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DESIGN BUILDER WORKBOOK

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					                                                            DESIGN BUILDER WORKBOOK

DESIGN BUILDER WORKBOOK
Introduction:
         Design is all too often considered as an end in its own right, rather than as a
process with a specific and unique aim in mind. The conception of design as an end
in itself runs parallel to the making of assumptions and omissions and an inadequate
understanding of the problem. Solutions are sought before the full extent and
implications of the design problem are fully grasped. Designs specified from this type
of groundwork are generally of poor quality and fail to meet the requirements in the
most effective way - at least the first time round! Below are the main considerations that
iDer feel are imperative to good design, a lack of regard for which results in a design
of poor quality:

       <      inadequately defined PDS - sometimes even a complete absence of one
       <      little consideration of manufacture and assembly of product
       <      over-design due to pursuit of excellence
       <      inaccurately defined bought out parts

        A traditional conception of design, regarding ‘design’ as one isolated element of
the design to manufacture process, fails to see how what in these terms is called
‘design’ - in fact applies at all stages of the process, right up to manufacture of the
product. This has been a problem associated with algorithmic based CAD systems: the
assumption that the designer actually ‘designs’ the final product does not now fit with
the conception of the designer=s role in modern industrial times. His or her strength
now lies in the ability to derive a concept guided by a product design specification
(PDS), only the basis of the design and not the design itself.
        This is the situation Design Builder, with its interactive interface and emphasis
on communication, simulates - creating a virtual world of industry through multimedia
techniques which really enables students to step into the designer’s shoes’ without
incurring any of the risks involved in real life design and manufacture.
        Considering the role of CAD in improving the efficiency of engineering design
relates to the controversial and ongoing debate regarding the extent to which
computers should be ‘allowed’ to aid humans in their daily lives. But really the concept
of CAD should be exempt from such controversy since it aims to optimise the ‘best’
aspects of both human and computer. For example, the human learns rapidly and can
make intuitive leaps - which on the down side leaves us open to error, The computer
is more reliable in this latter respect, and can store and assess large and detailed
banks of information. Its weaknesses include the extraction of significant or specific
information from this vast store, and the editing of that material. Of course, the
computer facilitates this job on the part of the human, but it is in the human that these
strengths lie.
        CAD is a technique which seeks to combine and optimise these respective
strengths, and if properly implemented, produces the proverbial scenario where the
whole is greater than the sum of the parts’. It implies, by definition, that the computer
is not used when the designer is most effective and vice versa.
        CAD can certainly prove an invaluable resource to the design process.

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Visualisation of complex production geometry through conventional engineering takes
aptitude an considerable experience on the part of engineers. Advanced systems, such
as solid modelling, allow better visualisation of product geometry and may be
considered as a form of ’electronic model making’. Parts libraries allow easy and rapid
insertion of standard and frequently used parts and components into assemblies so
reducing the tedium and promoting the use of CAD as a means of rapidly trying
different design options.
        CAD itself promotes teamwork in so far as it enables different parts of a design
scheme to be produced by different members of the design team and for these
components to be assembled electronically when appropriate. But this is not
necessarily the type of ’teamwork’ iDer exhort through their multimedia CAL system,
Design Builder. By themselves, CAD systems, their attributes described as above,
could foster the traditional approach to design where each department carries out their
’contribution’ to the design in isolation , with no inter-action or communication.
        Design Builder incorporates many useful elements of CAD, and reflects a
similar optimum partnership between man and computer through its interactive
interface and the responsibility placed on human input within the virtual industrial
environment, and on the user him or herself. By incorporating CAD techniques into a
system which reminds the user of the importance of such communicative, interactive
teamwork, iDer show the real benefits of properly implemented CAD procedures.
        ’Design’ then relating both to components and manufacturing methods, is a
multidisciplinary process, comprising creativity and intimate knowledge of existing
resources. ’Design’ requires not just the determination of the functional, geometrical
and aesthetic characteristics of the product, but also the anticipation of cost
effectiveness, ease of manufacture and feasibility in relation to available resources.
        So, far from being a linear sequence of processes, design is very much an
integrated affair that requires the effective communication of all the relevant information
from one team to another in a mutually acceptable format. It is a vehicle for merging
the skills, experiences and knowledge of both what we commonly term the ’design’ and
manufacturing teams to optimise cost effectiveness, whilst maintaining a means of
control and co-ordination of all related activities.
        The antithesis of this sort of approach is reflected in the proportional cost of the
so-called ’design’ phase: an average of between 5-7% of the total life cycle costs. BUT
- as a result of decisions made during this initial stage, something like 75% of the total
life cycle costs have already been committed. Pareto observed that when 10% of the
project time scale has elapsed, 90% of the total cost has been committed. For
example, the study carried out at Rolls Royce Ltd. detailed sources of unnecessary cost
for both new and well-established products as follows:
     • design schemes                 50%
     • detail drawing                 30%
     • production engineering         20%

       The rewards to be gained by improvements made at the product’s design stage
are clearly illustrated by the above findings, and are further demonstrated by the cost-
time curve.



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                               Committed cost curve: Decis ions
                    Costs      taken early in the design process
                               commit you to the actions taken later




                                                         Accumulated cost curve:
                                                         Manufacturing incurres high
                                                         cost and hencewhere cost
                                                         reductions are demanded


                            Specification       Detail            Manufacture

                               Concept Design        Production Planning    Time


                     Fig1. Costs v Lead Time of Design to Manufacture

        These proportional values indicate the fundamental importance of that initial
phase in a product’s life that is referred to as ’design’. iDer perceive this initial phase
as the definition of a need; its relation to the outcome, i.e. the product, and the human
is expressed in two ways. The first regards the product, the response to a need, as
man’s response to changes in the environment: the second account designates a more
active role to the human, whereby the man understands his present environment and
is able to predict certain things about it. Thus, under this exposition of ’need’, man is
able to effect change in his environment by design.
        The recognition that a need exists and constitutes a design problem is the first
stage of creativity in the design process. A ’design’ is not successful unless it fulfils a
need: it may be fully functional, cost effective, aesthetically pleasing, etc. - but its
functionality, and all these design aspects, are inextricably bound up with the role it is
to perform - which translates as the need it is to fulfil.
        The concept of need and the subsequent design of a product to meet it are very
complex issues. The media and advertising are often condemned for creating a need;
making people dissatisfied with what they have, or suggesting they lack something
fundamental to their health, comfort or happiness. Some advertisements appeal
unashamedly to our subconscious, colours and packaging of products attract and
seduce us, juxta-position of music and image moves us.
        In the engineering field, ’need’ becomes less a question of psychological
analysis, but retains its double-edged complexity. The customer pinpoints a need,
which in the case of Design Builder is expressed as a demand - the call for a specific
product to satisfy that need. But in many instances the customer is not sure how to
satisfy the need; as suggested earlier in relation to TV advertising - is sometimes not
even aware of a need at all! Often it is a case of recognising a problem on the
customer’s part: the awareness of a need, but translated as a want, a more ambivalent
desire simply to satisfy that need. The creative aspect of the designer’s role is to
produce a means of fulfilling this need through the generation of a concept for a specific

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product.
        The concept of a ’need’ highlights the three-fold phase of the design to
manufacture process: underlining the importance of a clear understanding of the
problem before possible solutions are sought: a sequence paralleled in Design
Builder’s virtual industrial environment by the compilation of a detailed PDS leading
into the generation of concepts. The third phase - detail design - reflects the pooling
of all pre-established data and the construction of the product which will go out to the
customer.
        The subconscious, or perhaps simply indeterminate, aspects of a need are also
reflected in Design Builder. Although the customer letter specifies a particular need
and involves a demand for a specific product, the questioning of customer and experts
is intended to convey the fact that certain necessities, either sub-divisions, corollaries
or consequential factors of the customer’s need remain implicit. The customer is not
an expert in this field any more than the designer is an expert in the domain of
manufacturing or sales - his or her expertise encompasses the ability to interpret the
customer’s request, the creative capacity to produce potential solutions; possible
means of fulfilling the need, and good interpersonal and communication skills that
enable him/her to pool the expertise of all departments in the design chain.
        Despite all the evidence uncovered by research, and ‘everyday’ instances of
iteration, resulting from poor communication and necessitating irritating changes to your
own deadlines, the importance of this initial phase in the design to manufacture process
is overlooked. There are many incidences of designs requiring modification at late
stages of the design to manufacture process; sometimes even after the product has
reached the customer. Such a situation raises the related questions: if a design has
undergone several modifications throughout its life cycle,
1) how ‘good’ was it on its initial release? - and 2) after several modification cycles, how
well does it now satisfy its functional requirements?
        The cost incurred through modifying a design increases as the process nears
completion. Thus changing a tolerance, dimension or even shape prior to manufacture
costs relatively little - but effecting such changes during manufacture could incur costs
of hundreds of thousands of pounds, as well as time delays that risk losing a company
its clientele. A simple decision pertaining, for example, to basic shape, determined
from basic pencil sketches can have far reaching consequences. Take for instance a
chain of decisions that results in a defined shape being a sharp cornered cube, to be
produced in large quantities and cheaply. These two latter factors contribute to the
choice of polyethylene as a material and the method of production as injection
moulding. Do you foresee any problems?
        The discipline of engineering is extremely diverse, covering a large range of very
different subjects. However, although knowledge in a number of these fields may be
required in order for sound decisions to be made during the design process, we still
tend to view ‘design’ as isolated and carried out by an individual: the ‘designer’. Sound
design decisions leading to a right first time approach to manufacturing output demands
a team approach as reflected in Design Builder. A good design considers all aspects
relating to a product’s life cycle, both technical and non-technical, and taking into
account right from the start what it really is the customer requires. Thus interaction
between members of the design team and communication with the customer
throughout the design to manufacture process are imperative elements of a successful

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design outcome, elements which use of Design Builder will foster and encourage.

        The aim of this workbook is to help you as tutor/lecturer to optimise the use of
Design Builder as a teaching aid and learning resource. It will suggest ways of
integrating the software into current engineering design courses, as well as highlighting
the different ways in which the system can be made use of, for example:

   •   during formal design sessions to assist the teaching of design
   •   in student groups as a basis for assignment and project work
   •   by individual students for assignment and project work

         Use of Design Builder in lectures and tutorials can be supported and
supplemented by the private use of the Student Edition of the system, available to
individual students at a lower price than the academic version.
         iDer are concerned that, as engineers, it is important that we all become less
involved in the maintenance of domain boundaries and a great deal more involved in
a multidisciplinary role. The team members embrace a concurrent approach to
engineering design and recognise that such a change to industrial practices as the
concurrent philosophy brings, will necessitate parallel changes in the educational
experience. Perhaps you have felt that academia is slow to adopt the changes many
businesses are putting into practice; maybe you have first hand experience that
undergraduate engineers are rarely provided with the required knowledge, expertise,
communication and interpersonal skills necessary to work concurrently in an effective
manner - but are frustrated with the similar physical limitations of your own range of
expertise - and the economic inviability of the alternative team teaching approach.
Engineering design has always been a notoriously difficult subject to teach, for this very
reason: that the range of knowledge and expertise required in the design to
manufacture process is simply too vast for any one individual to master. This is
something we want to get across in Design Builder - whilst at the same time
emphasising to students the importance of their contribution to a team effort and the
parallel importance of each department’s input in the design chain within industry.
Industrialists report that undergraduates do not grasp the importance of their own
endeavours when involved in a small portion of a major project; nor do they appreciate
the infrastructure of inherently multidisciplined organisations. Both these vital, yet
undeveloped, aspects of an engineering undergraduate’s education are targeted by
iDer’s Design Builder.
         The system also spells a way out of the vicious circle created by the poor team
working and communication skills exhibited by many students, and the consequent
difficulty creating an atmosphere of concurrency’ - which would facilitate, encourage
 and show to advantage those communication skills. It is a chicken and egg argument:
which comes first - the poor communication skills - or the difficulty of creating the
concurrent environment? Either way, iDer hope the integration of Design Builder into
your engineering design courses will create that atmosphere of concurrency, enabling
interaction between system experts and user, demonstrating the advantages of a
parallel interaction between departments in the design chain within industry and with
the customer - and therefore encouraging students to employ similar interaction in their


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own design projects. We hope you agree and that you find Design Builder an
invaluable aid for you and your students.

       In order for students to find their way about the bookshelf and to be able to
optimise its use both as a stand-alone resource and an aid to decision making in the
design process within Design Builder, we have compiled a sample assignment:

Bookshelf Assignment 1:

      A company is seeking, using cost as their main criterion, the best combination
of power unit and transmission system to suit the following criteria:

              maximum output speed                1500 r.p.m.
              output power                        28 kW

        Use the catalogues supplied in the bookshelf to make a recommendation,
providing information on the primary power source, power transmission type/model and
total cost.

Comments:
        The problem is admittedly much simplified, with the intention of providing a
simple context within which the student can explore the bookshelf. Combinations may
be built using various heat engines, electric and hydraulic motors coupled with v-belt
drives. Consideration needs to be given to the required power output value when the
appropriate service factor is taken into account. A point for discussion could be the
advantages of multi-belt drives against a single belt drive, with particular reference to
belt failure.

Bookshelf Assignment 2:

       Parametric analysis is a powerful tool for establishing a product’s relative merits
in comparison with competitors’ products. Information on carrying out a parametric
analysis may be found on the bookshelf under marketing. Using the manufacturing
data contained in the bookshelf catalogue, carry out a parametric analysis. Examples
to use as a basis for the analysis are:

              I) drive transmissions    -         power capabilities v. cost
              ii) primary power sources -         power output v. weight
                                        and       power output v. cost
              iii)materials             -         tensile strength v. density


       The definitive expression of the term concurrent engineering has posed
problems: iDer have come up with a working definition’ which they feel encompasses
the holistic nature of the concurrent philosophy. Thus they perceive a designer of the
concurrent engineering school as one who ‘takes into account a wide range of
downstream considerations that have an influence on the overall life cycle of the

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produc’.
        This ‘holistic nature’ is what distinguishes CE design from more traditional
design procedures, where decisions at each stage in the process are made in isolation
and without a sense of their implications and relation either to the initial design brief or
the finished product. Such an approach results in iteration, as the ‘developing’ product
must be returned to earlier stages for modification, and a subsequent increase in
product lead-times and costs.
        There is little doubt that industry needs to adopt a concurrent philosophy of
engineering design - and iDer feels it is vital that academia responds accordingly. At
the moment, a great many graduates enter their industrial careers with little experience,
and therefore appreciation, of the advantages of a concurrent philosophy of
engineering design. This then, is the situation iDer aim to alleviate with their system
Design Builder. The team members became aware that the conventional educational
environment was not conducive to an understanding of the CE approach. Having
highlighted three aspects of concurrent engineering, they then had to produce a system
which expressed, but most importantly, enabled the user to implement, these aspects.
 These are the already-mentioned holistic nature of the philosophy; the necessity of
interaction and communication between individuals and departments along the
design chain=; and the fact that design is ultimately a compromise.
        This third aspect perhaps requires further elucidation: design is a compromise
partially because it must take into account all aspects of the customer’s requirements
- yet in cases where those requirements conflict (e.g. in the design for a motor car,
where the desire for speed competes with a desire to keep running costs low) - the
designer must employ his or her own judgement. There are also other requirements,
such as manufacture, assembly, standards, disposal, etc, to be met which may not be
 perfectly reconcilable without similar intervention on the designer’s part.
        How does the system convey these aspects of CE? Design Builder simulates
a concurrent engineering environment, enabling students to experience and implement
a concurrent approach to engineering design. Domain specific experts, integrated
within the system as knowledge bases, provide a valuable resource, as well as
exemplifying the CE approach. The nature of these ‘experts’ diverges from both
traditional methods of design and of teaching design, and from traditional knowledge-
based systems. The experts provide an important means of interaction between user
and system, reflecting the necessary interaction between team members and
departments, their advice available both on demand and unprompted. Their presence
and role also emphasises the holistic nature of CE design: they are all ‘present’
throughout the program, all available for advice at any stage in the process. Whether
the advice is in response to a direct question from the user, an unexpected piece of
information provoked by a user’s decision, or as result of a difference of opinion
between experts, the advice can be over-ridden at any stage by the user. This
reflects the third aspect of CE design referred to above, whereby the designer must
exercise his or her own judgement in a situation where conflicting statistics, facts and/or
advice demand a compromise of sorts.
        This sense of compromise should not be understood as something negative: it
does not imply the product falls below the high expectations of today’s market led
economy, or outside the requirements stated by the customer. On the contrary, CE
design as compromise ensures a product which best fits those criteria laid down in the

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product design specification (PDS), and therefore the customer’s requirements as
stated in the initial system-generated letter. The ranking of the questions asked and
answers received in the first phase of the program is an integral part of compiling the
PDS and reflects 1) this ‘compromise’, 2) the importance of the designer’s own
informed judgement, and 3) his/her interaction with colleagues along the design chain
which will ensure that judgement is adequately and comprehensively ‘informed’.
         This act of ranking information in compiling the PDS reflects the questioning
approach to engineering design that iDer aim to emphasise throughout Design
Builder. The system-generated customer letter which presents a design scenario; a
basic ‘design brief’ - is expressly vague, stating only the minimal requirements and
omitting certain factors (such as environment, labour source, etc. ) and consequently
containing implicit requirements which it is the user’s job to draw out and state explicitly
in the PDS. This reflects the essential aim of the PDS phase in Design Builder, which
is to underline the importance of a thorough understanding of the problem before a
solution is sought. An incomprehensive and therefore ambiguous PDS and a ‘leaping
in’ to the concept design stage results, in the long term, in increased product lead-time
as the finished product may be found insufficient for the customer’s need. In a worse
case scenario, the lack of or a poorly constructed PDS may result in the manufacture
of a product for which there is no need at all and hence no market. An example of such
a product could be the innovative, yet ill-received, Sinclair C5. A more thorough survey
would have established whether or not such a product would be well-received by the
public - i.e. would have highlighted a need and a market.
         The ranking of the information collated from the customer and expert responses
is a further stage of the questioning approach since the user must consider whether a
particular element of the design is really necessary - as well as the order of importance
of each element, in view of the data he/she has already collected. It is important to
stress that the system’s rankings, effected by the experts, are only ‘correct’ for this
company and this product. This section is designed to challenge students rather than
present them with a definite ‘paradigm’ design solution. Thus a student may disagree
with an expert’s ranking and still be able to produce a feasible and appropriate concept.
 The vital point here is that the student who does disagree gives careful thought as to
why this is the case.
         At the second phase, where the user is required to generate a minimum of 3 and
a maximum of 6 concepts, he/she is also required to choose materials, joining and
processing methods relating to each component and their assembly. This ensures that
the user keeps the PDS constantly in mind, relating all future decisions regarding the
product to the customer requirements it aims to meet. Design Builder encourages the
user to recognise the inter-relation of all design decisions through the intervention of
its domain experts, who will react to the user’s decision or answer any queries
regarding the implications of certain decisions. Thus the second phase - concept
design - emphasises the 3 highlighted aspects of CE design: the interaction of team
members and customer, the holistic nature of the design process, and the compromise
that is made through selecting certain combinations of materials and processes.
         In the second phase - concept design - when possible solutions to the now fully
understood problem are sought, similar interaction occurs. Concept design is a gradual
‘honing down’ of information, involving decisions on several levels. For example, the
student must choose how to arrange the various components (motor, transmission,

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winch drum, side plates, base plate) as well as deciding which type of motor,
transmission, materials, processes and joining methods to use. Details of how to
assemble the components are available on the bookshelf (icon at the toolbar at the
bottom of screen) under ‘layout of concepts’. Once again, experts are available to
advise prior to choice, but also comment unprompted, activated by the student’s
decisions. They remind the student of the disadvantages of his/her choice of material
or method, and the system allows the student to reassess his/her design in view of this
information. However, the experts do not only intervene to criticise or highlight
problems: the student also receives positive feedback and encouragement throughout
the program. This can mean though, that a student receives commendation from one
expert on one particular design decision, but is alerted to a potential problem regarding
the same decision by another expert. This aspect of Design Builder emphasises 1)
the compromise involved in design, 2) the importance of referring to the PDS to aid
decisions in such situations 3) the necessity for the intervention of the designer and the
employment of his/her judgement 4) the importance of interaction with experts to
ensure that judgement is informed, and 5) how Design Builder reflects real life
situations in industry.
         The second half of the concept design phase is another example of how Design
Builder encourages the student to take responsibility - whilst emphasising the
necessity of interaction at all times. It is also an element of the system which enables
self-evaluation: a vital aspect of the learning process in any field.
         In order to select an optimum concept - one that best fits the requirements
stated in the PDS - the technique employed is a form of matrix analysis. The system
selects one concept as the ‘benchmark’ - against which students are required to
measure the appropriateness of their other concept designs. Continuation is achieved
by the division of the criteria to be met into the 5 already mentioned categories of
materials, cost, manufacture, assembly and marketing. These categories are weighted
by the system to represent their relative importance in the overall design. Even at this
stage of self-evaluation, experts intervene if the student’s scoring of a concept does not
agree with their own. Once again students have the opportunity to modify their rating
in the light of expert opinion, but are able to override advice at any time. This occasion
for self-assessment is supported by further opportunities in the concluding ‘feedback’
section of the system.
         The third phase - detail design - reflects the convergence of all the information
accumulated during the design decision making process undertaken up to the present
stage. Knowledge and understanding of mechanical related sciences, manufacturing
technology, marketing information, assembly skills and experience, cost awareness
must be brought together and put into effect in order to specify and select components
of a suitable size, type, dimension, material, etc. that will result in a final design to
comply with the previously compiled PDS.
         It is a process of analysis whereby the student builds up specific details relating
to each component, with the constant overview of the design solution as a whole and
its accordance with the PDS.
Many of the components, and assembly devices such as bolts, will be bought in. At this
stage it is advisable to check upon what materials and components the company holds
in stock - and which have to be bought in. This information will have bearing on product
lead time since bought-in parts may incur delays of up to a week. The optimum time

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for checking is during concept design when decisions can be taken and changes made
accordingly, without huge increase to product lead time. The necessary data is to be
found on the bookshelf under ‘company policies’.
         In the industrial environment, the design engineer must select the most suitable
component from reams of manufacturers’ catalogues and data, aware, as always, of
the conception of design as a compromise between different aspects of its function.
 Integrated within Design Builder is considerable store of specific data pertaining to
individual components displayed in the form of manufacturers’ catalogues. Once again,
the student is required to interact with the system and make decisions and selections
in a manner analogous to a design engineer in industry.
         As the various aspects begin to merge into the final design outcome, Design
Builder continues to emphasise the importance of concurrency: of communication
between departments and interaction with the customer through reference to the PDS,
in making that outcome successful. As throughout the program, the system’s experts
will comment, unprompted, on student’s decisions, and are available for advice at any
time.
         The opening screen displays nine individual component icons, representing the
constituent parts of the final design. Although the components are not displayed in a
specific order, the fact remains that selection and refinement of one provides the basis
for decisions regarding another, underlining the holistic nature of the design process.
 For example: once you have decided on the length, type and material from which to
make the rope , other decisions must be made relating to whether it will comprise a
large number of small strands or a small number of large strands. Any decision made
requires consideration of a number of factors and influences future decisions, in this
case the details pertaining to the drum. It is however up to the user to judge in piecing
together the parts; the system will respond to each suggestion or attempt on behalf of
the user. For example, casing design has to be carried out last, whilst some
components can be altered prior to this final decision (e.g. bearing/transmissions) The
system emphasises that there is little point in considering the components in isolation;
this approach only leads to iteration in the design decision making process and an
extension of product lead time.
         Clicking on each component icon activates the relevant manufacturer’s
catalogue. Each entry is preceded by an introduction explaining how to calculate the
necessary dimensions, etc. and the student can return to this introduction at any time
during the selection of a specific component by clicking on the tab at the right of the
catalogue. As well as these summative introductions, there is more detailed and in-
depth information pertaining to the components available on the bookshelf. It is
recommended that the student refer to this and other virtual design aid tools in
compiling his/her detail design. Design Builder continues to emphasise its concurrent
message through the function and availability of these aids. For example, the filing
cabinet is a particularly useful resource at this stage, not only enabling the student to
refer back to the customer letter and PDS, but also to his/her chosen concept design
and any components already designed in detail. Selecting ‘current selection’ from the
list activated by clicking on ‘filing cabinet’ displays the student’s current concept design.
 There is also the opportunity to change components or even concepts at this late stage
(simply click on ‘change concept’ icon) - but such last minute alterations are not
encouraged, since they go against the whole message of Design Builder: to preclude

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the necessity of alteration at later stages in the design process by compiling a complete
and comprehensive PDS and referring to it constantly before making any subsequent
design decisions, thus reducing iteration and, consequently, cost and lead-times. If a
change is considered imperative at this stage (e.g. if failure to change now would result
in impossibility of manufacture or a failed product) - then the system will take this into
account - but the necessity for change at this stage should always be avoided in the
ways Design Builder has hitherto encouraged and facilitated, hence alterations to the
design at the detail design stage will cost the student dear in performance rating - as
it would the company in the parallel industrial environment, incurring costly delays to
the delivery date.
       Below are some useful notes on assumptions made, ratios and tolerances used
and potentially problematic elements, pertaining to each section of the detail design:

safety factor:
        It may be worth explaining to students that the safety factor is a sort of insurance
to build into a design to offset unforeseen occurrences. This presents another good
example of how design is a compromise, for whilst raising a factor of safety generally
improves the component’s ability to withstand forces applied by its environment, the
increase of materials required in the component’s design will inevitably raise costs.
Perhaps one of the most striking instances of this to date has been the freak wind
conditions which obliterated the Tokamotta bridge in the USA.

drum design:
        The system assumes that a drum has to be at least 12 times the rope diameter.
 This is a ‘rule of thumb’ estimate used by winch manufacturers to allow the rope to
bend around the drum. The ropes used on industrial winches are of a heavy duty type,
and this is reflected in the limited size of coil radius they are able to form. If the coil
radius for a particular rope is larger than that decided upon for the drum dimension, the
rope will not sit properly on the drum. This will result in poor winch performance and
possible rope damage.
        In rope dimensions that result in a portion of a turn being occupied on the drum,
the number of turns specified is rounded up to the nearest integer.
        One rule of thumb for drum manufacture is that the side plate diameter should
allow for an extra two layers of rope beyond that specified to prevent it sliding off the
winch drum.

shaft length:
        It is assumed that there is an overhang at each end of the drum and a clearance
between the drum and side plates.
        The method for calculating the magnitude of stress applied to the side plate has
been simplified: stress in a real shaft would be tri-axle. In Design Builder’s analysis
of these values, shear and tensile stress are considered separately.
        It is assumed that the load on the shaft is a point load at the centre of the shaft
and does not take into account the effect the drum will have on the shaft. Shear stress
would be significant due to the forces acting at the contact areas between shaft and
drum side plates. Additionally, no account is taken of the fact that the drum adds
rigidity.

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                                                           DESIGN BUILDER WORKBOOK

          The ‘company’ manufactures to the tolerance N8' and prefers working with
steels.
          The maximum radius of curvature has been taken from bearing manufacturers’
data.


drive selection:
       It is assumed that all electric motors, hydraulic motors and engines are fixed
speed to ease system design. The reason for such simplification is to preclude the
need for individual torque characteristics for the 200+ motors in the system’s database.
 A manual handle is not a recommended choice since the torque required is unlikely to
be achieved by manual drive alone.

V-belt selection:
       Information on v-belts stored in the system’s database was kindly provided by
Fenner Power Transmission’s UK. The company’s procedure for selecting belts and
pulleys has been greatly simplified in Design Builder. However, the revised procedure
does allow realistic decisions to be made, without unnecessary distraction from the
base process.

service factors:
       Service factor selection for all transmissions has been simplified by ignoring
additional situation dependent factors.

adhesives:
      It is assumed that adhesives will fail due to peeling and that they are
inappropriate to this design situation.

welding:
      To simplify the process, actual weld bead sizes are not considered; it is
assumed that the correct size for the situation is used.

calculations using pi:
       The system uses a value of pi to 6 decimal places. We have experienced times
when calculators produce more accurate answers than the system. If the expert
reports that an answer is incorrect, recommend to students that they try using a value
of 3.14 for pi.

coefficients of friction:
        The system assumes that the bottom of the lifeboat and the runners are made
of steel. The information required to select the correct value for the coefficient of
friction is available through the customer’s letter and in the relevant table included on
the bookshelf.


          As well as the knowledge based ‘domain experts’, Design Builder contains


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                                                            DESIGN BUILDER WORKBOOK

several additional learning resources. The bookshelf is one such facility, where users
can access ‘real’ design-related data to assist decision making during the design
process.
        The information stored on the bookshelf is designed to be of use at each and
any stage in the design process, containing information and specific data (e.g. ‘values
of coefficients of friction’ and ‘ergonomic data’), manufacturers’ catalogues of bought
out components, as well as more general instructive and background information (such
as ‘how to write a PDS’ and ‘What is Design Builder?’)
        Thus the bookshelf provides a more specific yet also more wide-ranging source
of information than the experts alone could offer. Not only is it available throughout the
program, it is also an invaluable ‘stand-alone’ learning resource, accessible via an icon
on the Windows Program Manager screen.
        The information on the bookshelf is grouped under 5 main category headings:

books                - a set of hypertext documents relating to the important aspects of
the design to manufacture process: materials, costing, manufacture, assembly and
marketing - as well as instructive information on ‘how to write a PDS’ and background
information on mechanical systems’

general info.- includes specific data relevant to design decisions on materials and
                    dimensions (‘values of coefficients of friction’ and ‘ergonomic
                    data’) - as well as background information contrasting the
                    traditional design procedure with a CE approach and highlighting
                    the 5 areas of expertise involved in the design to manufacture
                    process (‘what is Design Builder?’). This section also contains
                    an ‘example specification’ - which may be of use to students
                    having difficulties compiling their own PDS.

standards            - a brief list of relevant British standards with functional details
                     under hypertext headings

catalogues           - a wide range of product catalogues based upon information and
                     data supplied by a variety of manufacturers. The products
                     detailed include gear boxes, V-belt drives, heat engines, bearings,
                     couplings, electric motors, hydraulic motors.


FEEDBACK:

        Feedback is available in a variety of forms, at different stages and from diverse
perspectives. iDer intend, through this aspect of Design Builder, to optimise learning
and improve personal skills of self-evaluation, whilst the diverse nature of the feedback
reflects the holistic nature of design and the compromise it necessarily entails.
        One element of feedback is constantly renewed and updated as the student
works. This ‘ongoing’ report - termed ‘company assessment’ - is accessible at all times
via the filing cabinet under ‘assessment’. It also covers the opportunity existing for
students to record their own perception of their performance as a self-assessment.

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                                                             DESIGN BUILDER WORKBOOK

       iDer have highlighted certain points where they feel a hard record of the
student’s movements would be particularly beneficial to tutors, enabling them to pick
out areas of weakness in individuals - perhaps perceiving patterns among a group. In
this way, the feedback is intended to highlight points for further work and greater
emphasis in future sessions. These areas include a hard copy of the list of questions
asked by the student in compiling the PDS. A short list may reflect an unwillingness to
communicate with the experts or to interact with the customer, or a failure to utilise the
example specification and other guidelines available on the bookshelf. The general
feedback provides a more definitive analysis of the cause, stating that the student ‘did
not ask for advice when writing the PDS’ or ‘did not check the bookshelf for help on
writing a PDS’.
       Final feedback is subdivided into 5 categories representing different aspects of,
and perspectives on, the design. These are set out on a menu screen as 5 icons next
to a 3-D animated winch, a unique representation of the current student’s design. The
categories are:

              - final product specification
              - product manufacture
              - customer feedback
              - expert feedback
              - company assessment

         The final category is ‘company assessment’ - mainly because it offers an
overview of all aspects of the student’s progress through the design process, and
reiterating the comments provided under the former categories on the menu screen.
 It is worthwhile noting however, that the opportunity for self-assessment is included
here - and hence the student should be encouraged to click here and work through this
section before selecting the other categories.
         At the end of the detail design phase, the student is automatically taken to a
screen displaying a final product specification; the manufacturing specification created
as a result of the design process gone through by that student. This is equivalent to the
first icon on the main feedback menu screen and provides a useful overview for the
student, reminding him/her of, and placing in context, all design decisions made. A
print out of this screen is available. The comprehensive company assessment is
subdivided into several categories, 3 of which cover the three phases of the design
process - the fourth giving additional feedback which corresponds to the other three
categories.
         Of the first three categories in the company assessment profile, 1) the design
specification is broken down into:
                i) general feedback
                ii) the question stage - listing questions asked by the student in compiling
                     the PDS
                iii) ranking - displays expert’s comments on student’s decisions regarding
                     relative importance of questions and related design aspects.

      The second category - concept design - covers the self-assessment facility.
Headings relating to main components are provided: the student is required to account

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                                                           DESIGN BUILDER WORKBOOK

for his/her choices at this stage. This provides useful reflection upon, and hopefully
therefore reiteration of, reasons behind design decisions for the student, and for the
tutor an invaluable aid for pinpointing areas of weakness and further work.
        The third category - detail design - involves more general feedback pertaining
to decisions taken (calculations made, dimensions selected, etc.) during this phase.
        The remaining category headed ‘other feedback’ covers:
               1) manufacture - relating to decisions taken at this stage of the process
and corresponding to the ‘product manufacture’ icon on the main feedback menu.
               2) customer feedback - reiterating the information available from this
category on the main menu.
               3) overall assessment - equivalent to the technical manager’s overview
given under ‘expert feedback’ on the main menu.

      An exposition of the other categories recaps and reiterates what type of
feedback is available in each:


final product specification        A manufacturing specification created as a result of
                                   decisions made throughout the design process;
                                   displays itemised criteria of individual components
                                   and calculates total mass, cost, time taken, etc.

product manufacture                Displays a 3-D animation of the student’s design
                                   being assembled; having once established whether
                                   chosen materials and/or components are in stock,
                                   this section displays, for each component, the cost
                                   incurred by, and the time required for, its
                                   manufacture. It will report whether the student
                                   thought to consult ‘company policies’ on the virtual
                                   bookshelf to verify which components would have to
                                   be bought in.

customer feedback                  A report of the product’s performance: how well it
                                   carries out its function, plus any problems
                                   encountered.     Major failures can include the
                                   following, and are often attributable to the following
                                   causes:
                                   - rope breaking - a low safety factor used
                                   - over-stressed side plate - wrong interpretation of
                                   the stress and shear graphs, or a low safety factor
                                   - an under-powered motor -
                                   - an over budget winch -

expert feedback                    Gives an overview from the perspective of the
                                   technical manager with regard to overall general
                                   success or otherwise.


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                                                              DESIGN BUILDER WORKBOOK




Acknowledgements:
      iDer wish to thank the following companies for assistance provided during the
development of Design Builder:

       Bridon International Ltd.
       Brook Hansen
       David Brown Radicon
       David Brown Special Products Ltd.
       Davy International
       Fenner Power Transmissions
       Hydrostatic Transmissions Ltd.
       LGH Group
       Renold Gears
       The Royal National Lifeboat Institution
       Unisys Corporation
       The Wellman Bibby Co Ltd.

ider team members include:
                  Robin Barker
                  Paul Hudson
                  Brian Parkinson
                  Richard Senior
                  Chris Short

       Special thanks to Jan and Gemma Baxter for their patience and advice and to
the evaluation team for the time they spent and feedback provided during the system’s
development. Also to TLTP for their continued support and assistance throughout.

WARNING
        The software contains compression/decompression capability covered by Unisys
Patent No 4,558,302 and corresponding foreign patents. No use, sale, lease,
disclosure, copying, modification, distribution or transfer of this software, either directly
or indirectly, is permitted.

       Information provided in the Design Builder Network Edition is accurate for the
purpose of carrying out an assignment using the system. However, adjustments have
been made to some of the values used, and, as a result, they should not be included
or used for any design calculations outside of the system. The developers or their
collaborators accept no liability for the accuracy of such information.




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                                                                    DESIGN BUILDER WORKBOOK

Design scenarios
In the network edition of Design Builder, the problem as presented to a user is based upon 21
different scenario=s. The standard setting for Design Builder is for any problem to be presented
randomly, however, a setting can be made to ensure that all users on a network receive the same
problem. The table below provides details of the 21 individual sets of criteria.



                                                                            Target
                     Lifeboat Ramp                        Time             Delivery              Target
  Letter    Lifeboat Weight Length          Ramp        Required   Batch     Time   Winch         Cost
 Number      Name (tonnes)     (m)          Angle        (mins)     Size    (days) Colour           ,
                                                                                                   (,)

      1      Severn      37.5      100        15           5        1          21        Grey    46400

      2       Trent      26.5      110        20           7        1          21        White   42000

      3      Mersey       14        80        30           5        37     45 f / 11 s   Blue    25000

      4       Tyne        26       130        30           7        40     35 f / 12 s   Black   38000

      5       Brede       9         85        25           4        12     45 f / 12 s Yellow    25500

      6      Thames       22        50        20           4        1          35        Green   35500

      7     Waveney       19        90        25           6        22     46 f / 16 s   Blue    30000

      8       Arun       31.5      120        16           5        46     42 f / 14 s Green     49000
                                                                                        Blue

      9       Tees        5        100        20           5        1          35        Red     16000

      10       Exe        9        150        20           3        24     34 f / 12 s   Red     26000

      11      Wear        12       150        10           1        26     35 f / 10 s   White   34000

      12      Clyde       35        80        12           4        28     25 f / 14 s   Blue    32000

      13     Medway       11       200        10           1        30     22 f / 28 s   Blue    31500

      14       Dee        15       100        20           5        32     35 f / 13 s Yellow    25500

      15      Forth       21       150        20           3        34     36 f / 9 s    Black   32500

      16     Tweed        40        80        12           6        1          44        Green   37000

      17      Spey        45       100        10           5        1          35        Green   40000
                                                                                          Blue

      18      Tamar       8        200        15           1        37     41 f / 14 s   Grey    35000

      19      Orwell      6        150        20           1        40     36 f / 13 s Green     36000

      20     Humber       16       125        25           7        35     39 f / 16 s   White   30500

      21      Swale       24       150        20           6        27     27 f / 12 s Green     39000
Key             f - The delivery time for the first winch in a batch
                s - The subsequent delivery time for each winch in the batch


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DOCUMENT INFO