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1

Biomechanical
Design
(051:083)

Lecturer:


-

Tae
-
Hong Lim, Ph.D.

1420 Seamans Center

335
-
5810 (office);
talim@engineering.uiowa.edu

(email)



-

David Wilder, PhD and Nicole Grossland, PhD



Office Hours:



M, W, F: 4:00


5:00 PM



Appointment


Pre
-
requisites:

57:007

Statics

57:019

Mechanics of Deformable Bodies

51:050

Biomechanics

2

Text and Grading


Text:

“The Mechanical Design Process, 3
rd

Edition”

David G. Ullman

McGraw
-
Hill (ISBN: 0
-
07
-
237338
-
5)



Grading:

15%

Homework and Quiz

20%

Individual Design Notebook

10%

Reverse engineering report

40%

Team Project

15%

Final Exam


Final exam will be a short answer exam covering the terminology and concepts studied
throughout this course


3

Individual Design Notebooks


You are to keep a design notebook for use in this course.


This is to be a spiral bound notebook.


Every page must be numbered at the beginning of the term.


No pages can be removed and each page must be dated and initialed when used.


All work related to this course (homework and design project) will be entered into
this note book.


Each notebook will be collected at the end of the term and graded on the number of
“quality entries” it contains.


A quality entry is a significant sketch or drawing of some aspect of design; a listing of
functions, ideas or other features; a table such as morphology or decision matrix; or a
page of text.


Unintelligible entries are not quality entries.

4

Team Project


Design Team:


Design teams will be organized by the instructor.


Team members will determine the leader (CEO).



Team Project:


Each team will determine a design problem (new invention or modification) related to
biomechanical devices through discussion with the instructor.


The team project will be considered completed by obtaining final product documentation
(drawings, part list with specified materials, and assembly instructions).


No final product in physical form is required.



Each team should record the whole history of the design in the
Product Development
File

(PDF).

5

Documents in the PDF

Problem Appraisal Phase


Understanding the Problem:

1.
Description of Customers

2.
Customer’s Requirements

3.
Weighting of Customer’s
Requirements

4.
Competition’s Benchmarks vs.
Customer’s Requirements

5.
Engineering Requirements

6.
Competition’s Benchmarks vs.
Engineering Requirements

7.
Engineering Targets


Planning the Project

8.
Task Titles

9.
Objectives of Each Task

10.
Personnel Required for Each
Task

11.
Time Required for Each Task

12.
Schedule of Tasks

Conceptual Design Phase


Concept Generation:

13.
Function Decomposition

14.
Literature and Patent Search
Process and Results

15.
Function
-
Concept Mapping

16.
Sketches of Overall Concepts


Concept Evaluation and

Assessment of Tech. Readiness:

17.
Identification of Failure Modes

18.
Identification of Critical
Parameters


Concept Selection:

19.
Decision Matrices to Determine
Best Concepts

20.
Analsysi, Experiments and
Models Supporting Evaluation

Product Design Phase


Product Generation:

21.
Usable off
-
the
-
shelf Products

22.
Shape Development Driven by
Function

23.
Materials Selection

24.
Manufacturing Process
Selection


Product Evaluation:

25.
Comparison to Engineering
Function

26.
Functional Changes Noted

27.
Design for Assembly Evaluation

28.
Cost Evaluation

29.
Analysis, Experiments and
Models Supporting Evaluation


Final Product Documentation:

30.
Layout Drawings

31.
Detail Drawings of
Manufactured Parts

32.
Parts List (Bill of Materials)

33.
Assembly Instructions

*

The file is to be maintained by the group in a binder. This PDF, when completed, is effectively a
final report. It will be graded on completeness and quality of both the design and the
documentation itself.

6

Biomechanical Design


Design:


Deliberate purposive planning


A mental project or scheme in which means to an end are laid out


A preliminary sketch or outline showing the main features of something to be executed: DELINEATION


The arrangement of elements or details in a product or work of art


The creative art of executing aesthetic or functional designs



Biomechanical Design:


Design something related to biomechanics, such as:


Biomechanical devices


Medical devices: orthopedic implants, scissors, scalpers, staplers, etc.


Exercising devices: treadmill, weight
-
lifting, helmets, wrist
-
guards, etc.


Rehabilitation devices: wheel
-
chairs, canes, etc.


Biomechanical activities


Exercises for fitness or strengthening body parts



Biomechanical design includes
:


Development (or invention) of new biomechanical stuffs; and


Modification of existing biomechanical stuffs



7

What will we learn in this class?


Typical design process:


Identification of design problems


Design


Evaluation of the design


Decision making


Final report


Techniques helping generate better quality designs in less time:


Concurrent engineering


Computer aided drawing


Legal and regulation issues:


Safety and liability


Patent, FDA, CE, and UL


Importance of communication of design data:


Records of design data, design process, and final report


Oral presentations


8

The Life of A Product

*Process of idea development,
production, use, and end of product
life.


*The whole process must be
considered in the design process.



9

Design Process


What is the design process?


Design process is the organization and management of people and the information they develop in the
evolution of the product.



Why study the design process?


Design process determines the efficiency of new product development.


85% of the problems with new products not working as intended, taking too long to bring to market, or costing
too much are the result of poor design process.


The design process needs to improved consistently and executed for developing better products because:


There is a continuous need for new, cost
-
effective, high
-
quality products.


Most products require a team of people from diverse areas of expertise to develop an idea into hardware.


We will study the design process to get the tools to develop an efficient design process regardless of the
product being developed.



3 types of knowledge used by designers:


Knowledge to generate ideas


Experience and natural ability


Knowledge to evaluate ideas


Experience and formal training (focus of most engineering education)


Knowledge to structure the process


Non
-
domain
-
specific knowledge


What we will study in this class

10


One person, with sufficient knowledge of the physics, materials and manufacturing
processes to manage all aspects of the design and construction of the project, could
design and manufacture an entire product in the past.


By the middle of the 20
th

century, products and manufacturing processes had become
too complex for one person to have sufficient knowledge or time to focus on all
aspects of the evolving product.


Different groups of people for marketing, design, manufacturing and overall management










One
-
way communication over the wall:


What is manufactured is not often what the customer had in mind.


Inefficient, costly, and greater possibility for making poor
-
quality products


History of the Design Process

11


Simultaneous Engineering (in late 1970s and early 1980s):


Simultaneous development of the manufacturing process with the evolution of the product by assigning
manufacturing representatives to be members of design team


Concurrent Engineering (in late 1980s):


Integrated Product and Process Design (IPPD) in the 1990s


A greater refinement in thought about what it takes to efficiently develop a product


Primarily focusing on the integration of teams of people, design tools and techniques, and information about
the product and the processes used to develop and manufacture it.


10 Key Features of Concurrent Engineering


Focus on the entire product life (chap 1)


Use and support of design team (chaps 3 and 5)


Realization that the processes are as important as the product (chaps 4 and 5)


Attention to planning for information
-
centered tasks (chap 5)


Careful product requirements development (chap 6)


Encouragement of multiple concept generation and evaluation (chaps 7 and 8)


Awareness of the decision
-
making process (chap 8)


Attention to designing in quality during every phase of the design process (throughout)


Concurrent development of product and manufacturing process (chaps 9
-
13)


Emphasis on communication of the right information to the right people at the right time (throughout)


A key point of concurrent engineering is a concern for information.


Drawings, plans, concept sketches, meeting notes, etc.

History of the Design Process

12

Controllable Variables in Concurrent Engineering

13

Overview of the Design Process

14

Design Problems

What size SAE grade 5 bolt should be
used to fasten together two pieces of
1045 sheet steel (4 mm thick and 6 cm
wide) which are lapped over each other
and loaded with 100 N?


-

Well defined analysis problem finding
the diameter of the bolt

Design a joint to fasten together two
pieces of 1045 sheet steel (4 mm thick
and 6 cm wide), which are lapped over
each other and loaded with 100 N?



Ill
-
defined design problem with number
of potential problems

-
How to connect the sheets? (Bolted,
glued, welded, etc.?)

-
Disassembly required later?

-
What working environment?

-
etc.

HWK#1:

Change a problem from one of your engineering science classes into a design problem by
changing as few words as possible. Do your home work in your design notebook. Due is
one week.

15

Design problems have many satisfactory solutions and no clear
best solution.

Design problems

-
are ill
-
defined;

-
have no correct answer;

-
have no clear best answer.


Design process knowledge is based
upon the domain knowledge.

Mechanical design problems begin
with an ill
-
defined need and result in
a piece of machinery that behaves in
a certain way.


PARADOX:

A designer must develop a machine
that has the capabilities to meet
some need that is not fully defined.

16

Basic Actions of Design Problem Solving


ESTABLISH

the need or realize that there is a problem to be solved.


New needs also can be established throughout the design effort because new design
problems arise as the product evolves. Design of these details poses new subproblems.


PLAN

how to solve the problem.


Planning occurs mainly at the beginning of a project. Plans are always updated because
understanding is improved as the process progresses.


UNDERSTAND

the problem by developing requirements and uncovering existing
solutions for similar problems.


Formal efforts to understand new design problems continue throughout the process. Each
new subproblem requires new understanding.


GENERATE

alternative solutions.


Concept Generation vs. Product Generation


EVALUATE

the alternatives by comparing them to the design requirements and to
each other.


Evaluation techniques also depend on the design phase; there are differences between the
evaluation techniques used for concepts and those used for products.


DECIDE

and acceptable solutions


Decision making requires a commitment based upon incomplete evaluation.


Decision requires a consensus of team members.


COMMUNICATE

the results


Communication of the information developed to others on the design team and to
management is an essential part of concurrent design.

17

Basic Terminologies used to describe the Design Process


“Communication” as a one key feature of concurrent engineering


Communication depends on a shared understanding of terminology.


Function:


What a product or a system is supposed to do;


Described using action verbs and a noun describing the object on which the
action occurs:


Record images; quantify the blood pressure; fix an unstable spine segment; etc.


System:


A grouping of objects that perform a specific function;


Shutter system; timer system; CD
-
R system; cooling system; etc.


A system can be decomposed into another subsystems or further into individual
components (or parts).


Multiple systems can be assembled into a higher level system or further into a
final product.


Feature: the important form and function aspects of mechanical devices


dimensions, material properties, shapes, or functional details (speed of opening and
closing for shutter system)

Decomposition of design disciplines

In general, during the design process, the
function of the system and its
decomposition are considered first. After
the function has been decomposed to the
finest subsystems possible, assemblies and
components are developed to provide
these functions.

18

Function, Behavior, and Performance


Function:


describes what a device does.


But, function provides no information about how a device accomplishes the function.


Form:


The term “form” relates to any aspect of physical shape, geometry, construction, material,
or size.


provides some information on how a device accomplishes the function.


Behavior and Performance in association with Function.

-
Function is the desired output from a
system yet to be designed.

-
Behavior is the actual output, the response
of the system’s physical properties to the
input energy or control.

-
Performance is the measure of function
and behavior


how well the device does
what it is designed to do.

-
A clear picture of desired performance
should developed in the beginning of the
design process.

19

Types of Mechanical Design Problems


Selection Design:


choosing one item (or more) from a list of similar items


choosing a bearing, bolt, motor, etc. from a catalog


Configuration Design:


How to assemble all the components into the completed product


Parametric Design:


Finding values for the features that characterize the object being studied or that meet the
requirements


Design a cylindrical tank: V =

r
2
l,
determine
r

and
l

for known V


Original Design:


Design a process, assembly or component not previously in existence


Redesign:


Redesign of an existing product


Most design problems are redesign problems since they are based on prior,
similar solutions. Conversely, most design problems are original as they contain
something new that makes prior solutions inadequate.

20

Languages of Mechanical Design

A mechanical object can be described by:


Semantic language:


Verbal or textual representation of the object


“bolt” or “The shear stress is equal to the shear forces on the bolt divided by the
x
-
sectional area.”


Graphical language:


drawing of the object


Sketches, scaled representations of orthogonal drawings, or artistic renderings


Analytical Language:


Equation, rules, or procedures representing the form of function of the object




= F/A


Physical Language:


Hardware or physical model of the project

-

In most cases, the initial need is expressed in a semantic language as a
written specification or a verbal request by a customer or supervisor, and
the final result of the design process is a physical product.

21

Design, State, Constraints and Decision


Design State:


Collection of all the knowledge, drawings, models, analyses and notes thus far
generated


In the beginning, design state is just the problem statement


Design Constraints:


Factors limiting the design process


Examples: size, strength of material, corrosion properties, anatomy, etc.


In the beginning, the design requirements effectively constrains the possible
solutions to a subset of all possible product designs.


Two sources of constraints added during the design process:


Designer’s knowledge of mechanical devices and the specific problem being solved


Result of design decisions


Design Decision:


Continuous comparison between design state and the goal (requirements for the
product given in the problem statement)


The difference controls the process.


Design is the successive development and application of constraints until only
one unique products remains.


Each design decision changes the design state.


The design progresses in increment punctuated by design decisions.

22

The Value of Information

*The most valuable information is the decisions that are communicated to others.

23

Design as Refinement of Abstract Representations

Graphical Refinement

See Table 2.2 for levels of abstraction in
other languages.

24

Information
-
processing Model of Human Problem Solving

Information
-
Processing System used by the human mental system
in solving any type of problem

25

Chunks of Information

26

Information
-
processing Model of Human Problem Solving

Types of Knowledge that might be in a chunk of information:


General knowledge


Information that most people know and apply without regard to a specific domain


“red is a color.” “4 is bigger than 3.”


Gained through everyday experiences and basic schooling


Domain Specific Knowledge:


Information on the form or function of an individual object or a class of objects


Bolts are used to carry shear or axial stress


The proof stress of a grade 5 bolt is 85 kpsi.


Gained from study and experience in the specific domain


It may take about 10 years to gain enough specific knowledge to be considered an expert in a domain


Procedural Knowledge:


The knowledge of what to do next


If there is no answer to problem X, then decompose X into two independent subproblems of x1 and x2 that
are easier to solve.


Gained mostly from experience


Required for solving mechanical design problems


27


The size of STM is a major limiting factor in the ability to solve problem.


To accommodate this limitation, breakdown problems into finer and finer subproblems
until we can “get our mind around it”


in other word, manage the info in our STM


Human designers are quite limited although our expertise about the constraints and
potential solutions increases and our configuration of chunks becomes more efficient as we
solve problems.


These limitations would preclude our ability to solve complex problems.

Implications of the Information
-
processing Model

28

Mental Processes that Occur during Design


Understanding the problem:


A problem is understood by comparing the requirements on the desired function to information in the
long
-
term memory.


Every designer’s understanding of the problem is different, we need to develop a method to ensure that
the problem is fully understood with minimal bias from the designer’s own knowledge.


Generating a solution:


Use the information stored in LTM that meets the design requirements.


If no solution found from LTM, then use a three step approach


Decompose the problem into subproblems


Try to find partial solutions to the subproblems


Recombine the subsolutions to fashio a total solution


Creative part of this approach is in knowing how to decompose and recombine cognitive chunks


Evaluating the solution:


Evaluation requires comparison between generated ideas and the laws of nature, the capability of
technology and the requirements of the design problem itself.


Evaluation requires modeling the concept to see how it performs.


The ability to model is usually a function of knowledge in the domain.


Deciding:


A decision is made at the end of each problem
-
solving activity to accept the generated and evaluated
idea or to address another topic that is related to the problem.


Controlling the design process:


Path from initial problem to solution seemed random.


29

Problem
-
Solving Behavior


A person’s problem
-
solving behavior affects how problems are solved individually and has a significant
impact on team effectiveness.


Four Personal
-
Problem Solving Dimensions (or styles):


Individual Problem
-
solving Style:


Introvert:


Solve problem internally (reflective); a good listener; think and speak; enjoy having time alone for problem solving


Extrovert:


Sociable; tend to speak and think


About 75% Americans and 48% of engineering students and executives


Individual Preference to work with Facts or Possibilities:


Facts oriented people:



literal, practical, and realistic


75 % of Americans, 66% of top executives, 34% of all engineering students


Possibility oriented people:


Like concepts and theories and look for relationship between pieces of information and meaning of the information


Objectivity with which decisions are made:


Objective:


Logical, detached and analytical


Taking objective approach to make decisions


51% of Americans, 68% of engineering students, 95% of top executives


Subjective:


Make decisions based on an interpersonal involvement, circumstances, and the “right thing to do”


Need to Make Decisions:


Decisive:


Tend to make decisions with a minimum of stress and like an ordered, scheduled, controlled and deliberate environment


50% of Americans, 64 % of engineering students, and 88% of top executives


Flexible:


People goes with flow is flexible, adaptive, and spontaneous, and finds making and sticking with decisions difficult


Please make sure to read section 3.3.6 carefully for better design team activities.

30

Characteristics of a Creative Designer


Problem solving involves:


Understanding the problem, generating solutions, evaluating the solutions, deciding on the best one, and
determining what to do next


Criteria of Creative Solution:


It must solve the design problem.


It must be original.


Originality and creativity are assessed by society.


Creativity in relation to other Attributes


Intelligence: no correlation with creativity


Visualization Ability:


Creative engineers have good ability to visualize, to generate and manipulate visual images in their head.


The ability to manipulate complex images can be improved with practice and experience.


Knowledge:


A person must have knowledge of existing products to be a creative designer


A firm foundation in bioengineering science is essential to being a creative biomechanical designer.


Partial Solution Manipulation: important attribute


Risk Taking: certainly required


Conformity: Creative people tend to be nonconformists.


Constructive nonconformists take a stand because they think they are right and might generate a good idea.


Obstructive nonconformists take a stand just to have an opposing view and will slow down the design progress.


Technique:


Creative designers have more than one approach to problem solving.


Environment:


Higher creativity when the work environment allows risk taking and nonconformity and encourages new ideas.


Practice:


Creativity comes with practice.


Practice enhances the number and quality of ideas.


31

Creative Designer


A creative designer is a:


Visualizer;


Hard worker; and


Constructive nonconformist with knowledge about the domain and
ability to dissect things in his or her head


Good News:


Designers with no strong natural ability can develop creative methods by
using good problem
-
solving techniques to help decompose the problems
in ways that maximize the potential for understanding it, for generating
good solutions, for evaluating the solutions, for deciding which solution is
best and for deciding what to do next


A design project requires:


much attention to detail and convention;


demands strong analytical skills; and thus


People with a variety of skills.


There are many good designers who are not particularly creative
individuals.

32

Engineering Design Team


A team is a group of people working toward a common understanding.


Team vs. Individual Problem Solving


There are social aspects of team work.


Each team member may have different understanding of the problem, different alternatives for solving
it, and different knowledge for evaluating it. (more solutions but also more confusion)


Team Goals:


A small number of people with complementary skills who are committed to a common purpose, common
performance goals and a common approach for which team members hold themselves mutually
accountable are required for an effective team.


Team members must:


learn how to collaborate with each other, i.e., to get the most out of other team members.


Comprise to reach decisions through consensus rather than by authority.


Establish communications.


Be committed to the good of the team.


Team Roles:


Organizer; Creator; Resource
-
investigator; Motivator; Evaluator; Team worker; Solver; Completer
(finisher or pusher)


Building Team Performance:


For developing productive teams;


Keep the team productive


Select team members on the basis of skills in both primary and secondary roles


Establish clear rule of behavior


Set and seize upon a few immediate performance
-
oriented goals.


Spend time together.


Develop a common understanding

33

Overview of the Design Process

An Ideal Flow Chart of Activities During Design Process

34

What initiates a Design Project?


Need for a New Design:


Market:


About 80% of new product development is market
-
driven.


Assessment of the market is most important in understanding the design problem
because there is no way recover the costs of design and manufacture without market
demand.


Incorporation of the latest technology can improve its perception as a high quality
product.


New product idea without market demand


To use new technologies whose development requires an extensive amount of capital
investment and possibly years of scientific and engineering time


High financial risk but greater profit due to uniqueness


Examples of successful products: sticky notes; Walkman


Need for Redesign


By market demand for a new model


Desire to include a new technology


Fix a problem with an existing product


Redesign process can be applied to the subproblems that result from the
decomposition of a higher
-
level system.


35



Project Planning:



to allocate the resources of money, people, and equipment to accomplish the design activities:


Planning should precede any commitment of resources although requiring speculations about the
unknowns


Easier to plan a project similar to earlier projects than to plan a totally new one


Plans are often updated whenever unknown demands become certain with the progress of design
project


Specifications Definition:


Goal is to understand the problem and to lay the foundation for the remainder of the design project.


Identify the customers: Generate the customer’s requirements: Evaluate the competition: Generate engineering
specifications: Set targets for its performance


Design Review:


formal meeting for progress report and design
-
decision making


Conceptual Design:


To generate and evaluate the concepts for the product


Generate concepts based on the defined specifications for developing a functional model of the product


Evaluate concepts by comparing the concepts generated to the targets for its performance


Design Review


Product Development:


Evaluate the product for performance, cost, and production


Make product decisions


Documentation and Communication


BOM (Bill of Materials), Drawings, etc.


Product Support:


Support for vendors, maintenance of engineering change, customer, manufacturing and assembly, and
retirement of the product

Overview of the Design Process

36

Why Do We Have to Follow The Design Process Techniques?


Paradox:


Techniques in the design process may imply “RIGIDITY” whereas the creativity implies
“FREEDOM.”



Following the techniques in the design process helps the designers develop a quality
product that meets the needs of the customer by several ways:


Eliminating expensive changes later


Developing creative solutions to design problems systematically


Creativity does not spring from randomness.


“Genius is 1 percent inspiration and 99 percent perspiration.”


The inspiration for creativity can only occur if the perspiration occur early is properly directed
and focused.


The techniques that make up the the design process are only an attempt to organize the
perspiration.


Forcing documentation of the progress of the design (record of the design’s evolution) that
will be useful later in the design process.

37

Design Process Examples

Simple Process

Complex Process

38

Communication during the Design Process



Design Records:


Importance of documents in design file:


To demonstrate the state
-
of
-
the
-
art design practices


To prove originality in case of patent application


To demonstrate professional design procedures in case of a lawsuit


Design Notebook:


A diary of the design tracking the ideas development and the decision made in a design notebook


Name; Affiliation; Title of the problem; Problem Statement; and all sketches, notes and calculations that concerns the design


A design notebook sequentially numbered, signed and dated pages is considered good documentation whereas
random bits of information scrawled on bits of papers are not.


Good evidences for legal purposes (patent or lawsuit) as well as a reference to the history of the designer’s own work


Documents Communicating with Management:


Needed for periodic presentations to managers, customers, and other team members for design review


Regardless of its form (oral or written);


Make it understandable (consider the recipients’ level of knowledge about the design problem)


Carefully consider the order of presentation (whole


parts


whole: 3
-
step approach: gradual
introduction of new ideas)


Be prepared with quality material (good visual and written documentation; following the agenda;
being ready for questions)


Documents Communicating the Final Design:


Material describing the final design, e.g, Drawings (or data files) of individual components and of
assemblies


Written documentation to guide


manufacture, assembly, inspection, installation, maintenance, recruitment, and quality control


39

Team Project


Select an original design problem to solve throughout the
remainder of the course.


The problem should concern biomechanical devices in which some of
the design team members have some knowledge or training.


The final product will be data from analyses and evaluation and final
drawings, not an actual hardware.


Design Team Activity :


Each student should start gathering the design ideas immediately and
recording the ideas in the design notebook.


Start the team meeting ASAP for:


Organization of the team


Planning the design process to finish the project by the end of April.


Each team will present their design project in May.


Any discussion about the design project with the instructor is welcome.

40

Project Definition and Planning


Concurrent engineering encourages involvement
through out the entire product life cycle from the
project definition to product retirement.



Project definition and planning is the first phase of
the mechanical design process.

41

Project Definition


Why developing new products?


To fill some market need


Mostly driven by the customer


To exploit a technological development


Driven by new technologies and what is learned during the design



Project Definition:


the challenges of choosing from the many suggestions as to which products to
spend time and money on to develop or refine


“Fuzzy front end” of dealing with vague design ideas



Specific Questions in Project Definition Phase:


Is there a good potential return on investment (ROI)?


Does the new product or improvement fit the company image?


Does it fit the distribution channels?


Is there sufficient production capacity in
-
house or with known vendors?


What will the project cost?


42

Project Planning


Planning is like trying to measure the smile of the Cheshire cat; you are
trying to quantify something that isn’t there.



Planning is the process used to develop a scheme for scheduling and
committing the resources of time, money, and people.


Producing a map showing how product design process activities are scheduled.


The whole activities of specification definition, conceptual design, and product
development must be scheduled and have resources committed to them


Planning generates a procedure for developing needed information and
distributing it to the correct people at the correct time.


Important information: product requirements, concept sketches, system
functional diagrams, component drawings, assembly drawings, material
selections, and any other representation of decisions made during the
development of the product.


Typical Master Plan (a generic process) of a Company for Specific Products:


A blue print for a process:


product development process; delivery process; new product development plan; or
product realization plan, etc.


We will refer to this generic process as the product development process
(PDP).

43

ISO
-
9000


A quality management system of the International Standard Organization


First issued in 1987 and now adopted by over 150 countries


Over 350,000 companies worldwide and 8500 U.S. companies have the ISO
-
9000
certification


ISO
-
9000 registration means that the company has a quality system that:


Standardizes, organizes, and controls operations.


Provides for consistent dissemination of information.


Improves various aspects of the business
-
based use of statistical data and analysis.


Enhances customer responsiveness to products and services.


Encourage improvement.


To receive certification,


One should develop a process that describes how to develop products, handle product
problems, and interact with customers and vendors.


Required written procedures that:


Describe how most work in the organization gets carried out (i.g., the design of new products, the
manufacture of products, and the retirement of products).


Control distribution and reissue of documents.


Design and implement a corrective and protective action system to prevent problems from recurring.


Evaluation of the effectiveness of the process by an accreditted external auditor


Certification expires in 3 years and audits at 6
-
month intervals to maintain the currency of
the certificate.


ISO
-
9000 requires a company to have a documented development process on which
the plan for a particular product can be based.

44

Background for Developing a Design Project Plan


A plan tells how a project will be initiated, organized, coordinated, and monitored, e.g.,
managerial activities.


Types of Design Projects:


Variation of existing product:


Improvement of existing product:


Redesign of some features of an existing product due to:


Customers request; no longer supply of materials or components from the vendor; needed improvement in
manufacturing; or New technology or new understanding of an existing technology


Development of a new product for a single (or small) run or for mass production


Members of the Design Team:


Product design engineer:


Product manager (product marketing engineer):


Manufacturing engineer; Detailer; Drafter; Technician; Materials specialist; QC/QA specialist;
Analyst; Industrial engineer; Assembly manager; Vendor’s or supplier’s representatives


Structure of Design Teams:


Functional Organization (13 %):


Each project is assigned to a relevant functional area, focusing a single discipline


Functional Matrix (26 %):


project manager with limited authority is designated to coordinate the project across different functional areas


Balanced Matrix

(16 %):


A project manager is assigned to oversee the project and shares the responsibility and authority with functional
managers.


Project Matrix

(28 %):


A project manager oversees the whole project and functional managers assign personnel as needed.


Project Team

(16 %)


Organize the talent around the project whenever possible.


Structures focus on the project are more successful than those built around the functional areas in the company.

45

Planning for Deliverables


Deliverables:


All models of the product, such as drawings, prototypes, bills of materials, analysis results, test results,
and other representations of the information generated in the project


Measure of the progress in design project


Models vs. Prototypes:


Models are analytical and/or physical representations of design information.


Prototypes are physical models. Solid models in CAD can replace the physical models these days.


4 Purposes of Prototypes:


Proof
-
of
-
concept:


Developing function of the product to compare with the goals


Learning tool


Proof
-
of
-
product:


Refine the components and assemblies


Geometry, materials and manufacturing processes are as important as functions


Rapid prototyping and CAD models have greatly improved the time and cost efficiency in building prototypes.


Proof
-
of
-
process:


Verify both the geometry and manufacturing process.


Exact materials and manufacturing processes are used to build sample for functional testing.


Proof
-
of
-
production


Verify the entire production product.


The result of preproduction run.


46

Types of Models





Phase


Physical

(Form and Function)

Medium

Analytical

(mainly Function)


Graphical

(mainly Form)

Concept





Final Product

Proof
-
of
-
concept prototype



Proof
-
of
-
product prototype


Proof
-
of
-
process and proof
-
of
-
production prototype


Back
-
of
-
the envelope
analysis


Engineering science analysis


Finite element analysis;
detailed simulation

Sketches



Layout drawings


Detail and assembly
drawings; solid models

An important decision in planning the project:


-
How many models and prototypes should be scheduled in the design process?


Because of cost effectiveness, there is a strong move toward replacing physical prototypes with
computer models. But not always right.


Be sure to set realistic goals for the time required and the information learned.

47

Five Steps in Planning


Step 1: Identify the Tasks


Tasks in terms of the activities that need to be performed (generate concepts,
producing prototypes, etc.)


Make the tasks as specific as possible.



Step 2: State the Objective for Each Task


Each task must be characterized by a clearly stated objective


The results of the tasks (or activities) should be the stated objectives.


Task objectives should be:


Defined as information to be refined or developed and communicated to others.


This information should be contained in deliverables


Easily understood by all in the design team.


Specific in terms of exactly what information is to be developed. If concepts are
required, then tell how many are sufficient.


Feasible, given the personnel, equipment, and time available



Step 3: Estimate the Personnel, Time, and Other Resources Needed to meet
the Objectives


Step 4: Develop a sequence for the tasks


Step 5: Estimate the Product Development Costs

48

Step 3: Estimate the Personnel, Time, and Other
Resources Needed to Meet the Objective


Necessary Identification for each Task:


Who on the design team will be responsible for meeting the objectives?


What percentage of their time will be required?


Over what period of time they will be needed?



Time (in hours) = A x PC x D
0.85


A = a constant based on past projects


A = 30 for a small company with good communication


A = 150 for a large company with average communication


PC = product complexity based on function



PC =


樠x⁆
j
(j = the level in the functional diagram; F
j

= the number of functions at that level)


D = project difficulty


D = 1, not too difficult; D = 2, difficult; D = 3, extremely difficult



Time estimation = (o + 4m + p)/6


O = optimistic estimate; m = most
-
likely estimate; p = pessimistic estimate



Time Distribution across the Phases of the Design Process


Project Planning (3

5 %); Specifications Definition (10


15%); Conceptual Design (15


35%); Product Development (50


70%); Product Support (5


10%)

49

Step 4: Develop a Sequence for the Tasks


The goal is to have each task accomplished before its result is needed and to make
use of all of the personnel, all of the time.


For each task, it is essential to identify its precessors and successors.


Tasks are often interdependent


two tasks need decisions from each other in order to be
completed.


Sequential vs. Parallel (uncoupled and coupled) tasks


Bar Chart (or Gantt Chart)


best way to develop a schedule for a fairly simple
project


Design Structure Matrix (DSM)


for a complex project with coupled tasks


Showing the relationship (or inter
-
dependence) among tasks (example: see page 104


Useful tool for to help sequence the tasks (Page 104)


50

Step 5: Estimate the Product Development Cost


The planning document can serve as a basis for estimating the cost of
designing the new product in terms of:


Personnel cost


Resources (supplies and equipment)

Team Project:

-

Planning must be done and written in the PDF.

-

Read examples in pages from 105


109 for planning.

-

Gantt chart or DSM should be good entries.

51

Understanding the Problem and

the Development of Engineering Specifications


Importance of finding the right problem to be solved:


Unnecessary effort to design a retarder (dampener) determining the final
position of the solar panels in the Mariner IV satellite


Finding the right problem to be solved is often not easy although it may seem a
simple task.


Creeping Specifications:


Specifications changing during the design process


More features can be added as more is learned during the process


New technologies or competitive products introduced during the design (ignore,
incorporate or start all over?)


Changes in any spec. affecting the previous decisions depedent upon that spec


Engineering Specifications (requirements) should be:


Discriminatory:


Reveal the difference between alternatives.


Measurable (most important and major topic of chap 6)


Orthogonal


Each specification should identify a unique feature of the alternative.


“Product must give smooth ride over rough road.” vs. “Product should reduce shocks from bumps.”


Universal


Characterizing an important attribute of all the proposed alternatives


External


Only external features are observable.

52

Quality Function Deployment (QFD)


Most popular technique used to generate engineering
specifications in an organized manner


Developed in Japan in the mid
-
1970s and introduced to the US in the late
1980s


69% of the US companys use the QFD method recently



Important Points


Employ QFD no matter how well the design team thinks it understands a
problem.


QFD takes time to complete, but time spent for QFD saves time later.


QFD can be applied to the entire problem and also any subproblems.


QFD helps overcome our cognitive limitation.


We tend to try to assimilate the customer’s functional requirement (what is
to be designed) in terms of form (how it will look).


53

Quality Function Deployment (QFD)

House of Quality

54

Example of QFD

Step 1: identify the customers


Step 2: determine the requirements


Step 3: determine the relative


importance of requirements


Step 4: identify and evaluate the


competition


Step 5: generate engineering specification


Step 6: Relate customers’ requirements to


engineering specifications


Step 7: Set engineering targets


Step 8: identify the relationships between


engineering requirements

55

QFD Step 1: Identify the Customers: Who are they?

For general products:


Who are the customers?

-
Consumers

-
Designers’ management

-
Manufacturing personnel

-
Sales staff

-
Service personnel

-
Standard organizations

-
Etc.


For many products,

there are 5 or more
classes of customers
whose voices need to be
heard

For a spinal implant system:


Who are the customers?

-
Orthopaedic surgeons

-
Neurosurgeons

-
Nurses

-
Hospitals

-
Distributors

-
Sales Reps

-
Patients ?



56

QFD Step 2: Determine the Customer’s Requirements: What
do the customers want

Consumers:

-

works as it should,

-

lasts long,

-

is easy to maintain,

-

looks attractive,

-

incorporates the latest technology,

-

and has many features.


Production Customer:


-

is easy to produce (both manufacture and assemble),

-

uses available resources (human skills, equipment, and raw materials),

-

uses standard parts and methods,

-

uses existing facilities,

-

produces a minimum scraps and rejected parts.


Marketing/Sales Customer:

-

easy to package, store, and transport,

-

attractive and suitable for display


Types of Requirements:

-
Basic features: neutral satisfaction with existence

-
basic assumed functions; not included in QFD

-

Performance Features: good satisfaction with existence

-

verbalized in the form that the better the performance, major part of QFD

-

Excitement (or WOW) Features: high satisfaction with existence

57


How to collect customer’s requirements
:


Observation of customers


Surveys: mail, telephone, face
-
to
-
face


Focus
-
group technique


A group of surgeons for orthopaedic implants



Steps for developing useful data for requirements
:


Specify the information needed:


Reduce the problem to a single statement. If impossible, more than one data collecting effort may be warranted.


Determine the type of data
-
collection method to be used:


Depending on the use of data collection methods


Determine the content of individual questions:


Write a clear goal for the results expected from each question.


Design the questions:


Each question should seek unbiased, unambiguous, clear and brief information.


Do not: assume that the customers have more than common knowledge; use jargon; lead the customer toward the answer
you want; tangle two questions together.


Do use complete sentences


Order the questions:


Order them to give context


Take data:


Any set of questions should be considered a test or verification.


Repeated application is required to generate usable information.


Reduce the data:


Make a list of customer’s requirements in the customer’s own word (easy; fast; other abstract terms).


The list should be in positive terms, i.e., wanted, not unwanted


QFD Step 2: Determine the Customer’s Requirements:


What do the customers want?

58

Types of Customers’ Requirements:


Functional Performance


Performance about the product’s desired behavior


Flow of energy, information, or materials; Operational steps; operation sequence


Human Factors


Required in any products that is seen, touched, heard, tasted, smelled or controlled by a human


Appearance; Force and motion control; Ease of controlling and sensing state


Physical Requirements


Available spatial envelope; Physical properties


Reliability


Mean time between failures; Safety (hazard assessment)


Life
-
Cycle
-
Concerns


Distribution (shipping); Maintainability; Diagnosability; Repairability; Testability; Cleanability; Installability;
Retirement


Resources Concerns


Time; Cost; Capital; Unit; Equipment; Standards; Environment


Manufacturing Requirements


Materials; Quantity; Company capabilities


**For Spinal Implants:

-
Functional performance (flow of energy, operational steps and operation sequence)

-
Human Factors

-
Physical Requirements

-
Reliability (mechanical failure, corrosion, biocompatibility, and complications due to the failure)

-
Other requirements are not as critical as for other common products

QFD Step 2: Determine the Customer’s Requirements:


What do the customers want?

59

Resource Concerns


Time requirements:


Timing to introduce a new product


Cost Requirements:


Capital Cost:


Cost per Unit:


Cost estimation will be covered in Chap 12.


Standards (Codes):


Types of Standards:


Performance: seat
-
belt strength, helmet durability


The
Product Standards Index

lists US standards that apply to various products.


American National Standards Institute (ANSI) does not write standards but is a clearing house for
standards written by other organizations


Test Methods:


American Society for Testing and Materials (ASTM
) publishes over 4000 individual standards covering the
properties of materials, specifying equipment test the properties and outlining the procedures for testing.


Underwriters Laboratories (UL)

testing standards.


Codes of Practice:


Give parameterized design methods for standard mechanical components, such as pressure vessels, welds,
elevators, piping and heat exchangers


Knowledge of which standards apply to the current situation are important to
requirements and must be noted from the beginning of the project


Environment Concerns:

60


Evaluate the importance of each of the customers’
requirements


Generate a weighting factor for each requirement considering


To whom is the requirement important


How is a measure of importance developed for this diverse group of
requirements


How to determine the weight factor


Customer’s rating from 1 (unimportant) to 10 (important)


Fixed Sum Method:


Distribute the importance on all the listed requirements


QFD Step 3: Determine the Relative Importance of the
Requirements: Who vs. What

61


Determine how the customer perceives the competition’s ability
to meet each of the requirements.


1 The product does not meet the requirement at all.


2 The product meets the requirement slightly.


3 The product meets the requirement somewhat.


4 The product meets the requirement mostly.


5 The product meets the requirement completely.



Why studying existing products?


It creates an awareness of what already exists.


It reveals opportunities to improve on what already exists.



This process is called “Competition Benchmarking.”

QFD Step 4: Identify and Evaluate the Competition:


How satisfied is the customer now?

62


Engineering Specifications:


Restatement of the design problems in terms of parameters that can be measured and have target
values.


Measurable behaviors of the product
-
to
-
be


If units for an engineering parameter can not be found, the parameter is not measurable and must
be readdressed.



Examples:


Easy to attach


The number of steps; time to attach; number of parts; number of tools used



Every effort must be made to find as many ways as possible to measure customer’s
requirements.



Carefully check each entry to see what nouns are or noun phrases have been used
because each noun refers to an object that is part of the product or its environment
and should be considered to see if new objects are being assumed.


“easy to adjust suspension system …” then “an adjustable suspension system” has been
assumed as part of the solution.

QFD Step 5: Generate Engineering Specifications:


How will the customers’ requirements be met?

63

QFD Step 6: Relate Customers’ Requirements to Engineering
Specifications: How to measure what?

Strong, medium, weak, and no relationship

QFD Step 7: Set Engineering Targets: How much is good
enough?

1.
Ascertain how the competition meets the engineering goal.

2.
Establish targets for the new product.

Remember:


-

Set the target early.


-

Too tight target may eliminate new ideas.


-

If a target is much different than the values achieved by the competition, it should be
questioned.

Strong negative; negative; Positive; Strong positive

QFD Step 8: Identify Relationships between Engineering
Requirements: How are the “HOWS” dependent to each
other?

64

Example of QFD

Step 1: identify the customers


Step 2: determine the requirements


Step 3: determine the relative


importance of requirements


Step 4: identify and evaluate the


competition


Step 5: generate engineering specification


Step 6: Relate customers’ requirements to


engineering specifications


Step 7: Set engineering targets


Step 8: identify the relationships between


engineering requirements

65

Basic Methods for Idea Generation


Brainstorming:


Record all the ideas generated.


Generate as many ideas as possible, then visualize them.


Think wild.


Do not allow evaluation of the ideas


6
-
3
-
5 Method (Brainwriting):


Brainwriting to force equal participation by all.


6 (optimal number of members); 3 (number of ideas); 5 (minute interval)


No verbal communication allowed until the end.


Use of Analogies in Design:


Consider needed function and then ask, What else provides this function?


Use of Extremes and Inverses:


Transform current concepts into others by taking them to extremes or considering
inverses


Finding Ideas in Reference Books and Trade Journals:


Using Experts to Help Generate Concepts:


Needed to design in a new domain

66

Guideline for Team Project


Use Brainstorming Method to determine a design item.


Make sure to write your own ideas in an individual notebook and finalized
team project item in PDF with minutes of brainwriting.


Do not try to make a fancy and complete product. Any improvement in a
small component can be a product for the design team project as long as the
techniques introduced in this class are well executed.




Make sure to follow all the steps suggested in this book and
produce a good design records.

67

Concept Generation


Concept:


An idea that is sufficiently developed to evaluate the
physical principles that govern its behavior.


Goal of concept generation is to confirm that the proposed
product will operate as anticipated and that, with
reasonable further development, it will meet the targets
set.


Concepts must be refined enough to evaluate the
technologies needed to realize them, to evaluate the
basic architecture (form) of them, and to evaluate the
manufacturability to some extent


Concepts can be represented in deliverables (sketch,
flow diagram, a set of calculations, prototypes, etc)


Examples of weak methodology
:


Start design with a concept to be developed into a
product.


There is a tendency for designers to take their first
idea and start to refine it toward a product.


If you generate one idea, it is probably a poor one. If you
generate twenty ideas, you may have a good one. (or,
alternatively, he who spends too much time developing a single
concept realizes only that concept.


Main goal of this chapter is to learn techniques
for the generation of many concepts.


Functional decomposition


Concept variant generation

68

Understanding the Function of Existing Devices


Bench marking (review of existing devices) is always a good practice because:


There is nothing so new that ideas for it can not be borrowed from other devices.


Lots of engineering hours have been spent developing the features of existing products (it is
foolish to ignore it).


Defining Function:


Remember that
function

tells
what

the product must do, whereas its
form

conveys
how

the
product will do it.


Develop the
what

and then map the
how

as we mapped
what

the customer required into
how

the
requirements were to be measured in QFD.


Function is the logical
flow of energy (including static forces), material, or information between
objects

or the change of state of an object caused by one or more of the flows.


Functions required to attach any component to another are GRASP, POSITION, ATTACH. In
undertaking these actions, human provides information and energy in controlling movement and in
applying force to it. (Flow of energy, material, and information)


Functions associated with flow of energy:


Types of energy: mechanical, electrical, fluid and thermal


Its action: transformed, stored, transferred (conducted), supplied, and dissipated



Functions associated with flow of material:


Through
-
flow: position, lift, hold, support, move, translate, rotate and guide


Diverging flow: disassemble, separate


Converging flow: assembling or joining materials (mix, attach, and position relative to)


Functions associated with flow of information:


In the form of mechanical signals, electrical signals or software


Generally used as part of automatic control or to interface with a human operator


Function associated with the change of state of an object:


Changes in energy storage, kinetic or potential energy, material properties, form or information content

69

Using Product Decomposition to

understand the Function of Existing Product


Step 1: For the whole device, examine interfaces with other objects.


Examine the flows of energy, information and material into and out of the device


Step 2: Remove a component for more detailed study.


Carefully note how it was fastened to the rest of the device and also any relationship it
has to other parts that may not contact.


It may have a clearance with some other parts in order to function.


Step 3: Examine each interface of the component to find the flow of energy


Understand:


How the functions identified in step 1 are transformed by the component;


How the parts are fastened together;


How forces are transformed and flow from one component to anther; and


The purpose of each feature of component


70

Patents as a Source of Ideas


Patent Literature:


Good source of ideas although
hard to read


Sources for Patent Searches


http://www.uspto.gov/patft/index.
html


http://www.delphion.com/home



http://gb.espacenet.com

-

source
for European and other foreign
patents



Types of Patents:


Utility Patents:


Claiming how an idea operates or
is used


Design Patents:


Covering only the look or form of
the idea


71

Technique for Designing with Function


Goal of Functional Modeling:


To decompose the problem in terms of flow of energy, material, and
information


Decomposition forces a detailed understanding of what the product
-
to
-
be is to
do.



4 Basic Steps:


Find the overall function that needs to be accomplished.


The goal is to generate a single statement of the overall function on the basis of
the customer requirements.


Create subfunction descriptions.


The goal is to decompose the overall function.


Order the subfunctions.


Refine subfunctions.

72

Step 1: Find the overall function


Most important functions must be
reduced to a simple clause and put it in
a black box.


Inputs into and outputs out of this black
box are all flows of the energy, material
and information.


Guidelines:


Energy must be conserved.


Material must be conserved


All interfacing objects and known, fixed
parts of the system must be identified.


List all the objects (all features,
components, assemblies, humans, etc)
that interact, or interface, with the
system.


Ask how will the customer know if the
system performing?


Answers to this question will help
identify information flows that are
important.


Use action verbs to convey flow.


Typical mechanical design functions:


See Table 7.1

The BikeE suspension Example:


Overall function:


transfer and absorb


To transfer forces between wheel,
chain, and frame and absorb peak
loads between wheel and frame


Goal: alter the energy flow





Make sure to state the overall function
of your design in individual design
notebook (personal ideas) and finalized
overall function in the PDF.


73

Step 2: Create subfunction description


Goal is to decompose the overall function into subfunctions.


Reasons for Decomposition:


The resulting decomposition controls the search for solution to the design problem.


Since concepts follow function and products follow concepts, we must fully understand the function
before wasting time generating products that solve the wrong problem.


Decomposition into functional detail leads to a better understanding of the problem.


Most good ideas come from fully understanding the functional needs of the design problem.


It is useful to begin function decomposition before the QFD and use the functional development to help
determine the engineering specifications.


Decomposition may lead to the realization that there are some already existing components that
can provide some of the functionality required.



Guidelines:


Consider what needs to happen (the function) not how.


Detailed, structured
-
oriented how consideration must be suppressed as they add detail too soon, which
limit the number of possible concepts too early.


Use only objects described in the problem specification or overall function.


Use only “nouns” previously used to describe the material flow or interfacing objects to avoid the new
components creeping into the product.


Break the function down as finely as possible.


Let each function represent a change or transformation in the flow of material, energy, or information.


Use standard notation when possible.


Whenever available, use common notations, such as block diagrams used to represent elec. circuits,
piping system, or transfer functions in systems dynamics and control, although there is no standard
notation for general mechanical product design.


Consider all operational sequences.


Think of each function in terms of its preparation, use, and conclusion.

74

Functional Decomposition for the Space Shuttle aft Field Joint

75

Step 3: Order the Subfunctions


Order the functions found in step 2 to accomplish the overall function in step
1.



Guidelines:


The flows must be in logical or temporal order.


Arrange the subfunctions in independent group (preparation, use, and conclusion).


In each group, arrange them so that the output of one function is the input of another.


Redundant functions must be identified and combined.


Similar subfunctions must be combined into one.


Functions not within the system boundary must be eliminated.


This step helps the team come to mutual agreement on the exact system boundary; it is
often not as simple as it sounds.


Energy and material must be conserved as they flow through the system.


Inputs to each function must match the outputs of the previous function.


76

Step 4: Refine Subfunctions


Examine each subfunction to see if it can be further divided
into sub
-
subfunctions.


This step should be continued until:


‘atomic’ functions are developed; or


“atomic” implies that the function can be fulfilled by existing objects.


new objects are needed for further refinement.


It is a struggle to develop the suggested diagram of function
decompositions.


It is a fact that the design can be only as good as the understanding of the
functions required by the problem.


This exercise is both the first step in developing ideas for solutions and
another step in understanding the problem.



The functional decomposition diagrams are intended to be
updated and refined as the design progresses.

77

Concept Generation


Concepts are the means for providing function.


Any form that gives an indication how the function can be achieved.


What to do


Function vs. How to do


Concepts (forms)


Remember that the idea is often not original.



Many methods for concept generation are available, but no
single method is best.


A good designer is familiar with these methods and uses them, or a
combination of them, as needed.


78

Basic Methods for Concept Generation

79

Morphological Method


This technique uses the functions identified
to foster ideas.


Powerful method that can be used formally or
informally as part of everyday thinking


2 step approach



Step 1
-

Developing Concepts for Each
Function:


Goal is to find as many concepts as possible
that can provide each function identified in the
decomposition.


How to store mechanical energy: springs,
elastomers (rubbers or plastics), etc.


If there is a function with only one conceptual
idea, this function must be re
-
examined.


Situations explaining the lack of more concepts.


The designer has made a fundamental
assumption.


The function is directed at how, not what.
-

e.g.
“store energy in coil spring” rather than “store
energy”


Domain knowledge is limited.


Keep the concepts as abstract as possible and at
the same level of abstraction for better
comparison of developed concepts.


The force required for moving an object can be
provided by a hydraulic piston, a linear electric
motor, the impact of another object, or magnetic
repulsion.


Refined mechanical components vs. basic physical
principles.

Morphology for BikeE Suspension System

80

Morphological Method


Step 2
-

Combining Concepts:


to combine these individual concepts into
overall concepts to meet all the functional
requirements.


Select one concept for each function and
combine those into a single design.


Pitfalls:


This method may generate too many ideas.


It erroneously assumes that each function of
the design is independent and that each
function satisfies only one function.


The results may not make any sense.



Concept generation process is the time
that back
-
of
-
the
-
envelope sketches begin
useful.


We remember functions by their forms


Only way to design an object with any
complexity is to use sketches to extend the
short
-
term memory.


Sketches made in the design notebook
provide a clear record of the development of
the concept and the product.


Combined Concepts for BikeE Suspension System

81

Logical Methods for Concept Generation


The Theory of Inventive Machines, TRIZ:


Developed by Genrikh Altshuller (a ME engineer, inventor, and Soviet patent
investigator) in Soviet Union in the 1950s based on patterns found in patented
ideas


Goal of TRIZ:


Find the major contradiction that is making the problem hard to solve, then


Use TRIZ’s 40 inventive ideas for overcoming the contraindication


With TRIZ, we can systematically innovate; we don’t have to wait for an
inspiration or use the trial and error common to other methods.



Axiomatic Design:


Evolved in MIT by Prof. Nam Suh in an effort to make the design process
logical.


1
st

Axiom:


Maintain the independence.


Then, a change in a specific design parameter should have an effect only on a single function.


2
nd

Axiom:


Minimize the information content of the design.


The simplest design has the highest probability of success and is the best alternative.

82

Concept Evaluation


How to choose the best of the concepts generated for
development into a quality product?


Goal is to expend the least amount of resources on deciding which concepts
have the highest potential for becoming a quality product.


It is difficult to evaluate concepts, or to choose which concepts to spend time,
particularly when we still have very limited knowledge and data on which to
base this selection.


Design is learning, and resources are limited.


Techniques for systematic evaluation of rough concepts.


Evaluation implies both “comparison” and “decision making.”


It is the comparisons between alternative concepts and the requirements that they
must meet that gives the information necessary to make decisions.


For all design decisions:


Itemizing the alternatives and the criteria for their evaluation


Comparing the alternatives to the criteria to each other


For comparisons:


Alternatives and criteria must be in the same language and they must exist at the
same level of abstraction


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Concept Evaluation Techniques

Be ready during concept
evaluation to abandon your
favorite idea, if you can not
defend it in a rational way.


Abandon if necessary “the
way things have always have
been done around here”.

84

Information Presentation in Concept Evaluation

Design Evaluation Cycles

85

Evaluation based on Feasibility Judgment


Three Immediate Reactions of a Designer as a concept is generated based on
designer’s “gut feel”:


It is not Feasible.


It might work if something else happens.


It is worth considering.



Implications of Each of these Reactions:


It Is Not Feasible.


Before discarding an idea, ask “Why is it not feasible?”


Make sure not to discard an idea because:


a concept is similar to ones that are already established, or


a concept is not invented here (less ego
-
satisfying).


It is Conditional.


To judge a concept workable if something else happens.


Factors are the readiness of technology, the possibility of obtaining currently unavailable
information, or the development of some other part of the product.


It is Worth Considering.


The hardest concept to evaluate is one that is not obviously a good idea or a bad one, but
looks worth considering.


Such a concept requires engineering knowledge and experience. If sufficient knowledge is
not immediately available, it must be developed using models or prototypes that are easily
evaluated.

86

Evaluation based on GO/NO
-
GO Screening


Measures for deciding to go or no
-
go:


Criteria defined by the customer requirements:


Absolute evaluation by comparing each alternative concept with the customer
requirements.


A concept with a few no
-
go responses may be worth modifying rather than
eliminating


This type of evaluation not only weeds out designs that should not be considered
further, but also helps generates new ideas.


Readiness of the technologies used:


This technique refines the evaluation by forcing an absolute comparison with
state
-
of
-
the
-
art capabilities.


6 Measures for a Technology’s Maturity:


Are the critical parameters that control the function identified?


Are the safe operating latitude and sensitivity of the parameters known?


Have the failure modes been identified?


Can the technology be manufactured with known process?


Does hardware exist that demonstrates positive answers to the preceding four questions?


Is the technology controllable throught the product’s life cycle?


If these questions are not answered in the positive, a consultant or vendor is
added to the team.

87

Evaluation based on a Basic Decision Matrix


Decision
-
Matrix Method (or Pugh’s
Method):


effective comparison of alternative concepts
(basic form Table 8.2)


Iteratively test the completeness and
understanding of requirements, rapidly
identifies the strongest



Step 1: Choose the criteria for Comparison.


Criteria are the functional requirements and
engineering specification determined in QFD.


The concepts must be refined enough to
compare with the engineering targets for
evaluation (mismatch in the level of
abstraction).


Step 2: Develop Relative Importance
Weightings.


Step 3 in QFD should provide the data for
relative importance.


Step 3: Select the Alternatives to be
Compared.


Step 4: Evaluate Alternatives.


Relative evaluation among alternatives


Step 5: Compute the Satisfaction.

**

This method is most effective if
each member performs it
independently and the individual
results are then compared.


-

have BDM in individual notebook.

88

Decision Matrix for Energy Management System

S indicates “Same as datum”

89

Robust Decision Making


Robust decision refers to make decisions that are as insensitive
as possible to the uncertainty, incompleteness, and evolution of
the information that they are based on.


For robust decision making, we need to improve the method
used to evaluate the alternatives (step 4 in decision
-
matrix
method).


Word Equations used for Robust Decision Making