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: Describe a specification Describe a decision matrix Categorize potential failures for a design Perform a functional decomposition Create a personna

EPICS Balance Service Learning Service-learning is a balance of the learning of design and the service we contribute the communities through completed designs and support Service To our partners, meeting needs in the community Learning Becoming good designers, professionals & active citizens Complimentary goals that enhance each other

Design Tool: Engineering specifications

Specifications Development What does your project partner need? Don’t just rely on what they want, find out what they need Understand the problems and issues you are addressing Who will use product and who will benefit from it? Gather Data Talk to Project Partner and others impacted by the project How will the problem be worked? Criteria for design teams How will teams be integrated Transition plans for multiple semesters Gather input from project partner on specifications Develop a specifications document and share it

Customer Requirements Types of customer requirements Functional performance Human factors Physical Time (reliability) Cost Standards Test Method Service & maintenance

Customer Requirements For a cell phone, make a list of Ten customer requirements

Design Specifications Answers the “how” question Quantified 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 What is available Why did they use their approach Patent searches avoid infringement Protect IP Are we smarter than everyone else? Or did we miss something?

Design Targets Set standards to meet with your design How good is good Can be a living document Don’t compromise on goals, but refine as the design progresses Tool make design trade offs Design decisions Communication with project partner

Decision Matrix Table with alternatives Quantify categories and score alternatives Importance in different categories Use judgement to do reality checks Leaves documentation of thought process of design Can be shared in design reviews

Criteria for Comparison Decision Matrix   Ideas to be compared Criteria for Comparison Weights Scores Totals

Decision Matrix Example: Getting a Job Criteria Wts Co. A Co. B Co. C Co. D Location 5 5x5=25 5x1=5 5x3=15 5x4=20 Salary 4 Bonus 2 Job 3 Training Boss Totals

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 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 An action verb The object(s) on which the verb acts Possibly a modifier giving details of the function 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 Review the design Brainstorm potential failure modes List potential effects of failure Rank failures Severity Occurrence Detection RPN = Severity X Occurrence X Detection Develop action plan Implement fixes Revisit potential failure risks

Describe the project so the whole group understands it 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? 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 Severity Occurrence Detection Rating (1 to 10) How severe are the consequences to the failure Occurrence How often are the failures likely to occur? Detection How easily are the failures detected?

DFMEA Calculations Scores for Severity, Occurrence and Detection 1 to 10 1 = Low 10 = High Risk Priority Number (RPN) RPN =Severity X Occurrence X Detection

DFMEA Matrix Failure mode Effect of 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 Prioritize Eliminate failure scenarios Continue until risks are below determined thresholds Show to the design reviews for confirmation

Questions/Discussion