondary datum B is added in the profile of a line, then this new datum feature B is invoked to constrain an additional rotational degree of freedom of the datum reference frame

AND NOT TO what characteristics (size, form, orientation, location) profile of a line is controlling?

Is my understanding valid?

 

[Belanger]

Adding datum B to the profile of a line control would not only constrain one additional d.o.f. but actually two: orientation and location (distance from datum B). That's because the relationship to B is given by basic dimensions, so both profile tolerances would be locked at the given heights (this creates some redundancy, of course).

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[greenimi]

Belanger,

Just a quick question: Is the tolerance zone of the profile of a line 0.1 allowed to violate the profile of a surface?


Or in other words, if 8-23 (picture from the same 2009 standard is considered), -just for a second---- is the first segment profile of a surface within 0.1 allowed to violate FRTZF or PLTZF?

How 40 basic will influence (if it does) the relationship between the holes/ irregular features shown?

 

[Belanger]

Just a quick question: Is the tolerance zone of the profile of a line 0.1 allowed to violate the profile of a surface?

The profile of a line's tolerance zone of 0.1 may partially drift outside of profile of a surface's tolerance zone. But that would be less overall tolerance with which to work.
The main idea is that every tolerance on a drawing must be met on its own terms.

Or in other words, if 8-23... is the first segment profile of a surface within 0.1 allowed to violate FRTZF or PLTZF?

It operates separately from the composite tolerance. So it cannot violate the composite. All three geometric tolerances must be met, but the key there is that the composite tolerancing is for the pattern of two cutouts, but the 0.1 tolerance is refining each one's individual size and shape.

How 40 basic will influence (if it does) the relationship between the holes/ irregular features shown?

The 40 mm helps set up all three profiles, but any deviation from the 40 itself is only captured by 0.1 profile tolerance.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[axym]

greenimi,

I agree with J-P that there are three tolerance requirements, that can be evaluated independently. So the feature could pass the 0.1 profile of a line requirement, but fail the PLTZF and FRTZF requirements. Or it could fail the 0.1 profile of a line requirement and the PLTZF requirement but pass the FRTZF requirement - any combination is possible. I find things easier to visualize this way, rather than looking at the tolerances superimposed on each other with the "portions are not usable" description that some Y14.5 figures have.

Regarding the influence of the 40 mm basic dimension, here's how I like to think of it. The specification must mean exactly the same thing if the basic dimension was not present (as in the case of a 3D model-based version of the specification in which no basic dimensions are shown). This approach was introduced in Y14.5-2009 in the position section (Fig. 7-3) and expanded a lot in Y14.5-2018. Some of the figures in the profile section now have model-based versions, including Fig. 11-28 which has the same part geometry and tolerances as Fig. 8-23 from 2009.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[Andera]

Thank you Evan.

Looks like greenimi piggyback on my original question on the other discussion I've posted. No problem with that, but I have a follow-up question: if the basic dimension was not present then what is keeping those 2 features connected?
How can I see the difference with and without INDIVIDUALLY note if basic dimension doesn't matter?

[pre][/pre]

 

[axym]

Andera,

The idea with 3D model-based definition is that the basic relationships between the features are defined implicitly in the model instead of using explicitly annotated basic dimensions. So the basic distance between the features is still 40 mm.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca