Composite Profile Tolerance

[ASHWA]

Dear All,
Have a doubt in Profile Tolerance,

The 2nd part of Callout leads to Pattern located by composite profile tolerance,

What does the 1st part 0.1 INDIVIDUALLY refer?

Sorry, if it's a already asked query.

- Ashwa.

 

[Burunduk]

The uppermost segment indicated to apply individually controls the form and size of each of the two complex features without controlling the spatial relationship between them.

 

[ASHWA]

Thanks Burunduk (Mechanical)...!!

 

[trinhhle]

I have three questions related to the one above.

1. Is the term INDIVIDUALLY applicable to the 1994 standard?

2. For Composite Profile Tolerance, does PLTZF and FRTZF apply in 1994 standard? I didn't see any mentions of PLTZF and FRTZF in section 6.5.9 of 1994.

3. My goal is to locate two profiles at .8, but have each profile surface within the .2 tolerance zone(similar to the example above without the first segment). I do not want the FRTZF to be .2.
Am I allowed to add INDIVIDUALLY to the lower segment?

 

[greenimi]

See this discussion:

https://www.eng-tips.com/viewthread.cfm?qid=453586

 

[greenimi]

Is the term INDIVIDUALLY applicable to the 1994 standard?

Yes, it is.




For Composite Profile Tolerance, does PLTZF and FRTZF applicable in 1994 standard? I didn't see any mentions of PLTZF and FRTZF in section 6.5.9 of 1994.


Yes, it is.

 

[chez311]

Is the term INDIVIDUALLY applicable to the 1994 standard?

Yes the INDIVIDUALLY notation occurs in at least one place in the 1994 standard - in fig. 5-39 and associated text para 5.7(c). It wasn't expanded on in the way it was in 2009 and later but at least it was introduced.

For Composite Profile Tolerance, does PLTZF and FRTZF applicable in 1994 standard? I didn't see any mentions of PLTZF and FRTZF in section 6.5.9 of 1994.

I'd say it has less to do with whether the actual term was used* and whether the concept was applied to profile for pattern location using composite tolerances. It was strangely not directly utilized or shown in a figure (why they didn't think it would be useful or important to show location of patterns of features using composite profile/multiple single segment is beyond me) however I personally don't think that alone rules out its use. For use with the 1994 standard I would say that falls under the realm of "extension of principle" since it is clearly defined in the position section and introduced at least for single features in the profile section.

My goal is to add locate two profiles at .8, but have each profile surface within the .2 tolerance zone(similar to the example above without the first segment). I do not want the FRTZF to be .2.
Am I allowed to add INDIVIDUALLY to the lower segment?

Yes I would say you are allowed to add INDIVIDUALLY to the lower segment.
Its possible that you don't need a composite tolerance at all - depending on what, if any, datum references you desire for the second .2 segment. If you have datum references and you want to preserve the location to those datum feature(s), then it should be a separate segment. If you have datum references that constrain location DOF but you only want your tolerance zone oriented to them then it should be composite profile. If your datum references don't constrain any location DOF (say just A in the above example) or its datumless then either could be used.

*To note, for whatever reason in 1994 they decided to use "profile locating control" and "profile size/forrn/orientation refinement control" for composite profile tolerance instead of following the PLTZF/FRTZF convention established in the position section. Strange - this was obviously changed in 2009 and on.

 

[Burunduk]

trinhle,

1. Yes, the meaning of INDIVIDUALLY is interpretable per the 1994 standard. See fig. 5-39 (page 138).

2. These exact abbreviations are not used within the text in the context of profile tolerances. But I think it has to do with the fact the patterns are missing altogether from the section where profile tolerances are defined in the 1994 standard. Nevertheless specifying the profile tolerance "2X" will create a pattern similarly to the way it is in the newer standards, and since the abbreviations are defined for patterns in the section about position tolerances, I think they are interpretable for profile too.

3. Yes.

 

[trinhhle]

Chez,

You have me thinking maybe I do need to separate the lower segment. Can you elaborate more, I am confused by your statement? I want to locate the three cutouts .060 relative to the datums in the first segment. The second segment is there to meet the requirements for the connector. I don't care about the relationship between the 3 cutouts as long as the meet .060 location from the first segment.

https://files.engineering.com/getfi...dbe-0da7ce75fec7&file=Composite_Tolerance.png

 

[Andera]

I think the way you show it (datum D in the lower segment) is NOT correct.
That is not composite (per ASME Y14.5)

Should have been multiple single segments and NOT composite

 

[chez311]

trinhhle,

First thing I'm noticing is that for a composite tolerance your datum references in all of the lower segments (FRTZF) should be in the same order of precedence as the first segment (PLTZF). Ie: |A-B|C|D|, |A-B|C|, |A-B|, and datumless would all be viable options for a lower segment. |A-B|D| or |D| are not.

If you wish to reference only |D| then a Multiple Single Segment scheme must be used. That said, since the material is thin sheet metal I have a hard time rationalizing that you truly care about orientation to D, at least above and beyond what any tolerance applied to the face which the hole goes through and that which is guaranteed by the .060 tolerance.

Sounds to me like you probably just want a datumless .01 profile tolerance in the lower segment.

Can you elaborate more, I am confused by your statement?

Essentially I was laying out the difference between a multiple single segment (ie: separate segements) and composite tolerance. A multiple single segment is essentially a special case of, as its name implies, several separate locational (position or profile) tolerances applied to the same feature(s) - they must obey the rules of any other standard position/profile tolerance and location constraint to any referenced datum features is preserved. This is in contrast to a composite tolerance, which for any lower segments (FRTZF) the location constraint to any referenced datum features is NOT preserved ie: orientation constraint ONLY.

Therefore if in the lower segment(s) no datum features are referenced (datumless) or only datum features which constrain orientation DOF, then there is no difference between specifying a composite or multiple single segment tolerance.

 

[greenimi]

trinhhle,
Maybe the lower segment should not have had datum feature D in the FRTZF.

What do you mean by "The second segment is there to meet the requirements for the connector"?
If you do not need the orientation to datum D, THEN a datumless is a better option.

 

[greenimi]

chez311,
We've posted in the same time.

 

[trinhhle]

If I modify the callout to have two segments and make the lower segment datumless, is the term INDIVIDUALLY still required?

 

[trinhhle]

Greenimi,

What I mean by "the second segment is there to meet the requirements for the connector" is that the cutouts require a bilateral tolerance of +/- .005. That is why I added the surface profile of .010.

 

[chez311]

If I modify the callout to have two segments and make the lower segment datumless, is the term INDIVIDUALLY still required?

Yes because you stated you do not wish to constrain the elements in the pattern relative to each other in the lower segment. As the "3X" is still applicable, they are still part of a pattern and will be held in location relative to each other unless otherwise specified (ie: INDIVIDUALLY specified).

greenimi,
Seems like we both have a quick trigger finger

 

[trinhhle]

Thank you all for your help!