Building and testing prototypes

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Building and testing prototypes

• Why test?
• Form, fit function
• Types of tests
• Types of prototypes
• Test plans
• Summary

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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.

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What do form tests determine?
Form test Will the part/product have an
acceptable appearance?
4
What do fit tests determine?
Fit test Will the parts fit together or fit the
user, with an acceptable precision?
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What do function tests determine?
Function Will the part/product perform as
required?
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Tests Types Timing -A
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Tests Types Timing - B
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Tests Types Timing - C
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Testing Sequence

• Product concept
• Proof of concept
• Virtual prototype
• Alpha prototype
• Beta prototype
• PreProduction prototype

need physical prototype
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Physical Prototypes
Prototype is a replica or model of the part
showing principal geometric features

• Prototypes differ in
• Scale - Reduced, Full, Expanded
• Fabrication Process - Same as mfg, Similar,
  Different
• Material - Same as final, Different, Similar

Two ways to make prototypes Traditional Rapid
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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.

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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

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Rapid Prototyping

• NC/CNC Machining
• Selective Laser Apparatus
• Fused Deposition Modeling
• 3-D Ink Jet
• Laminated Object Manufacturing
• Selective Laser sintering
• Service Bureaus

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NC/CNC Prototyping (Subtractive process)
workstation
Solid Modeling CAD software
Saved Part Solid model file .PRT
NC code generation
NC Machine instruction code file
NC/CNC Machine e.g. mill, lathe
Fabricated Prototype
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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

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NC Machined part example
Mars rover wheels
(Courtesy of HAAS Automation)
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Rapid Prototyping Additive processes
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Stereo Lithographic Apparatus (SLA)
Solidified lamina
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3-D Systems SLA 7000
(Courtesy of 3D Systems)
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SLA Jaguar manifold
(courtesy 3-D Systems, Inc)
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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

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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.
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FDM Process
Molten filament
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FDM Stratasys 3000
(Courtesy of Stratasys Corporation)
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Cowling (courtesy of Stratasys)
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Trike (courtesy of Stratasys)
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Fused Deposition Modeling (FDM)

• Parts can be made from
• high strength ABS plastic, impact resistant ABS,
• investment casting wax, and an
• elastomer.
• Prototype parts are well suited for form and fit
  testing.
• Some function testing

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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.

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Z-Corporaton Z406 (Inkjet)
(Courtesy of Z-Corporation)
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Chrome Wheel (courtesy of Z-Corporation)
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Electrolux (courtesy of Z-Corporation)
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Baby seat (courtesy of Z-Corporation)
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3-D Inkjet Manifold
(courtesy of Z-Corporation)
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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.  
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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.

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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?

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Engineering Tests

• Mechanical / modes of failure
• Manufacturability
• Operation / maintenance
• Safety
• Environmental

Engineering tests ? Experiments
(Experiments validate phenomena)
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1. Mechanical modes of failure

• static strength
• fatigue
• deflection/stiffness
• creep, impact
• vibration
• thermal/heat transfer/fluid
• energy consumption / production
• friction (i.e. too much, too little)
• wear
• lubrication
• corrosion
• life, reliability

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2. Manufacturability concerns

• process compatibility/precision
• process technology readiness
• raw material quality
• assembly

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3. Operation and or maintenance concerns

• styling/aesthetics
• ergonomics
• maintenance
• repairs

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4. Safety concerns

• risk to user, products liability
• risk to consumer /society
• safety codes, standards (UL, NHTSA)
• risk to production worker (e.g. OSHA)

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5. Environmental protection concerns

• air quality, noise
• water - quality, quantity
• solid waste hazardous materials
• radioactivity fallout

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Test plans written and approved

• Objectives
• list of items (parts, systems, models) to be
  tested
• purposes 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.
• Budget
• Schedule

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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.