Introduction
Engineering 7936
Design Project
• 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.
Prototyping
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Four Uses of Prototypes
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Physical vs. Analytical Prototypes
• Learning
Physical Prototypes
• Tangible approximation of the
product.
• May exhibit unmodelled
behavior.
• Some behavior may be an
artifact of the approximation.
• Often best for communication.
– 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
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Focused vs. Comprehensive Prototypes
Comprehensive Prototypes
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Many comprehensive
prototypes are built.
Some comprehensive
prototypes build (and sold?).
One prototype may be
used for verification.
Few or no comprehensive
prototypes are built.
High
Technical or Market Risk
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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Low
Focused Prototypes
• Implement one or a few
attributes of the product.
• Answer specific
questions about the
product design.
• Generally several are
required.
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.
Low
High
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Cost ofENGI
Comprehensive
Prototype
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Rapid Prototyping Methods
Prototyping Strategy
•
•
•
•
Use prototypes to reduce uncertainty.
Make models with a defined purpose.
Consider multiple forms of prototypes.
Choose the timing of prototype cycles.
• 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...
–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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BMW Virtual Crash Test
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 ...
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From: Scientific American, March 1999
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Planning for Prototypes – 4 steps
Traditional Prototyping Methods
• Step 1: Define the purpose of the prototype.
•
•
•
•
– What is the prototype for? Is it for learning, communication,
integration, or milestone?
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).
• 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?
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Summary
Summary (Continue)
• 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.
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• 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.
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Readings and Resources
• Check out Inventor’s Digest website:
www.inventordigest.com
• People to talk to: Steve Foster (model
shop), Paul Bishop (student machine
shop), Andy Fisher (rapid prototyping lab).
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