Rapid Prototyping

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Rapid Prototyping
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• Rapid prototyping is the automatic construction
  of physical objects using additive manufacturing
  technology.
• used to produce models and prototype parts. 

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Development

• Manual Prototyping by craftsman
• 1970 prototyping in CAD , virtual environment
• 1980, Rapid Prototyping (RP) by layer-by-layer
  material deposition. CAD/CAM

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• The standard data interface between CAD software
  and the machines is the STL file format.
• An STL file approximates the shape of a part or
  assembly using triangular facets.
• Smaller facets produce a higher quality surface.
• SLC Slice format, CLI Common Layer Interface

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• Some solid freeform fabrication techniques use
  two materials in the course of constructing
  parts.
• The first material is the part material and the
  second is the support material (to support
  overhanging features during construction).
• The support material is later removed by heat or
  dissolved away with a solvent or water.

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• Advantages during development ...No tooling
  costs
• Short production times
• Comparatively low unit prices
• Constructional simplification e.g. instead of
  housing, lid and screws, 1 complete sintered unit
  can be made
• Test- and functional products can be produced in
  small batches
• Formal- and functional variants possible

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• ... production ...
• No tooling costs for small- and medium-sized
  batches
• Low tooling costs for larger batches
• Product customization possible without additional
  costs
• ... and the production of spare parts.
• No tooling management necessary
• Spare parts need no longer be kept but produced
  as required
• Unlimited subsequent delivery

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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) Paper
Electron beam melting (EBM) Titanium alloys
3D printing (3DP) Various materials
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• Stereolithography (SL) is an additive
  manufacturing technology for producing models,
  prototypes, patterns, and in some cases,
  production parts.
• UV laser and liquid photo curable resin
• Laser cures resin

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• can be used as master patterns for injection
  molding, thermoforming, blow molding, and also in
  various metal casting processes
• Costly

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• To create an SLA rapid prototype, first a
  three-dimensional CAD part is "sliced"
  horizontally into cross-sections between 0.002"
  and 0.006" thick.
• The slices are fed to 3D Systems'
  Stereolithography Apparatus. Inside the
  stereolithography chamber of the apparatus, an
  ultraviolet laser traces the first layer of the
  part on a metal platen, submerged just below the
  surface of a vat of photo-sensitive polymer.

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• Wherever the laser touches the liquid, it
  solidifies. Once the layer is traced, the platen
  sinks the thickness of a layer below the level of
  the liquid.
• A sweeper bar moves across the surface of the
  last layer, making sure there is the exact amount
  of resin on top.
• The next layer is then built upon the previous
  layer. In this manner the entire part is built
  from the bottom up, with the completed sections
  of the part remaining submerged.

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• In the Selective Laser Sintering (SLS) process,
  three-dimensional parts are created by fusing (or
  sintering) powdered thermoplastic materials with
  the heat from an infrared laser beam. 
• The objects creation is accomplished by
  repeatedly fusing thin powder layers using a
  laser beam.  
• This additive manufacturing sequence produces
  parts that gradually increase in size until they
  reach the prescribed dimensions. 
• These prototypes are created directly from 3D CAD
  models.

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• Selective laser sintering is an additive
  manufacturing technique that uses a high
  power laser (for example, a carbon dioxide laser)
  to fuse small particles of plastic, metal (Direct
  Metal Laser Sintering), ceramic, or glass powders
  into a mass representing a desired 3-dimensional
  object

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powder

•  polymers (nylon, also glass-filled or with other
  fillers, and polystyrene), metals
  (steel, titanium, alloy mixtures, and composites)
  and green sand.

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• 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,

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• The model or part is produced by extruding small
  beads of thermoplastic material to form layers as
  the material hardens immediately after extrusion
  from the nozzle.
•  acrylonitrile butadiene styrene (ABS) polymer,
  the FDM technology can also be used
  withpolycarbonates, polycaprolactone, polyphenylsu
  lfones and waxes.

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• In it, layers of adhesive-coated paper, plastic,
  or metal laminates are successively glued
  together and cut to shape with a knife or laser
  cutter.

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• The process is performed as follows
• Sheet is adhered to a substrate with a heated
  roller.
• Laser traces desired dimensions of prototype.
• Laser cross hatches non-part area to facilitate
  waste removal.
• Platform with completed layer moves down out of
  the way.
• Fresh sheet of material is rolled into position.
• Platform moves up into position to receive next
  layer.
• The process is repeated.

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Features

• Low cost due to readily available raw material
• Dimensional accuracy is slightly less than that
  of Stereolithography and Selective laser
  sintering but no milling step is necessary.
• Relatively large parts may be made, because no
  chemical reaction is necessary