Dynamic Profile Modifier questions 2

[SeasonLee]

Hello All

Please ref to the snap shot below, this is from Y14.5-2018 Figure 11-35, I'm interested to know what will be the differences by removing the Dynamic Profile Modifier from the lower segment.

Thanks in advance

Season

 

[pmarc]

greenimi,
I think that ISO GPS standards are definitely much more rule based than Y14.5. People seem to like Y14.5 more because it shows numerous examples which are often very similar to the real-life cases they have to deal with every day. However, when it comes to details - for example, when trying to mathematize some of the concepts shown in the standard - Y14.5 has some serious gaps, even for very fundamental concepts. This creates room for multiple creative interpretations.

chez311,
I agree with your assessment.

 

[pylfrm]

CheckerHater,

Definitely b) and the illustration on the left.


chez311,

I suppose I should have complained about your mention of a ratio. It looks like you've mostly sorted that out now though.

I forgot about the possibility of applying the dynamic modifier to a non-uniform tolerance. Covering that case would probably require a lot more than 36 words, so I don't think I'll try to revise my earlier explanation.

I believe it would be much easier for everybody if Y14.5 explained their dynamic profile modifier in a similar fashion.

And maybe if they used the symbol OZ instead of Δ?

I find it interesting that in ISO 1101:2017 the offset for OZ is shown as a sphere radius, but the offset for UZ is shown as a sphere diameter. It seems like these approaches are probably equivalent, but I haven't fully convinced myself of this.


pylfrm

 

[CheckerHater]

@pylfrm:
Case b) and picture on the left are clearly about offset, so is ISO OZ modifier mentioned by pmarc.
The interpretation by Geotol referenced by greenimi mentions changing "size" while maintaining "form", which is more like picture on the right.
So, naturally, I am asking if anywhere in ASME there is clear definition of what "progression" is.
Anybody knows if math standard (a.k.a. Y14.5.1) is finally out?

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

 

[greenimi]

Anybody knows if math standard (a.k.a. Y14.5.1) is finally out?

Even if (Y14.5.1) it were out would be irrelevant because the new math standard revision is (written) to support Y14.5-2009 and not 2018 version within which dynamic profile has been initially released/ introduced. My opinion.

 

[chez311]

CH,

I would assume Y14.5.1-20xx has not yet been released since only the 1994 edition appears on the ASME site. Regardless as I noted earlier "dynamic profile" does not appear on the draft I have and thus I would not expect it on the final released version. Greenimi is correct in that the latest revision of Y14.5.1 is only meant to be Y14.5-2009 compliant, though there is limited support for some of the new concepts in 2018 (notably single solution of datum features).

https://www.asme.org/codes-standard...rtBy=bestselling&sortByDir=desc&query=y14.5.1

https://www.asme.org/codes-standard...lerancing-principles?productKey=N13294:N13294

That said, I think the current Y14.5-2018 provides an outline of the behavior expected in section 11.10:

When the dynamic tolerance modifier is applied to a lower segment of a composite tolerance without datum feature references, the tolerance zone controls the form but not the size of the feature and it uniformly progresses (expands or contracts) normal to the true profile, UOS.

I think the inclusion of the term "size" in their description communicates the intent to allow progression (expansion/contraction) of the tolerance zone but is maybe misleading as it conflates the meaning of size with the established definition for FOS. Its probably best then to ignore this and focus instead on the portion describing uniform progression normal to the true profile as well as the examples and figures shown. Unless presented with significant evidence and reasoning to the contrary, I would expect the behavior to be almost identical to the ISO concept of OZ that pmarc showed.

 

[CheckerHater]

@chez:
I have a copy of Y14.5.1-1994.
Thank you for actual quote of 11.10.1.
It looks like "offset" interpretation has a merit. I guess I just leave it right there.

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

 

[chez311]

CH,

Of course you do, I figured you did it didn't even occur to me to think otherwise - I know from your previous posts that you're well acquainted with it. I was just showing that when you search the ASME site the 1994 edition is the only thing that comes up.

 

[axym]

Hi All,

Here are a few quick thoughts.

I agree that dynamic profile involves consistent offsets from the true profile, not maintaining the original aspect ratio of the feature. It's offsetting/progressing, not scaling. I also agree with pylfrm's description that dynamic profile is like a generalization of total runout - that is a good way to describe it. If no datum features are referenced, then dynamic profile becomes a general form control. Another way to describe dynamic profile is that it is like unequally disposed profile, with the amount of unequal disposition (value after the (U) being variable instead of fixed.

The next version of Y14.5.1 is not published yet - I'm hoping for first quarter 2020. There will not be any coverage of dynamic profile, as it was not in Y14.5-2009.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[DeanD3W]

Regarding "progressing" (which I would prefer be called "Normal expansion or contraction" in the standard) vs. scaling, with the dynamic profile modifier, I think the best way to describe why the tolerance zone boundaries are both a normal expansion or contraction from true profile, with the distance between the boundaries fixed at the specified tolerance value, is that this is the same way normal profile tolerance zone boundaries are defined.

Scaling is not ever used for profile tolerance zone boundaries, but for simple features like cylinders and slots scaling would yield the same result as normal expansion/contraction.

 

[SeasonLee]

Thanks for All help and assists.

Season