Building and testing prototypes
Why test? Form, fit & function Types of tests Types of prototypes Test plans Summary
Why Do Product Testing?
Finished parts do not always look the same as designed
Finished parts do not always fit together as designed
Finished parts do not always work the way they were designed.
What do “form” tests determine?
2. Will the housing appear old-fashioned?
5. Will the customer be satisfied with the overall size?
13. Would the part be more attractive with a mirror finish?
Form test– Will the part/product have an acceptable appearance?
What do “fit” tests determine?
4. Will the product “feel” good in the hands of the user?
6. Will the fabricated parts assemble without interference?
15. Will the manufacturing group be able to fabricate the
new part to acceptable tolerances?
Fit test – Will the parts fit together or fit the user, with an acceptable precision?
What do “function” tests determine?
1. Will the new product work at extreme temperatures and humidity? 3. Will the new part actually work as predicted by the equations. 7. Will the finished product meet industry mandated safety tests? 8. Will the new housing material be compatible with intended lubricants? 9. Will the customer be able to easily replace worn parts? 10.Will the new part be stiff enough? 11. Will the new part have an acceptable wear rate? 12. Will the product present an electric shock hazard? 14. Does the finished product meet minimum performance requirements
Function – Will the part/product perform as required?
Tests: Types & Timing -A
Formulation
Concept Design “Proof of Concept” tests validate physical principles
“Product Concept” tests validate product / appearance
Product concept and Proof-of-concept models
Mercedes F700
Tests: Types & Timing - B
Parametric Design
Configuration Design
“Virtual prototype” tests solid modeling CAD
“Alpha prototype” tests actual geometry & materials but may not use actual mfg. processes
Virtual prototype
Mercedes F700 MIT Smart City 2020
Alpha prototype
Sky Commuter is on the block on ebay.Starting bid: $55,600.Labels: Future Past, Technology
The flying saucer
Tests: Types & Timing - C
Detail Design
Manufacture
“Beta prototype” tests parts made with planned mfg. processes volunteer customers / panel actual operating conditions, environment
“Preproduction prototype” tests parts made with final mat’s & processes independent labs: UL, CPSC, NHTSA
http://www.youtube.com/watch?v=U9CfHGnsPqs
Testing Sequence
1. Product concept2. Proof of concept3. Virtual prototype 4. Alpha prototype5. Beta prototype6. PreProduction prototype
less expensive
more expensive
need physical “prototype”
More prototypes
Toyota Winglet Toyota i-Real
Toyota i-Foot Toyota PM
Physical Prototypes
Prototypes differ in:Scale - Reduced, Full, Expanded Fabrication Process - Same as mfg, Similar, Different Material - Same as final, Different, Similar
Prototype… is a replica or model of the part showing principal geometric features
Two ways to make prototypes:Traditional Rapid
Traditional prototypes
Clay models of new auto body for appearance testing,
Wood models of heavy equipment patterns for metal castings,
Manually machined metal airplane wings for function testing in a wind tunnel,
Reduced-scale balsa wood models of large facilities, to examine equipment layout.
Clay modeling: 1, 2, 3, 4, 5
Some Disadvantages of Traditional Prototyping
Uses tools and fabrication methods that are labor intensive.
Often require significant mechanical or artistic skills. Take a long time to fabricate an original. Revisions may require complete rebuilding of part Costly for duplicates. May not facilitate tooling design and construction
Rapid Prototyping
NC/CNC Machining Selective Laser Apparatus Fused Deposition Modeling 3-D Ink Jet Laminated Object Manufacturing Selective Laser sintering Service Bureaus
NC/CNC Prototyping (Subtractive process)
Solid ModelingCAD software
NC code generation
Saved Part Solid model file*.PRT
FabricatedPrototype
NC Machine instruction codefile
NC/CNC Machine e.g. mill, lathe
workstation
Numerical Control Machining (NC/CNC)
CAD files are converted to NC – machine instruction codes for automatic machining
•Part can be made of metal•Dimensions have excellent tolerances•Multiple copies of parts can be made easily
Prototyped parts are well suited for form, fit and function tests
CNC
NC Machined part example
(Courtesy of HAAS Automation)
Mars rover wheels
Rapid Prototyping – Additive processes
Solid ModelingCAD software
Rapid PrototyperSlicing Program
FacetedModel file*.STL
Saved Part Solid model file*.PRT
FabricatedPrototype
RP Machine instruction codefile
RP Machine
workstation
Stereo Lithographic Apparatus (SLA)
laser
projectionmirror (xy-axes)
elevator(z-axis)
Photopolymer(liquid resin)
object being prototyped
tankSolidified lamina
SLA
3-D Systems SLA 7000
(Courtesy of 3D Systems)
SLA Jaguar manifold
(courtesy 3-D Systems, Inc)
Stereo Lithography Apparatus (SLA)
Parts exhibit superior finishes polymeric prototypes are weaker than metal prototypes
(i.e.CNC)
Prototyped parts are well suited for form, and fit tests.
Some function testing
Selective Laser Sintering (SLS)
Uses a high power laser to sinter together fusible materials, such as powdered metals, layer by layer.
Sintering is the heating and fusing of small particles resulting in a hard bonded material block.
The un-sintered powder supports the part as the layers are sintered.
SLS
Fused-deposition modeling (FDM) process
Molten filament
FilamentSpool
Heater
Drive Wheels
Table
Fused Part
Head motion
Table motion
Head
FDM, PDF
FDM – Stratasys 3000
(Courtesy of Stratasys Corporation)
Cowling (courtesy of Stratasys)
Trike (courtesy of Stratasys)
Fused Deposition Modeling (FDM)
Parts can be made from high strength ABS plastic, impact resistant ABS, investment casting wax, and anelastomer.
Prototype parts are well suited for form and fit testing.
Some function testing
3-D Inkjet prototyping
Glue-like binder selectively “printed” onto a layer of dry powder, layer by layer, which dries into a solid prototype.
Similar process uses a print head to deposit a thermoplastic material, layer by layer.
• Quick and inexpensive• The processes work well as concept modelers.• Prototypes have limited dimensional tolerances• Somewhat fragile unless coated with a hardener
Prototypes made with this process are typically not function tested. 3DP
Z-Corporaton Z406 (“Inkjet”)
(Courtesy of Z-Corporation)
Chrome Wheel (courtesy of Z-Corporation)
Electrolux (courtesy of Z-Corporation)
Baby seat (courtesy of Z-Corporation)
3-D Inkjet Manifold
(courtesy of Z-Corporation)
Laminated Object Manufacturing (LOM)
Laminating thin layers of paper, polymer or sheet steel, which have been cut using a numerically controlled laser.
LOM prototypes can be sanded to reduce jagged edges, but are not able to be function tested such as for stress or strain due to the allotropic material properties of the laminate.
LOM
Service Bureaus
Product manufacturer emails the solid model part file to the service bureau, typically as an *.STL file.
The bureau uses its software to convert the *.STL file to a “sliced” file format specific to the selected prototyping hardware (i.e. FDM, SLA, SLS, LOM),
Part is fabricated along with any duplicates.
Part(s) may then be overnight-mailed to the product manufacturer.
Which Prototyping Method is Best: Traditional or Rapid?
Shape generating compatibility – Can the material be formed into the needed geometric features to adequately represent the part?
Function testing validity – Are the material properties representative, or scalable such that the part when reduced (or expanded) in size, can be validly tested?
Fabrication costs – Will the prototype costs for materials and labor be acceptable?
Fabrication time – How long will it take to fabricate the original and one or more duplicates?
Engineering Tests
1. Mechanical / modes of failure
2. Manufacturability3. Operation / maintenance4. Safety5. Environmental
Engineering tests ≠ Experiments
(Experiments validate phenomena)
Engineering Tests
Briefly describe the difference between engineering tests and scientific experiments.
Scientific experiments establish relationships between causes and effects. That is, they determine scientific principles. For example, a force exerted on a mass causes it to accelerate (effect).
Engineering tests validate the application of principles given specific assumptions. For example, will a given sized motor produce enough torque given the frictional losses in the system.
1. Mechanical modes of failure
static strengthfatiguedeflection/stiffnesscreep, impactvibrationthermal/heat transfer/fluidenergy consumption /
productionfriction (i.e. too much, too
little)wearlubricationcorrosionlife, reliability
2. Manufacturability concerns
process compatibility/precision process technology readiness raw material quality assembly
3. Operation and or maintenance concerns
styling/aesthetics ergonomics maintenance repairs
4. Safety concerns
risk to user, products liability risk to consumer /society safety codes, standards (UL, NHTSA) risk to production worker (e.g. OSHA)
5. Environmental protection concerns
air quality, noise water - quality, quantity solid waste – hazardous materials radioactivity – fallout
Test plans – written and approved
Objectives – list of items (parts, systems, models) to be testedpurposes for which the tests are being conducted
Workscope – narrative description:type of tests, test descriptions/procedures, experimental setup, experimental controls, design of experiments test matrix, and list of deliverables.
BudgetSchedule
Examples: 1, 2, 3
Summary
Companies build and test prototypes to ensure form, fit and function.
Product development tests include: product-concept, proof-of-concept, virtual, alpha, beta, and preproduction.
Prototypes can be built using traditional and rapid prototyping methods and materials.
Rapid prototyping methods include NC/CNC, SLA, FDM, LOM, SLS, and 3-D Inkjet printing.
Rapid prototyping takes advantage of CAD Part and product testing can include tests for: mechanical
modes of failure, manufacturability, user operation & maintenance, safety and environmental protection.
Product development often requires the preparation and completion of a detailed test plan.
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