Chapter 1. Mechanical Design Process - Yuan Ze...
Transcript of Chapter 1. Mechanical Design Process - Yuan Ze...
Copyright 2010. All rights reserved.1
What is Design? Design Starts with a Problem.
In 1946, Bell Telephone Labs (AT&T) asked designer Henry Dreyfuss to improve the
phone used in millions of American homes and offices.
1. Thinking: What needed to be improved ?
Chapter 1. Mechanical Design Process
Receiver easily falls over the
hook
Handset needs to fit better
in cradle
Awkward appearance
and proportions
Easily toppled
Have to use two hands
Can’t cradle handset
between ear and shoulder
Can’t read the number
while dialing
Material easy to break and
chip
Too
heavy
“Candlestick” and “Series 300” telephone
Awkward cord
Copyright 2010. All rights reserved.2
2. Sketching the idea
Designers used sketches to envision, develop, and evaluate new ideas.
Design Example: Telephone Improvement (I)
Copyright 2010. All rights reserved.3
3. Making models
Designers created models of wood and clay to give form to their ideas for
the phone’s handset, base, and dial. They also used models and drawings
to share their ideas with the clients, AT&T.
Design Example: Telephone Improvement (II)
Copyright 2010. All rights reserved.4
4. Evaluation
Based on the models, designers and clients could see how the phone would
fit the user’s hand and ear. They then created prototypes to test the
performance of the whole phone. Together, they determined the final design.
5. Manufacturing
Designers proposed a new kind of plastic for the final product because it’s
more efficient and cost-effective in manufacturing. Also, this plastic was
lightweight but durable and came in many colors. AT&T agreed and mass-
produced 25 million phones from this one design. They called it “Series
500”.
Design Example: Telephone Improvement (III)
Design Ends with a Solution.
Design is a problem solving process.
Copyright 2010. All rights reserved.5
Knowledge Needed for Mechanical Design
The route from “problem” to “solution” can be along many different paths.
Designer’s knowledge of the process and the problem’s domain determines
the path.
Knowledge used in the design process includes domain knowledge and design
process knowledge, how to effectively integrate the domain knowledge to
generate the solution.
Culvethouse[1993] classified design into 4 types: Repeat order design, variant
design, innovative design, and strategic design.
Design process plays an important role to the success of development of a
product. Design process influences performance, quality, cost, and developing
time of the product.
Copyright 2010. All rights reserved.6
“T-shaped” People (IDEO CEO Tim Brown)
T-shaped people have two kinds of characteristics, hence the use of the letter
“T” to describe them.
The vertical stroke of the “T” is a depth of skill that allows them to contribute
to the creative process. That can be from any number of different fields: an
industrial designer, an architect, a social scientist, a business specialist or a
mechanical engineer.
The horizontal stroke of the “T” is the disposition for collaboration across
disciplines. It is composed of two things.
First, empathy. It’s important because it allows people to imagine the problem
from another perspective- to stand in somebody else’s shoes.
Second, they tend to get very enthusiastic about other people’s disciplines, to the
point that they may actually start to practice them.
T-shaped people have both depth and breadth in their skills.
Inter-disciplinary Trans-disciplinary
Copyright 2010. All rights reserved.7
IDEO’s Design Thinking
“Design thinking is an approach that uses the designer’s sensibility and
methods for problem solving to meet people’s needs in a technologically
feasible and commercially viable way. In other words, design thinking is
human-centered innovation.” —Tim Brown
Copyright 2010. All rights reserved.8
Design Process Models
Most researches in design process try to establish a structured model to describe or
facilitate design.
Design process models are usually categorized into descriptive models,
prescriptive models, and cognitive models [Finger and Dixon, 1989; Cross, 1994].
• According to Cross, descriptive models simply describe the sequences of
activities that typically occur in designing.
• Prescriptive models attempt to prescribe a better or more appropriate pattern of
activities. They usually offer a more algorithmic, systematic procedure for the
whole design team to follow.
Cross[1994] presented a simple descriptive design process model:
Exploration Concept generation Evaluation Communication
Ullman[1992] stated that the life cycle of a product consists of 6 phases, and the
first 3 phases focus on design:
Specification development/planning Conceptual design Product design
Production Service Product retirement
Copyright 2010. All rights reserved.9
Ullman’s Prescriptive Design Process Model
市場
新科技
子問題
成立設計小組
了解設計問題
計畫安排
產生設計記錄
劃分子系統
階段一:規範建立/規劃
設計回顧
產生設計記錄
更新計畫
建立子系統
概念產生 概念評估
中斷計畫
設計回顧
子問題
設計回顧
中斷計畫
階段二:概念設計
產生產品雛形
評估產品產生設計
記錄
中斷計畫子問題
階段四:製造
階段五:服務
階段六:淘汰
階段三:產品設計
建立子裝配
Copyright 2010. All rights reserved.10
Specification Development/Planning (I)
The Design Process Paradox (Ullman [1992])
Copyright 2010. All rights reserved.11
1. Identifying the customers
• Those who have certain needs to the products are all customers. Besides consumers
or users, the designer’s own management, manufacturing personnel, sales staff, and
service personnel must also be considered as customers.
2. Determining customer requirements
• Market investigation, questionnaires,observing product in use, and interviewing lead
users
• Types of customer requirements:
Performance: functional performance and spatial constraints
Appearance
Time
Cost: capital and unit
Manufacture/assembly: quantity to be manufactured, company capability
Standards
Safety
Environment issues
Specification Development/Planning (I)
Copyright 2010. All rights reserved.12
3. Determining relative importance of the requirements
• Some requirements are “musts”, and some requirements are “wants”.
Specify the “musts” and determine the “wants” in a 1-5 scale.
4. Competition Benchmarking
• The competitors include similar products available in the market, as well as
any alternative methods that can achieve the same functions.
5. Transferring customer requirements into measurable engineering requirements
• A product specification includes a “metric” and a “value”.
• There are standard specification items in products such as computers,
automobiles, audios, etc. These items should be considered first.
6. Setting engineering target for the design
• Quality Function Deployment, QFD
Specification Development/Planning (II)
Copyright 2010. All rights reserved.13
三
、
決
定
顧
客
需
求
之
間
相
對
重
要
性
比
重
二、了解顧客需求
四
、
競
爭
對
手
的
評
估
五、建立設計規格項目
六、設定設計目標
設 計
名 稱
比
重
尺
寸
裝
配
時
間
重
量
輕
壽
命 …規
格
A
規
格
B
競
爭
者
1
競
爭
者
2
重量 * ‧ 1 4
需求 A 2 ‧ 1 2
需求 B 4 ‧ 4 2
性
能
需
求 需求 C 2 ‧ 1 2
美觀 1 ‧ 3 4外
觀 需求 D 2 1 3
易裝配 4 ‧ … 3 2
需求 E * ‧ 3 1
需求 F 1 1 4
製
造
組
裝 需求 G 3 3 1
.
.
.
.
.
.
.
.
安 全 * ‧ 4 4
成 本 3 1 3
單位 m sec kg 年 … # #
目標 6× 6× 7 <60 <45 6 3 2
競爭者 1 5× 8× 7 <130 45 5 3 1
競爭者 2 7× 6× 9 >100 76 3 5 2
Quality Function Deployment, QFD