EPT 221 ENGINEERING DESIGN BUILDING AND TESTING PROTOTYPES

EPT 221 ENGINEERING DESIGN BUILDING AND TESTING PROTOTYPES

Building and Testing Prototypes Why test? n Form, fit & function n Types of tests n Types of prototypes n Test plans n Summary n

Why Do Product Testing? n Finished parts do not always look the same as designed n Finished parts do not always fit together as designed n Finished parts do not always work the way they were designed.

What do “form” tests determine? Form test– Will the part/product have an acceptable appearance?

What do “fit” tests determine? Fit test – Will the parts fit together or fit the user, with an acceptable precision?

What do “function” tests determine? Function – Will the part/product perform as required?

Physical Prototype n n n A tangible replica of the part/product showing principal features (e. g. length, width, height, holes, fillets, rounds, projections, slots, cavities, and surface texture). Scale: reduced scale, expanded scale, full-scale representations Materials: similar to or exact material intended for the product/part. Manufacturing process: similar to, different from or exact manufacturing process intended for the product/part. Therefore, the ability of the prototype to be tested form, fit and function will vary. So, need to use the right prototype to test critical aspects.

Types of Tests During the Various Development Stages Formulation Concept Design “Product Concept” tests validate product / appearance “Proof of Concept” tests validate physical principles

Continued… Configuration Design Parametric Design “Virtual prototype” tests solid modeling CAD “Alpha prototype” tests actual geometry & materials but may not use actual mfg. processes

Continued… B“ Detail Design Manufacture

Product Concept Tests n n A reduced-scale or full scale model (usually the exterior of the product) that looks like the ‘finished’ product. Shown to potential customers to get their reaction and willingness to purchase the product. Done early in the development cycle to make sure that the product will have the right look, or appearance, and have the right combination of features. Eg. An automobile manufacturer would use a clay scale model of a new sports car to examine the acceptability of a two-seat, rearengine convertible. A mobile phone company would make prototypes of the casing of its new mobile phones to examine the effects of the various colours and shape.

Proof-of-Concept Tests n n n Built to prove that it will function of perform according to the function concept or the physical principles and abstract embodiment that were selected. Benchtop, pilot-plant, and/or laboratory experiments are performed to prove the working principle will work in the final product. Eg. An electronics manufacturer would test the concept of a newly improved circuit using a prototype board. ¨ An office printer manufacturer could machine parts for a benchtop ‘working model’ of a new electrostatic paper feeder to replace mechanical roller-feeder in its new line of printers.

Virtual Prototype Tests n n A part/product can be prototyped or modeled inside the memory of a computer as a virtual prototype using computer-aided design packages, which can create and analyze 3 -D, solid models. Solid modeling is done to: • • • n Develop the form of a part Examine the mobility and/or potential interference of parts in an assembly Analyze forces, moments, motions, stresses, strains, etc. Eg. A construction equipment manufacturer would use solid modeling and finite element analysis to develop a CAD model or virtual prototype of its new gearbox and analyze its strength and/or rigidity.

Alpha-prototype Tests n n n A reduced-scale or full-scale part or product is prototyped using the same geometric features, materials, and layout as the intended final assembly (Otto and Wood, 2001). Not usually prototyped using the same manufacturing processes that will be used in the final production. Conducted in a company’s laboratory. Focuses on the part/product’s appearance and/or its functional performance. Eg. A screwdriver manufacturer would fabricate an alpha prototype by machining plain carbon steel to examine the ‘feel’ of its newly shaped handle, even though in final production stainless steel and stamping would be used. The parts of a new desktop printer case could be machined from a production polymer to prove its functionability, even though injection moulding would be used in final production.

Beta-prototype Tests n n n n A full-scale, functional part/product is prototyped using materials and manufacturing processes that will be used in production. Tested in company’s lab but are often tested by volunteers or potential customers in their home or work environment (Crawford and Di. Benedetto, 2003) To confirm intended mass-production and assembly processes. To demonstrate the approximate performance of the product. Results used to make the last remaining changes to the product, and to complete the production planning and initiative to production tooling. Group of potential customers = ‘customer panel’ Eg. Customer panel are often used to evaluate beta prototypes such as new vacuum cleaners, kitchen appliances, hand tools, sports equipment, and Beta version softwares on their home or work computers

Preproduction prototype Tests n n n A full-scale part/product made and assembled with final materials and production-like process is tested. Tests made on the prototype similar to ones that customer purchased. Tests confirm and document production and assembly processes and demonstrate the actual performance of the ‘final’ product. Tests result used to make last minute revisions to the production tooling and assembly processes and to make minor design revisions to comply with state and federal codes. Also to verify and document that the products have no defects in design or manufacture, which could be tested in a product liability lawsuit. Eg. An electric toaster manufacturer tests its products with the electric shock and fire safety tests which is conducted by an independent laboratory. An automobile manufacturer has production prototypes tested for crashworthiness by the National Highway Transportation Safety Administration.

Testing Sequence less expensive more expensive 1. 2. 3. 4. 5. 6. Product concept Proof of concept Virtual prototype Alpha prototype Beta prototype Pre. Production prototype need physical “prototype”

n Prototypes n Models

Physical Prototypes Prototype: 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

Traditional Prototypes n n 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.

The Choice of Material and Fabrication Method n n 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 acceptable? Fabrication costs. Will the prototype costs for materials and labour be acceptable? Fabrication time. How long will it take to fabricate the original and one or more duplicates?

Some Disadvantages of Traditional Prototyping n n n Uses tools and fabrication methods that are labour intensive. Often require significant mechanical or artistic skills. Takes 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 n n An alternative technology that uses computers and computer-controlled equipment to automatically and rapidly fabricate prototypes (Jacobs, 1996; Wood, 1993). Includes the following: • • NC/CNC Machining Selective Laser Apparatus (SLA) Fused Deposition Modeling (FDM) 3 -D Ink Jet Laminated Object Manufacturing (LOM) Selective Laser Sintering (SLS) Service Bureaus

How it works? Ref: Intergrated Design and Manufacture Lecture Notes, Imperial College London

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

Numerical Control Machining (NC/CNC) n n n n NC Machining CNC Machining Not fully ‘automatic’ because a skilled operator is needed to run the machine and making fixture changes. Can make multiple copies of a part and with a high level of precision. Can make prototypes out of strong, hard and/or stiff metals. Has the best accuracy and tolerances among the various prototyping methods and so can be subjected to operating loads approaching the actual in-use conditions. Prototyped parts are well suited form, fit and function tests

NC Machined part example Mars rover wheels (Courtesy of HAAS Automation)

Rapid Prototyping – Additive processes workstation Solid Modeling CAD software Rapid Prototyper Slicing Program Saved Part Solid model file *. PRT Faceted Model file *. STL RP Machine instruction code file RP Machine Fabricated Prototype

Stereo Lithographic Apparatus (SLA) laser elevator (z-axis) projection mirror (xy-axes) object being prototyped Photopolymer (liquid resin) n n n Solidified A material additive process tank lamina Uses a high-power laser to selectively solidify a liquid photopolymer, layer by layer, into the shape of the finished product. Prototypes has superior finishes. Uses polymers. Prototypes weaker than metal prototypes produced by NC/CNC. Prototyped parts are well suited form, and fit tests. Some function testing

3 -D Systems SLA 7000 (Courtesy of 3 D Systems)

SLA Jaguar manifold (courtesy 3 -D Systems, Inc)

Fused-Deposition Modeling (FDM) n n n A process that deposits a thin filament of melted (fused) material in precise locations on a horizontal layer, using numerically controlled positioners. Prototype typically 10 inch x 10 inch in cross section and up to 16 inches high. Parts can be made from a number of materials such as high strength ABS plastic, impact resistant ABS, polycarbonate and polyphenylsulfone which are nontoxic and nonhazardous. Fully automated process. Prototypes used to verify form, fit and function. Prototype parts are well suited form and fit testing. Some function testing.

FDM Process Filament Spool Drive Wheels Head Heater Head motion Molten filament Fused Part Table motion Table

FDM – Stratasys 3000 (Courtesy of Stratasys Corporation)

Cowling (courtesy of Stratasys)

Trike (courtesy of Stratasys)

Laminated-Object Manufacturing (LOM) Prototypes are build by laminating together thin layers of paper, polymer, or sheet steel which has been cut using numerically controlled laser. n Can be sanded to reduce jagged edges n Not able to be function tested, such as for stress and strain, owing to the allotropic material properties of laminate. n

Selective Laser Sintering (SLS) Uses a high-power laser to sinter together fusible materials, such as powdered metals, layer by layer. n Sintering is the heating and fusing small particles resulting in a hard bonded material block. The unsintered powder supports the part as the layers are sintered. n

3 -D Inkjet Prototyping n n n n Selectively deposits a glue-like binder 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. Prototype has limited dimensional tolerances Prototype is fragile unless coated with a hardener to help maintain part integrity. Typically, not function tested. The processes work well as concept modelers. Quick and inexpensive.

Z-Corporation Z 406 (“Inkjet”) (Courtesy of Z-Corporation)

Chrome Wheel (courtesy of ZCorporation)

Electrolux (courtesy of ZCorporation)

Baby seat (courtesy of ZCorporation)

3 -D Inkjet Manifold (courtesy of Z-Corporation)

Ref: Intergrated Design and Manufacture Lecture Notes, Imperial College London

Advantages of Rapid Prototyping n n Time: The overall time from hand sketches to physical prototype can be on the order of hours or days, compared to traditional methods, which can require days, weeks, or even months. Duplication ease and costs: duplicate prototypes can be fabricated quickly, less expensive, and with greater precision than traditional methods. Flexibility: changes to the virtual model and subsequent generation of revised prototypes are facilitated with rapid prototyping, because the data are stored parametrically. Rapid tooling: Prototype models and data can be conveyed electronically, and easily, to downstream departments, such as production and facilities planning, to communicate tooling concepts to mold makers, or generate master patterns for tooling, or generate tooling inserts.

Disadvantages of RP Cost n Limited in the type of materials that can be used. n Strength of models n Surface quality n Post-processing n

Service Bureaus n n 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. Some might take a few days.

Which Prototyping Method is Best: Traditional or Rapid? n Shape generating compatibility – Can the material be formed into the needed geometric features to adequately represent the part? n Function testing validity – Are the material properties representative, or scalable such that the part when reduced (or expanded) in size, can be validly tested? n Fabrication costs – Will the prototype costs for materials and labor be acceptable? n Fabrication time – How long will it take to fabricate the original and one or more duplicates?

Testing Prototypes n n n Tests conducted to validate form, fit and function. Specific Tests: prototype evaluations often include specific tests and mechanical modes of failures, manufacturability, operation/maintenance, safety (Hales, 1993), and environmental protection. Tests Plans: a description of the type of tests to be performed, the timing when they are to be completed, and the resources to be expended. ¨ Provides a structure for organizing, scheduling, and managing the testing program, and a means to communicate the test program details to all the stakeholders, eliciting feedback and delegating responsibilities. ¨ Its is required in some cases. ¨

Basic Components in a Test Plan 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

Specific Tests for Part/Product Prototypes: Engineering Tests 1. 2. 3. 4. 5. Mechanical / modes of failure Manufacturability Operation / maintenance Safety Environmental Engineering tests ≠ Experiments (Experiments validate phenomena)

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

2. Manufacturability concerns process compatibility/precision n process technology readiness n raw material quality n assembly n

3. Operation and/or maintenance concerns styling/aesthetics n ergonomics n maintenance n repairs n

4. Safety concerns risk to user, products liability n risk to consumer /society n safety codes, standards (NIOSH) n risk to production worker (e. g. OSHA) n

5. Environmental protection concerns air quality, noise n water - quality, quantity n solid waste – hazardous materials n radioactivity – fallout n

Summary n n n n Companies build and test prototypes to ensure form, fit and function. Product development tests include: product-concept, proof-ofconcept, 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.