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Control location of a feature-set separately from form of the feature-set?

Control location of a feature-set separately from form of the feature-set?

Control location of a feature-set separately from form of the feature-set?

(OP)
Is there an acceptable practice to control runout (axial location) of a feature-set separately from the form of the feature-set (which is controlled on another print)?



On this print, essentially, what I want to convey is:
THE FORM OF ALL FEATURES FROM POINT X TO POINT Y IS CONTROLLED BY PRINT 109-2367
THE LOCATION OF ALL FEATURES FROM POINT X TO POINT Y IS CONTROLLED BY THE RUNOUT TOLERANCE ON THIS PRINT


Here's what I came up with - I just wanted to get some feedback on whether or not the intent is clear, and if you think this is an acceptable depiction of the requirements as described.
*Our drafting standard for the most part adheres to ASME requirements - Y14.5M-2009, Y14.100 (*our flags are special...), etc.




The background:

I have two prints: a machined part print, and a print which describes a modular feature-set used on the machined part.
This common feature-set (colloquially known as "the profile") is used on multiple parts.
Since each profile feature-set may be used on 1,000's of prints, we keep all dimensions relating to the profiles on their own prints for purposes of maintenance and consistency.

The profile print itself controls the form of the profile feature-set (profile of a surface tolerance of .002").
This is inspected using a contour tracer, which historically has worked very well and I'm told is within an acceptable limit for capability.

The profile has a tight tolerance because it has to fit with a mating part, however the location of the profile feature-set is determined ad-hoc for each application.
For this application, we want to control the runout of the profile in relation to another feature of the part. The entire profile can be allowed to runout by up to .020" and the assembly will function as intended.



RE: Control location of a feature-set separately from form of the feature-set?

I suggest you explain your intent on the face of the drawing in form of a verbal note, exactly the way you explained it to us:

"THE FORM OF ALL FEATURES FROM POINT X TO POINT Y IS CONTROLLED BY PRINT 109-2367
THE LOCATION OF ALL FEATURES FROM POINT X TO POINT Y IS CONTROLLED BY THE RUNOUT TOLERANCE ON THIS PRINT"

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

RE: Control location of a feature-set separately from form of the feature-set?

cbrf23,
The approach you described makes sense, however...:
1. The profile of a surface tolerance of .002 specified on the profile print does not only control form, but also size of the profile, thus you may want to modify first part of your note accordingly.
2. I assume the print you showed us is intentionally incomplete, and that there is something on that print that controls location of the profile along the axis of the feature. If not, I think you may want to consider use of profile tolerance instead of circular runout, as the circular runout does not locate the profile axially.

RE: Control location of a feature-set separately from form of the feature-set?

cbrf23,

To clarify, is "the profile" (X <--> Y) a surface of revolution? You're using a circular runout tolerance, but your drawing doesn't have diameter symbols on the 3.500 or 2.375 dimensions.

Could you show us "PRINT 109-2367", or at least the relevant portions of it? The actual dimension and tolerance values aren't important, but the general scheme and the notes might be.

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

pmarc -- Like you, I believe profile controls size, but unfortunately that was debated here a while ago and the conclusion seemed to be that it doesn't have to. (Imagine a cylindricity tolerance replaced with profile of a surface, while keeping the size as a ± tol. I say no but others seem to think that's OK.)

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

RE: Control location of a feature-set separately from form of the feature-set?

(OP)
Hi all,

I greatly appreciate the input. I like the idea of supplementing the depiction with the notes, so I will add that.

To answer some questions:
The example shown is just a representation to describe the situation, not the actual drawing I'm working with - the actual drawing, and the profile, are proprietary designs that I cannot share. The profile drawings have all the basic dimensions and a profile tolerance from x to y - that's about it.

Yes, from x to y (the profile) is a surface of revolution. Missing diameter symbols are a result of a hasty draft to serve as analog for the real print (see answer above) :)

Yes the profile is intended to control both form and size.


As far as profile being used to control form independent of size, I think ASME Y14.5 (2009) is pretty clear that it can be used that way.
For example, in 8.2 the distinction between controlling form and controlling a combination of form, size, orientation, location is clearly made:

In 8.4.2, again a very clear distinction is made between the use of profile to control form independently, or to control a combination of form, size, etc.

And then we have clear examples showing profile controlling form, with size controlled through a ± tolerance:

And profile controlling both form and size together:

RE: Control location of a feature-set separately from form of the feature-set?

J-P,
Well, if the diameter of the "profile" on the profile print is dimensioned with +/- tolerance, or there is no diameter dimension and a "radial" height of the profile height is given as basic dimension (could you confirm, cbrf23?), then I say the profile of surface tolerance controls form only sad

If the diameter is basic, the profile of a surface tolerance controls size and form.

I am still missing one more answer from cbrf23. What controls location of the profile between points x and y on the print of the entire part?

RE: Control location of a feature-set separately from form of the feature-set?

cbrf23,

If the profile is fully defined with basic dimensions (including diameter) on the profile print, then to control its axial location you could replace the circular runout tolerance with profile of a surface. You would need to change the datum feature references to include an appropriate feature, and add a basic dimension from the profile to that feature. Your flag note could read "SEE PRINT 109-2367 FOR BASIC DIMENSIONS AND ADDITIONAL TOLERANCES" or similar. I don't think the note would need to explain the goal of each print; the tolerances should speak for themselves.


While it is true that the profile tolerance in ASME Y14.5-2009 Fig. 8-17 does not control size, that is only because there is no such thing as size for a conical surface in isolation. A cone is fully defined by included angle alone. Size is only meaningful for a cone in relation to something else. The profile tolerance has no datum feature references, so that is not the case here.


pmarc,

For a complex shape like the one in question, I'm not sure there's a meaningful or well-defined distinction between "form" and "size". Do you mean that the lack of a basic diameter dimension would allow the profile of a surface tolerance zone to uniformly expand or contract radially?

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

pylfrm,
Yes, that is basically what I mean.

Even if that is not the case here, it is possible to imagine that the profile print fully defines FORM the contour between points X and Y by giving all necessary basic dimensions on one side of the axis only. In that case additional +/- diameter dimension will be nothing but a separate SIZE control, and, like you said, the profile of a surface tolerance zone will be allowed to uniformly expand or contract radially.

This concept has been covered/clarified in the draft of new Y14.5? Figures 8-17 and 8-18 from 2009 version have been modified and now they do not have +/- diameter dimensions at all. Basic diameters have been used instead, extra profile callouts replacing +/-0.2 size tolerances have been added, and the 0.02 profile callouts have been changed to dynamic profile tolerances - callouts that define tolerance zones that are allowed to uniformly expand or contract radially within the larger profile tolerance zones. These new figures in the draft still need to be improved, but their intent is quite clear, at least in my opinion.

RE: Control location of a feature-set separately from form of the feature-set?

pmarc,

Understood. I can indeed imagine the concept, but I'm still not convinced it's kosher. The main sticking point for me is the following:

Quote (ASME Y14.5-2009 para. 8.2)

Profile tolerances are used to define a tolerance zone to control form or combinations of size, form, orientation, and location of a feature(s) relative to a true profile.

Quote (ASME Y14.5-2009 para. 8.2)

A true profile is a profile defined by basic radii, basic angular dimensions, basic coordinate dimensions, basic size dimensions, undimensioned drawings, formulas, or mathematical data, including design models.

For what (little) it's worth, the second sentence of para. 11.10 of the 24 November 2015 draft supports that the true profile must be fully defined by basic dimensions.

I've never had a problem with Figs. 8-17 or 8-18 because the profile-toleranced surface is fully defined by the basic angle in both cases. The toleranced dimensions are only involved in defining the relationship between the toleranced surface and some other feature.

Fig. 11-20 from the draft seems fine to me, although I wonder if the datum feature reference for the lower segment was supposed to be A instead of B based on the "Means this" explanation.

I have my doubts about Fig 11-19 from the draft though. I don't see how it would be possible to meet the lower segment requirement but not the upper, and I don't see that the dynamic tolerancing modifier has any effect in this case.

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

pylfrm,

The sticking point with Figs. 8-17 and 8-18 was that the toleranced dims were defining the very contour of the feature being toleranced by profile of a surface. Thus, it was not a "true profile." When the standard mentioned that a profile zone may be a refinement of a toleranced dimension, they meant a refinement of a location (such as in Fig. 8-27). Unfortunately, they didn't make that distinction, although maybe it's in the new draft.

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

RE: Control location of a feature-set separately from form of the feature-set?

Belanger,

I disagree. All cones with the same basic included angle have the same contour. Changing the diameter at a gage line or an intersection with a flat surface effectively shifts the cone axially, but does not change the contour itself.

For that reason, I think Fig. 8-18 is just another example of location refinement like Fig. 8-27 shows. This would be more obvious with a basic diameter dimension and a toleranced axial dimension, but I don't think it actually matters which is which. The dimensions only have meaning as a pair.

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

It all comes down to what we mean by the term "true profile." Is a circle that's given a diameter tolerance a "true profile"? I would say no.

To me, Fig. 8-17 is OK (using the Ø30 ± 0.2) only because it has no datum to locate that zone. So the profile zone can move left/right and of course the diameter then changes, depending on where the zone is superimposed, simply because it's an angle. But Fig. 8-18 seems to have been the problem (in my estimation, at least). That's because of datum B, which locks the profile tolerance zone at a precise left/right location. By doing that, the Ø24 should have been basic.

Here's another approach to the topic -- see the attached graphic. Would you say that the first picture is acceptable per Y14.5? (The one that's a partial arc.)
What about the second picture? (The one that's a full circle.)

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

RE: Control location of a feature-set separately from form of the feature-set?

pylfrm,
I see what you are saying and agree that most people may find my idea illegal. I personally think that the approach I tried to describe falls under "reasonable extension of principles" category, because as of today there is no other way (apart from a tricky note) to separate radial size of a surface of revolution from its longitudinal form than use of a profile tolerance (and for that purpose the true profile in axial direction has to be fully defined with basic dimensions) in combination with a directly toleranced diameter.

With regard to your comments about figs. 11-19 and 11-20 from the draft:
- Yes, in fig. 11-20 I also think there should be A, not B, referenced in the lower segment of the composite profile callout;
- In fig. 11-19, I do not see anything wrong in the callout itself. If we imagine that both conical tolerance zones have certain axial length identical for both segments (or in other words, that the smaller tolerance zone does not/cannot move axially relative to the larger tolerance zone), the lower segment of the profile callout (with the triangle symbol) is solely a form control - the 0.02 tolerance zone is free to expand or contract within the 0.2 tolerance zone. If the lower segment did not have the triangle symbol, the callout would make no sense, because the requirement from the lower segment would always override the upper segment.

For those who are interested to see both mentioned figures from the draft, they are here:
http://files.engineering.com/getfile.aspx?folder=b...
http://files.engineering.com/getfile.aspx?folder=8...

My apologies for their poor quality and some traces of my markups, but like I said before, these figures, in my opinion, still need to be improved (for example I do not understand why both "Means this" pictures have 29.8 and 30.2 limits drawn perpendicular to the cone axis).

RE: Control location of a feature-set separately from form of the feature-set?

Belanger,

I'd say the picture with the partial arc (R42±0.5) and the picture with the full circle (diameter 84±1) are equally questionable because in both cases the true profile is not fully defined by basic dimensions.

For Fig. 8-18, would you say that the true profile of the conical surface itself (not in relation to anything else) is fully defined by basic dimension(s)? If not, what about a modified version with diameter 24 BASIC instead of diameter 24±0.2, and 18±0.72 instead of 18 BASIC for the axial dimension?


pmarc,

I don't want to say for sure that what you propose is illegal, just that I'm not convinced it's legal. You certainly have a point about the current lack of alternatives though. Personally, I'd probably go with the "tricky note" approach (perhaps specify the dimension as basic, but note that it can take any single value within some defined range), but I don't have a terribly strong opinion on the matter.

For the draft Fig. 11-19, could you describe a part would meet the lower segment requirement but not the upper? I still can't imagine one.

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

Quote (pylfrm)

For the draft Fig. 11-19, could you describe a part would meet the lower segment requirement but not the upper? I still can't imagine one.

Sure. Take a cone that has a form error (straightness, roundness and taper) within 0.02, but its actual diameter at the right end is for example 60, not 30. That feature will meet the lower segment requirement, but not the upper segment.

RE: Control location of a feature-set separately from form of the feature-set?

pylfrm,
In Fig. 8-18, I would say that the cone is currently not defined as a true profile. Changing the diameter to a basic dim of 24 would make it a true profile.
As for changing the diameter to a basic 24 and then changing the axial dim of 18 to a plus/minus tolerance, I think that would still be a true profile. The diameter of the cone is what directly impacts the true profile, but the 18 is merely relating the cone to the datum, which is not required to be basic.

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

RE: Control location of a feature-set separately from form of the feature-set?

pmarc,

Since there are no datum feature references, what's to stop me from simply shifting the surface axially relative to the upper segment tolerance zone until it falls in? Doesn't the tolerance zone extend to cover the entire actual feature, even if the extent of that feature differs substantially from nominal?


Belanger,

Please see the attached image for another modified version of Fig. 8-18. Would you say that the spherical surface is a true profile fully defined by basic dimension(s)?

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

Probably to understand better the dynamic TZ symbol worth to explain what would be the differences between 11-20 and 11-20 with no "delta". --of course datum feature A on both cases in FRTZF.

RE: Control location of a feature-set separately from form of the feature-set?

greenimi,

Now that I think about it again, I believe changing the datum feature reference in the lower segment from B to A would actually make the "delta" modifier meaningless. What to you think?

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

That spherical-type part seems confusing; At first glance I would say the plus/minus tol of 0.2 is in conflict with the basic dim on the sphere.
The general rule as I see it would be that when applying a profile tolerance, any dim that defines the shape of the feature must be locked as a basic dim for the profile to make sense. (A dim that ties that feature to a datum reference doesn't have to be basic.)

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

RE: Control location of a feature-set separately from form of the feature-set?

Quote (pylfrm)

I believe changing the datum feature reference in the lower segment from B to A would actually make the "delta" modifier meaningless

Pylfrm,

As is currently shown –now-- on the draft (Nov 2015), in my opinion, is incorrect because it is a composite callout (not single segments callout) so,
- either A is added as primary (and keep also B secondary),
- either replace B with A (as primary)
- either have no datum feature shown on the FRTZF
in order to follow the rules of the composite callout.
As far as explaining the differences between “delta” versus the ”non-delta”on Fig 11-20 (same draft) I would like someone with more knowledge than me to try to explain it in the layman terms what those differences would be. I am afraid that I will just muddy the waters, if I will try to do it myself with no gain for anyone.

RE: Control location of a feature-set separately from form of the feature-set?

Quote (pylfrm)

Since there are no datum feature references, what's to stop me from simply shifting the surface axially relative to the upper segment tolerance zone until it falls in? Doesn't the tolerance zone extend to cover the entire actual feature, even if the extent of that feature differs substantially from nominal?

What's to stop you from doing this? Other than - if you did that it would mean the composite callout (with or without dynamic zone modifier), and actually any other single segment profile callout applied to a cone (like in Figs. 4-3 or 4-44 in Y14.5-2009), would never be able to control size of that cone - I guess nothing.

RE: Control location of a feature-set separately from form of the feature-set?

pmarc,

May I ask you, why do you think that 11-20 in the draft, in the left picture the PLTZF profile is shown as 0.2 A primary and B secondary but in the right picture named "or this on the model" the PLTZF is shown as 0.02 (assuming you are ignoring the FRTZF missing callout). Basically I am asking why 0.2 versus 0.02 on the locating pattern TZF?

This picture looks like a mess in my opinion.

RE: Control location of a feature-set separately from form of the feature-set?

Yes. The figure indeed looks like a mess. It is one of the reasons (main) why I said it needed to be improved. Notice that this is rev. C of the figure. I am wondering how did revs. A and B look like, if the committee considered rev. C as an improvement. wink

RE: Control location of a feature-set separately from form of the feature-set?

Okay. I understood.

Let’s pretend for a moment that the composite callout on fig 11-20 has datum feature A shown as a primary for the lower segment FRTZF ( instead of datum feature B).

I still would like to go back to my original question: what would be the differences (if any) between FTTZF with “delta” versus the same composite callout with “no-delta”

Could anyone clarify what would be the dynamic TZ effect and how to practically use it?

Thank you

RE: Control location of a feature-set separately from form of the feature-set?

Quote (pmarc)

if you did that it would mean the composite callout (with or without dynamic zone modifier), and actually any other single segment profile callout applied to a cone (like in Figs. 4-3 or 4-44 in Y14.5-2009), would never be able to control size of that cone

I don't think the profile tolerances in the figures you mention can control "size" either, at least not by themselves. In combination with other tolerances not shown though? Sure.

Please see the attached image. I would expect the diameter of the cone at the large end could be anywhere between 370 + 150 + 0.2 * sqrt(2) = 520.28 (at maximum material condition of both profile tolerances) and 370 - 150 - 0.2 * sqrt(2) = 219.72 (at least material condition of both profile tolerances). Would you agree?

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

pylfrm,
Yes, I would agree with the numbers. Profile tolerance in axial direction definitely has influence on size of the diameter of the cone at the large end. So if we are going to apply axial profile of approx. 228 to the large end of the cone in fig. 11-19 from the draft, then yes, the large end may have an actual diameter of 60 smile

But let's imagine we applied much smaller axial profile callout, say 0.1. Do you still not see how it would be possible to meet the lower segment requirement with the delta modifier but not the upper? If so, is it because in your opinion the tolerance zone defined by the lower segment is able to shift in axial direction relative to the tolerance zone defined by the upper segment?

RE: Control location of a feature-set separately from form of the feature-set?

pmarc,

I'll try to answer your first question for two scenarios. In both cases, I'll answer based on a sample part that has an actual diameter of 60 at the large end, but is otherwise perfect basic geometry.

--------

Secnario 1:
The additional tolerance (0.1 profile) applied to the large end face has no datum feature references, and applies as a simultaneous requirement with the upper segment tolerance (0.2 profile). The lower segment tolerance (0.02 dynamic profile) is a separate requirement.

In this case, I'd say that the sample part would meet the lower segment requirement, but cannot meet the simultaneous requirement of the other two tolerances. I don't think you can narrow down the failure any further than that.

--------

Scenario 2: The additional tolerance (0.1 profile) applied to the large end face references the conical surface as primary datum feature.

In this case, I'd say the sample part meets both the upper segment tolerance (0.2 profile) and the lower segment tolerance (0.02 dynamic profile), but fails the additional tolerance (0.1 profile) by a large margin (approx. 227.9 based on your number above).

========

I don't believe my answers above rely on the lower segment tolerance zone shifting axially relative to the upper segment tolerance zone.

I do believe that such shifting is allowed though, by two different mechanisms in this case. First, by the usual rules of composite profile (no translational constraint for lower segments). Second, by the equivalence between a shift of X axially and a shift of X * sin(15° / 2) normal to the profile (as allowed by the dynamic tolerancing modifier).

Thoughts?

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

pylfrm,

First, my apologies for late response. I was really busy during last 2-3 days and simply could not find enough time to sit down and write a reply.

Second, with regard to proposed scenarios...

Scenario 1:
I do not see a reason to disagree with your interpretation. Also, looks like you agree that there is a way to meet the lower segment of the composite profile callout (with dynamic zone modifier), but not the upper segment, don't you?

Scenario 2:
While I agree that: "a sample part that has an actual diameter of 60 at the large end, but is otherwise perfect basic geometry meets both the upper segment tolerance (0.2 profile) and the lower segment tolerance (0.02 dynamic profile), but fails the additional tolerance (0.1 profile) by a large margin", I do not think the sample part is ever allowed to have an actual diameter of 60 at the large end. It is because the composite profile callout and the additional profile tolerance of 0.1 must both be met to have the actual cone produced according to the print, regardless of whether the callouts consitute simultaneous requirement or not. In other words, in order to meet the additional profile requirement of 0.1 wrt A, the large end of the cone can't be anywhere else except within the two-parallel-planes tolerance zone which center is located at basic distance of ~113.9 from the apex of the theoretical perfect cone (theoretical datum feature A simulator). To make it possible, the actual diameter of the large end of the cone must be of ~30 in first place.

Third, because I am not sure if the underlined part of your statement from July 2nd: [/]"I have my doubts about Fig 11-19 from the draft though. I don't see how it would be possible to meet the lower segment requirement but not the upper, and I don't see that the dynamic tolerancing modifier has any effect in this case."[/i] has been answered, do you now see the effect of the dynamic zone modifier or not really?

RE: Control location of a feature-set separately from form of the feature-set?

pmarc,

No worries about the delay. I appreciate the time you're taking to discuss this. Anyway, it's been 2 weeks already, so what's another few days?

Scenario 1:
I don't think you can specifically say that the upper segment is failed in this case because it is now just one component of a single (simultaneous) requirement. The sample part could be moved around such that it falls within the upper segment tolerance zone, the additional flat tolerance zone, or neither, but not both at the same time. So I guess I still disagree, but only on a nitpicky semantic level that's probably not worth worrying about. I think we're in agreement on the important part here.

Scenario 2:

Quote (pmarc)

In other words, in order to meet the additional profile requirement of 0.1 wrt A, the large end of the cone can't be anywhere else except within the two-parallel-planes tolerance zone which center is located at basic distance of ~113.9 from the apex of the theoretical perfect cone (theoretical datum feature A simulator). To make it possible, the actual diameter of the large end of the cone must be of ~30 in first place.
I agree completely.

Quote (pmarc)

do you now see the effect of the dynamic zone modifier or not really?
Still not really in this case.

Because it is established by a lower segment of a composite FCF, the 0.02 tolerance zone is free to translate relative to the 0.2 tolerance zone of the upper segment. Agreed?

As mentioned at the end of my previous post, I think a relative axial shift can accomplish the same thing as a shift normal to the profile, so the dynamic tolerancing modifier doesn't allow anything that is not already allowed in another way. Thoughts?

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

Hi All,

This looks like a very interesting thread. I am quite interested in people's opinions on dynamic profile and the combination of directly toleranced dimensions and profile - it's nice that there are other people who care about these things. I will read through the posts over the next day or so and see if I have anything to add.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

RE: Control location of a feature-set separately from form of the feature-set?

Hi All,

Here are some thoughts.

First, I applaud both pylfrm and pmarc for being able to discuss this in such fine detail. These examples are very difficult, because of several subtle complicating effects occurring at the same time.

I will try to briefly explain my understanding of the effect of the dynamic profile (delta) modifier. It allows the profile zone to "grow" and "shrink", so that it does not control the size of the feature. In mathematical/geometric language, it allows the profile zone to freely "offset" or "progress". I would say that the best illustration of dynamic profile in the new draft is Fig. 11-37, because it is relatively free of complicating effects. You can see that the dynamic profile zone is oriented and located relative to the datum features, but is allowed to progress (grow and shrink while maintaining the same thickness) in order to adapt to the as-produced "size" of the feature.

I would say that the effect of dynamic profile is much more difficult to see in the figures with the conical considered feature. As pylfrm has pointed out, there are other transformations that would achieve the same overall result. One of them is the conical geometry, which has the special-case property of axisl translation having the same effect as radial expansion/contraction. The other is the dynamic profile modifier being in the lower segment of a composite FCF, which allows the tolerance zone to freely translate.

The axial translation effect with the cone also brings up some deep issues relating to tolerance zone extent. Here's a question. Let's say that I manufacture a perfect conical surface whose smaller diameter is 30, length is 40, and larger diameter is 40.5322 (i.e. the included angle is exactly 15 degrees). Would it pass the 0.2 profile tolerance requrement in Fig. 11-19? How about the 0.02 dynamic profile?

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

RE: Control location of a feature-set separately from form of the feature-set?

Evan, pylfrm,

There is no doubt that things are more complicated because the considered features are conical.

I think the key part of the problem is exactly the tolerance zone extent issue. Where exaclty in axial direcion is the start and the end of the tolerance zones? Do the tolerance zones have infinite length or maybe the lengths are limited by other tolerances? If they are limited, can they be different for different segments of composite profile callouts?

In one of my first posts in this thread I said:

Quote:

In fig. 11-19, I do not see anything wrong in the callout itself. If we imagine that both conical tolerance zones have certain axial length identical for both segments (or in other words, that the smaller tolerance zone does not/cannot move axially relative to the larger tolerance zone), the lower segment of the profile callout (with the triangle symbol) is solely a form control - the 0.02 tolerance zone is free to expand or contract within the 0.2 tolerance zone. If the lower segment did not have the triangle symbol, the callout would make no sense, because the requirement from the lower segment would always override the upper segment.

You may ask, why should we imagine/assume this at all? I think it is because in absence of any datum feature reference that would constrain upper segment TZ relative to a datum or datums, any possible movement of lower segment TZ within the upper segment TZ does not really matter, because the upper segment TZ is also free to shift and can always be brought back to stay perfectly "centered" (axially and radially) on the lower segment TZ. So as a matter of fact, the only "movement" the lower segment TZ has relative to the upper segment TZ is its ability to shrink and grow. And this is what the dynamic profile modifier does in fig. 11-19. Like I said before, in my opinion, if the lower segment did not have the triangle symbol, the callout would make no sense, because the requirement from the lower segment would always override the upper segment. Does it make sense what I am saying?

With regard to fig. 11-20, I believe we would not have any discussion if "only" the composite FCF was changed to two single segment callouts: |prof|0.2|A|B| and |prof||0.02 Δ|A|B| (similar to what has been done in fig. 11-38). Or would we?

RE: Control location of a feature-set separately from form of the feature-set?

I did not read every line of this thread so forgive me if this has already been addressed or if this is super obvious.

If you end up using profile to control the surface of revolution then I believe you need to use profile of a line and not profile of a surface. I would also recommend calling out how many instances of measurement are required for your profile of a line requirement (e.g., every 10°).

RE: Control location of a feature-set separately from form of the feature-set?

Quote (AndrewTT)

If you end up using profile to control the surface of revolution then I believe you need to use profile of a line and not profile of a surface.

I don't know if I would agree with you.
Are you saying that the profile on a cone is not a functional requirement? Never?

Quote (AndrewTT)

I would also recommend calling out how many instances of measurement are required for your profile of a line requirement (e.g., every 10°).

I would also stay away from defining the design intent based on a chosen inspection method and I would not specify on the product drawing in how many instances this surface to be measured. This is exactly the same thing to specify that a straight cylindrical pin is to be measured in 10 places or .010 measurements apart or something like that. It is a risk management to define in how many places the part to be measured.

RE: Control location of a feature-set separately from form of the feature-set?

Lets highjack this tread for a bit and discuss profile of a line vs. profile of a surface. When to use POL is a question that has come up at my work a few times b/c no one really understands it here. I could totally be wrong but my understanding is if you use POS then the entire surface of revolution must be checked. If you use POL then you check individual line segments. How many line segments do you need to check? I believe that it is up to the inspector unless there is written instructions (on the drawing or some other controlling document).

Yes, I would say absolutely design the part based upon its intent but the part also has to be made and inspected.

I would appreciate any input from someone who has an opinion/knowledge on POL vs. POS.

Thanks.

RE: Control location of a feature-set separately from form of the feature-set?

Please, do not hijack this thread. It is quite interesting to learn about dynamic tolerance zone.

Could you, please, start a new thread about profile surface versus profile of a line and their respective measurements issues.

RE: Control location of a feature-set separately from form of the feature-set?

AndrewTT,

I did it for you. Please provide more info in the applicable thread

RE: Control location of a feature-set separately from form of the feature-set?

After unsuccessful attempt to "steal" this thread I would ask you guys where we are?

Please, Please, do not let his thread to die as is quite interesting to learn and specially to understand new stuff.
- Composite on 11-20 draft with and without dynamic TZ
- Also pmarc dropped in the mix two single segment callout ( and I will add " with and without dynamic delta TZ" just for fun)

RE: Control location of a feature-set separately from form of the feature-set?

Quote (axym)

The axial translation effect with the cone also brings up some deep issues relating to tolerance zone extent. Here's a question. Let's say that I manufacture a perfect conical surface whose smaller diameter is 30, length is 40, and larger diameter is 40.5322 (i.e. the included angle is exactly 15 degrees). Would it pass the 0.2 profile tolerance requrement in Fig. 11-19? How about the 0.02 dynamic profile?
As you've probably guessed from my earlier posts in this thread, I'd say it would pass both tolerances.

Here's a related example that might be useful to consider:
Drawing specifies a short piece of tube with inside diameter 19.4678 BASIC, outside diameter 30 BASIC, and length 8 BASIC. A profile tolerance of 0.2 without datum feature references is applied to one of the flat end faces. Now imagine I manufacture a tube with inside diameter 30, outside diameter 40.5322, and length 8. Cylindricity, concentricity, flatness, perpendicularity, etc. are all perfect. Would it pass the profile tolerance?

Despite some superficial differences, I think thread1103-363314: ASME Y14.5-xxxx Profile of a Surface - clarification was basically a discussion of the same issue. It seems to me the overwhelming consensus was that the extent of a surface is not controlled by a profile tolerance applied to that surface. While this may not be explicitly stated by the standard, I think any other answer will be pretty hard to justify.

Quote (pmarc)

If we imagine that both conical tolerance zones have certain axial length identical for both segments
How would you determine this length? Also, how would you determine where to place the tolerance zone ends relative to the part for inspection?

Quote (pmarc)

With regard to fig. 11-20, I believe we would not have any discussion if "only" the composite FCF was changed to two single segment callouts: |prof|0.2|A|B| and |prof||0.02 Δ|A|B|
Agreed. That would would also have the benefit of matching the description in the "Means this" section.

Quote (grenimi)

Also pmarc dropped in the mix two single segment callout ( and I will add " with and without dynamic delta TZ" just for fun)
I'd say |prof|0.02|A| would be equivalent to |prof|0.02 Δ|A|B| for the second single segment.

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

Quote (pylfrm)

How would you determine this length? Also, how would you determine where to place the tolerance zone ends relative to the part for inspection?
I was trying to say that it doesn't really matter in fig. 11-19. My point was that since the upper callout does not contain any datum feature references, the ability of the smaller tolerance zone to shift relative to the larger tolerance zone is actually taken away by the fact that the larger tolerance zone can always be aligned radially and axially with the smaller tolerance zone.

Quote (pylfrm)

Here's a related example that might be useful to consider:
Drawing specifies a short piece of tube with inside diameter 19.4678 BASIC, outside diameter 30 BASIC, and length 8 BASIC. A profile tolerance of 0.2 without datum feature references is applied to one of the flat end faces. Now imagine I manufacture a tube with inside diameter 30, outside diameter 40.5322, and length 8. Cylindricity, concentricity, flatness, perpendicularity, etc. are all perfect. Would it pass the profile tolerance?
I say it would. But let's say that instead of datumless profile callout of 0.2, a perpendicularity tolerance of 0.2 is appplied to the end face of the tube relative to the datum axis derived from the outside diameter. I am interested to know the value of maximum possible as-produced angle between the end face and the datum axis (assuming the face was manufactured perfectly flat). Would the answer be the same for OD manufactured to 30 in case 1, and 40.5322 in case 2?

RE: Control location of a feature-set separately from form of the feature-set?

Quote (pmarc)

But let's say that instead of datumless profile callout of 0.2, a perpendicularity tolerance of 0.2 is appplied to the end face of the tube relative to the datum axis derived from the outside diameter. I am interested to know the value of maximum possible as-produced angle between the end face and the datum axis (assuming the face was manufactured perfectly flat). Would the answer be the same for OD manufactured to 30 in case 1, and 40.5322 in case 2?

Maximum possible angle increases as the outside diameter decreases. Because we haven't established a minimum outside diameter, I'd say the angle is unbounded.

For cases 1 and 2, I calculate 0.382° and 0.283° respectively.

pylfrm

RE: Control location of a feature-set separately from form of the feature-set?

Quote (pmarc)

You may ask, why should we imagine/assume this at all? I think it is because in absence of any datum feature reference that would constrain upper segment TZ relative to a datum or datums, any possible movement of lower segment TZ within the upper segment TZ does not really matter, because the upper segment TZ is also free to shift and can always be brought back to stay perfectly "centered" (axially and radially) on the lower segment TZ. So as a matter of fact, the only "movement" the lower segment TZ has relative to the upper segment TZ is its ability to shrink and grow. And this is what the dynamic profile modifier does in fig. 11-19. Like I said before, in my opinion, if the lower segment did not have the triangle symbol, the callout would make no sense, because the requirement from the lower segment would always override the upper segment. Does it make sense what I am saying?
I would describe this differently. But I would also repeat that this example is very difficult to sort out, because of the multiple sources of "movement".
-the lower segment TZ can freely translate relative to the upper segment TZ because it's a composite FCF. The dynamic profile modifier allows the lower segment TZ to shrink and grow (offset).
-if the lower segment did not have the triangle symbol, I agree that the callout would make no sense. The lower segment would be allowed to shift relative to the upper segment, but this would provide no advantage and the optimal shift would be zero.

The callout in Fig. 11-19 may not make sense anyway, depending on what conclusion we reach on the tolerance zone extent issue. See below.

pylfrm,

My question about the "oversize" cone, and your related question, brings the issue of tolerance zone extent to a head. If the answer to these questions is yes, then the tolerance zone can extend a large distance past the boundary of the basic surface. I had not thought it through and come to this conclusion before, and yes seems like an uncomfortable result, but I can't come up with an argument that it should be no. Does this mean that a profile zone can extend an indefinite distance past its basic surface? There must be more to it, or we could reach some absurd conclusions.

Back to Fig. 11-19. If the profile zone can be extended, then the zone can accommodate a 15 degree cone of any "size". This would mean that the upper segment 0.2 profile tolerance would only control the form of the cone and not the size. This would make the use of a composite FCF unnecessary, because the upper and lower segments would both be controlling form only. Does that make sense?

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

RE: Control location of a feature-set separately from form of the feature-set?

axym,

It has never seemed like an uncomfortable result to me. The alternatives, on the other hand, do.

Do you have an example of an absurd conclusion this would allow? I haven't thought of any, although that may be due to a differing opinion of what constitutes absurdity.

Regarding Fig. 11-19, that is pretty much how I see it -- two different segments controlling the same thing. That interpretation makes sense to me, and so the figure does not.

pylfrm

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