Prototyping

Chapter 12EIN 6392, Product Design

summer 2012

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Product Design and DevelopmentKarl T. Ulrich and Steven D. EppingerChapter Table of Contents 1. Introduction2. Development Processes and Organizations3. Product Planning4. Identifying Customer Needs5. Product Specifications6. Concept Generation7. Concept Selection8. Concept Testing9. Product Architecture10. Industrial Design11. Design for Manufacturing12. Prototyping13. Product Development Economics 14. Managing Projects

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Concept Development Process

Perform Economic Analysis

Benchmark Competitive Products

Build and Test Models and Prototypes

IdentifyCustomer

Needs

EstablishTarget

Specifications

GenerateProduct

Concepts

SelectProduct

Concept(s)

Set Final

Specifications

PlanDownstreamDevelopment

MissionStatement Test

ProductConcept(s)

DevelopmentPlan

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PlanningPlanning

Product Development Process

ConceptDevelopment

ConceptDevelopment

System-LevelDesign

System-LevelDesign

DetailDesign

DetailDesign

Testing andRefinement

Testing andRefinement

ProductionRamp-Up

ProductionRamp-Up

Prototyping is done throughout the development process.

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Outline Definition Steps in prototyping decisions Purposes of prototypes Principles for choosing a prototype

type

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Definition An approximation of the product

along one or more dimensions of interest.

Physical prototypes vs. analytical prototypes

Comprehensive (with all the attributes of a product) vs. focused

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Purposes of prototypes Learning

Learn whether it will work and how well it will meet the customer needs

Communication Communicate with top management, vendors, partners, extended

team members, customers, and sources of financing. Integration

Integrate into the product assembly to ensure that components or subsystems fit well into the product design.

Milestones Establish milestones for demonstrating that the product has

achieved a desired level of functionality.

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Types of Prototypes

ComprehensiveFocused

Physical

Analytical

finalproduct

betaprototype

alphaprototype

Physical models of components

Simulation modelsof product components

equationsmodeling components

Components linked to other components or

models

notgenerallyfeasible

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Principles for choosing a prototype type Analytical prototypes are in general more flexible

than physical prototypes Physical prototypes are required to detect

unanticipated phenomena Prototypes may reduce the risk of costly iterations Prototypes may expedite other development steps

Example: add a prototyping step in the part design-mold design-molding process

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Purposes vs. prototype types Focused analytical

Learning Focused physical

Learning and communication Comprehensive physical

Learning, communication, integration, and milestones.

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Technical risk vs. comprehensive prototype cost Low risk- low cost (e.g., printed matters)

No need for comprehensive prototypes Low risk – high cost (ships, buildings)

Can’t afford comprehensive prototype. High risk – low cost (software)

Many comprehensive prototypes High risk high cost (airplanes, satellites)

Use analytical models extensively Carefully planned comprehensive prototypes Sell the first unit

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Physical vs. Analytical PrototypesPhysical Prototypes Tangible approximation

of the product. May exhibit un-modeled

behavior. Some behavior may be

an artifact of the approximation.

Often best for communication.

Analytical Prototypes Mathematical model of the

product. Can only exhibit behavior

arising from explicitly modeled phenomena. (However, behavior is not always anticipated.

Some behavior may be an artifact of the analytical method.

Often allow more experimental freedom than physical models.

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Focused vs. Comprehensive Prototypes

Focused Prototypes Implement one or a

few attributes of the product.

Answer specific questions about the product design.

Generally several are required.

Comprehensive Prototypes

Implement many or all attributes of the product.

Offer opportunities for rigorous testing.

Often best for milestones and integration.

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Prototype technologies 3D computer modeling Free-form fabrication

Stereolithography Using various materials including wax, resin,

paper, ceramics, and metals. Lamination

Using paper cut, lay by layer Rapid prototyping

Laser curing (solidifying) soft materials such as resin, layer by layer

3D printing

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Steps Define the purpose of the prototype Establish the level of approximation of the

prototype Outline an experimental plan Create a schedule for procurement,

construction, and test Plan milestones for prototypes (alpha, beta,

pre-production)

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Prototyping Example:Apple PowerBook Duo Trackball

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Boeing 777 Testing

Brakes Test Minimum rotor thickness Maximum takeoff weight Maximum runway speed Will the brakes ignite?Wing Test Maximum loading When will it break? Where will it break?

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Comprehensive Prototypes

Cost of Comprehensive PrototypeHighLow

Tec

hn

ical

or

Mar

ket

Ris

k

Hig

hL

ow

One prototype may be used for verification.

Few or no comprehensiveprototypes are built.

Many comprehensiveprototypes are built.

Some comprehensiveprototypes build (and sold?).

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Prototyping Strategy Use prototypes to reduce uncertainty. Make models with a defined purpose. Consider multiple forms of prototypes. Choose the timing of prototype cycles.

Many early models are used to validate concepts.

Relatively few comprehensive models are necessary to test integration.

Plan sufficient time to learn from prototype cycles.

Avoid the “hardware swamp”.

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Rapid Prototyping Methods Most of these methods are additive,

rather than subtractive processes. Build parts in layers based on CAD model. SLA=Stereolithogrpahy Apparatus SLS=Selective Laser Sintering 3D Printing LOM=Laminated Object Manufacturing Others every year...

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Virtual Prototyping 3D CAD models enable many kinds of analysis:

Fit and assembly Manufacturability Form and style Kinematics Finite element analysis (stress, thermal) Crash testing more every year...

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BMW Virtual Crash Test

From: Scientific American, March 1999

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Traditional Prototyping Methods

CNC machining Rubber molding + urethane casting

Materials: wood, foam, plastics, etc. Model making requires special skills.