Rapid Pro To Typing

“An original, full-scale, and usually working model of a new product or new version of an existing product.”

 Be creative

•Prototype as part of the creative process

 Evaluate

•With real users •Within a design team •Usability and usefulness

 Communicate

•Sell’ a design idea •Request design requirements •Prove a concept’

Rapid Prototyping (RP) can be defined as a group of techniques used to quickly fabricate a scaled model of a part or assembly using three-dimensional computer aided design (CAD) data.

The history of RAPID PROTOTYPING dates back to the late 80s of 20th century in which modern prototyping machines takes virtual designs from computer aided design (CAD) or animation, modelling software, transforms them into thin, virtual, horizontal cross-sections and then creates each cross-section in physical space, one after the next until the model is finished. It is a WYSIWYG (What you see is What you get) process where the virtual model and the physical model correspond almost identically.

 Not

overly detailed  Easy to create  Flexible  Easily modifiable  Cheap & ‘throw-away’  No need to invest too much too early  Can explore many alternative designs  They quickly and clearly convey a message

A large number of competing technologies are available in the market. As all are additive technologies, their main differences are found in the way layers are built to create parts. Some are melting or softening material to produce the layers (SLS,FDM) where others are laying liquid materials thermosets that are cured with different technologies (SLA, MJM, PolyJet). In the case of lamination systems, thin layers are cut to shape and joined together.

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Selective laser sintering (SLS)

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Thermoplastics & Metal powders

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Fused Deposition Modelling

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Thermoplastics & eutectic metals

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Steriolithography

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Photopolymer

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Multi jet Modelling



Photopolymer

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Laminated Object Modelling

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Paper



Electron Beam Melting



Titanium alloys



3D Printing



Various materials



Object Polyjet Modelling



photopolymer

Stereolithography is a common rapid manufacturing and rapid prototyping technology for producing parts with high accuracy and good surface finish. A device that performs stereolithography is called an SLA or Stereolithography Apparatus. Stereolithography, also known as 3-D layering or 3D printing, allows you to create solid, plastic, threedimensional (3-D) objects from CAD drawings in a matter of hours.

The SLA has four main parts A tank filled with several gallons of liquid photopolymer. The photopolymer is a clear, liquid plastic. 

A

perforated platform immersed in the tank. The platform can move up and down in the tank as the printing process proceeds. An

ultraviolet laser

A

computer that drives the laser and the platform

When LASER light falls on photopolymer it hardens

You create a 3-D model of your object in a CAD program

A piece of software chops your CAD model up into thin layers -- typically five to 10 layers/millimeter

The 3-D printer's laser "paints" one of the layers, exposing the liquid plastic in the tank and hardening it

The platform in the tank of photopolymer at the beginning of a print run.

The platform drops down into the tank a fraction of a millimeter and the laser paints the next layer This process repeats, layer by layer, until your model is complete

The platform at the end of a print run, shown here with several identical objects

Once the run is complete, you rinse the objects with a solvent and then "bake" them in an ultraviolet oven that thoroughly cures the plastic.

The ultraviolet "oven" used to cure completed objects.

Selective Laser Sintering is an additive rapid manufacturing technique that uses a high power laser (for example, a carbon dioxide laser) to fuse small particles of plastic, metal, or ceramic powders into a mass representing a desired 3-dimensional object. The laser selectively fuses powdered material by scanning crosssections generated from a 3-D digital description of the part (e.g. from a CAD file or scan data) on the surface of a powder bed. After each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied on top, and the process is repeated until the part is completed.

Laser beam selectively fuses powder materials: nylon, elastomer, and some metals Advantage over SLA: Variety of materials and ability to fabricate common engineering plastic materials. Process is simple: There are no milling steps required Uncured material is easily removed after a build by brushing or blowing it off.

Like most other RP processes (such as 3D Printing and stereolithography) FDM works on an "additive" principle by laying down material in layers. A plastic filament or metal wire is unwound from a coil and supplies material to an extrusion nozzle which can turn on and off the flow. The nozzle is heated to melt the material and can be moved in both horizontal and vertical directions by a numerically controlled mechanism, directly controlled by a Computer Aided Design software package. In a similar manner to stereolithography, the model is built up from layers as the plastic hardens immediately after extrusion from the nozzle.

Parts up to 600 × 600 × 500 mm (24 × 24 × 20 inches) can be produced

CAD MODEL

EBM has a wide range of applications specially in biomedical Here are the artificial pelvic musels made by this technology

Fabrication using EBM

Laminated Object Manufacturing (LOM) is a rapid prototyping system developed by Helisys Inc. In it, layers of adhesive-coated paper are successively glued together and cut to shape with a laser cutter.

The SGC process uses photosensitive resin hardened in layers as with the Stereolitheography (SLA) process. However, in contrast to SLA, the SGC process is considered a high-throughput production process. The high throughput is achieved by hardening each layer of photosensitive resin at once.

The flat work surface is sprayed with photosensitive resin.

A photomask is produced

The photomask is positioned over the work surface and a powerful UV lamp hardens the exposed photosensitive resin.

All uncured resin is vacuumed for recycling. The cured layer is passed beneath a strong linear UV lamp to fully cure it and to solidify any remnant particles

wax replaces the cavities left by vacuuming the liquid resin

In the final step before the next layer, the wax/resin surface is milled flat to an accurate, reliable finish for the next layer

Once all layers are completed, the wax is removed, and any finishing operations such as sanding, etc. can be performed.

• Rapid prototyping makes it possible to manufacture an artificial limb.

FOR TEXTUAL DATA  www.e-funda.com www.en-wikipedia.org www.medicaldesign.com www.redeyerpm.com http://home.att.net/~castleisland/rp_int.htm

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 www.youtube.com

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