HSE Teachers’ Workshop Jean Kampe Summer 2011 Delivered by Jonathan Riehl

1. HSE Teachers’ WorkshopJean KampeSummer 2011Delivered by Jonathan Riehl Design I

2. Engineering design the process the language Today’s Focus

3. What engineers do … Problem Solution Design

4. is a process is modeled in many different ways involves the use of tools has its own language/vocabulary Design … in an engineering context

5. Engineering Design Process A Linear Model (Not very realistic) Client’s Need Problem Definition Conceptual Design Preliminary Design Documentation of Fabrication Specifications Detailed Design Ref: Dym, C.L. and Patrick Little, Engineering Design, a Project-Based Introduction, 3rd Ed., John Wiley & Sons, Inc., 2009, Chapt.2.

6. Define Criteria Gather Information Choose a Strategy Start (Define the Problem) Engineering Design Process Develop Alternate Solutions Revise No A Cyclic Model – a much better view Does solution meet requirements? Build a Prototype Model and Analyze Yes Test and evaluate Documentation of Fabrication Specifications

7. Problem Definition Define Criteria Gather Information Choose a Strategy Start (Define the Problem) Engineering Design Process Develop Alternate Solutions Revise No A Cyclic Model Does solution meet requirements? Build a Prototype Model and Analyze Yes Test and evaluate Documentation of Fabrication Specifications

8. Define Criteria Gather Information Choose a Strategy Start (Define the Problem) Engineering Design Process Develop Alternate Solutions Conceptual Design Revise No A Cyclic Model Does solution meet requirements? Build a Prototype Model and Analyze Yes Test and evaluate Documentation of Fabrication Specifications

9. Define Criteria Gather Information Choose a Strategy Start (Define the Problem) Engineering Design Process Develop Alternate Solutions Revise No A Cyclic Model Does solution meet requirements? Build a Prototype Model and Analyze Yes Preliminary Design Test and evaluate Documentation of Fabrication Specifications

10. Define Criteria Gather Information Choose a Strategy Start (Define the Problem) Engineering Design Process Develop Alternate Solutions Revise No A Cyclic Model Does solution meet requirements? Build a Prototype Model and Analyze Yes Test and evaluate Documentation of Fabrication Specifications Detailed Design

11. Engineering Design Is a cyclic process real-life design does not happen in a linear sequential way Uses tools and procedures we need to know how to use those tools Has its own language we need to understand that language

12. Realm of our design focus Define Criteria Gather Information Choose a Strategy Start (Define the Problem) Engineering Design Process Develop Alternate Solutions Revise No A Cyclic Model Does solution meet requirements? Build a Prototype Model and Analyze Yes Test and evaluate Documentation of Fabrication Specifications

13. Team Activity Staple Remover Exercise

14. Design Criteria(a.k.a. Objectives) Attributes the solution should have (Think in terms of “The design should be ______.”) • Determined from a manufacturing viewpoint • Weighted by their importance • Used to rate each candidate design through metrics

15. Confusing Terms These two items are very different things in design. design criterion (a.k.a. “Objective”) n: Designer chosen characteristic of the solution that is related to the problem, such as durability, size, or weight, and used as an evaluation factor. Plural: design criteria design constraintn: An imposedlimit or boundary placed on the design solution by an external source, such as nature, your boss (i.e., company management), a government agency, or other vested stakeholder.

16. Getting it right … The “right” constraints, criteria, weights, and metrics are the bases of a good Decision Matrix.

17. Engineering is diminished and impoverished by a lack of diversity. At a fundamental level, we all experience the world differently, and those differences in experience are the “gene pool” for creativity. We will never be able to engineer as well as we could until all stakeholders are adequately represented on engineering design teams. Paraphrasing William A Wulf (NAE): (Former president of the National Academy of Engineering, 1996-2007)

18. On the lack of diversity in engineering ... “There is a real ... cost to that ... it is an opportunity cost ... measured in design options not considered, in needs unsatisfied and hence unfulfilled.* It is measured in ‘might have beens,’ and those kinds of costs are very hard to measure. That doesn’t change the fact that they are very real and very important.” Quoting Wm. Wulf: * He’s talking about criteria and constraints that are either not anticipated or not correctly interpreted because the design team does not adequately represent all the stakeholders.

19. The “right” constraints, criteria, weights, and metrics are the bases of a good Decision Matrix.

20. Decision Matrix Score = Rate x weight Design with highest sum wins!!

21. Design Tools • Objective tree • Pair-wise comparison chart • Metrics for Criteria • Decision Matrix

22. Design Tool Use • To organize Criteria (a.k.a. Objectives) • Use an Objective Tree • To assign Weights to Criteria • Use a Pair-wise Comparison Chart • To Rate Alternate Designs for a given Criterion • Use the metric for the criterion to decide on a rating

23. Where does all this get you? To a Decision Matrix that is generated according to real engineering design procedures instead of guesswork

24. Tool: The Objective Tree • Objective Trees help us organize our design objectives (criteria), so that we can use the objectives in other tools. • Objective trees should be solution independent. • Stop when functions and implementations (which are not objectives) begin to appear Ref: Dym, C.L. and Patrick Little, Engineering Design, a Project-Based Introduction, 3rd Ed., John Wiley & Sons, Inc., 2009, Chapt.3.

25. Tool: Pair-wise Comparison Chart Used to help us weight our objectives • Compare only objectives emanating from a common node at the same sub-level in the objective tree • Compare two objectives in a one-on-one fashion: Compare higher-level objectives first • Know whose perspectives are being assessed. Results give an approximate subjective judgment of relative value and importance (i.e., weight) rather than a strong meaningful measurement Ref: Dym, C.L. and Patrick Little, Engineering Design, a Project-Based Introduction, 3rd Ed., John Wiley & Sons, Inc., 2009, Chapt.3.

26. Tool: Pair-wise Comparison Chart Example pair-wise Comparison Chart for marketability of the ladder. • How did we get this? • In the cost row, compare cost to portability, then to usefulness, and then to durability. • Enter 1 if cost is more important, 0 if cost is less important , 0.5 if equally important (rare) • Add the row entries to get a subjective ranking of criterion importance by “Score.” Ref: Dym, C.L. and Patrick Little, Engineering Design, a Project-Based Introduction, 3rd Ed., John Wiley & Sons, Inc., 2009, Chapt.3.

27. Use metrics to measure how well a design alternative achieves the objective, then rate the designs using those measurements (e.g., use a scale of 1-5 with higher ratings being better). Good metrics are essential to rate the design alternatives. To develop metrics Identify units and scale of something appropriate to measure about the objective (e.g., $$, kg, or a defendable subjective scale) Identify the way to measure the designs in those units (tests, surveys) Determine if the measurement is feasible (remember, the designs are only conceptual at this point) Tool: Metrics for the criteria (objectives)

28. Measures something directly related to the criterion in a way that gives you a number or value Is capable of appropriate level of precision or tolerance Is repeatable Is expressed in understandable units of measure Promotes clear interpretation e.g., criterion = ease of assembly Possible metrics Number of parts Estmated time to assemble Characteristics of a “good” metric

29. Decision Matrix Score = Rate x weight Design with highest sum wins!!

30. Summary Engineering design: • is a cyclic process • has its own language (criteria/constraints) • uses tools (objective tree, pair-wise comparison chart, metrics, decision matrix)