Profile of a Line and Position (Boundary) Together Legal? 1

[Tarator]

Hi all,

I never saw this before but it got me thinking... is it legal to use a Profile of a Line (All Around) with Position (Boundary)?

Please see the attached file.

Thanks,
Tarator.

 

[CheckerHater]

ASME Y14.5-2009 Para. 7.2 starts with the phrase “Position is the location of one or more features of size relative to one another or to one or more datums.”

I would stop right there because your feature doesn’t look like feature of size to me.

Nevertheless, I would like to see other opinions.

 

[fsincox]

My guess would be it is a legitimate extension of the profile-boundary concept.
Frank

 

[Belanger]

Sure -- see Fig. 8-24 of the Y14.5 standard (and paragraph 8.8). It's almost the same as yours, although using profile of a line would change the depth aspect of its interpretation.

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

 

[CheckerHater]

According to Para. 8.8 the entire feature surface should lie within a boundary.

How do you guys visualize the boundary of TAPERED feature?

 

[fsincox]

I am not sure if there is much difference in a single line, single value profile of a line callout to a complete datum framework with all dimensions stated basic and a profile if a surface callout to the same number and datum framework? J-P or pmarc?
Frank

 

[fsincox]

Sorry,
"profile OF a surface", not "if".
Frank

 

[Belanger]

CH -- I have reservations about that too. While it's OK to use profile of a line so that variations depth-wise are allowed, that takes away from the idea of a constant boundary that position is trying to establish. I wanted to bring Fig. 8-24 into the discussion, but I await other comments about whether it's totally kosher to use this on a tapered feature.

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

 

[CheckerHater]

JP, this is what bothering me. "Boundary" in connection with Position usually refers to virtual condition which requires size of some sort. The feature on OP's picture won't qualify even as irregular FOS.

And second question: why? This looks exactly like the situation when Profile of a surface should be used to control position. And it would be perfectly legal. I am really lost trying to imagine benefits of NOT using it.

 

[Tarator]

The internal feature I tried to sketch doesn't have a constant draft angle. And the mating part that goes through is extruded (with zero draft angle). The function of the opening is clearance only.

I thought, if this is legal, it would be easier to call it out on the drawing, gives better consistent gap (nominal gap) around the mating part, etc.

My concern was profile of a line is a 2D control, where position is a 3D control. However, logically, the curve edge is an irregular feature of size, and position should be able to control the location. Maybe I'm wrong, it's not legal to use them together.

 

[CheckerHater]

By definition, irregular feature of size is something that can be controlled by an envelope.
If you showed that envelope (like inscribed circle) on your drawing and applied position to it, that would be extension of principles I could live with. Then you would control the outline using profile separately.

 

[TheTick]

As stated, can't use position. Not allowed for oddball shapes like this.

Use 2x profile tolerances. The first, profile to A, controls the shape but not the position or orientation. The second, profile to A-B-C, controls the position and orientation. this way you can control the shape to a tight tolerance but allow it to float over a larger region.

 

[SeasonLee]

A tapered internal feature is a 3D feature, so profile of a surface will be more reasonable to control the orientation, how do you think?

BTW, the all around leader line need to touch the profile FCF I/O position FCF.

Season

 

[Tarator]

CheckerHater,

The envelope you mention.. would it be the same outline shape extruded all the way down?

 

[axym]

Hi All,

I don't think that this "combined controls" applications works with Line Profile.

I'm okay with the Position tolerance itself. Applying Position at MMC to an irregular enclosed feature is fine, even if it's tapered - this is a standard application of Boundary Position.

The way I understand it, the Line Profile tolerance would control individual cross-sectional slices of the feature. The slices are parallel to Datum A. The problem is that this doesn't fully control the feature's size and form - it's like a deck of cards. So there is no definite size-and-form "MMC" boundary for the Position boundary to be defined from.

If Surface Profile was specified instead of Line Profile, then the application would work.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[Tarator]

Axym,

There is only one slice (because of the tapered geometry!! And the position only controls that slice.

 

[axym]

Tarator,

If the intent is that there is only one slice, I'm not sure that the drawing conveys that. By default, geometric characteristics apply to the entire surface of the feature. This includes Line Profile.

You might consider an additional annotation, showing a limited depth that the tolerances apply to (probably in a side view).

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[Tarator]

Line Profile is applied to 2D line elements not surfaces (and it depends on the view angle)... if the internal feature in my sketch had 0 draft angle all around, then the Line Profile would apply to each section/slice element.

 

[axym]

Tarator,

I maintain that Line Profile is applied to surfaces. The surface is sliced into 2D line elements, that each have a tolerance zone.

I agree that the view angle comes into play. The slices (and thus the 2D line elements) are perpendicular to the view direction.

Can you point me to something in the standard that mentions the influence of the draft angle? I haven't heard of anything that states that the tolerance applies to only one element for a surface with draft, and to multiple elements for surfaces with no draft.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[SeasonLee]

Evan
You are absolutely right, profile of a line will not create a MMC position boundary.

Season