14Physical PrototypesPrototype… is a replica or model of the part showing principal geometric featuresPrototypes differ in:Scale - Reduced, Full, ExpandedFabrication Process - Same as mfg, Similar, DifferentMaterial - Same as final, Different, SimilarTwo ways to make prototypes:TraditionalRapid
15Traditional 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
16Some 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 partCostly for duplicates.May not facilitate tooling design and construction
19Numerical Control Machining (NC/CNC) CAD files are converted to NC – machine instruction codes for automatic machiningPart can be made of metalDimensions have excellent tolerancesMultiple copies of parts can be made easilyPrototyped parts are well suited for form, fit and function testsCNC
20NC Machined part example Mars rover wheels(Courtesy of HAAS Automation)
25Stereo Lithography Apparatus (SLA) Parts exhibit superior finishespolymeric prototypes are weaker than metal prototypes (i.e.CNC)Prototyped parts are well suited for form, and fit tests.Some function testing
26Selective 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
27Fused-deposition modeling (FDM) process FilamentSpoolHeaterDrive WheelsTableFused PartHead motionTable motionHeadMolten filamentFDM, PDF
28(Courtesy of Stratasys Corporation) FDM – Stratasys 3000(Courtesy of Stratasys Corporation)
31Fused Deposition Modeling (FDM) Parts can be made fromhigh strength ABS plastic, impact resistant ABS,investment casting wax, and anelastomer.Prototype parts are well suited for form and fit testing.Some function testing
323-D Inkjet prototypingGlue-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 inexpensiveThe processes work well as concept modelers.Prototypes have limited dimensional tolerancesSomewhat fragile unless coated with a hardenerPrototypes made with this process are typically not function tested.3DP
33Z-Corporaton Z406 (“Inkjet”) (Courtesy of Z-Corporation)
38Laminated 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
39Service BureausProduct manufacturer s 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.
40Which 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?
42Engineering TestsBriefly 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.
431. Mechanical modes of failure static strengthfatiguedeflection/stiffnesscreep, impactvibrationthermal/heat transfer/fluidenergy consumption / productionfriction (i.e. too much, too little)wearlubricationcorrosionlife, reliability
442. Manufacturability concerns process compatibility/precisionprocess technology readinessraw material qualityassembly
453. Operation and or maintenance concerns styling/aestheticsergonomicsmaintenancerepairs
464. Safety concerns risk to user, products liability risk to consumer /societysafety codes, standards (UL, NHTSA)risk to production worker (e.g. OSHA)National Highway Traffic Safety Administration (NHTSA)Underwriters Laboratories Inc. (UL)Occupational Safety and Health Administration (OSHA)
48Test plans – written and approved Objectives –list of items (parts, systems, models) to be testedpurposes for which the tests are being conductedWorkscope – narrative description:type of tests,test descriptions/procedures,experimental setup,experimental controls,design of experiments test matrix, andlist of deliverables.BudgetScheduleExamples: 1, 2, 3
49SummaryCompanies 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 CADPart 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.