"Global" GD&T Standard? 2

[hygear]

I work in a regional (U.S.) development office for a Japanese company. We primarily design parts to be sourced from local suppliers and use the ASME Y14.5M standard for most of our drawings. We also source many parts from Italy, Spain, Japan and China but most of these drawings do not use GD&T. Recently our Japanese manager has requested that we determine a single standard for drawings so that anyone in the world can understand them. Unfortunately, he's leaning towards our internal standards as the way of doing things so I'm trying to gather up some more information to determine what is the best "Global" standard for GD&T. Here are a few of the issues/concerns that we have:

1. We are encouraged to use the internal standard even though we believe it is wrong. It allows things like concentricity between two parts (instead of a single solid of revolution), position with no datum references, it allows diameter symbols on things like flatness, it doesn't allow the use of MMC, and we are discouraged from using more than a couple of datums (even on parts where 5 or 6 datums would be ideal).
2. All of the engineers in this office understand the ASME standard and a few even have the certification. Unfortunately, we are told that virtually all Chinese suppliers and most Japanese suppliers don't understand the ASME standard.
3. We understand that the ISO standard is similar to ASME, but aren't clear of the differences/similarities because we do not have a copy of the standards. We use ISO design/safety standards for pretty much everything else, so it makes sense to me to use the ISO standard for GD&T as well.

Can anyone provide feedback on what standard is best for this situation?

 

[KENAT]

"Recently our Japanese manager has requested that we determine a single standard for drawings so that anyone in the world can understand them."

Well that's a fallacy, not all US suppliers will immediately understand ISO (some struggle with ASME but that's another issue).

Many (Most?) suppliers from around the world won't immediately understand ASME.

I'd have thought internal standards will be even more of an issue with vendors not understanding them - unless you have 'captive shops'.

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[juergenwt]

Your Japanese Manager is absolutely right. You are an international company. It is time to tell your us suppliers to get on the band wagon and they will. Are you going to keep on holding and catering to your suppliers and risk loosing your company's international business? Go ISO - period.

 

[CheckerHater]

ISO.

National standards in Italy, Spain, Japan and China are either ISO-based or leaning heavily towards ISO.

American suppliers struggling with ASME still have to start somewhere - why not ISO as well?

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

 

[dgallup]

The problem with ISO (which we use), is it's not a nice unified standard like Y14.5. It's a mishmash of disjointed standards written by different committees, some of them are seriously flawed and some contradict each other. So you have to read through them all and try to figure out which ones to use and which ones to not use and then write some kind of document stating what you do and don't do.

When I worked for a French company I asked them what they used. They never could give me a set of standards, the best they could come up with was "We all go to the same schools and get taught the same way". Yeah, right.

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[CheckerHater]

@dgallup

Just out of curiosity, how many years ago did you work for French company, and how old are the standards you are using now?

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

 

[juergenwt]

Yes, there are many national standards, but if you as a US manufacturer want to do business on an international level you are best advised to go with ISO. ISO is for the most part a copy of DIN (Deutsches Institut Fuer Normung) the most complete standard anywhere. There will for a time to come be some occasions when let's say a French or a German or British print will contain something taken from the national standard of that country. You will just have to deal with that on a case by case basis. The same would be true if someone in the rest of the world would get an American print made to ISO standards but still containing something from ASME, ANSI or any of the standards used in the US. If there was something on that print that did not conform to ISO than you would just have to go back to where the print came from. But chances are, that on new print where ISO is specified, you would not have a problem at all. Do NOT try to revise the print to accommodate your suppliers. If they value your business - they will learn very fast. It is in their best interest. The worst mistake companies make when working with international customers, is to allow a time period (let's say "over the next five years"} for a changeover to ISO. It will kill you. Nothing will get done. Assemble your key people (incl. suppliers) and say: Gentlemen! As of "THIS DAY" all our new product will be as per ISO. It will get done.
Best example: The change over from many national currencies to the Euro - overnight!
Sweden changes from left to right hand driving (H-day)
Worst example: UK change over to metric - years - still going on!
Absolute worst example: USA change to metric - the biggest (and most costly) screw up.

 

[Belanger]

ISO is for the most part a copy of DIN (Deutsches Institut Fuer Normung) the most complete standard anywhere.

Is ISO (and/or DIN) really the "most complete standard" in the singular sense? Because one big issue holding many back from switching to ISO is the very thing mentioned by dgallup -- that ISO is not really one complete standard.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[3DDave]

What language are the notes in that everyone in the world will understand them?

GD&T stands for Geometric Dimensioning and Tolerancing; since there is no definition for Geometric Dimensioning that appears in any standard, you need not worry about it.

Dimensioning and Tolerancing standards, like Y14.5, include directly applied dimensioning and tolerancing that does not require the use of feature control frames. Drawings without feature control frames use just as much 'GD&T' on them as drawings that do. Just add "Interpret per ASME Y14.5" and tada - instant compliance. There is probably a similar note for ISO compliance.

Your problem isn't that you need a single standard, it's that you are working with companies that have not used standards and are probably unwilling to use them even if supplied for free. They don't want to educate workers, buy any software, buy any tools, or risk being able to argue for payment over potentially rejected work, and they certainly don't want to spend money up front for copies of the standards.

There is nothing in any 'standard' that could not be copied into notes or procedures that are part of a drawing package. The only benefit to a 'standard' is avoiding doing the work to copy it. You can make the drawings completely standalone of any international committee work and be just fine.

 

[dgallup]

CH - The French sold us to Americans about 12 years ago. They owned us for about 10 years, I spent 1996-98 working in France. Before that we were British owned.

Most of the ISO specs we use are 1980-1990 vintage. Some are still active, others have been superseded. You can't start using a new revision of a spec that completely changes the interpretation of a call out on a drawing. For instance, one of the ISO surface texture specs (there are several) now has a note that only something like 86% of a surface actually has to meet the requirement. When I put a surface finish requirement on a surface it is usually because it's an o-ring sealing surface and 100% of that surface absolutely has to meet that requirement. It is just absurd to think otherwise. So we don't use the current revision of that spec. Sorry I don't have it handy to to quote exactly.

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[juergenwt]

Belanger - Yes DIN is the most complete standard. ISO is still evolving with the help of many industrial nations. USA is a member and many US standards have found their way into ISO. There had been some screw-ups because of the US insistence on things like having our own metric fastener standards i.e. M6.3 x 1 screws etc. and a few others. Some US companies used those for some time but all are now discontinued. ISO is not complete but is more and more replacing national standards in international commerce.

 

[Belanger]

Juergenwt, I suppose ISO and DIN are complete in that they attempt to address everything from GD&T down to surface finish and corner breaks, etc. But the down side is that they are disjointed, with numerous standards, all with overlapping release dates. So I wonder if it can really be called one complete standard, in that sense.
Shrug.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[KENAT]

UK when they went true ISO tried to tie them together with BS8888 but it was still a bit messy - I find ASME 14.5 more put together than the equivalent ISO specs were.

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(probably not aimed specifically at you)
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[tbuelna]

You did not make any mention of the specific industry the company works in. If the engineering and manufacturing operations are certified to an ISO QA standard, then there are defined guidelines as to what standards should be used for engineering documentation, configuration control, QA, etc. And usually it depends on what the customer requires.

I work in the US aerospace industry, and most of the companies are certified and operate under the AS9100 QA standard, which incorporates the entire ISO 9000 QA standard. But even though they operate according to what is essentially an ISO standard, the engineering drawings conform with ASME standards, use imperial (inch) dimensions, and most of the material/process standards used are SAE/AMS or ASTM specs. If your Japanese manager asks you to use a single drawing GD&T standard that a supplier in any country will understand, ASME Y14.5 should be acceptable. Boeing Commercial Aircraft has suppliers in Italy, Spain, Japan and China that work to drawings using ASME Y14.5 GD&T practices. Attached are a couple paragraphs from the ASME Y14.5-2009 preface discussing some of the issues with unifying to ISO standards.

 

[CheckerHater]

Thank you dgallup,

That's what I expected.

The new generation of ISO standards is organized according to "Master plan" in order to be exact opposite of what you described - avoid gaps and overlaps in coverage.

The job isn't finished, the standards are being revised "as we speak", but there is no reason to support FUD spread by people who sell ASME for a living.

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

 

[3DDave]

If the job's not finished and there are gaps or contradictions then it's not entirely FUD, just an explanation of the current circumstance. Until they have a single volume on the topic of dimensioning and tolerancing then it's a collection of standards covering a variety of topics. ASME gets no love from me on their methods of Y14 standards creation, but it's one book to look through.

ISO 5459:2011 Datums and datum systems are 81 pages and 198 swiss francs or 210 US Dollars. For one spec.

ISO has a separate spec for Cones. It's 11 pages and 58 swiss francs, or 62 US Dollars.

"ISO 3040:2009 establishes the definition of cones and specifies the graphical symbol to be used for their indication and methods for their dimensioning and tolerancing.

For the purposes of ISO 3040:2009, the term “cone” relates to right-angle circular cones only"

The Master plan document lists 37 others in the bibliography. If the average is near $100 each, that's between $3000 and $4000 dollars for the set, though some are inspection methods docs, so maybe only $2000 to replace Y14.5.

 

[tbuelna]

Just noticed the attachment link in my previous post was bad. Here's the relevant part of the GD&T foreword text:

"Since many major industries are becoming more global, resulting in the decentralization of design and manufacturing, it is even more important that the design more precisely state the functional requirements. To accomplish this it is becoming increasingly important that the use of geometric and dimensioning (GD&T) replace the former limit dimensioning for form, orientation, location, and profile of part features. This revision contains paragraphs that give a stronger admonition than in the past that the fully defined drawing should be dimensioned using GD&T with limit dimensioning reserved primarily for the size dimensions for features of size. Additionally, recognizing the need to automate the design, analysis, and measurement processes, and reduce the number of “view dependent tolerances,additional symbology has been introduced for some more common tolerancing practices.
Work on this issue began at a meeting in Sarasota, Florida in January 1994. Numerous deferred comments from the public review for the previous revision, as well as proposals for revision and improvement from the subcommittee and interested parties from the user community, were evaluated at subsequent semi-annual meetings. The subcommittee divided into working groups for several meetings and then reconvened as a subcommittee as a whole to review and ensure the continuity of the revision.
Internationally, a new joint harmonization group formed in January 1993 was called the ISO/TC 3-10-57 JHG. The object was to harmonize the work and principles among ISO/TC3 Surface Texture, ISO/TC 10 SC 5 Dimensioning and Tolerancing, and ISO/TC 57 Measurement. The task of this group was to identify and suggest resolutions to problems among the three disciplines. Many representatives of the ASME Y14.5 subcommittee participated in the meetings of this group from September 1993 through June 1996. In Paris in June 1996 the ISO/TC 3-10-57 JHG became ISO/TC 213, and the responsibilities of the three other ISO committees were transferred to ISO/TC 213. Representatives of the U.S. have participated in all of the ISO/TC 213 meetings from June 1996 through January 1999. Because of difficulties, the U.S. was not represented again until anuary 2006, and representation is now ongoing. In the U.S., a similar committee was formed following the formation of ISO/TC 213 as a home for the U.S. TAG (Technical Advisory Group) to ISO/TC 213 and also to serve as an advisory committee to the three U.S. committees and subcommittees that are parallel to the ISO groups (Surface Texture B46, Dimensioning and Tolerancing Y14.5, and Measurement B89). This new committee, called H213, was formed at a meeting in 1997 by representatives of the three U.S. committees or subcommittees. H213 does not have responsibility for all three subjects as does the ISO committee, but rather serves as an intermediary to identify and facilitate a resolution to problems that may exist among the three disciplines as well as the home for the U.S. TAG."

 

[3DDave]

Even the committee can't get it right:

"the use of geometric and dimensioning (GD&T)" sic

The link failed because the "&" in the gd&t part of the name.

 

[tbuelna]

Forget about the grammar of the ASME editors. What made me scratch my head was the fact that ANSI/ASME/SAE/ISO have been working on this issue since 1994, which is over 2 decades. This means some of the committee members have possibly spent half of their professional career on this project.

 

[3DDave]

If the people creating a grammar for expressing D&T can't get the grammar right in the language they use to define it, it reflects really poorly on them, particularly when it's in a sentence dedicated to their primary subject. They shouldn't have been rushed, it was 15 years since the previous issue. Even a proof-reader unfamiliar with the topic would flag the sentence, so they apparently didn't perform that task.

I think the committees have too many members with no clear view of the entire scope of describing limitations to geometric variation. A large number seem to be CMM oriented and are otherwise QA/QC directed; this leaves the committee weak in analysis of variation, which in turn leaves the specs weak in variation descriptions, hence the disagreement in Fig 4-16(c) interpretation which a variational model will show does not result in the QA/QC defined behavior represented in the spec.

The only certain way out is to create software that is the single interpretation/analysis standard. It works for compiler writers and mathematicians. I don't see those skills available within ASME 14.5 and would anticipate that many who depend on teaching and consulting would push back as automated analysis eliminates the need for users to have more than a cursory understanding of the detailed effort required. With a compiler to interpret PRINT "Hello World", one doesn't need to know anything about graphics cards, memory allocation, reading the keyboard, loading or linking the code, no understanding of CPU registers or pointers or any of a hundred other processes.

A spec would still get written, but the software and spec can be cross checked without users adding their own undocumented prejudices to the mix that happen now. Where the expected spec behavior is different from what the software actually produces, one or both can be seen as needing a change. As interpretations are improved, only one place needs to be updated for everyone to have that same, new version. This ability was possible 20 years ago, and it's only become easier to accomplish. VSA was well on its way before being absorbed and buried.