i-b-4 design alternatives evaluation 2014 v1

8/13/2019 I-B-4 Design Alternatives Evaluation 2014 v1

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COMPARISONOF

ALTERNATE DESIGNS(design, concept, configuration)

MEP202

Design, Innovation and Manufacturing


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The need

Given: An idea

Next: What design (or concept) can meet the requirements of

the idea?

Constraints: Laws of physics (nature), i.e. scientific

Answer: Many (possible) designs. All are right .

Q: Which design should we make?

A: Use the methods of evaluating alternate designs.

Q: Then we will get the best design?A: Not always. Not necessarily. But you get a good idea.

Because, methods reflect individual biases (judgments).


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Examples

Car:Auto Expo 2014 (2011) Car designsPen: Roller, Ball, Fountain, Gel, - many designs

Bicycle: .

Chair with (or without) coasters:

Mouse trap:

You complete the data, and add to the list.


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The methods

Pughs method (1991)

Dominic method

Pahl and Bietz

widely used in industry

used on products in market or at design stage

Will they give the same conclusion?


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Methodology

List the customer attributes that the design is supposed tosatisfy.

Designate (label) each design as (1, 2, 3, ..) or any otherscheme.

Use one or more of the three techniques. Do the comparison analysis. Interpret the result (caution!) Identify the best design, which is to be worked upon. What if there is no clear best design?


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Pughs Method (1991)

Evaluate each design alternative for each attribute, onthree point basis

Same as Datum SBetter than Datum +

Poorer than Datum

Count no. of +, and S for each alternative and

compare.

Datum means


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Pughs method - example

Attribute Design-1 Design-2 Design-3 Design-4

Stays closed

Inexpensive

Waterproof

Identify contents

Attractive

Total Pluses (+)

Total Minuses ()

Total Datum (S)

Net scoreRANK


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Dominic method

Evaluate each design alternative based onfive values AND three priorities

Values Symbol Priority criterion Symbol

Excellent E High Priority H

Good G Moderate Priority M

Fair F Low Priority L

Poor PUnacceptable U


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Dominic method - example

High prioritycriteria Mediumprioritycriteria

Lowprioritycriteria

Excellent

Good

Fair

Poor

Unacceptable

Enter design alternative no. in appropriate box for each

customer attribute.

Then, see patterns, if any.

Trend? Upper left vs. Lower right. Identify better design.


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Pahl and Beitz method

List all customer attributes (i) Assign a weight to each attribute, wi ; the sum of all

weights should be 1.00 (1.000?!)

For each design j , give a performance rating for eachcustomer attribute on 0-4 scale:

Performance criterion Rating points (Vj,i)

Unsatisfactory 0Just tolerable 1

Adequate 2

Good 3

Ideal 4

Overall weighted value for Design-j= (wi Vj,i)

Rank designs by overall weighted value; Best? (!)


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Pahl and Beitz method - example

Attributes Weight Design-1 Design-2 Design-3 Design-4

Stays closed 0. 30

Inexpensive 0. 05

Waterproof 0. 25

Identify contents 0. 10

Attractive 0. 20

Compact 0. 10

TOTAL VALUE 1. 00

R NK ----


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Practice exercises

In class #3:

Evaluate the different types of CD/DVD carrying

cases. (Individual work, followed by consolidation)

Alternate: Chairs, washing machine, cooking stoves,solar collectors,


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i-b-4 design alternatives evaluation 2014 v1

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