chapter 1 of the mechanical design process

1. THE MECHANICAL DESIGN PROCESS
By David G. Ullmann

2. CONTENT
o About the author
o Introduction
o Chap1: Why Study the Design Process
o Chap2: Understanding Mechanical Design
o Chap3: Designers and Design Teams
o Chap4: The Design Process and Product Discovery
o Chap5: Planning for Design
o Chap6: Understanding the Problem and the Development of Engineering Specifications
o Chap7: Concept Generation
o Chap8: Concept Evaluation and Selection
o Chap9: Product Generation
o Chap10: Product Evaluation for Performance and the Effects of Variation
o Chap11: Product Evaluation: Design For Cost, Manufacture & Assembly
o Chap12: Wrapping Up the Design Process and Supporting the Product

3. ABOUT THE AUTHOR
David G. Ullman is an:
o active product designer
o taught, researched, and written about design for over thirty years.
o president of Robust Decisions, Inc., a supplier of software products and training for
product development and decision support.
o Emeritus Professor of Mechanical Design at Oregon State University.
o professionally designed fluid/thermal, control, and transportation systems.
o published over twenty papers focused on understanding the mechanical product
design process and the development of tools to support it.
o founder of the American Society Mechanical Engineers (ASME)—Design Theory and
Methodology Committee and is a Fellow in the ASME.

4. INTRODUCTION
o designer all my life. I have designed bicycles, medical equipment,
furniture, and sculpture, both static and dynamic. Designing objects has
come easy for me. having whatever talents are necessary to be a
successful designer.
o However, after years of teaching mechanical design courses, I came to
the realization that I didn’t know how to teach what I knew so well.
o I could show students examples of good-quality design and poor
quality design. I could give them case histories of designers in action. I
could suggest design ideas. But I could not tell them what to do to solve
a design problem.

5. INTODUCTION
Ice skates experience
How to skate backward
!?

6. INTRODUCTION
o The only way to learn about design is to do design.
o Knowledge about the design process is largely independent
of domain-specific knowledge.
o A design process that results in a quality product can be
learned
o A design process should be learned in an academic
environment and, in an environment of industrial realities.

7. Chap1:
Why Study the Design Process

8. KEY QUESTIONS
o What can be done to design quality mechanical products on
time and within budget?
o What are the key features of design best practice that will
lead to better products?
o What are the phases of a product’s life cycle?
o How are design problems different from analysis
problems?
o Why is it during design, the more you know, the less design
freedom you have?

9. INTRODUCTION
 Old potter’s wheel  transportation systems
• humans have been designing mechanical objects for nearly five thousand years
• Each of these objects is the end result of a long and often difficult design process
• whether we are designing heat exchangers, satellites, or doorknobs, there are certain
techniques that can be used during the design process to ensure successful products.

10. INTRODUCTION
QUESTION???
If people have been designing for five
thousand years and there are literally millions
of mechanical objects that work and work
well, why study the design process???

11. INTRODUCTION
ANSWER
continuous Need for :
New
Cost-effective
Higher quality
products

12. INTRODUCTION
Complex products Design team
Communication and structure

13. INTRODUCTION
Global market competition
Time, cost, quality
Efficient design process
85% of the problems with new products not working as
they should, taking too long to bring to market, or costing
too much are the result of a poor design process.

14. INTRODUCTION
 Factors that determine the success or
failure of a product development

15. MEASURING THE DESIGN PROCESS
o The three measures of the effectiveness of the design
process are product cost, quality, and time to market.
o Regardless of the product being designed: an entire
system, some small subpart of a larger product, or a
change in an existing product:
Customer and management always want it cheaper (lower
cost), better (higher quality), and faster (less time)

16. MEASURING THE DESIGN PROCESS
o The actual cost of designing a
product is usually a small part of the
manufacturing cost of that product
o This number varies with industry and
product, but for most products the
cost of design is a small part of the
manufacturing cost.
o The effect of the quality of the
design on the manufacturing cost is
much greater than 5%.
based on data from Ford Motor Company.
only 5% of the manufacturing cost of a car is for design
activities that were needed to develop it.

17. MEASURING THE DESIGN PROCESS
o manufacturing efficiency
and design have about the
same influence on the cost
of manufacturing a
product.
o good design cuts the cost
by about 35%. In some
industries this effect is as
high as 75%.
detailed study of 18 different automatic coffeemakers
Showing the effect of design on manufacturing cost

18. MEASURING THE DESIGN PROCESS
o Until early 1970s, Xerox controlled the copier market. However,
by 1980 Xerox realized that some producers were able to sell a
copier for less than Xerox was able to manufacture one.
o In one study of the problem, comparing plastic parts from their
machines and ones that performed a similar function, they found
that Japanese firms could produce a part for 50% less than
American firms.
o 25% of the difference was attributable to how the parts were
designed.

19. MEASURING THE DESIGN PROCESS
o the decisions made
during the design
process have a great
effect on the cost of
a product but cost
very little
o Product cost is
committed early in
the design process
and spent late in the
process.
Manufacturing cost commitment during design
75%
This means that decisions made after this time can influence
only 25% of the product’s manufacturing cost

20. MEASURING THE DESIGN PROCESS
The results of the design process have a great effect on product quality
A survey of determines quality for American consumers showing that “quality” is a mix of
factors that are the responsibility of the design engineer

21. MEASURING THE DESIGN PROCESS
 The design process
also affects the time
it takes to produce a
new product
Engineering changes during automobile development, which shows the number of design
changes made by two automobile companies with different design philosophies.

22. MEASURING THE DESIGN PROCESS
o Changes occurring
late in the design
process are more
expensive than
those occurring
earlier
Engineering changes during automobile development, which shows the number of design
changes made by two automobile companies with different design philosophies.

23. MEASURING THE DESIGN PROCESS
o The engineers in
Company B spend
much time
“firefighting” after
the product is in
production.
o In fact, many
engineers spend as
much as 50% of
their time firefighting
for companies similar
to Company B.
Engineering changes during automobile development, which shows the number of design
changes made by two automobile companies with different design philosophies.

24. THE HISTORY OF THE DESIGN PROCESS
 Definition:
The design process is the organization
and management of people and the
information they develop in the
evolution of a product.
 History:
In simpler times, one person could
design and manufacture an entire
product. Even for a large project such
as the design of a ship or a bridge.
The Eads Bridge named after its designer, James B. Eads.
When completed in 1874, it was the longest arch bridge in
the world, and the world's first all steel construction

25. THE HISTORY OF THE DESIGN PROCESS
 History:
Products and manufacturing
processes had become so complex
that one person no longer had
sufficient knowledge or time to
focus on all the aspects of the
evolving product.
Different groups of people
became responsible for
marketing, design, manufacturing,
and overall management.

26. THE HISTORY OF THE DESIGN PROCESS
Often what is manufactured by a company using the over-the wall
process is not what the customer had in mind.

27. THE HISTORY OF THE DESIGN PROCESS
in 1970s, the concept of simultaneous
engineering began to break down
the walls by assigning
manufacturing representatives to
be members of design teams.

28. THE HISTORY OF THE DESIGN PROCESS
■ In the 1980s the simultaneous design
philosophy was broadened and called
concurrent engineering, which, in the
1990s, became Integrated Product and
Process Design (IPPD).
■ the change in terms implies a greater
refinement in thought about what it
takes to efficiently develop a product

29. THE HISTORY OF THE DESIGN PROCESS
■ In the 1990s the concepts of
Lean and Six Sigma became
popular in manufacturing
■ Lean manufacturing seeks to
eliminate waste in all parts of
the system.

30. THE HISTORY OF THE DESIGN PROCESS
■ Where Lean focuses on time, Six
Sigma focuses on quality as a
way to help ensure that products
were manufactured to the
highest standards of quality.

31. THE HISTORY OF THE DESIGN PROCESS
■ However, quality begins in the design
of products, and processes, not in
their manufacture.
■ Recognizing this, the Six Sigma
community began to emphasize
quality earlier in the product
development cycle, evolving DFSS
(Design for Six Sigma)

32. THE HISTORY OF THE DESIGN PROCESS

33. THE HISTORY OF THE DESIGN PROCESS
All of these methodologies and best practices are built around
a concern for the ten key features listed in Table 1.2.

34. THE PRODUCT LIFE CYCLE

35. ■ PLM integrates six different major
types of information.
■ PLM focuses on the information
that must be managed to support
that life.
PLM (product life-cycle management)

36. MANY SOLUTIONS FOR DESIGN PROBLEMS
Design problems have many satisfactory solutions but no clear best solution
Bolt diameter?

37. MANY SOLUTIONS FOR DESIGN PROBLEMS
This problem is not as well defined as the first one.
To evaluate proposed concepts, more information about the joint will be needed.
Choices:
• bolted joint
• glued joint
• joint in which the two pieces folded
over each other
• a welded joint
• a joint held by magnets …
Questions:
• Will the joint require disassembly?
• Will it be used at high temperatures?
• What tools are available to make the
joint?
• What skill levels do the joint
manufacturers have?

38. MANY SOLUTIONS FOR DESIGN PROBLEMS
Problem one
 Analysis problem
 Well defines
 One correct solution
Problem two
 Design problem
 Ill defined
 Many correct solutions
All design problems have a multitude of satisfactory solutions and no
clear best solution.
The goal in design is to find a good solution that leads to a quality
product with the least commitment of time and cost.

39. THE BASIC ACTIONS OF PROBLEM SOLVING
 Establish the need or realize that there is a problem to be solved.
 Plan how to solve the problem.
 Understand the problem by developing requirements and
uncovering existing solutions for similar problems.
 Generate alternative solutions.
 Evaluate the alternatives by comparing them to the design
requirements and to each other.
 Decide on acceptable solutions.
 Communicate the results.

40. KNOWLEDGE AND LEARNING DURING DESIGN
the goal during the design
process is to learn as much
about the evolving product
as early as possible in the
design process because
during the early phases
changes are least expensive
design paradox
:
The more you learn the less freedom you have to use what you know