Real-world application of ALL OVER profile tolerance

[Nescius]

The concept of an ALL OVER profile tolerance is easy to understand in cookie cutter examples, but I'm very interested to learn how the forum membership has used and seen this tool in the real world.

From the 2009 standard, 8.3.1.6:

"A profile tolerance may be applied all over the 3 dimensional profile of a part unless otherwise specified."

As always, the phrase "unless otherwise specified" is problematic. Specified how?

Let's consider a cube, fully defined with basic dimensions, with an ALL OVER profile tolerance. If I apply a refining, tighter profile tolerance or flatness tolerance to a single face of the cube, is it no longer located/oriented relative to all the other faces?

It would be easy to say that the ALL OVER tolerance still applies to all surfaces and the single face in question must simply meet both tolerances...however, what if I desire to allow one face of the cube to vary by more than the ALL OVER tolerance? Meeting both tolerances becomes meaningless, then. Furthermore, if the more generous tolerance qualifies as "otherwise specified", and the ALL OVER tolerance is trumped, is the face in question no longer located/oriented relative to the other faces at all?

Must the part be fully defined with basic dimensions, no +/- allowed? This is a much-debated topic itself, +/- dimensions and a profile tolerance applied to a closed outline...profile not controlling size.

In theory, the ALL OVER profile tolerance is a powerful tool...perfect for a part with some very complex aesthetic or ergonomic surfaces, but also a handful of more conventional features that must be controlled differently.

Is this a gray area with open interpretation or am I missing something?

 

[CheckerHater]

The post looks a bit troll-ish, but I bite.

the phrase "unless otherwise specified" is problematic. Specified how?

Specified in unambiguous way according to standard(s).

If I apply a refining, tighter profile tolerance or flatness tolerance to a single face of the cube, is it no longer located/oriented relative to all the other faces?

Tolerances like flatness and other form controls DO NOT locate/orient anything, so nothing bad will happen.

if the more generous tolerance qualifies as "otherwise specified", and the ALL OVER tolerance is trumped, is the face in question no longer located/oriented relative to the other faces at all?

The face in question is located/oriented relative to the other faces according to control that YOU apply to it. It it YOUR responsibility to apply proper control when you override default setting.

Must the part be fully defined with basic dimensions, no +/- allowed? This is a much-debated topic itself, +/- dimensions and a profile tolerance applied to a closed outline...profile not controlling size.

Too many questions in one. Profile may be applied different ways, being combined with basic and toleranced dimensions, and every application will have different meaning. It is YOUR responsibility to keep application meaningful. GD&T is a tool, very much like a hammer. If you hit your finger instead of a nail, it is not hammer's fault.

And by the way - profile controls size quite well, if applied properly.



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

 

[Nescius]

Rest assured, I have much better things to do, both at work and at home, than troll any forum...let alone a GD&T forum. Quite frankly, I cannot tell if you're being deliberately obtuse in your reply.

The heart of the matter is this: What does it take to meet the burden of "otherwise specified" in the case of an all over profile tolerance? Read my questions again with this in mind. Of course, flatness does not control location or orientation...but if an all over profile tolerance can be nullified by applying a flatness tolerance to a single face, location and orientation control of that face is lost.

Is it the case that any control exerted on any feature, separate from the all over profile tolerance applied to the entire part, completely nullifies all control provided by the all over profile tolerance, in the case of that feature? If yes, then so be it. If I don't want it to work this way, there's nothing stopping me from spelling it out in plain english.

I'm merely seeking the experience of others...how have they used, seen, or interpreted the all-over profile tolerance. I have never seen even a single example "in the wild", only cookie cutter examples to explain the meaning of the callout, nothing about how it fits into an overall tolerancing strategy.

 

[CheckerHater]

Unfortunately for both of us things like “default”, “specified otherwise”, “direct”, “indirect”, "refine", etc. are really poorly defined in the world of ASME. (See, for example,

http://www.eng-tips.com/viewthread.cfm?qid=410353)

Other than that I am standing behind my words. Very often on this forum people are asking for some sort of magical solution that will automatically cover everything (all-around?) and not require thinking.

My answer is always "no" - If you think something is unclear, it is your job to clarify it.

You have casting with the hole machined in it. Surface of casting may be specified "all around", hole maybe specified "otherwise". Control applied to one single feature does not cancel out general requirements for the entire part. How exactly? There are hundreds of possibilities. Show us your case. If you ask overly generalized question, you get overly generalized answer.

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

 

[Nescius]

Some thoughts:

I'm not wanting a magic solution, just trying to use the GD&T as it is written in the standard to its fullest extent. I didn't invent the notion of an all over profile tolerance. It's there in the standard, a very powerful tool that looks to the future. Read on...It's not as if part geometry is more complex than it has been in the past...a caveman carving an idol can create geometry that's unreasonable to define on a traditional paper drawing. What has changed is our ability to make and measure very complex geometry very accurately.

See the attached pdf for an example part. Instead of a decorative door knocker, imagine that the complex geometry was a custom prosthetic or a scaffold to grow human tissue or whatever futuristic application you can imagine. You'll never fully define the part with a drawing alone. The manufactured part might be totally specified, made, and checked with nothing but 3D scanned data.

So, rather than use the all over profile tolerance as some sort of cheat or shortcut, I'm wanting to see instances where the power of this tool was used well.

In my attached example, if I apply any tolerances in addition to the all over profile tolerance, I can make the argument that something has been "otherwise specified" and that the all over tolerance does not apply AT ALL to the feature in question. Other arrangements would be required to define the relationship between this feature and all the others...the ones still under the umbrella of the all over tolerance because they have not been "otherwise specified".

I believe the inclusion of the phrase "unless otherwise specified" in the description of an all-over profile tolerance is a poor choice. The all AROUND profile tolerance doesn't appear to have this same caveat. When I place geometric tolerances on drawing, it is for a reason. When "unless otherwise specified" is introduced, interpretation of the drawing quickly becomes a horrible, fuzzy flow-chart of what-ifs and if-thens...especially when the "unless otherwise specified" is baked right into the callout, according to the standard. Yuck.

 

[CheckerHater]

OK, we are getting closer to something.

Here is the way I see it. This isn't "lion", more like a cube from your example, with flatness applied to one side of it.

Since flatness cannot restrict orientation or location, flatness tolerance zone is allowed to "float" within all-over tolerance zone.

If we had profile instead of flatness, situation could be different. Profile without datum references would be more like form control, while profile with datum references would be completely different animal.
I am sure in this case opinions about interpretation will differ between different experts.

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

 

[mkcski]

NESCIUS:

I want to weigh-in on this discussion in one area. Your statement "Let's consider a cube, fully defined with basic dimensions, with an ALL OVER profile tolerance. If I apply a refining, tighter profile tolerance or flatness tolerance to a single face of the cube, is it no longer located/oriented relative to all the other faces?" is not correct to my understanding.

As a side-bar: the 2009 Standard "suggests" that an ALL OVER profile be added to all drawings to guarantee all surfaces have geometric control – see paragraphs 2.11 and A.4.1. This allows "boundaries" to be determined, which is the current focus of the evolving approach to product definition taken by the Y14.5 Committee. The addition of the datum-specific terms RMB, MMB and LMB and the numerous "envelopes" are manifestations of the "boundaries" concept. Given this, I assume the ALL OVER profile is applied as a “worst case boundary” and refinements – based on function and fit-up - have a “tighter” tolerance than the ALL OVER profile.

The ALL OVER statement is a replacement for the default directive: "if not specified in the field or notes, go to the title block for the tolerance" typically applied to engineering drawings; except that ALL OVER profile offers much more control over the part features than most title blocks present (usually just size and angles). The ALL OVER profile indirectly controls the size and form of individual features, and the orientation and location between related features.

The root of your discussion is: how does the all-inclusive ALL OVER profile interact with “otherwise specified” refinements. In your cube example, flatness on the single face is a refinement of the form for that individual feature "offered" by the ALL OVER profile. So adding the flatness form control to the individual feature overrides the form tolerance from the ALL OVER profile; however, it does not override the orientation or location relationship between the cube faces "offered" by the ALL OVER profile. Additionally, if you make one side a datum and another feature perpendicular or parallel to it, the orientation relationship from ALL OVER profile would be refined by the specified orientation tolerance.


Certified Sr. GD&T Professional

 

[Belanger]

The 2009 Standard "suggests" that an ALL OVER profile be added to all drawings to guarantee all surfaces have geometric control – see paragraphs 2.11 and A.4.1.

I'm not sure how you read that suggestion within those two paragraphs

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

 

[mkcski]

John-Paul:

I attended a Y14.5 Committee meeting right after 2009 was released. At the event several of the Committee members (D. Day , A. Neumann, A. Anderson. A Krulikowski) gave seminars explaining the changes to the various sections. One focus was the calcification of "boundaries" - these are my paraphrased words and not statements from the presenters. Since then I have read materials published by the same Committee members and they have the default ALL OVER profile in their examples. So yes, it is pushing things a bit, but technically it makes lot of sense. There have been recent posts about how "bogus" title block tolerances are at covering "unless otherwise specified" dimensions and how they do not provide adequate default geometric control. The ALL OVER profile is much better at default conditions.

Certified Sr. GD&T Professional

 

[Nescius]

I want to weigh-in on this discussion in one area. Your statement "Let's consider a cube, fully defined with basic dimensions, with an ALL OVER profile tolerance. If I apply a refining, tighter profile tolerance or flatness tolerance to a single face of the cube, is it no longer located/oriented relative to all the other faces?" is not correct to my understanding.

Yes, it sure would be clunky if this were the case. I do agree that in the case of the cube, a refinement of a specific aspect could coexist with the all over tolerance. It works seamlessly; overlapping geometric tolerances coexist all the time, perhaps even within a single feature control frame. That's pretty much what a composite profile tolerance is...several overlapping requirements, all of which must be met. The sticking point is "unless otherwise specified". What is it? Are there degrees of it? Fully otherwise specified? Incidentally otherwise specified? Ha!

 

[mkcski]

Nescius:

I understand your post and agree. The interaction/interface between the default ALL OVER tolerance zone(s) and the tolerance zones from specified refinements is not defined anywhere that I am aware of. Clarity with ALL OVER might be easy for a cube, and would be very difficult for a part with more complex geometry - most are more complex than a cube, hahaha. But... a default ALL OVER profile stands a much better chance of defining unspecified geometry (boundaries)than a generic +/- title block.

Certified Sr. GD&T Professional

 

[mkcski]

Nescius:

On another related note: ALL OVER profile dovetails nicely with the expanding use of 3D CAD part models and CMM machines (gantry, articulating arm, laser tracking, etc.) The BASIC (perfect) shape from the 3D model is loaded into the CMM software. The part is scanned (probed) and the point-cloud placed "over" the perfect model. Deviations are noted - I think the report it called a "whiskers" plot. This exactly mimics the ALL OVER profile. We use this technique with rough-castings to confirm adequate stock for machining.

Certified Sr. GD&T Professional

 

[pmarc]

There aren't many examples in the Y14.5 standard (as well as in other Y14 standards) showing application of the all over profile tolerance in combination with other geometric controls, but I think fig. 4-43 in Y14.5-2009, although not showing all over profile application directly, may be useful to solve the dillemma.

In that figure there is a general profile of a surface callout |prof|0.8|A|B|C| applied to all surfaces unless otherwise specified. If the figure showed no other geometric controls than that general profile callout, I think we would agree that this general profile requirement would act as a all over control, right? However, since there are additional geometric requirements specified on the drawing, these requirements simply nullify the general profile callout for features controlled by the additonal callouts. It must be like this, otherwise for example the datum feature B would have to somehow magically meet the general profile requirement AND the 19+/-0.2 width requirement AND the perpendicularity callout. Otherwise the dia. 3.1 holes would have to meet the general profile requirement AND their size requirement AND the position callouts. This is definitely not how this drawing should be read/interpreted.

Now, if we apply the same logic to a simple cube controlled by UOS all over profile tolerance and having a flatness callout (regardless of its value) applied to one of the faces, the conclusion must be that the flatness tolerance nullifies the all over profile tolerance on this single face, meaning that the face becomes not fully defined (in terms of orientation and location relative to other faces of the cube).

In my opinion there is a simple way to eliminate the confusion. If someone wants to have the all over profile callout applied to all six faces with additional flatness callout acting just as a form refinement of one of the faces, the UOS term should not be used in conjuction with the all over profile callout at all. The all over profile callout without extra notation will well suffice.

 

[CheckerHater]

I have a question to pmarc:

Let say, we have requirement for part to be primed and painted Red "all-over"

Then, there is "otherwise" requirement to paint certain spot White.

Does "White" requirement nullify "prime" requirement?

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

 

[pmarc]

Not able to tell, because you did not tell how exactly the drawing notes look like.

Assuming the requirement is to have (1) the entire part primed and (2) the part painted red everywhere except for a certain spot that needs to be painted white, the dilemma can be easily solved by using following notes:
1. PRIME THE ENTIRE PART.
2. PAINT THE PART RED EXCEPT CERTAIN AREA SHALL BE PAINTED WHITE.
So without using words "unless", "all over" and "otherwise" everything is clearly defined.

If however, for some reason, you really want to use those words, the notes could look like this:
1. PRIME THE PART ALL OVER.
2. UNLESS OTHERWISE SPECIFIED PAINT THE PART RED.
In addition to that there would have to be a local note specifying that certain area shall be painted white.

Does that answer your question?

 

[CheckerHater]

Actually, no.

Take your second version.

According to your own logic, as soon as you specify certain area to be painted differently, it immediately nullifies EVERYTHING specified "all-over" for that area.

Or not?

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

 

[pmarc]

No, it does not nullify EVERYTHING specified for that area. It nullifies only that characteristic of area that has been specified in the UNLESS OTHERWISE SPECIFIED note. So in this case it nullifies painting red, but not priming.

Going back to the cube example, the flatness callout applied to a single face nullifies everything that has been specified in the UNLESS OTHERWISE SPECIFIED requirement for that face, which means it nullifies profile all over requirement for that face.

 

[CheckerHater]

OK, I am getting your point (not like I am agreeing with it).

The words UNLESS OTHERWISE SPECIFIED have that magical quality,that any added requirement immediately nullifies the default one.

So, if certain requirement can be specified without magic words, it will not be nullified?

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

 

[pmarc]

I already tried to explain that for the cube the all over profile tolerance will still control the sixth face (the one with flatness refinement) if the UOS notation is not used in conjunction with the all over profile requirement. It is that simple.

 

[CheckerHater]

Any solid standard reference to back it up?

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