Rapid prototyping technology


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Rapid prototyping technology

  2. 2. Introduction  Rapid Prototyping Technology is a group of manufacturing processes that enable the direct physical realization of 3D computer models.  This technology converts the 3D computer data provided by a dedicated file format directly to a physical model, layer by layer with a high degree of accuracy.  The presentation gives an overview on existing major RP techniques and their applications in engineering fields Fig 1: Flying sculpture called “the little shining man” created using rapid prototyping technique. Design & Manufacturing, NIT Silchar 08-10-2013 2
  3. 3.  RPT and Rapid Manufacturing (RM) offers great potential for producing models and parts.  By this reliability of product can be increased, investment of time and money is less risky.  RPT can automatically construct physical models CAD data.  Rapid prototyping is an "additive" process, combining layers of paper, wax, or plastic to create a solid object.  In contrast, most machining processes are "subtractive" processes that remove material from a solid block.  Most prototypes require from one to seventy-two hours. Fig 2: Rotors made using rapid prototyping techniques Design & Manufacturing, NIT Silchar 08-10-2013 3
  4. 4. The Basic Process  Create a CAD model of the design # Object to be built is modelled using CAD software. # Solid modellers like ProE yield better results. # Existing CAD file may also be used  Convert the CAD model to STL (Standard Tessellation Language) format # STL format is the standard of rapid prototyping industry. # This format represent 3D surface as an assembly of planar triangles and describes only surface geometry. (without any representation of colour, texture etc.)  Slice the STL file into thin cross-sectional layers # Several programmes are available for this. # STL models are sliced into a number of layers (.01mm to .7mm). # Orientation size and location are adjusted using the software. Design & Manufacturing, NIT Silchar 08-10-2013 4
  5. 5.  Construct the model one layer atop another # RP machine builds one layer at a time from polymers, paper, or powdered metal. # Fairly autonomous needing little human intervention.  Clean and finish the model # Post processing step. # Prototype may require minor cleaning and surface treatment. Design & Manufacturing, NIT Silchar 08-10-2013 5
  6. 6. Rapid Prototyping Techniques Most commercially available rapid prototyping machines use one of the five techniques  Stereolithography (SL or SLA)  Laminated object manufacturing  Selective Laser Sintering  Fused deposition modeling  Solid Ground Curing  3D ink jet printing Design & Manufacturing, NIT Silchar 08-10-2013 Fig 3: SL Machine 6
  7. 7. Stereolithography (SL or SLA)  Builds 3D model from liquid photo sensitive polymers when exposed to UV rays.  Model is built upon a platform situated just below the surface of liquid epoxy or acrylate resin.  A low power highly focused UV laser traces out the first layer, solidifying model cross section.  An elevator incrementally lowers the platform into the liquid polymer.  Process is repeated until prototype is complete.  Model is the placed in an UV oven for complete curing. Design & Manufacturing, NIT Silchar 08-10-2013 Fig 4: Stereolithography 7
  8. 8. Laminated Object Manufacturing        Layer of adhesive coated sheet materials are bonded to form a prototype. Paper laminated with heat activated glue is rolled up on spools. Heated roller applies pressure to bond the paper to the base. Feeder/collector mechanism advances paper. Laser cuts the outline of first layer. Platform is lowered and fresh material is advanced. Process is repeated and a roller bonds the layers. Design & Manufacturing, NIT Silchar 08-10-2013 Fig 5: Laminated Object Manufacturing 8
  9. 9. Selective Laser Sintering  Uses laser beam to selectively fuse powdered materials such as nylon, elastomer or metal into a solid object.  Parts are built on a platform which sits below the surface in a bin of heat fusible powder.  Laser traces the pattern of first layer, sintering it together.  Then platform is lowered, powder is reapplied and process is repeated. Design & Manufacturing, NIT Silchar 08-10-2013 Fig 6: Selective Laser Sintering 9
  10. 10. Fused Deposition Modelling  Filaments of heated thermoplastics are extruded from a tip that moves in the platform to form the first layer.  The platform is maintained at a lower temperature, so that the thermoplastic quickly hardens.  After the platform lowers, the extrusion head deposits a second layer upon the first. Design & Manufacturing, NIT Silchar 08-10-2013 Fig 7: Fused Deposition Modelling 10
  11. 11. Solid Ground Curing (SGC)  Similar to stereolithography in that both use ultraviolet light to selectively harden photosensitive polymers. Unlike SLA, SGC cures an entire layer at a time.  First, photosensitive resin is sprayed on the build platform.  The machine develops a photo mask (like a stencil) of the layer to be built. This photo mask is printed on a glass plate above the build platform using an electrostatic process.  The mask is then exposed to UV light, which only passes through the transparent portions of the mask to selectively harden the shape of the current layer.  After the layer is cured, the machine vacuums up the excess liquid resin.  The top surface is milled flat, and then the process repeats to build the next layer.  When the part is complete, it must be de-waxed by immersing it in a solvent bath. Design & Manufacturing, NIT Silchar 08-10-2013 11
  12. 12. Fig 8: Solid Ground Curing Design & Manufacturing, NIT Silchar 08-10-2013 12
  13. 13. 3-D Ink Jet Printing  Parts are built upon a platform situated in a bin full of powder material.  An ink-jet printing head selectively deposits or "prints" a binder fluid to fuse the powder together in the desired areas.  Unbound powder remains to support the part.  The platform is lowered, more powder added and levelled, and the process repeated.  Finished parts can be infiltrated with wax, glue, or other sealants to improve durability and surface finish.  Typical layer thicknesses are on the order of 0.1 mm.  This process is very fast, and produces parts with a slightly grainy surface.  There are also other different types of 3D printing available in the market which gives very good accuracy. Fig 9: 3-D Ink Jet Printing Design & Manufacturing, NIT Silchar 08-10-2013 13
  14. 14. Applications of Rapid Prototyping Engineering  Made use in space stations and space shuttles.  Planning to install an RP machine in ISS for making spare parts.  Functional parts in F1 racing cars and fighter jets like F-18. Medical Applications  Custom-fit, clear plastic aligners (braces) can be produced.  Used in hearing aids to make custom fit shells. Arts and Archaeology  Selective Laser Sintering with marble powders can help to restore or duplicate ancient statues. Rapid Tooling  Tools are made by CNC-machining, electro-discharge machining, or by hand.  All are expensive and time consuming.  Manufacturers would like to incorporate rapid prototyping techniques to speed the Design & Manufacturing, NIT Silchar process. 14 08-10-2013
  15. 15. Conclusion  Modern CNC machines have high removal rates which helps in fast machining.  For certain applications machining will continue to be a useful manufacturing process.  One should regard RPT as one more option in the toolkit for manufacturing parts.  Rapid prototyping will not make machining obsolete, but rather complement it. Design & Manufacturing, NIT Silchar 08-10-2013 15
  16. 16. References  en.wikipedia.org/wiki/Rapid_prototyping  www.protosystech.com/rapid-prototyping.htm  www.jharper.demon.co.uk/rptc01.htm  P.M. Pandey, N.V Reddy, S. G. Dhande, ‘Slicing procedure in layer manufacturing’, Rapid prototyping journal 9(5), 2003, page 274 to 288. Design & Manufacturing, NIT Silchar 08-10-2013 16
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