Composite Positional Tolerancing?
Composite Positional Tolerancing?
(OP)
Hello,
Short question:
What is the difference in interpretation of following two cases of composite positional tolerancing?
I know what Y14.5M standard says, but I am afraid I am not able to visualize this difference properly.
Thanks a lot for any hint.
Short question:
What is the difference in interpretation of following two cases of composite positional tolerancing?
I know what Y14.5M standard says, but I am afraid I am not able to visualize this difference properly.
Thanks a lot for any hint.





RE: Composite Positional Tolerancing?
The bottom one would allow the entire pattern to 'tilt' within the tol limits.
I know you've looked at ASME Y14.5M-1994 but make sure and read 5.4.1 section b bottom line of page 95
KENAT,
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RE: Composite Positional Tolerancing?
In short it contrls the pattern integrity only not that pattern's orientation to [A] as the lower segment of the upper composite control does.
Paul
Paul
RE: Composite Positional Tolerancing?
ht
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Composite Positional Tolerancing?
Jim, Thanks for the PowerPoint slide, it's very clear and easy to understand the differences in between, but I am anxious to know the differences between them if multiple single segment position tolerance called out for this case.
POS|Ø0.6MMC|A|B|C
POS|Ø0.4MMC|A|B
POS|Ø0.2MMC|A
SeasonLee
RE: Composite Positional Tolerancing?
I'll see what I can come up with for graphics for 2 single segments, and give the 3 segments some thought.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Composite Positional Tolerancing?
The first positional tolerance of DTZ of 0.06 mm controls the pattern (PLTZF) for location from datums B & C and perpendicularity to datum A.
The second positional tolerance of DTZ of 0.04 controls individuals (FRTZF) in the pattern to each other, perpendicular to datum A and parallel to datum B. The single segment FCF also controls the dimension or location from datum B to the pattern. This differs from a composite feature control frame where the individuals in the pattern are only parallel to datum B rather than parallel and dimensioned.
The third position tolerances of a DTZ of 0.2 control the individual features in the pattern (FRTZF) to each other and perpendicular to datum A.
Dave D.
www.qmsi.ca
RE: Composite Positional Tolerancing?
SeasonLee
RE: Composite Positional Tolerancing?
I think it's fine, as long as the considered feature is perpendicular to one datum and parallel to the other ;^)
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Composite Positional Tolerancing?
Extension of Principles
Did someone just pass out a bunch of those books?
RE: Composite Positional Tolerancing?
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Composite Positional Tolerancing?
If you don't mind, I would like to go back for a moment to the original question for composite postional tolerancing:
As SeasonLee said, Jim's PowerPoint slide shows very clearly the difference in between. But my question is can axes of these 2 holes be tilted in different directions if no datum is specified in bottom segment of FCF (so that they are not parallel to each other)?
RE: Composite Positional Tolerancing?
Sorry, I actually meant: can tolerance zones of the axes of these 2 holes be tilted in different directions if no datum is specified in bottom segment of FCF (so that the tolerance zones are not parallel to each other)?
RE: Composite Positional Tolerancing?
SeasonLee
RE: Composite Positional Tolerancing?
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Composite Positional Tolerancing?
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Composite Positional Tolerancing?
There are a lot of 3 single-segment position tolerance callout examples on the two books mentioned above not only on the text but also shows on the exercise, I am asking the differences between them since I believe Jim will have an better and excellent interpretation.
SeasonLee
RE: Composite Positional Tolerancing?
I have Alex's 'Advanced of GD&T Concepts' in front of me, and at the end of chapter 20 there is an exercise 20-1 which shows exactly the same situation like you are asking about. I am sure you noticed the statements in point 5 (page 20-13):
- top segment controls location of pattern relative to A, B, C;
- middle - location to B;
- bottom - spacing between holes as well as squarness to surface A.
I am not sure what does the 'squarness' exactly mean, but I assume it's simply a perpendicularity to A.
Regards
RE: Composite Positional Tolerancing?
The 3 single-segment position tolerance callout on the exercise is
POS|Ø1MMC|A|B|C
POS|Ø0.5MMC|A|B
POS|Ø0.2MMC|A
My understanding the squareness to surface A is the pattern (4 holes) perpendicular to datum A.
SeasonLee
RE: Composite Positional Tolerancing?
My Krulikowski reference books stayed with the old employer, so I can't comment on differences between his examples. If someone were to send me a scan, I could take a look.
The points pmarc presents from Alex's book make sense and don't contradict anything in the standard. In theory, then, you could have 5 single-segment position controls, though that wouldn't be useful as far as I can figure.
As for "squareness", indeed it does mean perpendicularity. It's a hold-over term long used in the shop, and is commonly used and understood by most of us "old-timers" that grew up with heavy interaction between shop and design ... ah, the painful memories of lessons past.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Composite Positional Tolerancing?
A scan of the Exercise 20-1 from Alex' book had sent to inquiries@profileservices.ca
SeasonLee
RE: Composite Positional Tolerancing?
I've added to the PowerPoint Show file that I posted earlier, to show a few more variations for further discussion. Before anyone comments, yes, a couple of animations are out of order and some of the animations don't keep the "child" zones absolutely within the "parent" zones; PowerPoint isn't my favorite tool for functionality.
Anyway, I think that the graphics mostly speak for themselves as to what the controls mean. Hopefully it helps.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Composite Positional Tolerancing?
ht
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Composite Positional Tolerancing?
ht
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Composite Positional Tolerancing?
Thanks for the valuable post, it worth an another star.
Thanks
SeasonLee
RE: Composite Positional Tolerancing?
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com