To GD&T or not to GD&T ??? 2

[dtmbiz]

This forum is a curiosity to me. Over the years it seems as if there are a number of comments that indicate the use of GD&T is only for certain situations . Besides the forum I have encountered many who believe that if the design involves; a “simple part, or a “one off”, or precision tolerances are not required; then GD&T (ASME Y14.5) shouldn’t be used or isn’t necessary; too confusing to manufacturers and/or too time consuming.

Personally, I recommend that it should be used on all components; simple or complex, loose or tight tolerances, prototypes,” one of a kind”, production or whatever the situation.

I have been taught over the years that it is a language which uses a set of symbols, rules and concepts to communicate design function and assembly interfaces by accounting for and applying all geometric characteristic requirements to features and by showing feature relationships to each other and feature datum’s; and allowing inspection to receive more parts that do function, along with costs savings.

Wondering how many forum members are advocates with successful experiences by applying GD&T or if the numbers lean toward the camp who actually don’t really see its value, but are more or less forced to use it?

Not sure if the majority of forum members value the standard or if it is just a nuisance that needs to be dealt with at times?

Yea or nay for GD&T?

 

[JNieman]

No.

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[KENAT]

No - except to highlight specific points or similar.

Posting guidelines faq731-376

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(probably not aimed specifically at you)
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[ctopher]

No

Chris, CSWA
SolidWorks '15
ctophers home
SolidWorks Legion

 

[dtmbiz]

OK LETS USE CAPS AND RED,
FOR THE MERCILESS, NO MERCY

I ACTUALLY THINK THERE ARE LAWS AGAINST YOU GUYS.
FEDERALLY PROTECTED SPECIES
WHINERS

 

[KENAT]

Hey, I said axym shouldn't do it - told you fair enough

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(probably not aimed specifically at you)
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[dtmbiz]

ok KENAT
got it
but its realyly reallly reali is hard givin up assertivness... exspshially when i
dident evan noe it

 

[ctopher]

Go back to bold, your spelling is terrible.


Chris, CSWA
SolidWorks '15
ctophers home
SolidWorks Legion

 

[3DDave]

D&T is more like a programming language than a game. It is a means of programming how the parts are supposed to function, and how the parts are supposed to be inspected. If you look at programming language blogs and commentaries you'll see a lot of discussion of what is suitable use.

D&T is also about communicating with people - also not a game. And those people may not be well versed in it or see no need for the language choice.

My take is that ASME is driving away from popular adoption in the most effective way possible. The cost of the standard is high, there are errors in the current version that should not have made it past a good editor, the latest version adds significant complexity without also increasing the clarity of explanation, and their certification program is ridiculously expensive. It should be tough and it should be cheap. And it should emphasize outcomes and not vocabulary. It doesn't matter if its a Least Material Boundary - it does matter what the wall thickness might be.

The main ASME failing is not pursuing an inexpensive, unbiased algorithmic program that can provide evaluation of tolerances and the resulting likely variations. With this in place users of the standard at any point in the product chain could evaluate the effect of tolerance choices* in an unambiguous way even if they don't know how to interpret the expected outcomes**. However, some of these programs have been made available by other parties and industry has generally decided that they are doing just fine without quantifiable feedback on the ability of the product chain to control variation in finished products.

*For example, manufacturing should be able to see how their fixturing deviations affect the final part.
**How many can, by hand, calculate the natural log of a number or even know how, yet can press the ln button on the calculator? Why should D&T be any harder to evaluate?

 

[dtmbiz]

спасибо (Thank you) Chris,
ti wereked,
It worked (see what I mean)


btw
observations demonstrated and this mind set is not uncommon IMO,

]

such disdain for the the ASME Y14.5 standard? yet you participate in the forum?
what is the draw for you?

 

[CheckerHater]

GD&T must become the analog of traffic rules - something that almost everybody understands (and uses) well enough to stay alive.

So far, in the world of GD&T, one has to hire Certified Road Sign Professional every time one takes car out for a spin.

That's the reason lot of people prefer to walk or stay home (figuratively speaking)

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[dtmbiz]

Funny CH
splains alot...

 

[3DDave]

dtmbiz,

I can like a subject and dislike it being handled poorly, both at the same time.

 

[JNieman]

There are a number of things I don't like doing, but have to do. And just because I don't like doing it, doesn't mean I shouldn't be able to do it well. The search of knowledge and practicing of the craft is not necessarily indication that it is enjoyed or thought to be a wonderful endeavor. Some of us just want to be competent at everything we do. I'm rather ambivalent toward Y14.5.... and even then, the feelings are not very strong either way.

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[Nereth1]

I find that I use things like runout, concentricity, parallelism, flatness quite a lot - these are things that can be somewhat difficult to cost effectively control with conventional dimensioning.

But I always worry a lot when doing it. I work in a weak manufacturing town of a weak manufacturing state of a weak manufacturing country. There is relatively little exposure to what everything means here. But people won't always admit it if they don't know. It's a very difficult topic to breach without making yourself look like an elitist.

By way of example, our company is a production line that probably has around 40-80 floor staff depending on market conditions. Amongst them are 10-20 qualified machinists/fitter turners/toolmakers etc. The most experienced amongst those, when asked if he knew what to do with a print with GD&T tolerances on it, said "Oh I've seen that before, those are what you find on really rough stuff like castings".

 

[MikeHalloran]

Star for Nereth1.

You are lucky, in a way, in that your machinists are merely ignorant, and therefore trainable.

I have faced a too-experienced drafting supervisor who really thought he understood GD&T, but clearly did not understand statistical tolerancing, or much else. Under his iron fist, his department came up with a piece of tooling plate that was 'located' with ~28 holes for a corresponding number of machine screws. In order to satisfy his understanding of geometric tolerancing, the clearance holes on the screws were bigger than the biggest dimension of a pan head, and hence field technicians had to be equipped with fixtures to locate the plate, which was R&R'd frequently, and of course if it was located correctly, you couldn't tighten any of the screws, and the plate would lift right off, if you forgot the fender washers.

You can't fix stupid.




Mike Halloran
Pembroke Pines, FL, USA

 

[3DDave]

The usual unhappy conversation I get involves pointing out that unusable items are acceptable per a crummy DRF and the response being, "they wouldn't make it that way."