FRTZF / PLTZF Composite Positional Tolerance.
FRTZF / PLTZF Composite Positional Tolerance.
(OP)
Hello,
I got a drw for the composite tolerance call out that shows no datum on the bottom call out, is this correct?
Or we suppossed to have datum A at least shown.
Also, why is it that the composite shows to different calls for the positional tolerance said for example .36 mm on top and .25 mm
at the bottom.
Thanks.





RE: FRTZF / PLTZF Composite Positional Tolerance.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: FRTZF / PLTZF Composite Positional Tolerance.
I'm sorry Kenat, somehow familiar but not good enough I guess.
So there is no datums at all on the bottom one or is implied.
Thanks
RE: FRTZF / PLTZF Composite Positional Tolerance.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: FRTZF / PLTZF Composite Positional Tolerance.
It is legal not to have datum features referenced in the lower segment of a composite feature control frame. This controls the location between the features in the pattern, just not orientation to any datum features (since there are not any called out). Figure 5-51 on page 147 of the 1994 standard provides a good illustration and example of this.
Drstrole
GDTP - Senior Level
RE: FRTZF / PLTZF Composite Positional Tolerance.
Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: FRTZF / PLTZF Composite Positional Tolerance.
Is this one of those times when the standard gives basic principles, but we are free to extend the concepts to other areas? Or should we stick to the script and say it's only for coaxial holes?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: FRTZF / PLTZF Composite Positional Tolerance.
My opinion is that from purely theoretical point of view both applications are acceptable (even if the pattern example is not shown in the standard).
RE: FRTZF / PLTZF Composite Positional Tolerance.
On coaxial holes I can absolutely see how this would work just fine.
Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: FRTZF / PLTZF Composite Positional Tolerance.
Paul
RE: FRTZF / PLTZF Composite Positional Tolerance.
http://p
Be patient as there is a 4-level single-segment fcf near the end which shows a final refinement with no datum reference, and what it means. To clarify someone's point above, there is an orientation control associated with the refined tolerance zone, as limited by the first level of the FCF. There is not, however, any refinement of the orientation in the second level of the FCF.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: FRTZF / PLTZF Composite Positional Tolerance.
Good Composite Position presentation.
Thank you.
RE: FRTZF / PLTZF Composite Positional Tolerance.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: FRTZF / PLTZF Composite Positional Tolerance.
I am thinking about a series of very long bores in engine block fixtures that are for say a rack and pinion system, entering from relatively small faces, no bigger than the actuator flange itself. The bores need to follow each other as a pattern tighter than to an outside surface. We generally used a "knocker" on the driving actuator in these systems so misalignment from the actuator mounting face was allowable. All the other intermediate bores come in from faces that are irrelevant except the system output bore (they would not even need to be coming in from the outside surfaces if there was a way to get the bore in without coming in from the outside, say like a stereolithography.
Frank
RE: FRTZF / PLTZF Composite Positional Tolerance.
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: FRTZF / PLTZF Composite Positional Tolerance.
The only other distinction between composite FCF's and multiple single-segment FCF's is that the rule of simultaneous requirements is waived for the lower tier of the composite FCF. Which raises an interesting question - does the rule of simultaneous requirements apply to single-segment FCF's with no datum feature references?
What do you guys think?
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: FRTZF / PLTZF Composite Positional Tolerance.
Before the 94 standard redefined the composite FCF giving its lower tier 6 DOF control of the pattern among the defined pattern features and only Rotational DOF "as limited" by the specified datum features and expanded the definition of the "simultaneous requirement" principle, we (Ford Motor Company) used either a lower tier composite FCF or an additional tolerance refined single segment with no datum features to control the coaxiality of each of the "spool valve bore patterns." There was an upper tier composite or upper segment that controlled the bore's position in the cast labyrinth for logic control but its tolerance was slightly relaxed compared to lower tier/segment that controlled the spool land diameters fit with the labyrinths land diameters.
The 94 standard changed all that and we were forced to use newly defined composite FCF to prevent the numerous individual bore lower segments from being considered "one composite pattern" since they all had the same datum features specified in the same order "none/null."
The upper tier/segments all had the same datum features as well, which controlled the bores in the structure, but that simultaneous requirement was already constrained by the datum structure specified by design... no problem! Other problems arose when single segment FCFs that had unconstrained translational or rotational by design were now linked as a simultaneous requirement... those had to be changed.
I understand that the simultaneous requirements rule was expanded address the rocking primary controversy but it did not have to blanket unconstrained Degrees-Of-Freedom. I also understand that it links datum feature mobility among identically referenced features or feature patterns but it still does not have to constrain all 6 Degrees-Of-Freedom among controls that are afforded translational or rotational liberty by design.
This makes me wonder if customized datum reference frames from the 2009 standard are immune to the blanket "one pattern" rule when their translational or rotational freedoms have been identically defined... I don't have time to look right now.
Paul