The Invocation Principle - see previous post - was part of the latest revision of ISO 8015. The FDIS (Final Draft International Standard) of 8015 has just recently been out for vote, and the results are back.
In order to be approved, two thirds of member organisations must vote in favour of the FDIS (66.66%), and no more than 25% of members must vote against. The actual results were 65% in favour, and 32% opposed. The FDIS has thus received a negative vote, and has been 'disapproved'.
Phew! But far too close for comfort!
Saturday 6 November 2010
Monday 1 November 2010
The Invocation Principle
How do you know which standards govern the interpretation of a specification, such as an engineering drawing? That is the problem that this principle is intended to address.
When we had our old British BS308 standard, it was easy. You were asked to put a note on the drawing along the lines of ‘DRAWN TO BS 308’. With the new British Standard, BS 8888, we suggest a similar note, such as ‘CONFORMS TO BS 8888’, and the Americans require that drawings produced to the American standard show a reference to that standard, ‘ASME Y14.5-2009’.
ISO have never had a formal method of indicating that drawings or specifications conform to ISO standards. One of the key ISO standards is ISO 8015, which defines the Envelope Requirement and how size tolerances are interpreted. ISO 8015 itself contains the requirement to mark specifications ‘TOLERANCING ISO 8015’ if they are to be interpreted according to its rules. As a result, this marking has become the way in which many organisations indicate that they are working to the ISO system, and is even now a requirement of BS 8888.
Arguably, specifications which are to be interpreted according to the ISO system should list all the other applicable ISO standards on the specification as well, or at least list them in a document referenced by the specification. For most organisations, this would be a lengthy list, including references to standards such as ISO 1101, ISO 2768, ISO 5458, and many others. Unsurprisingly, many organisations don’t bother.
The invocation principle was intended to avoid this difficulty, by introducing a rule which stated that if you are using one part of the ISO system, you are using all of it. This seems sensible to me. This approach does not require you use bits of the ISO system that you were not using previously, it just means that if you make use of any particular part of it, such as surface texture specifications, then all the relevant ISO standards apply. You don’t have to list them all, you just have to have some means of showing that one part of the ISO system applies, such as the ‘TOLERANCING ISO 8015’ indication.
The contentious stuff starts with a second part to this rule, which states that use of any ISO GPS symbol is sufficient to indicate that you are working to the whole ISO GPS system. In other words, you don't need to state ‘TOLERANCING ISO 8015’ or anything like that, you only need to use a geometrical tolerance, or a boxed dimension, or some other GPS symbol, and that makes it an ISO GPS document unless otherwise stated.
This is a REALLY BAD IDEA.
Reasons why:
1. In the UK, standards have a voluntary status. Their use cannot be imposed, and they work on an 'opt in' basis. This requirement would mean that many ISO standards would be imposed, quite possibly without the document owner being aware of this, unless they specifically 'opted out'. A requirement which is enforced by the absence of any alternative marking is liable to lead to confusion, misunderstanding, and resentment (and bring the system into disrepute).
2. ISO do not have ownership of all the symbols which are used in ISO GPS standards. Many symbols are shared with ASME, and many national standards organisations have used them in national standards which are still current. Some symbols are even used differently in other ISO standards
This requirement would mean that if someone forgot to put ‘ASME Y14.5’ on a drawing, it would then be regarded as an ISO GPS drawing, irrespective of the intention. It means that a sketch on the back of an envelope, which happened to include a dimension with a box around it, would suddenly be subject to the rules and requirements of an ISO GPS standard. It means that civil engineering or architectural drawings with tolerances might become subject to ISO GPS rules and requirements, without the relevant professions even being consulted.
3. As many of the symbols which ISO regards as ‘GPS symbols’ are either in the public domain, or widely used in different ways, in different contexts, an attempt to impose a requirement like this without consulting as widely as possible (other ISO technical committees, professional bodies, industry organisations, etc, etc,) is simply irresponsible.
4. A further consequence is that we would then need to introduce an exemption symbol or marking, such as ‘NOT AN ISO GPS SPECIFICATION’ for cases where it didn’t apply, at which point it is starting to get a bit silly.
5. What happens in the case of a nation which is not a member of ISO? What happens if ASME introduce a rule saying 'in the absence of any other marking, a technical specification is to be regarded as an ASME Y14.5 specification'?
The imposition of such a requirement would benefit no one, and simply lead to confusion, and quite possibly to litigation. ANSI have made their objections well known within ISO, but a number of people from other national bodies seem determined to force this through. I'm not clear on their motivation, but at least in part it seems to stem from a fear of 'Americanisation', and a desire to give ISO a higher status as the 'ultimate default'. These motivations may be sincere, but they are misguided. Industry will not benefit from this, and it will actually lead to the diminishment of the reputation of ISO standards if it goes through.
When we had our old British BS308 standard, it was easy. You were asked to put a note on the drawing along the lines of ‘DRAWN TO BS 308’. With the new British Standard, BS 8888, we suggest a similar note, such as ‘CONFORMS TO BS 8888’, and the Americans require that drawings produced to the American standard show a reference to that standard, ‘ASME Y14.5-2009’.
ISO have never had a formal method of indicating that drawings or specifications conform to ISO standards. One of the key ISO standards is ISO 8015, which defines the Envelope Requirement and how size tolerances are interpreted. ISO 8015 itself contains the requirement to mark specifications ‘TOLERANCING ISO 8015’ if they are to be interpreted according to its rules. As a result, this marking has become the way in which many organisations indicate that they are working to the ISO system, and is even now a requirement of BS 8888.
Arguably, specifications which are to be interpreted according to the ISO system should list all the other applicable ISO standards on the specification as well, or at least list them in a document referenced by the specification. For most organisations, this would be a lengthy list, including references to standards such as ISO 1101, ISO 2768, ISO 5458, and many others. Unsurprisingly, many organisations don’t bother.
The invocation principle was intended to avoid this difficulty, by introducing a rule which stated that if you are using one part of the ISO system, you are using all of it. This seems sensible to me. This approach does not require you use bits of the ISO system that you were not using previously, it just means that if you make use of any particular part of it, such as surface texture specifications, then all the relevant ISO standards apply. You don’t have to list them all, you just have to have some means of showing that one part of the ISO system applies, such as the ‘TOLERANCING ISO 8015’ indication.
The contentious stuff starts with a second part to this rule, which states that use of any ISO GPS symbol is sufficient to indicate that you are working to the whole ISO GPS system. In other words, you don't need to state ‘TOLERANCING ISO 8015’ or anything like that, you only need to use a geometrical tolerance, or a boxed dimension, or some other GPS symbol, and that makes it an ISO GPS document unless otherwise stated.
This is a REALLY BAD IDEA.
Reasons why:
1. In the UK, standards have a voluntary status. Their use cannot be imposed, and they work on an 'opt in' basis. This requirement would mean that many ISO standards would be imposed, quite possibly without the document owner being aware of this, unless they specifically 'opted out'. A requirement which is enforced by the absence of any alternative marking is liable to lead to confusion, misunderstanding, and resentment (and bring the system into disrepute).
2. ISO do not have ownership of all the symbols which are used in ISO GPS standards. Many symbols are shared with ASME, and many national standards organisations have used them in national standards which are still current. Some symbols are even used differently in other ISO standards
This requirement would mean that if someone forgot to put ‘ASME Y14.5’ on a drawing, it would then be regarded as an ISO GPS drawing, irrespective of the intention. It means that a sketch on the back of an envelope, which happened to include a dimension with a box around it, would suddenly be subject to the rules and requirements of an ISO GPS standard. It means that civil engineering or architectural drawings with tolerances might become subject to ISO GPS rules and requirements, without the relevant professions even being consulted.
3. As many of the symbols which ISO regards as ‘GPS symbols’ are either in the public domain, or widely used in different ways, in different contexts, an attempt to impose a requirement like this without consulting as widely as possible (other ISO technical committees, professional bodies, industry organisations, etc, etc,) is simply irresponsible.
4. A further consequence is that we would then need to introduce an exemption symbol or marking, such as ‘NOT AN ISO GPS SPECIFICATION’ for cases where it didn’t apply, at which point it is starting to get a bit silly.
5. What happens in the case of a nation which is not a member of ISO? What happens if ASME introduce a rule saying 'in the absence of any other marking, a technical specification is to be regarded as an ASME Y14.5 specification'?
The imposition of such a requirement would benefit no one, and simply lead to confusion, and quite possibly to litigation. ANSI have made their objections well known within ISO, but a number of people from other national bodies seem determined to force this through. I'm not clear on their motivation, but at least in part it seems to stem from a fear of 'Americanisation', and a desire to give ISO a higher status as the 'ultimate default'. These motivations may be sincere, but they are misguided. Industry will not benefit from this, and it will actually lead to the diminishment of the reputation of ISO standards if it goes through.
Saturday 30 October 2010
Prague in September
Painfully overdue for a post here, so here is a quick up-date, to be followed by something more detailed in due course.
The latest TC213 conference met in Prague, capital of the Czech Republic, early in September.
Prague is a rather beautiful city. The old town has many famous landmarks, and it is clearly popular with tourists. The place was absolutely heaving, with large gaggles of people following tour guides wherever you went. Most of these groups were equipped with ear pieces, so they could hear the tour guide above the general din. Most of them also seemed to be following the lead of the guide in singing 'Good King Wenceslas', with varying degrees of tunefulness, as they marched around.
Tributes to Franz Kafka are also to be found throughout the city, such as the statue of The Man Who Wasn't There (see left).
I like the name of this bar as well (see below).
This was a very brief visit on my part. I flew in on Wednesday evening, chaired a meeting on Thursday, and flew out again on Friday.
The hot topic of debate was the 'invocation principle' which has been proposed for a revised draft of ISO 8015. Quite what this is, I will explain in the next blog post. The American delegation is outraged by this, and circulated a letter listing their objections prior to this series of meetings. Some other nations are strongly in favour, and one German delegate in particular has been mounting a charm offensive to cultivate support. The UK delegation is strongly opposed to this new principle, supporting both the American objections, and a number of our own. Many national representatives are remarkably ambivalent over the whole issue, considering its potentially far reaching effects. As I say, more on this to follow ...
Prague is a rather beautiful city. The old town has many famous landmarks, and it is clearly popular with tourists. The place was absolutely heaving, with large gaggles of people following tour guides wherever you went. Most of these groups were equipped with ear pieces, so they could hear the tour guide above the general din. Most of them also seemed to be following the lead of the guide in singing 'Good King Wenceslas', with varying degrees of tunefulness, as they marched around.
Tributes to Franz Kafka are also to be found throughout the city, such as the statue of The Man Who Wasn't There (see left).
I like the name of this bar as well (see below).
The hot topic of debate was the 'invocation principle' which has been proposed for a revised draft of ISO 8015. Quite what this is, I will explain in the next blog post. The American delegation is outraged by this, and circulated a letter listing their objections prior to this series of meetings. Some other nations are strongly in favour, and one German delegate in particular has been mounting a charm offensive to cultivate support. The UK delegation is strongly opposed to this new principle, supporting both the American objections, and a number of our own. Many national representatives are remarkably ambivalent over the whole issue, considering its potentially far reaching effects. As I say, more on this to follow ...
Saturday 7 August 2010
New Courses
It has been a busy summer so far.
We have developed and piloted a new Stress Analysis course, introducing the basic principles of stress analysis for calculations with calculators and spreadsheets. The idea has been to give engineers and designers the tools to carry out basic calculations for stress, strain and deflection in fairly straight-forward structures. This is really covering a lot of the same ground that engineering students cover at degree level, but compressed into three days, with a strong emphasis on practical application.
We had hoped to compress this into a two-day course, but that proved overambitious. We will be trialing the latest version of the course with the client who requested it within the next few weeks. Once all the creases have been ironed out, we will be publicising this with the other courses on our main web site.
When running the geometrical tolerancing course for one of our main aerospace clients, we frequently get questions and feedback comments about datums and tolerances applied to assemblies. There is not time to cover this adequately in the standard course, so we have proposed working with the client in questions to develop an advanced, follow-on geometrical tolerancing course. This new, advanced course would look in particular at assembly datum structures and assembly-level tolerances. If any other organisations out there (particularly aircraft manufacturers) would be interested in collaborating with us on the development of such a course, please get in touch.
We have developed and piloted a new Stress Analysis course, introducing the basic principles of stress analysis for calculations with calculators and spreadsheets. The idea has been to give engineers and designers the tools to carry out basic calculations for stress, strain and deflection in fairly straight-forward structures. This is really covering a lot of the same ground that engineering students cover at degree level, but compressed into three days, with a strong emphasis on practical application.
We had hoped to compress this into a two-day course, but that proved overambitious. We will be trialing the latest version of the course with the client who requested it within the next few weeks. Once all the creases have been ironed out, we will be publicising this with the other courses on our main web site.
When running the geometrical tolerancing course for one of our main aerospace clients, we frequently get questions and feedback comments about datums and tolerances applied to assemblies. There is not time to cover this adequately in the standard course, so we have proposed working with the client in questions to develop an advanced, follow-on geometrical tolerancing course. This new, advanced course would look in particular at assembly datum structures and assembly-level tolerances. If any other organisations out there (particularly aircraft manufacturers) would be interested in collaborating with us on the development of such a course, please get in touch.
Sunday 20 June 2010
First NPL GD&T course
The first NPL GD&T course was held in the splendid setting of Bushy House in Teddington, where the National Physical Laboratory began over a hundred years ago. This is not far from Heathrow Airport, but you would never know it. Surrounded by the extensive grounds of Bushy Park, including cricket pitches, orchards and deer parks, we felt a bit like extras on a Jane Austin movie set.
This was one of the views from the museum room where the course was held. There are a herd of deer out there somewhere, but you can't see them in this picture.
The museum room itself was full of old bits of measuring equipment mapping some of the history of NPL since 1900, although some of the equipment looked older.
We had a great mix of people on the course, including three from Scotland, three from Ireland, and one from the Isle of Wight. They represented an equally diverse range of industries, including aerospace, boat building and medical equipment.
Feedback from the course has been highly positive, and we hope to run the next one in August or September.
Thursday 6 May 2010
Geometrical Tolerancing courses enter the NPL Training Framework
Two of our Geometrical Tolerancing courses are now available as accredited training courses through the National Physical Laboratory Training Framework.
As far as I know, this is the first time that accredited Geometrical Tolerancing courses have been available in the UK. The courses are accredited by the National Physical Laboratory and validated by The National Skills Academy for Manufacturing. Delegates who successfully complete the course receive a numbered certificate, registered with NPL Training, which also carries the National Skills Academy logo.
The same courses are also still available from us in non-accredited form (which means that they cost less). I have no idea yet how much interest there will be in accredited training in these subjects, but the response to the public course we are running at NPL later this month has been very good, and the course is almost full.
Email me if you want further details about these courses, or know anyone else who might be interested.
- Geometrical Tolerancing to BS 8888 and ISO Standards.
- Geometric Dimensioning & Tolerancing to ASME Y14.5.
The same courses are also still available from us in non-accredited form (which means that they cost less). I have no idea yet how much interest there will be in accredited training in these subjects, but the response to the public course we are running at NPL later this month has been very good, and the course is almost full.
Wednesday 28 April 2010
Gadgets
Also stumbled across a web site for some of the most amazing time pieces you are likely to see: check out the 'Horological Machines' at http://www.mbandf.com./ Will someone get me one for Christmas please.
Tuesday 16 March 2010
NPL Training Courses
The National Physical Laboratory (NPL) is the UK's National Measurement Insitute. They are responsible for measurement standards in the UK, and are a leading centre for scientific research. NPL provide guidance on good practice, wide ranging resources for education, along with commercial training and consultancy services.
The NPL Training Framework consists of a matrix of measurement-related training programmes. The framework has been developed in partnership with industry with the following objectives:
Iain Macleod Associates became an NPL Accredited Training Provider last year for the courses in dimensional measurement. These courses teach the fundamental principles of metrology for engineers, inspection and QA people.
Courses which teach people how to inspect engineering components obviously have a natural fit with courses which teach people how to specify engineering components, and make a logical extension to our training portfolio. This means that we can now offer a consistent range of training courses across the spectrum of design, manufacture and inspection.
Click here for a flyer describing these courses in more detail.
The NPL Training Framework consists of a matrix of measurement-related training programmes. The framework has been developed in partnership with industry with the following objectives:
- to develop core skills and competencies in practitioners
- to raise the level of technical knowledge
- to promote and instil good practice
- to foster a questioning and planning culture
Iain Macleod Associates became an NPL Accredited Training Provider last year for the courses in dimensional measurement. These courses teach the fundamental principles of metrology for engineers, inspection and QA people.
Courses which teach people how to inspect engineering components obviously have a natural fit with courses which teach people how to specify engineering components, and make a logical extension to our training portfolio. This means that we can now offer a consistent range of training courses across the spectrum of design, manufacture and inspection.
Click here for a flyer describing these courses in more detail.
Thursday 25 February 2010
Tuesday 23 February 2010
Frosty in Vienna
Recently returned from the ISO TC213 conference in Vienna. Vienna was beautiful, but bloody cold.Some useful progress was made in some of the working groups.
WG17, which I chair, has been given the task of updating a document which has the vaguely threatening title of 'ISO/TR 14638 - GPS Masterplan'. This document maps out the structure of the entire ISO GPS system, and describes how the different standards relate to each other.
The document has not been touched for about 15 years, and is very hard to understand, so there is quite a lot of work to do. In fact, most of the 'up-date' will probably involve redrafting large sections of the text just to try and make it comprehensible.
In the previous TC213 series of meetings in San Antonio, a new study group was set up to map out the differences between the ISO GPS system, and the American ASME Y14.5 standard. The study group is jointly led by Archie Anderson of the USA, who oversaw the development of Y14.5 for many years, and Renald Vincent of France, who has played a major role in the development of GPS over recent years.
Meeting again in Vienna, we have now mapped out a structure for the comparison, and can start to fill in some of the detail. I think that this could potentially be a very useful study, as the differences are not always well understood, and organisations in many areas of industry are having to work with both systems.
WG 18, which deals with the geometrical tolerancing standards, was a much patchier affair. Too many new options and possibilities being introduced, and not enough progress on sorting out what we already have.
Saturday 23 January 2010
Encouraging signs for 2010
It is a long time since I posted anything here. Happy New Year to anyone who reads this.
We seemed to turn an economic corner around Autumn last year. There was a noticeable upturn in the number of enquiries I was receiving in November, and then things started to get very busy indeed in December. The level of work has continued into this year - I've been away training for most of the last two weeks, and have a reasonable number of courses booked in for the next couple of months.
In the last few days, I've even had an enquiry from a company in the automotive supply chain, the sector which was probably hardest hit of all in the downturn, so all around there seem to be positive signs of recovery.
During the quieter bits of 2009, I became a licenced deliverer of some of the metrology courses offered by the National Physical Laboratory (NPL), and I intend to expand that area of activity in 2010. These courses teach the fundamentals of measurement and inspection, and are a perfect fit with the geometrical tolerancing training that I offer already. It means that we should be able to provide a seamless, and fully consistant, series of training programmes across the disciplines of design, manufacture and inspection.
One area of particular interest is Large Volume Metrology, where laser scanners or trackers are used to scan large components or assemblies to very high levels of accuracy. The aerospace insdustry is starting to use this technology extensively, and it also has applications in other industries.
New Years Resolution - to try and keep this blog updated more frequently.
We seemed to turn an economic corner around Autumn last year. There was a noticeable upturn in the number of enquiries I was receiving in November, and then things started to get very busy indeed in December. The level of work has continued into this year - I've been away training for most of the last two weeks, and have a reasonable number of courses booked in for the next couple of months.
In the last few days, I've even had an enquiry from a company in the automotive supply chain, the sector which was probably hardest hit of all in the downturn, so all around there seem to be positive signs of recovery.
During the quieter bits of 2009, I became a licenced deliverer of some of the metrology courses offered by the National Physical Laboratory (NPL), and I intend to expand that area of activity in 2010. These courses teach the fundamentals of measurement and inspection, and are a perfect fit with the geometrical tolerancing training that I offer already. It means that we should be able to provide a seamless, and fully consistant, series of training programmes across the disciplines of design, manufacture and inspection.
One area of particular interest is Large Volume Metrology, where laser scanners or trackers are used to scan large components or assemblies to very high levels of accuracy. The aerospace insdustry is starting to use this technology extensively, and it also has applications in other industries.
New Years Resolution - to try and keep this blog updated more frequently.
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