Chapter 12 EIN 6392, Product Design Fall 2009 Prototyping Chapter 12 EIN 6392, Product Design Fall 2009

Product Design and Development Karl T. Ulrich and Steven D Product Design and Development Karl T. Ulrich and Steven D. Eppinger 2nd 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 7/4/2019

Product Development Process Planning Concept Development System-Level Design Detail Design Testing and Refinement Production Ramp-Up Prototyping is done throughout the development process. 7/4/2019

Concept Development Process Mission Statement Development Plan Identify Customer Needs Establish Target Specifications Generate Product Concepts Select Product Concept(s) Test Product Concept(s) Set Final Specifications Plan Downstream Development Perform Economic Analysis Benchmark Competitive Products Build and Test Models and Prototypes 7/4/2019

Outline Definition Steps in prototyping decisions Purposes of prototypes Principles for choosing a prototype type 7/4/2019

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 See Exhibit 12-5 on page 250 for the types of prototypes 7/4/2019

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. 7/4/2019

Types of Prototypes Physical Focused Comprehensive Analytical not alpha prototype beta prototype ball support prototype final product trackball mechanism linked to circuit simulation Focused Comprehensive simulation of trackball circuits not generally feasible equations modeling ball supports Analytical 7/4/2019

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 7/4/2019

Purposes vs. prototype types Focused analytical Learning Focused physical Learning and communication Comprehensive physical Learning, communication, integration, and milestones. 7/4/2019

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 compre. Prototypes Sell the first unit 7/4/2019

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. 7/4/2019

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. 7/4/2019

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 7/4/2019

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) 7/4/2019

Prototyping Example: Apple PowerBook Duo Trackball 7/4/2019

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? 7/4/2019

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 Low High 7/4/2019 Cost of Comprehensive Prototype

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”. 7/4/2019

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... 7/4/2019

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... 7/4/2019

From: Scientific American, March 1999 BMW Virtual Crash Test From: Scientific American, March 1999 7/4/2019

Traditional Prototyping Methods CNC machining Rubber molding + urethane casting Materials: wood, foam, plastics, etc. Model making requires special skills. 7/4/2019