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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
A revised text that presents specific design methods within an overall strategy from concept to detail design
The fifth edition of Engineering Design Methods is an improved and updated version of this very successful, classic text on engineering product design. It provides an overview of design activities and processes, detailed descriptions and examples of how to use key design methods, and outlines design project strategies and management techniques. Written by a noted expert on the topic, the new edition contains an enriched variety of examples and case studies, and up to date material on design thinking and the development of design expertise.
This new edition opens with a compelling original case study of a revolutionary new city-car design by ex-Formula One designer Gordon Murray. The study illustrates the complete development of a novel design and brings to life the process of design, from concept through to prototype. The core of the book presents detailed instructions and examples for using design methods throughout the design process, ranging from identifying new product opportunities, through establishing functions and setting requirements, to generating, evaluating and improving alternative designs. This important book:
- Offers a revised and updated edition of an established, successful text on understanding the design process and using design methods
- Includes new material on design thinking and design ability and new examples of the use of design methods
- Presents clear, detailed and illustrated presentations of eight key design methods in engineering product design
Written for undergraduates and postgraduates across all fields of engineering and product design, the fifth edition of Engineering Design Methods offers an updated, substantial, and reliable text on product design and innovation.
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Veröffentlichungsjahr: 2021
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Table of Contents
Cover
Title Page
Copyright
Introduction
Part One: Design Fundamentals
1
The Activity of Design
What Designers Say
What Designers Do
Case Study
2
The Nature of Design
Design Problems
Problem Structures
How Designers Problem‐Solve
3
The Process of Design
Descriptive Models
Prescriptive Models
Integrative Models
Part Two: Design Practice
4
Design Procedures
Systematic Procedures
Design Methods
Creative Methods
Rational Methods
5
Identifying Opportunities
The User Scenarios Method
Summary
Examples
6
Clarifying Objectives
The Objectives Tree Method
Summary
Examples
7
Establishing Functions
The Function Analysis Method
Summary
Examples
8
Setting Requirements
The Performance Specification Method
Summary
Examples
9
Determining Characteristics
The Quality Function Deployment Method
Summary
Examples
10
Generating Alternatives
The Morphological Chart Method
Summary
Examples
11
Evaluating Alternatives
The Weighted Objectives Method
Summary
Examples
12
Improving Details
The Value Engineering Method
Summary
Examples
Part Three: Design Thinking
13
Design Strategies
What is a Design Strategy?
Strategy Frameworks
Strategy Control
Learning to Design
Developing Expertise
14
Design and Innovation
Product Planning
Systems Design
References and Sources
Index
End User License Agreement
List of Tables
Chapter 11
Table 11.1 Comparison of 11‐point and 5‐point evaluation scales
Chapter 12
Table 12.1 Components, functions and perceived values for a handtorch redesig...
List of Illustrations
Chapter 1
Figure 1.1 Very early idea sketches for a new city car. Source: Gordon Murra...
Figure 1.2 First concept sketches for the T.25 city car. Source: Gordon Murr...
Figure 1.3 A wire and cardboard early‐stage mock‐up. Source: Gordon Murray; ...
Figure 1.4 Part of a composite detail drawing of components in the T.25 prot...
Figure 1.5 The first prototype on‐the‐road version of the T.25. Source: Gord...
Chapter 2
Figure 2.1 Problem structure found in a housing design problem.
Figure 2.2 Decision tree derived from the design of a device for carrying a ...
Figure 2.3 Sketch design studies for town fortifications by Leonardo da Vinc...
Figure 2.4 Contemporary architect's sketch design drawings for a small house...
Chapter 3
Figure 3.1 A simple four‐stage model of the design process.
Figure 3.2 French's model of the design process. Source: French, ...
Figure 3.3 Conceptual design: alternatives for the drive connection in a sma...
Figure 3.4 Embodiment design: one concept developed in more detail. Source: ...
Figure 3.5 Detail design: redesign of a mounting plate to resist vibration. ...
Figure 3.6 Archer's model of the design process. Souce: Archer, Systematic M...
Figure 3.7 Archer's three‐phase summary model of the design process. Souce: ...
Figure 3.8 Pahl and Beitz's model of the design process. Source: Pahl and Be...
Figure 3.9 The VDI 2221 model of development from problem to solution.
Figure 3.10 March's model of the design process. Source: March, The Architec...
Figure 3.11 A co‐evolutionary model of how interpretations of the problem an...
Figure 3.12 The symmetrical relationships of problem/sub‐problems/sub‐soluti...
Chapter 4
Figure 4.1 A OneSeal single‐use container lock. Source: OneSeal
Figure 4.2 A Translift Benditruck forklift truck. Source: Translift
Figure 4.3 Eight stages of the design process positioned within the symmetri...
Chapter 5
Figure 5.1 Design sketches for the user‐centred redesign of a sewing machine...
Figure 5.2 Scenarios for digital radio use by a shift worker. Source: Myerso...
Chapter 6
Figure 6.1 Hierarchical diagram of relationships between objectives.
Figure 6.2 Expanded set of objectives for a new city transport system. Sourc...
Figure 6.3 An objectives tree for an impulse‐loading test rig. Source: Pahl ...
Figure 6.4 A functions‐means tree for an automatic teamaker. Source: Tjalve,...
Figure 6.5 Objectives tree for a surgical shoe. Source: Atike & Kaufman, 4th...
Figure 6.6 Concept drawing for the surgical shoe. Source: Atike & Kaufman, 4...
Figure 6.7 Objectives tree for a pump.
Figure 6.8 Grundfos pumps designed on similar principles to the objectives d...
Chapter 7
Figure 7.1 The ‘black box’ systems model.
Figure 7.2 A ‘transparent box’ model.
Figure 7.3 The existing method of filling, storing and dispatching bags of a...
Figure 7.4 Alternative formulations of the feed distribution problem. Source...
Figure 7.5 Analysis of principal functions for the packing of carpet squares...
Figure 7.6 Expanded function analysis for the packing of carpet squares. Sou...
Figure 7.7 Function analysis for an inkjet printer. Source: Otto & Wood, Pro...
Figure 7.8 Function analysis for a fuel gauge. Source: Pahl & Beitz, Enginee...
Figure 7.9 Black box model of a washing machine.
Figure 7.10 Function analysis of the washing machine.
Chapter 8
Figure 8.1 Specification for a one‐handed mixing tap. Source: Pahl & Beitz, ...
Figure 8.2 Specification for a seat suspension mechanism. Source: Hurst, Eng...
Figure 8.3 Performance specification for an electric toothbrush. Source: Lov...
Figure 8.4 Partial performance specification for a pill dispenser. Source: D...
Chapter 9
Figure 9.1 Example of beginning a partial interaction matrix for a motorcar ...
Figure 9.2 Interaction matrix of requirements for the bicycle splashguard. S...
Figure 9.3 House of quality for the design of a cordless drill. Source: Rama...
Figure 9.4 The network of physical properties influencing the engineering ch...
Figure 9.5 House of quality (partial) for the car door. Source: Hauser & Cla...
Figure 9.6 House of quality for a domestic fan heater.
Chapter 10
Figure 10.1 Morphological chart for a potato harvesting machine. The shaded ...
Figure 10.2 Morphological chart for a welding positioner, with one possible ...
Figure 10.3 Four possible combinations for the welding positioner worked up ...
Figure 10.4 Morphological chart for an indoor plant pot that assists the use...
Figure 10.5 Concept sketch for a plant pot based on the sub‐solutions marked...
Figure 10.6 Morphological analysis of a field maintenance machine. Source: T...
Figure 10.7 Design sketch for one preferred option derived from the morpholo...
Figure 10.8 A morphological chart for forklift trucks.
Figure 10.9 One selected combination of sub‐solutions from the morphological...
Chapter 11
Figure 11.1 Use of an objectives tree for assigning relative weights to sub‐...
Figure 11.2 Evaluation requirements for a van rain shield. Source: Axebourn,...
Figure 11.3 Three best concepts for the van rain shield.
Figure 11.4 Evaluation matrix for the van rain shield. Source: Axebourn, Gou...
Figure 11.5 Evaluation chart for alternative concepts for the bicycle splash...
Figure 11.6 Evaluation chart for alternative concepts for the pill dispenser...
Figure 11.7 A working prototype for further evaluation of the chosen pill di...
Figure 11.8 A comparison chart of three concepts for an emergency urban toil...
Figure 11.9 Initial evaluation chart for seven alternative concepts for a re...
Figure 11.10 Final evaluation chart for selected, combined and refined conce...
Figure 11.11 (a) Original sketches for syringe design concepts D and F; (b) ...
Chapter 12
Figure 12.1 Function/cost analysis of the tubular heater. Source: The Open U...
Figure 12.2 Proposals for redesign of the tube interconnector. Source: The O...
Figure 12.3 Proposals for redesign of the terminal cover assembly. Source: T...
Figure 12.4 Value analysis of an air conditioning ceiling diffuser. Source: ...
Figure 12.5 Redesign of a piston assembly to reduce the number of components...
Figure 12.6 Recommended design changes from a value analysis of a ceiling fa...
Figure 12.7 Exploded diagram of a handtorch.
Figure 12.8 The Durabeam handtorch. Source: Duracell
Chapter 13
Figure 13.1 The overall design process is convergent, but it includes period...
Figure 13.2 Typical design process timeline plots. Above: a student designer...
Figure 13.3 Timeline patterns exhibited by one student on two different prob...
Chapter 14
Figure 14.1 The roles of producer, consumer and designer.
Figure 14.2 A market analysis diagram for an emergency urban toilet. Source:...
Figure 14.3 The final concept and components of the toilet for urban emergen...
Figure 14.4 Matrix of opportunity areas for product planning.
Guide
Cover Page
Title Page
Copyright
Introduction
Table of Contents
Begin Reading
References and Sources
Index
WILEY END USER LICENSE AGREEMENT
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Engineering Design Methods
Strategies for Product Design
FIFTH EDITION
Nigel Cross
This edition first published 2021
© 2021 John Wiley & Sons Ltd
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Introduction
This book offers a strategic approach and a number of tactics as aids for designing new products. It is intended primarily for use by students and teachers of engineering design and industrial design. Its main emphasis is on the design of products that have an engineering content, although most of the principles and approaches that it teaches are relevant to the design of all kinds of products. It is essentially concerned with problem formulation and the conceptual and embodiment stages of design, rather than the detail design which is the concern of most engineering texts. The book can most effectively be used in conjunction with projects and exercises that require the formulation and clarification of design problems and the generation and evaluation of design solutions. It is much more than a manual of procedures: throughout, there is discussion and explication of the principles and practice of design.
This fifth edition of the book is an improved, revised and updated version. Chapter 1 has been enhanced with a case study of a new city car design, illustrating the complete process of design from early idea sketches through to detail design and prototyping. A new concluding chapter on Design Thinking presents up to date material on innovation and systems design. Elsewhere in the methods chapters (Chapters 5–12), new examples of the application of design methods in practice have been introduced.
The contents of the book divide into three parts. Part One, Design Fundamentals, provides an overview of what goes on in designing, the nature of design problems, and models of the design process. Chapter 1 introduces the kinds of activities that designers normally undertake, illustrated with the case study of the design of an innovative, economical city car. Chapter 2 discusses the particular nature and structure of design problems, and designers’ approaches to them. Chapter 3 reviews several of the models of the design process that have been developed in order to help designers structure their approach to designing, and suggests a new hybrid, integrative model that combines both the procedural and the structural aspects of the nature of design.
Part Two, Design Practice, explains the details of how to design, at various stages of the design process. Chapter 4 reviews the field of design methods, describes a number of methods that help to stimulate creative design thinking, and introduces the rational methods that are presented in the following chapters. Chapters 5–12 constitute a manual of design methods, presented in an independent‐learning format, i.e. students can be expected to learn the principle features of the methods directly from the book. These eight chapters follow a typical procedural sequence for the design process, providing instruction in the use of appropriate methods within this procedure. Each chapter presents a separate method, in a standard format of a step‐by‐step procedure, a summary of the steps, and a mixed set of practical examples concluding with a fully worked example. The eight methods included are:
user scenarios
objectives tree
function analysis
performance specification
quality function deployment
morphological chart
weighted objectives
value engineering
Chapter 13 outlines a strategic approach to the design process, utilising the most appropriate combination of creative and rational methods to suit the designer and the design project. The emphasis is on a flexible design response to problems and on ensuring a successful outcome in terms of good product design, and concludes with some insights into the process of learning to design and developing expertise in design.
In Part Three, Design Thinking, Chapter 14 introduces the current conception of design thinking, putting the role of design into a wider perspective of new product development and innovation and discussing the application of design thinking in strategic product planning and broader systems design.
Overall, the book embodies a concept of design that combines and extends the two traditional fields of engineering design and industrial design into a more comprehensive field of engineering product design. Although intended primarily for students of product design ‐ whether their courses are biased more towards engineering or industrial design ‐ the book is also useful as an introduction to design for the many teachers and practitioners in engineering who may have found this subject sadly lacking in their own education.
Part OneDesign Fundamentals
1The Activity of Design
What Designers Say
Design is all around us, and the wish to design things is inherent in human beings. One of the most basic characteristics of human beings is that they make a wide range of tools and other artefacts to suit their own purposes. As those purposes change, and as people reflect on the currently‐available artefacts, so refinements are made to the artefacts, and sometimes completely new kinds of artefacts are conceived and made. The world is therefore full of tools, utensils, machines, buildings, furniture, clothes, and many other things that human beings apparently need or want in order to make their lives better. Everything that isn't a simple, untouched piece of Nature has been designed by someone.
In pre‐industrial societies, craftspeople made things according to long‐established traditions, following the patterns transmitted through apprenticeship. It was during the emergence and growth of industrial societies, with the shift from craftwork to manufacturing, that designing became regarded as a different kind of occupation. Although there is now so much designing going on in the world, how people perform this activity of design was rather poorly understood for a very long time. An ability in design has been regarded as something that many, probably most, people possess to some degree, but only a few people have a particular design ‘talent’. However, through decades of design research, there is now an established and growing body of knowledge about design activity and how to conduct it, about the design process and how to improve it, and about design ability and how to develop it.
When designers are asked to explain how they work, and to discuss their abilities, a few common themes emerge. One theme is the importance of creativity and ‘intuition’ in design – even in engineering design. For example, the engineering designer Jack Howe has said:
I believe in intuition. I think that's the difference between a designer and an engineer… I make a distinction between engineers and engineering designers… An engineering designer is just as creative as any other sort of designer.
Some rather similar comments have been made by the industrial designer Richard Stevens:
A lot of engineering design is intuitive, based on subjective thinking. But an engineer is unhappy doing this. An engineer wants to test; test and measure. He's been brought up this way and he's unhappy if he can't prove something. Whereas an industrial designer… is entirely happy making judgements that are intuitive.
Another theme that emerges from what designers say about their abilities is based on the recognition that problems and solutions in design are closely interwoven; that ‘the solution’ isn't always a straightforward answer to ‘the problem’. For example, the furniture designer Geoffrey Harcourt commented on one of his creative designs like this:
As a matter of fact, the solution that I came up with wasn't a solution to the problem at all. I never saw it as that… But when the chair was actually put together (it) in a way quite well solved the problem, but from a completely different angle, a completely different point of view.
A third common theme to emerge is the need to use sketches, drawings or models of various kinds as a way to explore the problem and solution together. The conceptual thinking processes of the designer seem to be based on the development of ideas through their external expression in sketches. As the engineer‐architect Santiago Calatrava said:
To start with you see the thing in your mind and it doesn't exist on paper and then you start making simple sketches and organising things and then you start doing layer after layer… it is very much a dialogue.
This ‘dialogue’ occurs through the designer's perception of the sketched concepts, and reflection on the ideas that they represent and their implications for the resolution of the problem. The designer responds to the perceptions, reflections and implications, and so the ‘dialogue’ between internal mental processes and external representations continues.
The quotations above are taken from interviews conducted with successful and eminent designers by design researchers Robert Davies and Bryan Lawson. The designers’ comments support some of the hypotheses that have emerged from more objective observational studies of designers at work, and other research that has been conducted into the nature of design. Some of this research reflects and supports the view that designers have particular, ‘designerly’ ways of thinking and working.
What Designers Do
People have always made things. In traditional, craft‐based societies the ‘designing’ of artefacts is not really separate from making them; that is to say, there is usually no prior activity of drawing or modelling before the activity of making the artefact. For example, a potter will make a pot by working directly with the clay, and without first making any sketches or drawings of the pot. In modern, industrial societies, however, the activities of designing and of making artefacts are usually quite separate. The process of manufacturing something cannot normally start before the process of designing it is complete. In some cases, for example in the electronics industry, the period of designing may take many months, whereas the average period of making each individual artefact might be measured only in hours or minutes.
Perhaps a way towards understanding design is to begin at the end; to work backwards from the point where designing is finished and making can start. If making cannot start before designing is finished, then at least it is clear what the design process has to achieve. It has to provide a description of the artefact that is to be made. In this description, almost nothing is left to the discretion of those involved in the process of making the artefact; it is specified down to the most detailed dimensions, to the kinds of surface finishes, to the materials, their colours, and so on.
In a sense, perhaps it does not matter how the designer works, so long as he or she produces that final description of the proposed artefact. When a client asks a designer for ‘a design’, that is what they want: the description. The focus of all design activities is that end‐point.
Communication of designs
The most essential design activity, therefore, is the production of a final description of the artefact. This has to be in a form that is understandable to those who will make the artefact. The most widely‐used form of communication is drawing. For a simple artefact, such as a door‐handle, one drawing would probably be enough, but for a larger, more complicated artefact such as a whole building the number of drawings may well run into hundreds, and for the most complex artefacts, such as aeroplanes or major bridges, then thousands of drawings will be necessary.
These drawings will range from rather general descriptions, such as plans, elevations, and general arrangement drawings, that give an ‘overview’ of the artefact, to the most specific, such as sections and details, that give precise instructions on how the artefact is to be made. The drawings will often contain annotations of additional information. Dimensions are one such kind of annotation. Written instructions may also be added to the drawings, such as notes on the materials to be used.
Because they have to communicate precise instructions, with minimal likelihood of misunderstanding, all the drawings are themselves subject to agreed rules, codes and conventions. These codes cover aspects such as how to lay out on one drawing the different views of an artefact relative to each other, how to indicate different kinds of materials, and how to specify dimensions. Learning to read and to make these drawings is an important part of design education.
Other kinds of specifications as well as drawings may also be required. For example, the designer is often required to produce lists of all the separate components and parts that will make up the complete artefact, and an accurate count of the numbers of each component to be used. However, there is no doubt that drawings are the most ubiquitous form of communicating the description of an artefact that has yet to be made. Drawings are very good at conveying an understanding of what the final artefact has to be like, and that understanding is essential to the person who has to make the artefact.
It is not always a person who makes the artefact; some artefacts are made by machines that have no direct human operator. These machines might be fairly sophisticated robots, or just simple, numerically‐controlled tools such as lathes or milling machines. In these cases, therefore, the final specification of a design prior to manufacture might not be in the form of drawings but in the form of a string of digits stored on a disk or memory stick, to be used in computer software that controls the machine's actions. It is therefore possible to have a design process in which no final communication drawings are made, but the ultimate purpose of the design process remains: the communication of a proposal for a new artefact.
Evaluation of designs
For the foreseeable future, drawings of various kinds will still be used throughout the design process. Even if the final description is to be in the form of a string of digits, the designer will probably want to make drawings for other purposes.
One of the most important of these other purposes is the checking, or evaluating, of design proposals before deciding on a final version for manufacture. The whole point of having the process of design separated from the process of making is that proposals for new artefacts can be checked before they are put into production. At its simplest, the checking procedure might merely be concerned with, say, ensuring that different components will fit together in the final design; this is an attempt to foresee possible errors and to ensure that the final design is workable. More complicated checking procedures might be concerned with, say, analysing the forces in a proposed design to ensure that each component is designed to withstand the loads on it; this involves a process of refining a design to meet certain criteria and constraints such as minimum strength, or maximum weight or cost.
This process of refinement can be very complicated and can be the most time‐consuming part of the design process. Imagine, for example, the design of a bridge. The designer must first propose the form of the bridge and the materials of which it will be made. In order to check that the bridge is going to be strong enough and stiff enough for the loads that it will carry, the designer must analyse the structure to determine the ways in which loads will be carried by it, what those loads will be in each member of the structure, what deflections will occur under load, and so on. After a first analysis, the designer might realise, or at least, suspect, that changing the locations or angles of some members in the bridge will provide a more efficient distribution of loadings throughout the whole structure. But these changes will mean that the whole structure will have to be re‐analysed and the loads recalculated.
In this kind of situation, it can be easy for the designer to become trapped in an iterative loop of decision‐making, where improvements in one part of the design lead to adjustments in another part which lead to problems in yet another part. These problems may mean that the earlier ‘improvement’ is not feasible. This iteration is a common feature of designing.
Nevertheless, despite these potential frustrations, this process of refinement is a key part of designing. It consists, firstly, of analysing a proposed design, and for this the designer needs to apply a range of engineering science or other knowledge. In many cases, specialists with more expert knowledge are called in to carry out these analyses. Then, secondly, the results of the analysis are evaluated against the design constraints and criteria: does the design come within the cost limit, does it have enough space within it, does it use too much fuel, and so on.
Many of the analyses are numerical calculations, and therefore again it is possible that drawings might not be necessary. However, specialists who are called in to analyse certain aspects of the design will almost certainly want a drawing, or other model of the design, before they can start work. Visualisations of the proposed design may also be important for the client and designer to evaluate aspects such as appearance, form and colour. Sometimes the designer makes a complete, three‐dimensional mock‐up or prototype in order to evaluate and communicate the design.
Generation of designs
Before any of these analyses and evaluations can be carried out the designer must, of course, first generate a design proposal. This is often regarded as the mysterious, creative part of designing; the commissioning client makes what might well be a very brief statement of requirements, and the designer responds (after a suitable period of time) with a design proposal, as if conjured from nowhere. In reality, the process is less ‘magical’ than it appears.
In most cases, for instance, the designer is asked to design something similar to that which he or she has designed before, and therefore there is a stock of previous design ideas on which to draw. In some cases, only minor modifications are required to a previous design.
Nevertheless, there is something mysterious about the human ability to propose a design for a new, or even just a modified, artefact. It is perhaps as mysterious as the human ability to speak a new sentence, whether it is completely new, or just a modification of one heard, read, or spoken before.
This ability to design depends partly on being able to visualise something internally, in ‘the mind's eye’, but perhaps it depends even more on being able to make external visualisations. Once again, drawings are a key feature of the design process. At this early stage of the process, the drawings that the designer makes are not usually meant to be communications to anyone else. Essentially, they are communications with oneself, a kind of thinking aloud. At this stage the designer is thinking about many aspects together, such as materials, components, structure and construction, as well as overall form, shapes and functions.
Exploration of designs
At the start of the design process, the designer is usually faced with only a partially defined problem; yet he or she has to come up with a well defined solution. If one thinks of the problem as a space or territory, then it is largely unexplored and un‐mapped, and perhaps imaginary in places! It may therefore be appropriate to think of the designer as an explorer, travelling inquisitively through an unknown land, paying attention to unusual finds as well as the mundane.
Equally, if one thinks of all potential solutions as occupying a kind of solution space, then that, too, is relatively undefined, and perhaps infinite. Here, the designer is searching for possibilities, and often creating new ones. The designer's task is therefore two‐fold; understanding the problem and seeking a solution.
