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.