Hse teachers workshop jean kampe summer 2011 delivered by jonathan riehl
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HSE Teachers’ Workshop Jean Kampe Summer 2011 Delivered by Jonathan Riehl. Design I. Engineering design the process the language . Today’s Focus. What engineers do …. Problem Solution. Design. is a process is modeled in many different ways involves the use of tools

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

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Hse teachers workshop jean kampe summer 2011 delivered by jonathan riehl

HSE Teachers’ WorkshopJean KampeSummer 2011Delivered by Jonathan Riehl

Design I


Today s focus

Engineering design

the process

the language

Today’s Focus


What engineers do

What engineers do …

Problem Solution

Design


Design in an engineering context

is a process

is modeled in many different ways

involves the use of tools

has its own language/vocabulary

Design … in an engineering context


Engineering design process

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.


Engineering design process1

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


Engineering design process2

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


Engineering design process3

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


Engineering design process4

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


Engineering design process5

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


Engineering design

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


Engineering design process6

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


Team activity

Team Activity

Staple Remover Exercise


Design criteria a k a objectives

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


Confusing terms

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.


Getting it right

Getting it right …

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


Hse teachers workshop jean kampe summer 2011 delivered by jonathan riehl

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)


Hse teachers workshop jean kampe summer 2011 delivered by jonathan riehl

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.


Hse teachers workshop jean kampe summer 2011 delivered by jonathan riehl

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


Decision matrix

Decision Matrix

Score = Rate x weight Design with highest sum wins!!


Design tools

Design Tools

  • Objective tree

  • Pair-wise comparison chart

  • Metrics for Criteria

  • Decision Matrix


Design tool use

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


Where does all this get you

Where does all this get you?

To a Decision Matrix that is generated according to real engineering design procedures instead of guesswork


Tool the objective tree

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.


Tool pair wise comparison chart

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.


Tool pair wise comparison chart1

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.


Tool metrics for the criteria objectives

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)


Characteristics of a good metric

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


Decision matrix1

Decision Matrix

Score = Rate x weight Design with highest sum wins!!


Summary

Summary

Engineering design:

  • is a cyclic process

  • has its own language (criteria/constraints)

  • uses tools (objective tree, pair-wise comparison chart, metrics, decision matrix)


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