Prototyping

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Prototyping

• Chapter 12
• EIN 6392, Product Design
• Spring 2008

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Product Design and DevelopmentKarl T. Ulrich and
Steven D. Eppinger2nd edition, Irwin
McGraw-Hill, 2000.

• Chapter Table of Contents
• 1. Introduction
• 2. Development Processes and Organizations
• 3. Product Planning
• 4. Identifying Customer Needs
• 5. Product Specifications
• 6. Concept Generation
• 7. Concept Selection
• 8. Concept Testing
• 9. Product Architecture
• 10. Industrial Design
• 11. Design for Manufacturing
• 12. Prototyping
• 13. Product Development Economics
• 14. Managing Projects

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Product Development Process
Concept Development
System-Level Design
Detail Design
Testing and Refinement
Production Ramp-Up
Planning
Prototyping is done throughout the development
process.
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Concept Development Process
Mission Statement
Development Plan
Identify Customer Needs
Establish Target Specifications
Generate Product Concepts
Select Product Concept(s)
Set Final Specifications
Plan Downstream Development
Test Product Concept(s)
Perform Economic Analysis
Benchmark Competitive Products
Build and Test Models and Prototypes
5
Outline

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

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Definition

• An approximation of the product along one or more
  dimensions of interest.
• Analytical prototypes vs. Physical prototypes
• Focused vs. comprehensive (with all the
  attributes of a product)

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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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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
Physical
beta prototype
alpha prototype
ball support prototype
final product
trackball mechanism linked to circuit simulation
Comprehensive
Focused
simulation of trackball circuits
not generally feasible
equations modeling ball supports
Analytical
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Comprehensive Prototypes
Many comprehensive prototypes are built.
Some comprehensive prototypes build (and sold?).
High
Technical or Market Risk
One prototype may be used for verification.
Few or no comprehensive prototypes are built.
Low
High
Low
Cost of Comprehensive Prototype
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Physical vs. Analytical Prototypes

• Physical Prototypes
• Tangible approximation of the product.
• May exhibit unmodeled 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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Technical risk vs. comprehensive prototype cost

• Low risk- low cost (printed matters)
• Use one or no comprehensive prototypes
• Low risk high cost (ships, buildings)
• Build no compre. 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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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 time to learn from prototype cycles.
• Avoid the hardware swamp.

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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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Prototype types by purpose

• Learning
• Focused analytical
• Learning and communication
• Focused physical
• Learning, communication, integration, and
  milestones.
• Comprehensive physical

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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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Rapid Prototyping Methods

• Most of these methods are additive, rather than
  subtractive, processes.
• Build parts in layers based on CAD model.
• SLAStereolithogrpahy Apparatus
• SLSSelective Laser Sintering
• 3D Printing
• LOMLaminated Object Manufacturing
• Others every year...

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Traditional Prototyping Methods

• CNC machining
• Rubber molding urethane casting
• Materials wood, foam, plastics, etc.
• Model making requires special skills.

20
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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Prototyping ExampleApple PowerBook Duo Trackball
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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