mechanical design engineering handbook second edition pdf

Each chapter has been reviewed and developed.Chapters 1 and 2dealingwith the design process and specification have been updated with a development ofthe total design process and an intro

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Mechanical Design Engineering Handbook

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Preface to the second edition

This edition of the Mechanical Design Engineering Handbook has been extensivelyupdated Each chapter has been reviewed and developed.Chapters 1 and 2dealingwith the design process and specification have been updated with a development ofthe total design process and an introduction to project management.Chapter 3 hasbeen revised substantially incorporating developments in creativity and ideation pro-cesses relevant to engineering.Chapter 4has been further developed to illustrate thescope and context of machine elements

Chapters 5 and 6introducing the first of the machine elements to be considered indetail, bearings, have been expanded to include flow charts illustrating the design ofboundary lubricated, hydrodynamic and ball bearings The introductory and extendedworked examples have been retained throughout the chapters on machine elements inthe book to enable the reader to follow the detailed analysis and associated designdecisions.Chapter 7addressing shaft design has been expanded to include consider-ation of a factor of safety according to the DE Goodman, DE Gerber, DE ASME ellip-tic and DE Soderberg criteria.Chapters 8–11introducing gears have been expanded toinclude flow charts for the selection of spur gears, and the calculation of bending andcontact stresses, and the design of gear sets using the AGMA equations SimilarlyChapter 13 introducing belt and chain drives has been extended with flow chartsfor the selection and design of wedge and synchronous belts, and roller chain drives.Chapter 14on seals has been updated to include additional examples.Chapter 15has been extended to include selection and design flow charts for helical compressionspring and helical extension spring design.Chapters 16–18have been extended withadditional examples of various fastener, wire rope, and pneumatic and hydraulic tech-nologies, respectively Three short case studies have been included inChapter 19illus-trating the importance of a detailed consideration of tolerancing in precisionengineering.Chapter 20is a new chapter providing an overview of a diverse range

of machine elements as building blocks for mechanism design

Throughout the text an additional 100 or so images have been included in order toaid the reader in becoming familiar with the technology being considered

Mechanical engineering design is an engaging subject area with many applicationsand this major revision has been a pleasurable undertaking enabling implementation

of many updates from my engineering and design practice and associated interactions

I hope this text is able to aid the reader in the development of understanding of theprinciples and associated technology and in its implementation in worthwhile innova-tions and applications

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on exciting and ambitious commercial applications and research projects, the tunity to develop knowledge is limited I have had the privilege of working withdiverse companies and organisations including Rolls-Royce plc, Alstom, Snecma,DaimlerChrysler, BMW, MTU, Volvo, Johnson Matthey, Siemens, IndustrialesTurbinas Propulsores, Fiat Avio, Airbus, Ricardo Consulting Engineers, Ford, RioTinto, McLaren, Dyson, Naked Energy and Q-Bot Ltd, Innovate UK, the EPSRCand Horizon 2020 I would like to thank the engineers, designers and managers fromthese companies and organisations for the opportunity to engage in such excitingtechnologies.

oppor-Several colleagues in particular have been very helpful in the implementation ofthis edition including Shayan Sharifi and Andy Brand who assisted with proof reading,Ben Cobley and Ruth Carter who assisted with several of the images Many collab-orators and companies have kindly given permission to include key images to aid inthe effective presentation of this book and this is gratefully acknowledged Finally,

I would like to thank my wife Caroline for her patience over the last year when I haveexpended a significant number of hours working on this project

Peter ChildsProfessor and Head of School, Dyson School of Design Engineering,

Imperial College London, United Kingdom

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1.6 Conceive, design, implement, operate 19

1.7 Design for six sigma 20

1.8 Design optimisation 21

1.9 Project management 23

1.9.1 The Traditional Approach 25

1.9.2 PRINCE and PRINCE2 32

CDIO conceive, design, implement, operate

CDR critical design review

CTP critical to process

Mechanical Design Engineering Handbook https://doi.org/10.1016/B978-0-08-102367-9.00001-9

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CTQ critical to quality

DFM design for manufacture

DFSS design for six sigma

DMADV design, measure, analyse, design, verify

DoE design of experiments

ERP Enterprise resource planning

FMEA failure mode and effects analysis

IDOV identify, design, optimise, verify

ISO International Organisation for Standardisation

KPI key point indicator

MDO multiobjective design optimisation

PDS product design specification

PID project initiation document

QFD quality function deployment

PDR preliminary design review

PRINCE Projects IN Controlled Environments

R&D research and development

SMART specific, measurable, achievable, relevant, time-bound

a series of approaches to project management and concludes with an overview of the nology base serving as building blocks for machinery and mechanical design

tech-The term design is popularly used to refer to an object’s aesthetic appearance with cific reference to its form or outward appearance as well as its function For example weoften refer to designer clothes, design icons and beautiful cars, and examples of some clas-sically acclaimed vehicles are given inFigs 1.1 and 1.2 In these examples it is both visualimpact, appealing to our visual perception, and the concept of function, that the productwill fulfil a range of requirements, which are important in defining so-called good design.The word ‘design’ is used as both a noun and a verb and carries a wide range ofcontext-sensitive meanings and associations George Cox (2005) stated “Design iswhat links creativity and innovation It shapes ideas to become practical and attractivepropositions for users or customers Design may be described as creativity deployed to

spe-a specific end.” The word design hspe-as its roots in the Lspe-atin word ‘designspe-are’, whichmeans to designate or mark out Design can be taken to mean all the processes of con-ception, invention, visualisation, calculation, refinement and specification of details

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that determine the form of a product Design generally begins with either a need orrequirement or, alternatively, an idea It can end with a set of drawings or computerrepresentations and other information that enables a product to be manufactured, aservice or system realised and utilised While recognising that there are no widelyaccepted single definitions, to clarify what the term design means the following state-ment can provide a basis.

Design is the process of conceiving, developing and realising products, artefacts,processes, systems, services, platforms and experiences with the aim of fulfilling iden-tified or perceived needs or desires typically working within defined or negotiatedconstraints

This process may draw upon and synthesise principles, knowledge, methods skillsand tools from a broad spectrum of disciplines depending on the nature of the designinitiative and activity Design can also be regarded as ‘the total activity necessary to

Fig 1.1 Piaggio’s Vespa launched in 1946 The Vespa was an early example of monocoqueconstruction where the skin and frame are combined as a single construction to provideappropriate rigidity and mounting for the vehicle’s components and riders

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provide a product or process to meet a market need’ This definition comes from theSEED (Sharing Experience in Engineering Design, now DESIG the Design EducationSpecial Interest Group of the Design Society) model, seePugh (1990).

According to a Royal Academy of Engineering document, engineering can bedefined as

The discipline, art and profession of acquiring and applying scientific, mathematical,economic, social and practical knowledge to design and build structures, machines,devices, systems, materials and processes that safely realise solutions to the needs ofsociety

This definition is not attributed to a single individual andABET (2011), the tution of Mechanical Engineers and theNational Academy of Engineering (2004)allhave similar definitions for engineering involving the application of scientific andmathematic principles to design The following statement provides an indication ofthe scope of engineering

Insti-Engineering is the application of scientific and mathematic principles in combinationwith professional and domain knowledge, to design, develop and deliver artefacts,products and systems to realise a societal, commercial or organisation requirement

or opportunity

The terms ‘engineering design’ and ‘design engineering’ are often used changeably The inclusion of the word engineering in both suggests that they involvethe application of scientific and mathematical knowledge and principles It may beuseful to think of ‘engineering design’ sitting alongside ‘engineering science’ asthe strand of engineering that is concerned with application, designing, manufactureand building Design engineering suggests a process in which engineering (scientificand mathematical) approaches are applied in the realisation of activities that beganwith a design concept or proposal (Childs and Pennington, 2015) However such dis-tinctions remain subtle and subject to context

Design processes abound and have been widely documented, with many designschools, consultancies and engineering corporations developing their own brand ofapproaches (see, e.g.Clarkson and Eckert 2005) Commonly cited methods includethe educational approach CDIO (conceive, develop, implement, operate), total design,double diamond, concurrent engineering, six sigma, MDO (multiobjective designoptimisation) and gated reviews Design processes can be broadly categorised asactivity-based, involving generation, analysis and evaluation, and stage-based,involving distinct phases of, for example, task clarification and conceptual design

It is also widely recognised that experienced practitioners approach design in a ent manner to novice designers (see, e.g.Bj€orklund 2013)

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Probably from your own experience you will know that design can consist of ining a need or opportunity and working on the problem by means of sketches, models,brain storming, calculations as necessary, development of styling as appropriate, mak-ing sure the product fits together and can be manufactured, and calculation of thecosts The process of design can be represented schematically to levels of increasingformality and complexity.Fig 1.3represents the traditional approach associated withlone inventors This model comprises the generation of the ‘bright idea’, drawings andcalculations giving form or shape to the idea, judgement of the design and reevaluation

exam-if necessary, resulting in the generation of the end product The process of evaluationand reworking an idea is common in design and is represented in the model by theiteration arrow taking the design activity back a step so that the design can beimproved.Fig 1.4illustrates the possible results from this process for a helmet pro-viding peripheral and reverse vision

Fig 1.5shows a more prescribed description of a design process that might be ciated with engineers operating within a formal company management structure Thevarious terms used inFig 1.5are described inTable 1.1

asso-AlthoughFigs 1.3and1.5at first sight show design occurring in a sequential ion, with one task following another, the design process may actually occur in a stepforward, step back fashion For instance you may propose a solution to the design needand then perform some calculations or judgements, which indicate that the proposal isinappropriate A new solution will need to be put forward and further assessmentsmade This is known as the iterative process of design and forms an essential part

fash-Fig 1.2 The Audi TT, originally launched in 1998, and a contender for the most attractivesports car of the 20th century

Courtesy of Audi

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of refining and improving the product proposal The nonlinear nature of design is sidered byHall and Childs (2009).

con-Note that the flow charts shown inFigs 1.3and1.5do not represent a method ofdesign, but rather a description of what actually occurs within the process of design.The method of design used is often unique to the engineering or design team Designmethodology is not an exact science and there are indeed no guaranteed methods ofdesign Some designers work in a progressive fashion, while others work on several

Idea

Sketches and calculations

Evaluation

Final solution

Influencing factors

Iteration

Fig 1.3 The traditional and

familiar ‘inventor’s’ approach to

design

Fig 1.4 Panoramic helmet (A) The need: to be able to view around you (B) The idea: Use of a

VR visor and camera feeds to enable forward as well as peripheral vision (C) Practical sketchesshowing the concept

Sketches courtesy of Ruth Carter

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aspects simultaneously An example of design following the process identified inFig 1.5is given in the following example (Section 1.2.1).

1.2.1 Case study

Following some initial market assessments, the Board of a plant machinery companyhas decided to proceed with the design of a new product for transporting pallets aroundfactories The Board have in mind a forklift truck but do not wish to constrain thedesign team to this concept alone The process of the design can be viewed in terms

of the labels used inFig 1.5

Analysis and optimisation

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Recognition of need (or market brief )

The company has identified a potential market for a new pallet-moving device

Definition of problem

A full specification of the product desired by the company should be written Thisallows the design team to identify whether their design proposals meet the originalrequest Here a long list of information needs to be developed and clarified before

Table 1.1 Design phases

Recognition of

need

Often design begins when an individual or company recognises a need,

or identifies a potential market, for a product, device or process.Alternatively ‘need’ can be defined as when a company decides toreengineer one of its existing products (e.g producing a new carmodel) The statement of need is sometimes referred to as the brief ormarket brief

Definition of

problem

This involves all the specification of the product or process to bedesigned For example this could include inputs and outputs,characteristics, dimensions and limitations on quantities

Synthesis This is the process of combining the ideas developed into a form or

concept, which offers a potential solution to the design requirement.The term synthesis may be familiar from its use in chemistry where it isused to describe the process of producing a compound by a series ofreactions of other substances

Analysis This involves the application of engineering science; subjects explored

extensively in traditional engineering courses such as statics anddynamics, mechanics of materials, fluid flow and heat transfer Theseengineering ‘tools’ and techniques can be used to examine the design togive quantitative information such as whether it is strong enough or willoperate at an acceptable temperature Analysis and synthesis invariably

go together Synthesis means putting something together and analysismeans resolving something into its constituent parts or taking it topieces Designers have to synthesise something before it can beanalysed The famous chicken and the egg scenario! When a product isanalysed some kind of deficiency or inadequacy may be identifiedrequiring the synthesis of a new solution prior to reanalysis andrepetition of the process until an adequate solution is obtained.Optimisation This is the process of repetitively refining a set of often-conflicting

criteria to achieve the best compromise

Evaluation This is the process of identifying whether the design satisfies the

original requirements It may involve assessment of the analysis,prototype testing and market research

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design can proceed For example for the pallet-moving device being explored here thiswould likely include aspects for consideration such as:

What sizes of pallet are to be moved?

What is the maximum mass on the pallet?

What is the maximum size of the load on the pallet?

What range of materials are to be moved and are they packaged?

What maximum height must the pallet be lifted?

What terrain must the pallet-moving device operate on?

What range is required for the pallet-moving device?

Is a particular energy source/fuel to be used?

What lifetime is required?

Are there manufacturing constraints to be considered?

What is the target sales price?

How many units can the market sustain?

Is the device to be automatic or manned?

What legal constraints need to be considered?

This list is not exhaustive and would require further consideration The next step is

to quantify each of the criteria For instance the specification may yield informationsuch as that standard size pallets (seeFig 1.6) are to be used, the maximum load to bemoved is 1000 kg, the maximum volume of load is 2 m3, the reach must be up to 3 m,and use is principally on factory floor and asphalt surfaces The pallet-moving devicemust be capable of moving a single pallet 100 m and must be able to repeat this task atleast 300 times before refuelling if necessary, electricity, gas or diesel fuel, 7 year life-time, production in an European country, target selling price 20,000 Euros,12,000 units per year, manned use, design to ISO (International Organisation forStandardisation) and target country national standards (see, e.g BS ISO 509, BSISO 6780, BS EN ISO 445, BS EN 1726-1, BS EN 13545, 99/705213 DC, ISO

18334, 99/712554 DC, BS 3726, BS 5639-1 and BS ISO 2330) The task of cation is an involved activity and is considered more fully inChapter 2

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This is often identified as the formative and creative stage of design Some initial ideasmust be proposed or generated for them to be assessed and improved Concepts can begenerated by imagination, experience or by the use of design techniques such as mor-phological charts Some evaluation should be made at this stage to reduce the number

of concepts requiring further work Various techniques are available for this includingmerit and adequacy assessments

Analysis

Once a concept has been proposed it can then be analysed to determine whether stituent components can meet the demands placed on them in terms of performance,manufacture, cost and any other specified criteria Alternatively analysis techniquescan be used to determine the size of the components to meet the required functions

con-Optimisation

Inevitably there are conflicts between requirements In the case of the forklift truck,size, manoeuvrability, cost, aesthetic appeal, ease of use, stability and speed are notnecessarily all in accordance with each other Cost minimisation may call for compro-mises on material usage and manufacturing methods These considerations form part

of the optimisation of the product producing the best or most acceptable compromisebetween the desired criteria Optimisation is considered further inSection 1.8

Evaluation

Once a concept has been proposed and selected and the details of component sizes,materials, manufacture, costs and performance worked out, it is then necessary toevaluate it Does the proposed design fulfil the specification? If it appears to, then fur-ther evaluation by potential customers and use of prototype demonstrators may beappropriate to confirm the functionality of the design, judge customer reaction andprovide information of whether any aspects of the design need to be reworked orrefined

This case study is developed further in Chapter 3,Section 3.7.1

The process of design has been the focus of research for many years and a number ofdesign models and methodologies are available Design methodology is a frameworkwithin which the designer can practise with thoroughness One such approach called

‘total design’ has been proposed by the SEED programme(1985)andPugh (1990)comprising core activities of design: marketing, specification, conceptual design,detailed design and marketing/selling This model was developed from extensive

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industrial consultation and experience and is shown in an updated form inFig 1.7,accounting for consideration of addressing both needs and opportunities, the ability

to virtually model many attributes of a design at the detailed design phase, the cability of the model beyond traditional manufacture and consideration of the businessmodel and sustainability As in Figs 1.3 and 1.5, the iterative nature of design is

appli-Fig 1.7 The total design core Originally developed byPugh (1990)and updated hereaccounting for consideration of addressing both needs and opportunities, the ability to virtuallymodel many attributes of a design at the detailed design phase, the applicability of the modelbeyond traditional manufacture and consideration of the business model and sustainability

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accounted for where work on design results in the need to go back and redo previouswork to produce a better overall design to meet the requirements Indeed it is some-times necessary to go back a few or several levels An example might be the discovery

at manufacture that an item cannot be made as envisaged and a new concept altogether

is required Ideally such a discovery should not occur, as every other level of thedesign process illustrated in Fig 1.7 should be considered at each stage Each ofthe design activities illustrated in Fig 1.7 is described in more detail in Sections1.3.1–1.3.6 As it is the same fundamental process being described, these descriptionsare similar to those which are dealt withFig 1.5

1.3.1 Need/opportunity analysis

The need/opportunity analysis or marketing phase refers to the assessment of salesopportunities or perceived need to update an existing product, service, system or plat-form resulting in a statement sometimes called the market brief, design brief, brief orstatement of need

1.3.2 Specification

Specification involves the formal statement of the required functions, features andperformance of the product or process to be designed Recommended practice fromthe outset of design work is to produce a product design specification (PDS) thatshould be formulated from the statement of need The PDS is the formal specification

of the product to be designed It acts as the control for the total design activity because

it sets the boundaries for the subsequent design Further details of the PDS aredescribed inChapter 2

1.3.3 Conceptual design

The early stages of design where the major decisions are to be made is sometimescalled conceptual design During this phase a rough idea is developed as to how aproduct will function and what it will look like The process of conceptual designcan also be described as the definition of the product’s morphology, how it is made

up and its layout Conceptual design is the generation of solutions to meet specifiedrequirements It can represent the sum of all subsystems and component parts that go

on to make up the whole system.Ion and Smith (1996)describe conceptual design as

an iterative process comprising of a series of generative and evaluative stages that verge to the preferred solution At each stage of iteration the concepts are defined ingreater detail allowing more thorough evaluation It is important to generate as manyconcepts and ideas as possible or economically expedient There is a temptation toaccept the first promising concept and proceed towards detailed design and the finalproduct This should be resisted as such results can invariably be bettered It is worthnoting that sooner or later your design will have to compete against those from othermanufacturers, so the generation of developed concepts is prudent Some methodssuch as brainstorming, morphological analysis and SCAMPER used to aid the gener-ation of concepts are described inChapter 3

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1.3.4 Detailed design

The detailed design and virtual realisation phase consists of the determination of thespecific shape and size of individual components, what materials should be used, howare materials and subsystems going to be recycled, how they fit together and themethod of manufacture Detailed design makes use of the many skills acquired anddeveloped by engineers in the areas of analysis It is the detailed design phase thatcan take up the bulk of the time spent on a design However as implied earlier it iswise to only spend time on details once a sensible concept has been selected

1.3.5 Manufacturing and production

The manufacture and production phase, although identified as distinct within thestructure, is typical of other phases in that it influences all the others The design

of any item must be such that it is feasible to produce or manufacture the product,service, system or platform concerned In the case of a physical product, the materialsselected must be compatible with the manufacturing facilities and skills available, and

at acceptable costs to match marketing requirements Manufacturing is so importantthat design strategies to reinforce its importance have been developed such as designfor assembly (DFA) and design for manufacture (DFM) (see for instanceBoothroyd

1997) The concurrent engineering model provides a systematic approach that ages the developer from the outset to consider all the elements of a product lifecycle orprocess from concept through disposal including quality control, scheduling and userrequirements This is illustrated inFig 1.8

encour-Market drivers such as a need for shorter innovation cycles, more complicatedproducts and greater data volumes combined with requirements for individualisation,high productivity and energy and resource efficiency have led to the emergence ofIndustry 4.0 Industry 4.0 involves organisation and control of all design, engineeringand business activities across the entire product lifecycle and value chain, leveraginginsights from data flows to provide, in theory, seamless delivery of value to all stake-holders Central to Industry are data flows and a digital model, which needs to be up todate and complete across all activities associated with product design, productionplanning, engineering and execution, and services A schematic showing the

Fig 1.8 Concurrent engineering

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opportunity Industry 4.0 offers to manufacturing is given inFig 1.9 Sensors, puting power, data analytics and networking are all key enablers for the Industry4.0 vision.

com-Industry 4.0 first emerged as a concept at the Hannover fair in 2011 with aimsincluding assisting in the long-term sustainability of national industry enabled byleverage of information for quality and bespoke provision Since then the confluence

of increasing data connectivity, digitisation and opportunities associated with this (seeFig 1.10) have led to widespread consideration and adoption of Industry 4.0 princi-ples Many reports are available concerning the opportunity and challenges for indus-try aiming at engaging (see, e.g McKinsey, 2015; IMechE 2016; PWC, 2016).Industry 4.0 enables many new paradigms ranging from seamless product design torealisation and product design for mass individualisation (see Sikhwal andChilds, 2017)

1.3.6 Sustainable enterprise

The last phase, sustainable enterprise, is of course essential for the success of any ness Sales should match the expectations of the initial marketing analysis, otherwisethere may be a need to reconsider production runs Business factors have a fundamen-tal impact on other phases within the design core Information such as customer reac-tion to the product, any component failures or wear, damage during packaging andtransportation should be fed back to influence the design of product revisions andfuture designs If sales revenues exceed design and production costs then it will bepossible to invest in design updates for the product, service, system or platform con-cerned, as well as the development of brand new designs The concept of sustainability

busi-Fig 1.9 Schematic indicating the Industry 4.0 opportunity for manufacturing

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and a sustainable enterprise can be intertwined with service models or incentives, forexample by encouraging customers to return devices for recycling in return for anupdated model, thereby enabling control of the end-of-life dismantling and recycling

of components and retention of customers

1.3.7 Total design information flows and activities

The double arrows shown inFig 1.7represent the flow of information and controlfrom one activity to another as well as the iterative nature of the process For instancedetailed design activity may indicate that an aspect of the conceptual design is notfeasible and must be reconsidered Alternatively conceptual work may yield features,which have potential for additional marketing opportunities In other words, the activ-ity on one level can and does interact dynamically with activities on other levels.Fig 1.11 illustrates the possible flow of this process during the development of aproduct

Almost any product such as a vacuum cleaner, kettle, automobile or cordless tool requires input from people of many disciplines including engineering, legal andmarketing and this requires considerable coordination In industrial terms, the integra-tion comes about as a result of the partial design inputs from each discipline In

hand-Mobile devices

IoT platforms

Location detectionDigitisation of value

chains, productsand serviceofferings, businessmodels andcustomer access

Human machine interfaces

cation

Authentifi-3D printing Smart

Fig 1.10 Industry 4.0 principles

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Fig 1.12 additional activities, such as market analysis, stressing and optimisation,have been added to the design core as inputs The effective and efficient design ofany product invariably requires the use of different techniques and skills The disci-plines indicated are the designer’s toolkit and indicate the multidisciplinary nature ofdesign The forklift truck example mentioned in Section 1.2.1will require enginemanagement and control systems as well as the design of mechanical components.Although this text concentrates on mechanical design, this is just one, albeit an impor-tant, interesting and necessary aspect of the holistic or total design activity.

A number of circumferential inputs have been shown as arrows inFigs 1.3, 1.5, 1.7and 1.12 These represent elements of the specification listed in order of importancefor each phase of design The priority order of these specifications may alter for dif-ferent phases of the design activity The exact number will depend on the actual caseunder consideration

Industry is usually concerned with total design Total design is the systematic ity necessary from the identification of a market need to the commercialisation of theproduct to satisfy the market need Total design can be regarded as having a centralcore of activities consisting of the market potential, product specification, conceptualdesign, detailed design, manufacture and marketing

Revise specification Conceptual design

Conceptual design

Conceptual Design

Manufacturing options

Market testing

Revise specification

Market testing

Best concept Detail design Component design Pre-production prototype Physicalperformance

testing Production planning Production prototype Production Sales

Design for manufacture

General assembly

Tooling design

Specification

Best concept Design options Technical breakthrough

Materials options

Ideas for

new

products

Trigger for product development

Fig 1.11 Design activities at different stages in product development

Adapted from Baxter, M., 1995.Product Design Chapman and Hall, New York

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1 product planning and clarifying the task;

2 conceptual design;

3 embodiment design;

4 detail design

The approach acknowledges that because of the complex nature of modern technology

it is now rarely possible for a single person to undertake the design and development of

Need/opportunity analysis

Market analysis

Synthesis

Decision making

Optimisation Data handling

Costings Manufacture

Iterations

Detailed design and virtual realisation

Manufacture and production Materials

Sustainable enterprise

Fig 1.12 The total design process Originally developed byPugh (1990)and updated hereaccounting for consideration of addressing both needs and opportunities, the ability to virtuallymodel many attributes of a design at the detailed design phase, the applicability of the modelbeyond traditional manufacture and consideration of the business model and sustainability

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a major project on their own Instead a large team is involved and this introduces theproblems of organisation and communication within a larger network The aim is toprovide a comprehensive, consistent and clear approach to systematic design.Design models and methodologies encourage us to undertake careful marketingand specification Because of their sequential presentation, ‘design starts with a need’

or ‘design starts with an idea’, they inherently encourage us to undertake tasks tially This is not necessarily the intention of the models and indeed this approach iscountered within the descriptions and instructions given by the proponents of themodel who instead encourage an iterative feedback working methodology

sequen-Fig 1.13 The design process proposed by Pahl & Beitz

Adapted from Pahl, G., Beitz, W., 1996.Engineering Design: A Systematic Approach, second

ed Springer, London

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A criticism of the Pahl and Beitz and Pugh design models is that they tend to beencyclopaedic with consideration of everything possible As such, their use can beviewed as a checklist against which a personal model can be verified A further crit-icism of design models is that they are too serialistic as opposed to holistic and thatbecause of the serious manner in which the models are portrayed and documented theycan have a tendency to put the intuitive and impulsive designer off!

TheDesign Council (2007)reported a study of the design process in 11 leading panies and identified a four-step design process called the ‘double diamond’ designprocess model, involving the following phases: discover, define, develop and deliver

com-InFig 1.14, the divergent and convergent phases of the design process are indicated,showing the different modes of thinking that designers use

The CDIO (conceive, design, implement, operate) framework is widely used in designand engineering education and was developed in recognition of a divergence betweenacademic culture and practical engineering requirements The framework explicitlyrecognises the importance of holistic considerations for effective design outcomeswith application of both engineering practice skills such as design, manufacture, per-sonal, professional, interpersonnel and business in combination with disciplinaryknowledge from the sciences and mathematics as well as the humanities(Crawley 2001)

Fig 1.14 Schematic describing the design process

Adapted from Design Council 2007 The ’double diamond’ design process Model, 2007.www.designcouncil.org.uk/en/About-Design/managingdesign/The-Study-of-the-Design-Process/.Accessed December 2007

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1.7 Design for six sigma

Design for six sigma (DFSS) is an approach for designing a new product or servicewith a measurable high performance This requires the development of an understand-ing of customer needs prior to launch rather than afterwards

There are a number of methodologies applying six sigma principles includingDMADV (design, measure, analyse, design, verify), IDOV (identify, design, opti-mise, verify) as well as DFSS IDOV tends to focus on the final stages of engineeringoptimisation and may not address the selection of product features and attributes thatactually address customer requirements (Tennant 2002) DFSS comprises a number ofdefined activities as outlined inTable 1.2

Table 1.2 Design for six sigma

New product

introduction

Selection of the concept or service to fulfil a perceived need.Benchmarking, customer surveys, R&D, sales and marketinginput, risk analysis

of a team charter to provide a solid foundation for the project.Customer (measure) Identification of the full characteristics and needs of the

customer Use of Quality function deployment (QFD) (seeChapter 2) to identify the set of critical to quality (CTQ)metrics This arises from the set of customer needs along with

a list of potential parameters that can be measured andquantified defining the targets for each CTQ metric

Concept (analyse—

conceptual design)

A design is explored and developed for the new product andservice This requires a further round of QFD to identify thebest features that have the potential to deliver the critical toquality metrics During this phase there is a move from CTQ tocritical to process (CTP) metrics At the end of this stage aconcept or concepts together with a set of CTP metrics thatconstrain the formal and technical design will have beenproduced

Design (technical design) The team handovers the design brief for the design team to

complete using the CTP metrics Typical tools applied in thisphase include Design of Experiments (DoE) and statisticaloptimisation

prototyping and product or system testing approaches toenable fine-tuning of the design

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1.8 Design optimisation

Inevitably there are conflicts between the diversity of requirements driven by thestakeholders Optimisation can be viewed as the process of repetitively refining aset of often-conflicting criteria to achieve the best compromise In the case of a trans-portation system, size, manoeuvrability, cost, aesthetic appeal, ease of use, stability,safety and speed are not necessarily all in accordance with each other, for example(seeHall et al., 2012) Priorities can change within the lifetime of a product and varywithin markets and cultures Cost minimisation may call for compromises on materialusage and manufacturing methods These considerations form part of the optimisation

of the product producing the best or most acceptable compromise between the desiredcriteria

A traditional engineering design process often comprises a series of sequentialsteps, beginning with defined requirements or an opportunity and proceeding throughideation, synthesis, analysis and optimisation, to production This process can be con-trolled by a series of gate reviews (seeSection 1.9) in coordination with the stake-holders and the process can be iterative with phases being revisited when rework isrecognised as necessary This type of process can lead to bottlenecks in activityand a tendency to stick to a particular suboptimal solution as so much time and efforthas already been allocated to it

The range of optimisation tools used in design are reviewed byRoy et al (2008).MDO, for example, combines tools and approaches from a number of disciplines totackle the refinement of a set of parameters for a given problem area to deliver the bestcompromise between those parameters and has been widely applied in aerospaceapplications A key characteristic of MDO is that the solution is better than thatobtained by optimising each of the parameters sequentially The approach is resourceintensive in terms of computational power, however the Moore’s law enhancement ofprocessing means that this is not a hindrance to application of the approach Optimi-sation approaches and numerical strategies typically employed have included decom-position, approximation, evolutionary and mimetic algorithms, response surfacemethodologies, reliability and multiobjective The METUS methodology (METUS

2012), for example, has been used in Airbus development programmes to help provide

a holistic approach to product development, covering the phases of conception andoptimisation of product architecture, visualisation and integration of partners in thesupply chain A topological optimised cantilever is illustrated inFig 1.15

MDO can be considered to be a methodology for the design of an engineering tem that exploits the synergies between interacting parameters The principle of MDO

sys-is that it provides the collection of tools and methods that enables and permits thetrade-off between different disciplines inherent in design Proponents of MDO suggestthat this provides the justification for its application at an early stage in a productdevelopment programme (see, e.g.Sobieszczanski-Sobieski et al., 1984)

Ideally an MDO environment should permit the definition of the brief and fication constraints for all the various stakeholders (see, e.g.Kroll et al., 2009) This istypically achieved using a single parametric model for the whole system facilitating

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effective communication between the different stakeholders MDO offers the tial for the interactions between subsystems and systems to be explored from an earlystage in the design process by a number of stakeholders The purpose being to find theminima for the cost functions and reach an optimal solution for the holistic system.

poten-Fig 1.15 Cantilever beam optimisation case study: (A) Loading and boundary conditions, (B) vonMises Stress field on initial model and (C) Topological optimised model (Zhu et al., 2018)

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1.9 Project management

Project management is fundamentally concerned with getting significant activitiesachieved More formally, project management involves the application of processes,methods, knowledge, skills and experience to achieve predefined objectives A project

is generally a unique endeavour undertaken over a specific time period to achieve theplanned objective A project is usually deemed successful if it achieves the objectivesaccording to defined acceptance criteria relevant to the project, such as outputs, out-comes and benefits within an agreed timescale and budget.Fig 1.16illustrates thescope of a generic project at the core, and its links to time, quality and cost Invariablythese criteria are interlinked For example, it may be possible to deliver a projectsooner, but to the detriment of quality and cost

The core components of project management can include

l defining reasons why a project is necessary;

l capturing project requirements;

l specifying deliverables;

l estimating the resources required;

l defining timescales for each aspect of the project;

l preparing a business case to justify the investment for the project;

l securing organisational agreement and funding to commence;

l developing and implementing a management plan for the project;

l assembling the team and resources to implement the project;

l leading and motivating the project delivery team;

l managing the risks, issues and changes on the project;

l monitoring progress against plan and communicating progress to all relevant stakeholders;

l managing the project budget;

l maintaining communications with internal and external stakeholders;

l provider management (ensuring that contractors and suppliers deliver according to ments and managing these relationships);

require-l closing the project in a controlled fashion when the project has been completed or run itscourse

Projects tend to be distinct from business-as-usual activities, requiring a team to worktogether temporarily, to focus on a specific project or subtask within a project and its

Fig 1.16 The interrelationship between the scope of a project and time, quality and cost

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objectives (Association for Project Management 2017) Teamwork is often an tial component of project management with the need to leverage diverse resources toachieve the intended outcomes A common approach to tackling a significant chal-lenge is to subdivide it into a number or subtasks In project management these subtasks are often referred to as a work-package Each work-package may itself bedivided up into a number of discrete chunks of work The way an overall challenge

essen-is broken down will depend on factors such as scale, complexity, function and icance of the activity Designing a passenger aircraft, jet engine or new vehicle rep-resents a difference in scale of activity to designing a bearing housing, disc brake ordoor lock Both classes of examples may involve the application of similar principles,but represent different levels of risk and require significantly different levels ofresource

signif-It can be helpful to express objectives in terms of outputs, outcomes, benefits orstrategic aims For example, an output could be that a new clutch will be produced,

an outcome could be less staff required to manufacture a batch of clutches, a benefitcould be enhanced reliability and a strategic objective could be entrance into a newmarket sector

A wide range of approaches for project management have been codified including

l The traditional approach;

con-Project management typically occurs under the auspices of a project manager Theposition, responsibilities and contribution of a project manager can vary widely fromorganisation to organisation It can range from monitoring the performance of others,

to controlling their performance, to having the overall technical and operationalresponsibility for a complete activity, or project, or business Project managersmay be extra to the present teams, or an existing member may be given this additionaltask In general the project manager will be the reporting link to the person in charge ofthe complete project, but being just the reporter is a minimal responsibility, as thiscarries no authority for the information being passed To make project management

a worthwhile position, there must be some element of control, even if this is the result

of planning of the various activities as part of a critical path analysis (CPA) Just ning the work must not be mistaken for control

plan-A project manager can be the prime contact with the client, with suppliers and contractors The project manager is in a position of considerable responsibility, withthe ability to commit significant amounts of expenditure on behalf of the company

sub-A full understanding of the specification is essential sub-Any doubts must be resolved

at a very early stage of the project Even if the project manager does not have direct

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control of the people on the project, the expectation is still to deliver on time Theproject manager is the project champion and will be expected to promote the projectwith the company management in order to optimise the project performance.Fig 1.17shows the links that are essential for any project manager.

In a real world scenario, a project manager may be faced with the followingsituations:

l the specification is incomplete and ambiguous;

l the required resources are not available;

l the design is not correct first time;

l the production unit has made scrap;

l the supplies are late;

l the customer has changed his mind;

l the changes were not negotiated correctly due to a lack of understanding

The project manager has to maintain his reputation throughout such scenarios and uations, and still convince all concerned that his or her requests are credible andimportant

sit-1.9.1 The traditional approach

The traditional approach to project management uses a set of well-established niques and tools to deliver a product, service or outcome These techniques andtools arise from substantial experience and involve establishing the objectives of aproject, gathering information, leveraging resources, focussing on outcomes, esta-blishing a schedule, consideration of risks and their mitigation, reviews and good

Subcontractors Suppliers

Project

t c e

a n a

M

Fig 1.17 Some essential links between a project manager and stakeholders for the project

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communication, to ensure progress and delivery within time and budget constraintsand to the required level of quality.

It is important to ensure the project objectives and desired outcomes are defined atthe outset Knowledge of these can help motivate team members and guide activitytowards these goals The following steps represent well-established principles thatcan aid in establishing a project’s rationale and buy-in to it from the various stake-holders involved

l Identify the key stakeholders that you are performing the project for The key stakeholderswill invariably be represented by individuals in the organisations involved and are some-times referred to as project drivers The project drivers have authority to define the projectobjectives and desired outcomes

l Collect information and documentation that supports the project’s justification This caninclude the strategic plan for the organisation, annual reviews, aspects of a company missionand vision statements, any key point indicators (KPIs) for the organisation that relate to theproject

l Pay attention to meeting etiquette Planning and preparing for a meeting is important to getvalue from the time and effort that everyone will be putting in Ensure a meeting has clearpurpose and focus such as to address a problem, explore ideas, motivate personnel or to com-mence a new initiative An agenda is important This can be a simple list of items to considerwith an approximate time allocation for each item Attention should be given to the order ofitems to help the meeting make sense to the participants and aid the flow of ideas and deci-sions Ensure that the relevant people are present as this will help leverage the help needed inachieving goals and carrying out tasks A number of people can aid the dynamics of themeeting—by including relevant officers this can help in achieving goals, sharing dutiesand motivation Experience suggests that if 5–10 people are in a meeting taking

30–60min then all parties are likely to contribute in some way If the number is higher, then

it is unlikely that everyone will be able to speak, but it may still be necessary to engage thevarious stakeholders and help with the flow of information In meetings ensure notes aretaken and circulated afterwards to the relevant parties and filed In one-to-one meetings con-firm any salient points and decisions in writing to provide a written record that can bescrutinised later if required For informal meetings when speaking about important matters,

do so with at least three people present so that any decisions can be corroborated

l Focus on outcomes, not activities SMART objectives can be helpful in focusing attention ondefined outcomes SMART is an acronym for specific or strategic, measurable, achievable,relevant, time-bound and trackable (Doran 1981)

l Use clear language, so that objectives are not ambiguous and that information and tions can be understood

instruc-l Ensure each objective has at least one measure that relates to a specific performance target

As indicated previously the classic success criteria for a project are delivery on time,

to cost and to the expected quality level To deliver a project on time the traditionalapproach involves significant attention to scheduling and definition of resources Ingeneral a schedule needs to be achievable, responsive to changes and understandable

by the team involved The following steps can be helpful in establishing a schedule

l Identify the activities required for the project

l Break down each of the activities into subtasks with sufficient detail so that if each of thetasks is understandable and completing the tasks looks plausible

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l Consider both the duration of time required to complete an activity as well as the order inwhich the activities need to be performed (these are known as the interdependencies).

l Consider what strategies might be appropriate to perform an activity and the resourcesrequired This can assist in helping to define how long an activity will take

l Consider the availability of each resource required For example if a machining operationmust be done on a particular piece of equipment and the organisation only has one of these,then the limited capacity needs to be accounted for in defining the duration required for themachining operations concerned Some alternative strategies could be considered such asacquiring additional machines, running multiple shifts or outsourcing the manufacture oper-ations, subject to budget and quality considerations

l Consider what budget needs to be allocated to achieve a task Document the assumptionsassociated with this

l Consider the risks associated with each task For each risk, consider and develop a plan thatmitigates against the risk (seeTables1.3and1.4)

l Set out a draft schedule Review this, considering whether each task has sufficient resource

to achieve the task within the time defined Estimate the costs for the resource allocated.Redefine the schedule, iterating the overall plan to see if a more plausible and realisable plan

is possible One of the most popular methods of laying out the activities associated with aschedule is to use a Gantt chart Examples of information associated with these are given inFigs 1.18and1.19 Typically a Gantt chart will comprise a list of activities on the left and a

Table 1.3 Generic risk assessment table

to 10% ofscheduleAdditionalcost up to10% ofbudget

ModerateDelays up

MajorDelays up

CatastrophicProjectabandoned

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Table 1.4 Risk assessment example for a wheeled robot

or all of theprojectdeliverables

if the causehappens?

Whatis(are) thepossiblecause(s) of

Whataction(s)will youtake, and bywhen, toprevent,reduce theimpact ortransfer therisk of thisoccurring?

Who isresponsibleforfollowingthrough onmitigation?

failure

If the robot istoo fast, wewill not beable to brakeadequately

Potentialdanger

Possibleinjury topeople

Damage toobjects

speed ofrobot;

optimiserobot speed

Hardwarespecialist

sensors

Collisionwith a person

or object

Robotmalfunction

or operatorerror causesdamage tosensors

code isoperatingproperly

Specifyback-upsensors

Softwarespecialist

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Possible thatfinaldestinationnot reached

RFIDpositioningfailure

RFID signalnot strongenough

Wheelencoderfailure

encoders arefunctioning

Test signalstrength forRFID

Hardwarespecialist

failure

Robot doesnot move

Need torechargebattery

Chargecycle

batteryrechargingprior to 30%

batterychargeremaining

Project lead

completeproject

Poorplanning

resourcerequirementplanning

Project lead

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timescale along the top row Each activity can be represented by a bar indicating when itshould start and end, along with additional information such as who is involved and respon-sible for the task and an indication of what proportion of the task has been completed Thereare many templates readily available for Gantt charts along with software platforms to aidproject management.

l Once you are confident with the schedule, engage some of the project drivers in reviewingthe plan and aim towards getting project buy-in

Most projects require effort from many different people and facilitating effective fessional relationships can aid in realising successful outcomes The following generalprinciples can help foster high levels of effective professional relationships betweenteam members and stakeholders: clarify project objectives with the team; ensure thebenefits for the organisation and team members are understood; engage team members

pro-in helppro-ing to form the project plan; ensure you address any issues, concerns and tions promptly; communicate regularly within the team on issues and progress;acknowledge the contributions being made by members of the team A key facet ofproject management is responsibility If an individual accepts responsibility then indoing so they will also be taking on a level of accountability for their performance.This link between responsibility and accountability is helpful in transcending some

ques-of the traditional line management and hierarchical relationships in an organisation.For example someone more senior may accept responsibility for a task and are then byimplication responsible for that task and can be held to account for it

Good communication with all concerned is essential, including, for example,manufacturing and commercial departments, to ensure that the specification is stillbeing met in all respects, including the costs of design and manufacture Good com-munication at the specification stage ensures ‘ownership’ of decisions A desire orneed to change the design from the specification must be agreed, particularly bythe marketing department as it may affect the viability of the product in the market-place It cannot be assumed that the design team knows the capability of themanufacturing unit, or that the factory will understand, as intended, the information,which they receive from the designers A balance must be found between perfor-mance, availability and cost This decision must be taken at an early stage sincethe whole philosophy of the design is affected by these choices, which again dependupon the needs of the actual or potential customers

The following 12 point list provides a set of steps that can aid the planning processfor management of a project (Leach 1999)

1 Requirements capture and flow-down

2 Define the deliverables

Task No Person responsible Mar-19 Apr-19 May-19 Jun-19 Jul-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Task 1 PRNC

Fig 1.18 Generic project management Gantt chart

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ID Task Duration (days) Start End Predecessors 5/14/2018 5/15/2018 5/16/2018 5/17/2018 5/18/2018 5/21/2018 5/22/2018 5/23/2018 5/24/2018 5/25/2018 5/28/2018 5/29/2018 5/30/2018 5/31/2018 6/1/2018 6/4/2018 6/5/2018 6/6/2018 6/7/2018 6/8/2018 6/11/2018 6/12/2018 6/13/2018 6/14/2018 6/15/2018

Milestone Activity Activity

Fig 1.19 Example of a Gantt chart for a 100 kW commercial PV installation

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3 Create the work breakdown structure.

4 Define the performance measures

5 Identify and assess the risks

6 Define the activities

7 Identify the key dependencies

8 Define the milestones

9 Produce the schedule

10 Estimate resource and cost requirements

11 Assemble the plan, review this and revise it to help ensure it meets the requirements, and isachievable within the resources and time frame available

12 Obtain commitment acceptance

1.9.2 PRINCE and PRINCE2

A wide range of commercial project management tools and supporting software hasbeen developed PRINCE is an acronym for Projects In Controlled Environments.PRINCE2 was released in 1996 as a generic project management method, aimed athelping users to organise, manage and direct projects on time and to budget The meth-odology can be tailored according to the scope and scale of a project

A key principle of PRINCE is to gather information quickly at the start, to establishwhether a project is worth the investment of time and effort in planning in detail, and

to provide source data for subsequent planning if the decision is made to take it ward Some of the key elements of this initial phase include the following

for-l Gather information quickly

l The aim at the end of this phase is whether you are to progress to the next stage of full ning (known as initiation)

plan-l Assign key roles such as project executive and project manager

l Produce a project brief (seeChapter 2)

l Check whether the outline business case appears viable

l Check whether the risks appear acceptable based on the information available at this stage

l Set out a plan for the initiation stage that allows for more detailed consideration of risks andthe business plan

An important consideration in project management is the balance between planningand need for control As mentioned previously there can be a trade-off between cost,timeliness and quality Deciding the level of quality that is appropriate is an importantcriteria Following initiation, key items of PRINCE are to

l Produce product and activity plans for the project

l Produce product and activity plans for the first phases after initiation

l Undertake a full risk analysis

l Produce a full business case for the project

l Implement simple controls and reporting procedures for the project

l Assemble the Project Initiation Document (PID) This provides a foundation for the projectand aims to help all the stakeholders understand why they are doing the project Commonitems to cover in a PID include information on why the project is being undertaken, what is to

be delivered, who is responsible, how and when the project will be delivered, what are therisks, whether there are any issues and constraints, how much it will cost

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l Set up a project board The membership for this will vary depending on the nature of theproject but it will typically comprise high-level stakeholders and advisors.

Project management concerns effective delivery rather than being seen to be busy

A key focus in PRINCE is checking progress against the Product Checklist, the list

of tasks, and the quality of the outcome Decisions need to be taken regularly aboutwhether tasks are on track or whether an exception needs to be made An exception

is a piece of project management terminology for addressing a project plan issue Anexception plan can be made and then implemented to recover from a deviation caused

by a task taking longer, costing more or quality being below that required Exceptionsneed rapid and careful investigation It will be necessary to try and find out the under-lying reason for the exception, and to take a decision on whether to carry on, to develop anew plan or to stop the project Key to progress of any plan is to leverage the resourcesavailable so it is important to allocate work within the team and to monitor progress.Progress can be reported regularly and at set intervals to the Project Board using a high-light report function If there are any exceptions that cannot be met then these need to bereported to the Project Board at the earliest possible moment, to alert the Board membersand to see what measures need to be taken to address the situation

1.9.3 Waterfall

The central philosophy for the waterfall model is that time and effort is spent ensuringthe requirements and design are suitable at the start of the project, saving time, effortand resources later The waterfall model (Fig 1.20) has a significant heritage withabout 60 years of practice, particularly in software applications, systems integration,large engineering and government contracts

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The waterfall model is a sequential design process In the waterfall model, eachphase must be completed before the next phase can begin and there is no overlapping

of the phases Progress flows steadily downwards, like a waterfall, through phases ofconception, initiation, analysis, design, construction, testing, production/implementa-tion and maintenance

Various versions of the waterfall model have been developed.Royce (1970)givesthe following phases which are followed in order:

1 System and software requirements: captured in a product requirements document

2 Analysis: resulting in models, schema and business rules

3 Design: resulting in the software architecture

4 Coding: the development, proving and integration of software

5 Testing: the systematic discovery and debugging of defects

6 Operations: the installation, migration, support, and maintenance of complete systems

An alternative set of phases for waterfall project model includes the following stages:

l Definition and requirements analysis stage;

l Design stage;

l Development, implementation and production stage;

l Integration and test stage;

l Factory Acceptance Test

The waterfall model maintains that a team should move to the next phase only whenthe preceding phase has been reviewed and verified The sequential phases in a Water-fall model are outlined inTable 1.5

Table 1.5 Outline description of the phases associated with a typical waterfall project

Requirement gathering

and analysis

All possible requirements of the system to be developed arecaptured and documented in a requirement specificationsdocument

System design The requirement specifications from the first phase are studied

and the system design prepared System design helps inspecifying hardware and system requirements and also indefining overall system architecture

Implementation With inputs from the system design, the system is developed in

small programmes called units, which are integrated in the nextphase Each unit is developed and tested for its functionalitywhich is referred to as unit testing

Integration and testing All the units developed in the implementation phase are

integrated into a system after testing of each unit Postintegration the entire system is tested for any faults and failures.Maintenance There may be issues which arise in the client environment To

fix these issues patches can be released To enhance the productbetter versions can be released Maintenance is undertaken todeliver these changes in the customer environment

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