Design Tools 1
William Oakes, P.E
Director of EPICS
Assoc. Prof. Engineering Education
Learning Objectives
 At the end of this session, you will be
able to:
1.
2.
3.
4.
5.
Describe a specification
Describe a decision matrix
Categorize potential failures for a design
Perform a functional decomposition
Create a personna
EPICS Balance
Service-learning is a balance of the
learning of design and the service we
contribute the communities through
completed designs and support
Service
Learning
•To our partners,
meeting needs in
the community
•Becoming good
designers, professionals
& active citizens
Complimentary goals that enhance each other
Design Tool:
Engineering
specifications
Specifications
Development
 What does your project partner need?
o Don’t just rely on what they want, find out what they
need
o Understand the problems and issues you are
addressing
o Who will use product and who will benefit from it?
 Gather Data
o Talk to Project Partner and others impacted by the
project
 How will the problem be worked?
o Criteria for design teams
o How will teams be integrated
o Transition plans for multiple semesters
 Gather input from project partner on
specifications
o Develop a specifications document and share it
Customer Requirements
Types of customer requirements
o Functional performance
o Human factors
o Physical
o Time (reliability)
o Cost
o Standards
o Test Method
o Service & maintenance
Customer Requirements
For a cell phone, make a list of
Ten customer requirements
Design Specifications
Answers the “how” question
Quantified
o Should be able to measure whether
you meet it
Objective quantities
A set of units should be associated
with each specification
Forms the basis for your
specifications document
Design Requirements
Starting with the customer
requirements for a cell phone, make a
list of design requirements
Defining Requirements
Benchmarks
o What is available
o Why did they use their approach
o Patent searches
• avoid infringement
• Protect IP
Are we smarter than everyone else?
o Or did we miss something?
Design Targets
Set standards to meet with your design
How good is good
Can be a living document
o Don’t compromise on goals, but refine as
the design progresses
Tool make design trade offs
o Design decisions
o Communication with project partner
Decision Matrix
Table with alternatives
Quantify categories and score
alternatives
o Importance in different categories
Use judgement to do reality checks
Leaves documentation of thought
process of design
o Can be shared in design reviews
Decision Matrix
Ideas to be compared
Criteria for
Comparison
Weights
Scores
Totals
Decision Matrix
Example: Getting a Job
Criteria
Wts Co. A
Location
5
Salary
4
Bonus
2
Job
3
Training
2
Boss
2
Totals
Co. B
5x5=25 5x1=5
Co. C
Co. D
5x3=15 5x4=20
Design Tool:
Defining the
System
Functional Decomposition
Breaking tasks or functions of the
system down to the finest level
Create a tree diagram starting at the
most general function of your system
o What is the purpose of your system?
Break this function down into simpler
subtasks or subfunctions
Continue until you are at the most basic
functions or tasks
Functional Decomposition Diagram
Overall
Function
Subfunction
1
Subfunction
2
Subfunction
3
Sample Diagram – Bike Fender
Protect rider
from water and
dirt off wheel
Shield rider
Steer water
away
from rider
Attach
Splashguard
Functional Decomposition
Each function has a box with
o An action verb
o The object(s) on which the verb acts
o Possibly a modifier giving details of the
function
o Known flows of materials, energy, control
or information
Consider WHAT not HOW
Create a functional
decomposition diagram for
a mechanical pencil
Prepare them to share
DFMEA :
Design for
Robustness
DFMEA Steps
1.
2.
3.
4.
Review the design
Brainstorm potential failure modes
List potential effects of failure
Rank failures
a)
b)
c)
d)
Severity
Occurrence
Detection
RPN = Severity X Occurrence X Detection
5. Develop action plan
6. Implement fixes
7. Revisit potential failure risks
In a group, Identify one project
to use as an example for this
exercise
Describe the project so the whole
group understands it
Brainstorm Failures
What could go wrong?
What could break?
Are there systems your design relies
upon?
o e.g. myEPICS software authenticates
through Purdue’s career accounts. What if
the server goes down?
Are there things that could fail over
time?
Brainstorm a list of potential
failures for the project
Rate failures
Rating
(1 to 10)
Severity
Occurrence
Detection
How severe are the
consequences to
the failure
How often are the
failures likely to
occur?
How easily are the
failures detected?
DFMEA Calculations
Scores for Severity, Occurrence and
Detection
o 1 to 10
o 1 = Low
o 10 = High
Risk Priority Number (RPN)
o RPN =Severity X Occurrence X Detection
DFMEA Matrix
Failure Effect of
mode
Failure
Severity Occurrence Detection RPN Rating
Example
http://en.wikipedia.org/wiki/Failure_mode_and_effects_analysis,
accessed 22 Aug. 2011
Example Chart
Identify the failure scenario that
should be addressed first
Develop an action plan to
address the failure scenario
Continue the process
Implement the plan to eliminate the
failure scenario
Revisit other potential failure risks
o Prioritize
o Eliminate failure scenarios
Continue until risks are below
determined thresholds
o Show to the design reviews for
confirmation
Questions/Discussion