Pattern of Patterns/Repetative Patterns
Pattern of Patterns/Repetative Patterns
(OP)
Tried a quick search, as I'm sure it's been done to death before, but it didn't show up.
I'm having a mental blank or something so would appreciate a hand. We often have situation where we have a 'pattern of patterns'.
Tec-ease has a suggested way of doing it essentially making a feature in each pattern a datum, and minimizing dimensioning by using 'INDIVIDUALLY'.
Alternatively, round here I often see more like this sketch
Can someone remind me the pros/cons of each way, or if they're even both legitimate to 14.5M-1994. If there's a relevant section in 14.5 that would be great too, as I had trouble finding it.
Simplistically in the tec ease way am I right in thinking the smaller holes follow the datum hole of each pattern, so slightly relaxing tolerances on those smaller holes relative to global datums, almost comparable to composite tolerancing?. Where as in my sketch all features are tied to same global datums so slightly more restricted.
Also, on my sketch, if I wanted to make the 1in hole the datum for each pattern, could I just make it 'D' in the detail view, reference the 4 holes FCF to D and leave it at that. Or would I need to add 'INDIVIDUALLY' next to the "4X DETAIL A" or something?
Thanks.
I'm having a mental blank or something so would appreciate a hand. We often have situation where we have a 'pattern of patterns'.
Tec-ease has a suggested way of doing it essentially making a feature in each pattern a datum, and minimizing dimensioning by using 'INDIVIDUALLY'.
Alternatively, round here I often see more like this sketch
Can someone remind me the pros/cons of each way, or if they're even both legitimate to 14.5M-1994. If there's a relevant section in 14.5 that would be great too, as I had trouble finding it.
Simplistically in the tec ease way am I right in thinking the smaller holes follow the datum hole of each pattern, so slightly relaxing tolerances on those smaller holes relative to global datums, almost comparable to composite tolerancing?. Where as in my sketch all features are tied to same global datums so slightly more restricted.
Also, on my sketch, if I wanted to make the 1in hole the datum for each pattern, could I just make it 'D' in the detail view, reference the 4 holes FCF to D and leave it at that. Or would I need to add 'INDIVIDUALLY' next to the "4X DETAIL A" or something?
Thanks.
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What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?





RE: Pattern of Patterns/Repetative Patterns
I notice that the 2009 standard includes a new picture of the concept you're asking about -- see page 128 (Fig. 7-37). I don't think that picture introduces a new idea, but it at least formally addresses the topic.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Pattern of Patterns/Repetative Patterns
I don't have the 2009 standard, and we still work to 94 anyway.
Thanks.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Pattern of Patterns/Repetative Patterns
Fig. 5-39 on page 138 of the 94 standard reflects the thought of creating a datum on hole and placing a "8X INDIVIDUALLY" beside it. The problem in your situation is the fact that each of the 4 holes around that larger hole must be oriented.
If there was a greater relationship between the 4 holes and the larger hole, then I would use the example shown on page 138 of the standard. I would have the datum structure set up as primary A, secondary D (that is the larger hole) and a tertiary C. I need the tertiary for orientation.
If there is not a greater relationship, then I would suggest dimensioning the holes individually. The 16 smaller holes must then be dimensioned from B & C. I would also shown the larger hole as 4X (size) while the smaller holes would be 16X (size). I believe that is what JP suggested.
Food for thought.
Dave D.
www.qmsi.ca
RE: Pattern of Patterns/Repetative Patterns
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net
RE: Pattern of Patterns/Repetative Patterns
I dont think Note "Indiviually" will come into the Picture here as Holes need to be orientaed and located to center hole (4X)
NX 6.0.2.8 MP4
Teamcenter 2007
WINDOWS XP (64 Bit)
RE: Pattern of Patterns/Repetative Patterns
Seems I had it about right.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Pattern of Patterns/Repetative Patterns
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net
RE: Pattern of Patterns/Repetative Patterns
My sketch is just a really simplified example to help verify my understanding, the real application that brought this up is more complex.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?