QMT Features: January 2008
Design for manufacture
BS 8887-1:2006, the new Design for Manufacture British Standard. By Brian Griffiths, School of Engineering and Design, Brunel University, Uxbridge, England, chair of the BSI Committee: Design for Manufacture.


Since its inception, the British Standard Institution (BSI) has been involved with the specification of design.  There are essentially two sets of committees involved in design – those concerned with design specification and those concerned with design management. 

Both sets have zippy titles!  The former set has the title ‘the TDW/4’ committees, of which there are currently seven sub-committees and the latter the title ‘the MS/4’ committees, of which there are currently four seven sub-committees.
The standards produced by the design specification committee/s (TDW/4) apply to technical products.  They are concerned with providing a designer with a framework within which the selection, preparation and presentation of appropriate documentation is made.  They have the primary purpose of identifying and specifying the use of standards relevant to the design, manufacture and verification of technical products. 

They focus on how the designer ought to set about the task of preparing conceptualizations for manufacture.  Perhaps the most famous of the TDW/4 standards is the now withdrawn BS308.  This has now been replaced by BS8888:2006, which is in its 4th edition.  It is a route map through the large range of ISO standards relevant to design specification.  BS8888 provides the designer with an interpretation of the International Standards Organisation (ISO) standards concerned with design specification.  TDW/4 committee/s members are also members of equivalent ISO committees and make a UK national contribution to the development of ISO standards.

The standards produced by the design management committee/s (MS/4) deal with the design management process and supporting documentation that ensures management quality.  Their application is wider than just technical products and the various parts also cover construction, services and innovation.  The MS/4 standards are British Standards and have few links to ISO standards.  The two most famous sets of MS/4 standards are the BS 7000 series which deals with the broader concepts of design management and BS 7373 series which concerned with guidance on the definition of a product design specification (PDS), the identification of the criteria which make up a PDS and the declaration of product conformity. 
This article is concerned with the work of design specification committee (TDW/4) and a standard it recently produced – the ‘design for manufacture’ standard BS8887.   However, before we get into the detail of BS 8887, we need to see it in the context of a triumvirate of British Standards which gives the reader an idea of the direction BSI is taking. 

The TPR ‘Triumvirate’
The process of converting a concept to a correctly functioning product relies on the co-operation of a sequence of disciplines (specification, manufacture and verification).  The instrument best suited to achieving that coordination is a correctly formatted, unambiguously expressed technical product specification (TPS) and BS 8888:2006 is the British Standard that specifies how that TPS can most effectively be prepared.  BS 8888:2006 does not set out to provide instruction on “how to design” but it does seek to provide for the orderly presentation of the output of the design process, in a manner capable of conveying the requirements of the product through the manufacturing and verification processes. A TPS prepared in accordance with BS 8888:2006 therefore also carries briefing for the verification process most appropriate to the functional requirements of the product and can therefore be considered to govern the interface between both design and manufacture, and manufacture and verification.Application of the standard actually impacts upon all the three disciplines of specification, manufacture and verification. 

In an effort to convey this concept, TDW/4 has developed the term “Technical Product Realization (TPR)” defined as “system facilitating cooperation between engineering disciplines to effect conversion of a concept into correctly functioning workpieces or product, to time, to budget and with minimal rework/reject requirement”. Accordingly, the BSI has taken the view that there is a need for three standards and these are: design for manufacture (BS 8887), technical product specification (BS 8888) and technical product verification (BS 8889).  These three together can be termed the “TPR Triumvirate”.  BS8888 is published and in its 4th edition, BS8887 was published in late 2006 and BS8889 is still at the committee stage.  Yet, none of BS 8887, BS 8888 or BS 8889 can be stand-alone since none tells the whole “story”.  Indeed, during the preparation of BS8888 it was always the intention that the related TPR aspects of manufacture and verification would support it.  There is obviously overlap in content between the three standards and this is shown schematically in Figure 1. Here three circles represent the areas of design, manufacture and verification.  However, this is an over-simplification since the three are not of equal size and the overlaps are not the same, yet is serves to demonstrate the BSI’s intended approach. 

Background to BS8887
Recognising the need for design to take full cognisance of manufacture, it was in the late 1970’s, that the TDW/4 committee formed a subcommittee to produce a standard on design for manufacture (DfM), and eventually published the standard, ‘The management of design for economic production’ (PD6470).  This was in a time when design for production was a significant industrial focus.  The title says it all: the standard essentially concentrated on two things – the ‘productionising’ of designs and the importance of manufacturing economics.    This was DfM applied to the individual piece-parts.  This standard was well received but design is never static and in the late 1980’s there was a growing recognition that design for production could not be considered in isolation but that there was a need to include assembly.  Furthermore, since the 90’s, end-of-life (EoL) issues were recognised as being important to the designer.  Such EoL issues have an impact on the design right from the outset and should be included too. 

This is a salutary lesson and one experienced by many other standards: events can overtake standards.  Hence, it is now BSI and indeed ISO policy that standards need to be reviewed (or withdrawn) every three or five years depending on their status and application.  Any new standard must take account of the longer term.

In response to this ‘pressure’ the TDW/4 committee reactivated the DfM committee and it was designated TDW/4/5.  It consisted of engineering specialists from industry and academia; from small to large companies and design consultancies and some members were retired from DfM positions.  They had a variety of specialisations - for example: production, assembly, electronics, consultancy, design, design management, sustainability, product life-cycle, manufacturing research, low and high volume manufacturing industries.  Also on the committee were members of the BSI secretariat. 
The first meeting of TDW/4/5 was held in 2001, the ‘draft for public comment’ of BS8887 was issued in early 2006 and the first edition published in late 2006.  Although this might appear to be a long gestation period, it is par for the course.  Its sales have exceeded expectations in the short time it has been available.

The rationale of BS 8887
Bearing in mind the problems PD6470 encountered, it was decided that BS8887 should take a long-term and indeed holistic view of design for manufacture and that any ‘developments’ which would influence DfM should be included.  The work fell into three broad areas: the updating of piece-part manufacture sections and the inclusion of assembly as well as EoL issues. 
Much work on design for assembly had been done across the world, both manual and machine assembly, and the concepts have been incorporated into BS8887. 

Notable was the team at the University of Rhode Island [Boothroyd et al, 1994].  A significant conclusion was that a top-down approach to part reduction was needed and this depended on an analysis of assembly, design for assembly (DfA).  DfA needs to be an ab-initio design consideration because it asks systems questions such as the necessity of any one part.  This is a vital question since part count is the major contributor to the holding and handling costs. If a part is eliminated, it does not need to be ordered, received, catalogued, handled or assembled.  Thus, assembly as well as piece-part manufacture needs to be considered at the initial design stage.  However, there are design implications beyond assembly, there are the end-of-life influences on product design. 

Environmental pressures have produced new legislation; with the result that end-of-life processing is to be considered at the ab-initio design stage.  The sustainability of products is now main-stream in government funding programmes and policy development.  The Waste Electrical and Electronic Products Directive and the End of Life Vehicles Directive are stimulating companies into developing their own systems for designing products to meet the requirements, which include high levels of recycling at end-of-life and some eco-design.  There is the EU environmental legislation Energy Using Products Directive.  All this is attempting to force manufacturers to take responsibility for a product when the customer has finished with it. 

Many new acronyms entered the designer’s vocabulary.  People concerned with manufacture and assembly, coined terms like design for assembly (DfA) and design for manufacture and assembly (DfMA).  Others, concerned with end-of-life processing, coined terms like design for the environment (DfE), design for recycling and design for reprocessing (DfR).  Yet others considered that design should pervade the whole life-cycle and terms like lifecycle design (LCD) or design for life-cycle (DfLC) are used. 

More recently, the term DfX is used to refer to all these techniques since each is relevant in their own right. It is considered that all the DfX terms are limiting since they each force a focus at a particular point at one stage of design.  Furthermore, they represent an acronym rash.  A holistic view is taken in this standard and hence, for convenience, the generic term design for manufacture, assembly, disassembly and end-of-life processing (ie DfMADE) will be used throughout.
For the purpose of the BS8887 standard, there are considered to be five stages to the manufacture of a product - part production, assembly, the customer, disassembly and part reprocessing. These are shown schematically in figure 2 which shows the stages in the life of a product and the various ‘DfX’ terms. Design for manufacture considerations are applied to each of these five stages.

The sequence of events implied by the MADE sequence is not meant to be absolute since the process is iterative. In practice it will be found that many stages are revisited, perhaps many times, throughout the overall activity. This applies particularly to the design improvement element that by its very nature will influence and inform every activity. 
It was envisaged that the DfMADE concept would be relevant to a large range of products.  However, many product types or classes require specific DfMADE principles which do not necessarily apply to other product types or classes.  On the other hand, there are general DfMADE principles that are generic and would apply to all products.  Hence, from the outset, BS 8887 was planned as not a one-off but a series.  The first publication would be a general one, followed by standards tailored to specific industries or product types, eg mechanical, electrical, chemical, plastic, metal etc.  The standard published in 2006 is the first and general one and is designated ‘Part 1’.  It is sub-titled: Part 1: General concepts, process and requirements.  The full specification of this foundational BS 8887 is as follows: BS 8887-1:2006.  ‘Design output for manufacture, assembly, disassembly and end-of-life processing (MADE).’  Part 1: General concepts, process and requirements.


The BSI plan for the future of the BS 8887 series concept is to see how this Part 1 is received following publication and then for TDW/4 to evaluate the need for DfM standards in specific industries, sectors or product types and then to initiate work on further Parts in the BS 8887 series, starting with a Part 2 etc. 
If anyone out there feels they have a contribution to make to the development of future DfMADE standards, they are welcome to contact the author. l
email: brian.griffiths@brunel.ac.uk

References
Boothroyd G, Dewhurst P and Knight W, ‘Product design for manufacture and assembly’, Marcel Dekker, 1994.
British Standards Institution, ‘Design output for manufacture, assembly, disassembly and end-of-life processing (MADE)’ - Part 1: General concepts, process and requirements.   BS8887-1:2006.
British Standards Institution, ‘Technical product documentation (TPS) – Specification’.  BS 8888:2006.

 

  
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