Engineering 7936 Design Project

Transcription

1 Engineering 7936 Design Project Prototyping 1

2 Introduction Prototype = an approximation of the product along one or more dimensions of interest. Alpha prototypes: Used to assess whether product works as intended. Similar in material and geometry as production version, but made differently. E.g. machined instead of molded. Beta prototype: Used to assess reliability and to identify remaining bugs in the product. Given to customers for testing in the use environment. Parts are usually made with the actual production process and supplied by intended parts suppliers. Assembled by team rather than the manufacturer. 2

3 Four Uses of Prototypes Learning answering questions about performance or feasibility e.g., proof-of-concept model Communication demonstration of product for feedback e.g., 3D physical models of style or function Integration combination of sub-systems into system model e.g., alpha or beta test models Milestones goal for development team s schedule e.g., first testable hardware 3

4 Physical vs. Analytical Prototypes Physical Prototypes Tangible approximation of the product. May exhibit unmodelled 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 modelled 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. 4

5 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. 5

6 Comprehensive Prototypes Many comprehensive prototypes are built. Some comprehensive prototypes build (and sold?). Technical or Market Risk High Low One prototype may be used for verification. Few or no comprehensive prototypes are built. Low High Cost of ENGI Comprehensive Design Project Prototype 6

7 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

8 Rapid Prototyping Methods Most of these methods are additive, rather than subtractive, processes. Build parts in layers based on CAD model. SLA=Stereolithography Apparatus SLS=Selective Laser Sintering FDM=Fused Deposition Modeling LOM=Laminated Object Manufacturing New technologies every year... 8

9 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 Advances each year... 9

10 BMW Virtual Crash Test From: Scientific American, March

11 Traditional Prototyping Methods CNC machining Rubber molding + urethane casting Materials: wood, foam, plastics, etc. Model making requires special skills (see Steve Foster of Tech Services only certified model maker in NL). 11

12 Planning for Prototypes 4 steps Step 1: Define the purpose of the prototype. What is the prototype for? Is it for learning, communication, integration, or milestone? Step 2: Establish Level of Approximation. Is an analytical prototype good enough or a physical prototype necessary? Should it works like or just looks like? Step 3: Outline an Experimental Plan Decide on what measurements have to be taken. What combinations of configurations need to be tested? Test conditions? Step 4: Create a Schedule for Procurement, Construction, and Testing. Prototyping is a sub-project within the overall product development project. What parts need to be ordered, assembled? When must it be completed? How much time for testing? 12

13 Summary Prototypes are used for learning, communication, integration, and milestones. Physical prototypes are best for communication, and comprehensive prototypes are best for integration and milestones. Analytical prototypes are generally more flexible than physical prototypes. Physical prototypes are required to detect unanticipated phenomena. 13

14 Summary (Continue) 3-D computer modelling and free-form fabrication technologies have reduced the relative cost and time required to create prototypes. A 4-step method for planning prototype is: 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 testing. 14

15 Readings and Resources Check out Inventor s Digest website: People to talk to: Steve Foster (model shop), Paul Bishop (student machine shop), Andy Fisher (rapid prototyping lab). 15