lec. 11 rapid_prototyping

7/26/2019 Lec. 11 Rapid_Prototyping

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2010 by Pearson Education, Inc.All rights reserved.

Manufacturing Engineering and Technology, Sixth EditionSerope Kalpakjian and Steven R. Schmid

Introduction to RAPID PROTOTYPING

Rapid Prototyping is construction of physical objects using additivemanufacturingtechnology. The first techniques for rapid prototyping became available in the late 1980sand were used to produce models and prototype parts. Today, they are used for a muchwider range of applications and are even used to manufacture production-quality parts inrelatively small numbers.

The use of additive manufacturing for rapid prototyping takes virtual designs from (CAD),transforms them into thin, virtual, horizontal cross-sections and then creates successivelayers until the model is complete. It is a WYSIWYG process where the virtual and thephysical model are almost identical.

Machine reads data from a CAD drawing and lays down successive layers of liquid,powder, or sheet material, and in this way builds up the model from a series of crosssections.


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Advantages and Limitations

Need to produce a single example called PROTOTYPE prior to investing large capital onnew production facility, which the cost is very high.

Ideal for complex parts. Traditional method is very time consuming and staff, machinery

etc. cost money.

Efficient and rapid method of analysing final product

Stay ahead of competitors

Product design change very quickly, therefore need to accommodate

Certain cases, tooling can be produced using RP


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RP can be called 3D printing, optical fabrication, photo-solidification, solid free-formfabrication, and solid imaging.

The length of time to produce a part depends on the sizeand complexityof part and cantake from few hours to more than a day.

Most RP machines can produce parts up to size of 20 x 20 x 24.

Prototypes made by RP can be strong enough to be machined and can be used as masterpatterns for injection molding, thermoforming, blow molding, and also in various metalcasting processes.

The photo-curable resin can cost anywhere from $300 to $800 per gallon. An SL machine

can cost from about $100,000 to more than $500,000.

Entire process is labour intensive

Advantages and Limitations


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Commercialisation

Rapid prototyping worldwide
http://upload.wikimedia.org/wikipedia/commons/0/0b/Rapid_prototyping_worldwide_by_Zureks.png


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Parts made by RP processes: (a) selection of parts from fused-deposition modeling; (b)stereolithography model of cellular phone; and (c) selection of parts from three-dimensionalprinting.

Examples of Parts Produced


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Rapid prototyping of a Super Soaker squirt gun. (a) Fully functional toy produced

through fused deposition modeling; (b) original CAD design.

Examples of Parts Produced


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Various Processes

Prototyping technologies Base materials

Selective laser sintering (SLS) Thermoplastics, metals powders

Fused deposition modeling (FDM) Thermoplastics, eutectic metals.

Stereolithography (SLA) Photopolymer

Laminated object manufacturing (LOM) PaperElectron beam melting (EBM) Titanium alloys

3D printing (3DP) Various materials


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SLA Method

Stereolithography (SLA)uses UV light via a laser beam to solidify a liquid photo sensitiveacrylic polymer to build parts a layer at a time. On each layer, the laser beam traces a partcross-section pattern on the surface of the liquid resin. Exposure to the UV laser light cures,or, solidifiesthe pattern traced on the resin and adheres it to the layer below.

After a pattern has been traced, the SLA's elevator platform descends by a single layerthickness, typically 0.05 mm to 0.15 mm. Then, a resin-filled blade sweeps across the partcross section, re-coating it with fresh material.

SLA requires the use of support structures to attach the part to the elevator platform and toprevent certain geometry from not only deflecting due to gravity.


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SLA Method
http://upload.wikimedia.org/wikipedia/commons/1/1e/Stereolithography_apparatus.jpg


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SLA Method


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Stereolithography process. (a) Three-dimensional description of part. (b) The part is divided into slices, (c)Support material is planned. (d) A set of tool directions is determined to manufacture each slice. Also shown is theextruder path at section AA from (c) for a fused deposition-modeling operation.

SLA Method


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Fused Deposition Modelling(FDM) is an additivemanufacturing technology commonlyused for modelling, prototyping, and production applications. The technology was developedin the late 1980s and was commercialised in 1990.

FDM works on an "additive" principle by laying down material in layers. A plastic filament ormetal wire is unwound from a coil and supplies material to an extrusion nozzle which canturn on and off the flow. The nozzle is heated to melt the material and can be moved in bothhorizontal and vertical directions by a numerically controlled mechanism, directly controlledby a CAM software package.

Several polymers and waxes are available with different trade-offs between strength andtemperature properties. A "water-soluble" material can be used for making temporarysupports while manufacturing is in progress, this soluble support material is quickly dissolved

with specialized mechanical agitation equipment.

Fused Deposition Modelling (FDM)


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a) Schematic illustration of the fused-deposition-modeling process. (b) The FDM 900mc machine.



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Common Support Structures


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Characteristics of RP Technologies


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Mechanical Properties of Selected Materials for Rapid Prototyping


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Mechanical Properties of Selected Materials for Rapid Prototyping


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3D Printing (3DP) the printer head deposits an inorganic binder (glue). The binder createsa bond between the powder particles that it targets.

High speed

Low cost

Ease of use

Inco-operates colour

3D Printing Process


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3D Printing Process


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FIGURE 20.10 Three-dimensional printing using (a) part-build, (b) sinter, and (c) inf iltration steps to produce metal parts. (d) Anexample of a bronze-infiltrated stainless-steel part produced through 3D printing.

3D Printing Process


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Rapid-prototyped popular websites or games. (a) Second Life avatar, as appears on a computerscreen (left) and after printing (right); (b) an avatar known as Wreker from World of Warcraft.

3DP Process


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3DP Process


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Fitting required for a helicopter fuselage. (a) CAD representation with added dimensions. (b) Diesproduced by three-dimensional printing. (c) Final forged work piece. Total time of 45h.

Helicopter Fuselage3DP Process


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(a) An aligner for orthodontic use, manufactured by a combination of rapid tooling and thermoforming.(b) Comparison of conventional orthodontic braces with the use of transparent aligners.

Braces Using SLA


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The manufacturing sequence for braces. (a) Creation of a polymer impression of the patients teeth.

(b) Computer modeling to produce CAD representations. (c) Production of braces

Braces Using SLA


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Although material used to produced prototype is increasing, still majority of it is polymericbased.

Therefore, use components manufactured RP as aids for further processing, known asRapid Tooling (RT).

Rapid Tooling


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Investment casting with RP wax parts as blanks


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Production of tooling for injection molding by the sprayed-metal tooling process. (a) A pattern and base-plate areprepared through a RP; (b) a zincaluminum alloy is sprayed onto the pattern ; (c) the coated base-plate andpattern assembly are placed together in a flask and backfilled with aluminum impregnated epoxy; (d) after curing,the base-plate is removed from the finished mold; and (e) a second mold half suitable for injection molding isprepared.

Sprayed Metal


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2010 by Pearson Education, Inc.Manufacturing Engineering and Technology, Sixth Edition

A new faucet design, produced by casting from rapid-prototyped sand molds.

Sprayed Metal Parts

lec. 11 rapid_prototyping

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