The means to break a simultaneous requirement within a pattern

[Burunduk]

In the ASME Y14.5-2009 standard, the SEP REQ is always shown attached beneath two or more feature control frames. If these feature control frames control patterns, it means that each pattern as a group is controlled in a separate set up of the datum reference frame, but the tolerance zones of the features of the pattern are still established simultaneously and are mutually fixed.

What if SEP REQT is only shown beneath one feature control frame associated with a pattern? Does the SEPT REQT in this case dismantle the fixed interrelationship between tolerance zones of features within that pattern?

 

[3DDave]

You can submit a work order with your preferred solution to the ASME Y14.5 committee for consideration in the next version if it wasn't already addressed in the most recent version.

 

[pmarc]

Burunduk,
Could you provide an example that could be used to discuss options?

 

[chez311]

Agreed with pmarc, an example would be useful.

That said, simultaneous requirements is a specific type of pattern creation mechanism. Separate requirements is meant to break the relationship between features controlled with this specific type of pattern creation mechanism. If another mechanism/notation is utilized (ie: "nX") I don't believe theres anything to support that SEP REQT would break that pattern. Of course, again, we would have to see what exactly you're talking about.

 

[Burunduk]

Imagine that the two keyslots in fig. 4-41 had the same width size and tolerance. Could they be toleranced 2X 3.00-3.02 |POSITION|0(M)|A| with the notation SEP REQT, resulting in the unlocked alignment of the slots as shown in the figure?

 

[pmarc]

Of the options available in Y14.5, I would probably use the concept of INDIVIDUALLY.

In the light of simultaneous requirement definition given in para. 4.19, there is no need to apply SEP REQT to override simultaneity in this case because the single position callout is not enough to constitute simultaneous requirement in the first place.

 

[Burunduk]

So essentially this means that:

2X 3.00 - 3.02 |POSITION|0(M)|A|
is not a simultaneous requirement, but:

3.00 - 3.02 |POSITION|0(M)|A|
appearing twice on the drawing - is.

Correct?

 

[pmarc]

Correct.

The former is simply a pattern specification.

 

[Burunduk]

But, the two schemes would have exactly the same geometrical meaning, wouldn't they?

 

[greenimi]

Of the options available in Y14.5, I would probably use the concept of INDIVIDUALLY.

In the light of simultaneous requirement definition given in para. 4.19, there is no need to apply SEP REQT to override simultaneity in this case because the single position callout is not enough to constitute simultaneous requirement in the first place.

Could you explain a little bit in more details why and based on what you made those statements? I am a little confused myself.

Should I understand that IF "2X 3.00-3.02 |POSITION|0(M)|A|" position is used (for those two keyslots in fig. 4-41 that had the same width size and tolerance) then the way to break their alignment is to use INDIVIDUALLY?

Also if "3.00 - 3.02 |POSITION|0(M)|A|" is used for one keyslot and the same thing "3.00 - 3.02 |POSITION|0(M)|A|" is used for the other keyslot, THEN the way to break their alignment now is: to use SEP REQT?

This is what I understood from your replay. How far from your real intent am I?

 

[Burunduk]

greenimi, 4.19:
"A simultaneous requirement is where two or more geometric tolerances apply as a single pattern or part requirement"
Technically under "2X" it's just 1 geometric tolerance that applies on both slots.

 

[greenimi]

greenimi, 4.19:
"A simultaneous requirement is where two or more geometric tolerances apply as a single pattern or part requirement"
Technically under "2X" it's just 1 geometric tolerance that applies on both slots.

I am not sure I understand. Could you, please, debug my statements on my previous post and let me know where I was incorrect? (and I am not saying that everything I stated is up to par).
Thank you very much.

 

[greenimi]

pmarc,

We have also a parallel thread which might need your qualified opinion

https://www.eng-tips.com/viewthread.cfm?qid=469869

(ASME multi-leader lines and common datum feature)

Many many many thanks for your input pmarc.

 

[Burunduk]

greenimi, I don't think you are incorrect. You asked pmarc what he based his statements on and I just went ahead and suggested what I think is the basis to his statement - the words that matter are probably "two or more geometric tolerances" in the definition of a simultaneous requirement. Regarding the rest of your post - I made the same conclusions.

I still think that the cases of identical size and position specification shown for each of the slots separately and the same specification appearing only once preceded by "2X" are geometrically the same requirement. If I am wrong I would like to learn where my mistake is.
So for what it's worth I think that it's unfortunate that what seems to be a symbology related difference leads to different conceptual classifications per Y14.5 definitions and to different acceptable tools to override these differently named identical geometrical requirements. I am afraid it indicates that there are too many different words and definitions used over the given amount of substance.

 

[Dean Watts]

I think there are two position tolerances referencing the same datum reference frame whether they are shown separately, or by using 2X. I think simultaneous requirements apply in either case. I know that that grouping and patterns do need a lot of clarification. Hopefully the next version of Y14.5 will provide those needed improvements.

Dean

http://www.validate-3d.com

 

[pmarc]

But, the two schemes would have exactly the same geometrical meaning, wouldn't they?

Yes, they would.

 

[greenimi]

Quote (Burunduk)
But, the two schemes would have exactly the same geometrical meaning, wouldn't they?

Yes, they would.

So it's just terminology...
If there is simultaneous requirement or not who cares?, if those two schemes have the same mathematical definition and the same meaning....

"So essentially this means that:

2X 3.00 - 3.02 |POSITION|0(M)|A|
is not a simultaneous requirement, but:

3.00 - 3.02 |POSITION|0(M)|A|
appearing twice on the drawing - is."

 

[pmarc]

If the simultaneous requirement rule did not exist, then the second option would not be equivalent to the first.

 

[greenimi]

If the simultaneous requirement rule did not exist, then the second option would not be equivalent to the first.

Ok. Understood.
My point was with "simultaneous requirements rule in place" IF the two schemes have the same meaning, then it's a matter of preferred drafting on how "to break a simultaneous requirement within a pattern".
That means drafting is the driving force of subsequent GDT callout (INDIVIDUALLY or SEP REQT).

 

[Burunduk]

I think there are two position tolerances referencing the same datum reference frame whether they are shown separately, or by using 2X. I think simultaneous requirements apply in either case.

That also makes sense.