Profile Callout Bilateral 2

[Ksplice]

Hi,

I have a question on profile tolerances called out bilaterally. please see attached sketch. the profile callout is pointing to a line that is 0.10 inside the actual profile. my interpretation of this is that the tolerance zone is established centered on the 0.10 offset. is this correct or does the zone start at the 0.10 and is not centered on it. Also if someone could point me to the page in the ASME 2009 standard where this is addressed i would most appreciate it as i have been unable to find it.

thanks,

 

[SeasonLee]

Thanks, pmarc. Now I am anxious to know the reason why not, would you mind give me a light?

Season

 

[pmarc]

As this is composite callout, and in such case upper segment always controls location of toleranced feature or group of features relative to specified datum reference frame, the upper segment of composite profile of a line FCF does nothing that stand-alone profile of a surface FCF wouldn't do. That being said, profile of surface as the top callout (to locate the feature) and profile of a line as the bottom callout (to refine orientation and form) would be my choice in this case.

Does it literally mean we can't use current callout? Probably not. I just think that a callout expressing more precisely what is actually controlled is better option.

 

[SeasonLee]

Thanks, pmarc.

Your choice would be multiple single segment profile control, I saw this application example on Alex’s book, and it’s not a composite profile control. Indeed, I haven’t seen any profile of line used on composite control in any GD&T books, I will be highly appreciated if anyone who can provide an example.

Season

 

[CheckerHater]

The picture is from the Genium Manual.
Looks like Genium generally sees 2 uses for profile of a line:
a) Any cross-section
b) Doesn’t really matter if the part is very thin, A.K.A. “gasket”
I hope this picture tells more to you than it does to me.

 

[pmarc]

The thing with the picture (and this is what I was trying to say in my previous post) is that the blue zone as defined in the upper segment is exactly the same as if PROFILE OF SURFACE was defined in the upper segment. So why to apply profile of a line if the upper callout controls profile of a surface in reality?

 

[SeasonLee]

Great, CH

Very interesting, I am imaging the differences between them (profile of line and profile of surface) on composite profile callout. how do you think of it?

Season

 

[CheckerHater]

Well, I imagine part that looks like a deck of cards.
Every slice is almost perfect rectangle, but every rectangle is allowed to float within larger tolerance zone.
Don’t know if there is any practical application for that, that’s why I wonder if it means something special to you.

 

[pmarc]

For those who are still interested, I received Alex's answer about legality of composite profile tolerance application to a single surface - partial answer I would say.

Keeping long story short, he believes that the intent of the standard is to apply composite profile tolerances to patterns of features only. He also thinks that it would be better to accomplish the design requirement shown in my picture with using customized datum reference frame (just as I suggested in my post from 15 Apr 13 7:46). Unfortunately he did not point me to a place in the standard clearly proving that composite profile on single surface is illegal.

So I asked him additional question (haven't received answer yet):
Paragraph 2.13. Conical Tapers.
"A conical taper may also be specified by one of the following methods:
a) ...
b )...
c) ...
d) a composite profile tolerance".
If a composite profile tolerance can be used to specify a conical taper (which is a characteristic of a single surface as far as I can tell), why can't it be applied in my case?

 

[SeasonLee]

I joined Genium as a member in order to get more information about profile control, but I can’t get an answer so far:
1. Why can we apply profile of line to control profile of surface in composite profile control?
2. When should we apply profile of line on composite profile control? And when should we apply profile of surface on composite profile control? What are the differences between them?

pmarc, first page on the attached is an example of composite profile used to specify a conical taper,the 2nd page is an example of profile of line apply on a composite control.

Season

 

[pmarc]

SeasonLee,
So does the picture on page 1 of your attachment mean that there is a chance to convince you to the theory saying that composite profile can be applied to a single surface?
-----------
As for your two questions, consider 3 different scenarios for geometry shown in page 2 of the attachment (I will use following abbreviations: PRL = profile of line; PRS = profile of surface to keep things as short as possible):

Scenario 1 -- Composite PRL:
Upper segment - acts like it was profile of surface callout. It controls location of the ENTIRE 3D contour to |A|B|C| within .060;
Lower segment - controls orientation of the contour to |A|B|, its form and size IN EACH CROSS SECTION INDEPENDENTLY within .005;

Scenario 2 -- Composite PRS:
Upper segment - acts in the same way as in scenario 1 - absolutely no difference between the two;
Lower segment - controls orientation of the ENTIRE 3D contour to |A|B|, its form and size within .005;

Scenario 3 -- Two single segment FCFs - PRS .060 |A|B|C| in upper FCF, PRL .005 |A|B| in lower FCF:
Upper FCF - acts in the same way as upper segments in scenarios 1 and 2;
Lower FCF - controls LOCATION of the ENTIRE 3D contour to |A|B|, because this is single segment callout. So in fact the only requirement from upper FCF that is not overriden is location to C.

So if you compare scenarios 1 and 2, you will get the answer for the last portion of your point #2.
And if you compare scenarios 1 and 3, you will see why there is a reason to go with composite PRL. The only (?) intuitive alternative for scenario 1, which is PRS in upper FCF and PRL in lower FCF, ends up with different results, so cannot be used as 1:1 replacement.

Does it make sense?

 

[Belanger]

Keeping long story short, he believes that the intent of the standard is to apply composite profile tolerances to patterns of features only.

I'm sorry, but I still don't get this. Fig. 8-19 of the standard clearly shows a composite profile tolerance applied to something that is NOT a pattern -- it's a single cutout (although not of a continuous shape).

I must be missing something regarding the terminology. What exactly is a pattern?

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

http://www.gdtseminars.com

 

[pmarc]

Per Alex's understanding cutout from fig. 8-19 is pattern (collection) of surfaces tied together by all around symbol - this is what is shown in the snapshot of his book attached by SeasonLee (post from 15 Apr 13 13:34).

I don't buy it, but he is the committee member not me.

 

[Belanger]

Then anything other than a nice round hole or a planar FOS would count as a "pattern"!

Would the average reader here look at a single kidney-shaped hole and call it a pattern?
No. It might not be a single feature, but a collection of features. Yet it's not a pattern because those features making up the single hole are not identical. Now if there are [bold]two[/bold] kidney-shaped holes in the part, then we can use the term "pattern."

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

http://www.gdtseminars.com

 

[SeasonLee]

pmarc, I can image and accept the composite profile applied on the conical feature, thanks for your explanations on the three scenarios, I am still thinking about why not profile surface used on the composite callout?

J-P, I can recall and agree one gentleman just mentioned that “cannot find a true definition of a pattern” on the thread “Shortcomings of ASME Y14.5-2009?”.

Season

 

[Belanger]

Thanks, SeasonLee. I will rest my question and just chalk it up to the standard's lack of a defintion for "pattern."

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

http://www.gdtseminars.com

 

[axym]

Hi All,

Wow, this is quite a discussion. To be honest, I'm a bit puzzled by the whole thing. It underscores the fact that a third-party textbook may not completely agree with the standard, even when written by a member of the Y14.5 subcommittee. This means that what ends up in the standard may not be agreed to by all members of the subcommittee.

The title of Section 8.6.1.1 is Explanation of Composite Profile Tolerance for a Single Feature. It then makes the following statement:

"Figure 8-19 contains an irregular shaped feature with a composite profile tolerance applied".

I'm sorry, but how much more clear could this be? There are a lot of statements in Y14.5 that are ambiguous and debatable, but this isn't one of them. it clearly states that composite profile on a single feature is legal, and so to assert that this wasn't Y14.5's intent is a difficult case to argue.

I suppose that there could still be debate over whether the geometry shown in Figure 8-19 is a single feature or a pattern of features. This is another can of worms, isn't it? The geometry is annotated with basic dimensions as a series of tangent radii, allowing us to make the distinction between individual features in the all-around group. But what if it was just an annotated CAD model, with no basic dimensions shown? What if the cutout was modeled as a continuous curve? It bothers me when details like this would affect the meaning of the tolerance. Ideally, it shouldn't matter whether the geometry is thought of as a single feature or as a group of features - the rules should be the same.

This is why it also bothers me that Y14.5 disallows the application of certain tolerancing tools on certain feature types. It seems that this is sometimes done for the wrong reasons. If the intent was to disallow composite profile for a single feature, what would be the reason? I believe that the main reason would be to discourage the use of composite FCF's when another tolerancing tool would do (e.g. composite Profile on a single planar surface would be equivalent to an orientation tolerance such as Perpendicularity or Parallelism). But this disallows certain legitimate applications, such as the single irregular surface for which an orientation tolerance would not otherwise be possible.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[gabimo]

Mark E. Foster, Applied Geometrics, Inc, President/GD&T Instructor/Mentor wrote on linkedin website--if I am not allowed to copy and paste, I will ask the administrators to delete my post---I am just trying to be helpful. I am not working for Mark, nor I am affiliated with his company--

Beginning of post from Mark E. Foster
""""""So, where is it written that we "must" use composite position to a set of multiple features of size? You "can" use the composite positioning tool for a set of multiple features of size, but I would not recommend doing so unless it is functional. The issue is that position (composite or not) is used on features of size and profile is used (mostly) on surface features.

But I think the gist of your question is really using the composite tool on multiple features versus a single feature. You could apply composite position to a single feature of size, but the effect would be to simply tighten the orientation tolerance on that feature, so you could have the same effect with a non-composite position and an orientation refinement feature control frame. (There are some "fancy" things that someone could do with regard to simultaneous versus separate requirements here, but let's keep the discussion simple -- at least at first.)

With Profile, I could use composite profile on a single surface, but again one would really be simply refining form and potentially orientation, depending on datum references. If the surface in question were nominally flat, I would recommend simply using a single-line profile for location and then refining orientation/form feauture control frames as necessary. If, however, the surface in question were a complex contour (or not simply flat), then the use of composite profile for a orientation/form requirement might be necessary. "

In re-reading through the Composite Position section of the 2009 standard, it is clear to me that the *intent* of the definition is for it to apply to patterns of features of size, thus it is clear to me that the *intent* is for it to apply to more than one feature of size at a time. However, if I put my lawyer hat on (as much as that hurts to do), the Composite Definition, or any other definitions in the standard to my knowledge, never clearly define what constitutes a "pattern." There is a lot of implication, but no definitive definition. So, one could argue that I could have a "pattern of one" feature of size. And, of course, we see people do that exact thing all of the time out there in actual industry. The same interpretation (i.e. orientation only) would be the way we would interpret a single feature of size with a Position feature control frame back to a primary planar datum feature only when only an orientation relationship exists between the planar datum feature and the feature of size in question, such as when we are going to use that feature of size as our secondary datum feature. i.e. The Position callout in that case would really only be serving as an orientation control.

So, traditionally, we have simply interpreted the lower tier(s) of a composite postion feature control frame applied to a single feature of size to be an orientation refinement for that single feature of size. And, as such, one could instead use a single-segment position for that feature of size, then follow it up with whatever orientation refinements we might need using separate orientation feature control frame callouts. And in the case of the secondary datum feature of size with a Position feature control frame (rather than just an orientation control), we would normally advise simply using an orientation feature control frame instead.

THEN, we introduce the concept of "simultaneous requirements." Since the simultaneous requirement default ONLY applies to Position and Profile tolerances, then there may, in fact, be a valid argument for using a Postion callout on what otherwise would ONLY be an orientation control, simply to force a simultaneous requirement with other features that are also Positioned or Profiled back to that same datum reference frame.

I'm not a huge fan of specifying things that way unless it seems like the only way to get things done. We sometimes find ourselves doing things because we *can* and not because we *need* to do them that way. I advise trying to find ways to make things as clear as possible without delving into the "tricky" ways to accomplish something within the standard. On the other hand, there are occasions where making use of this simultaneous requirements rule is very handy, and sometimes the only way to truly achieve the maximum possible tolerances for a given design.

While I know and respect Alex K's GD&T knowledge, the quote that you are using is from his Fundamentals-level text as well as his online resources. When I teach GD&T to people new to the subject, I also make a similar statement (i.e. that composite feature control frames are to be used on multiple features at a time, not just for one feature) because that IS the intent of that tool, and it is probably the best use of that tool. However, when we get into more advanced topics, we find ways to combine various tools (e.g. composite and simultaneous requirements) in ways that we may not have thought of when we were at a Fundamental-level of knowledge. The Y14.5 standard is intended to be a book full of definitions, rules, guidelines, language tools in general, that we are able to use in order to communicate effectively. So just as there are some people who just barely speak a language and there are others who have a supreme command of that language, we have to learn as we go to move from the former to the latter. """""""""""""""" end of post from Mark E Foster

 

[greenimi]

Thank you
Certainly helps

Pmarc,
Do you have any replays/answers from Alex K. about your follow-up questions?
Thank you

 

[pmarc]

No, unfortunately not yet.

 

[SeasonLee]

Thank you for the quote, gabimot

Season