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What is rapid prototyping?

  Rapid prototyping is a method used to generate a physical model directly from 3D solid (CAD) geometry.  Typically, a prototype made using a rapid prototyping method can me made in matter of days.  However, the material properties of the rapid prototype will probably not be the same as the production version.  Below is a list and short description of different rapid prototyping processes.

  Stereolithography (SLA)
  These prototypes are made of a hardened photo-sensitive resin.  The model is built in layers in a vat of liquid (un-hardened) photo-sensitive resin.  An elevator mechanism in the vat lowers a platform one layer thickness (typically .02 to .002 inches) below the surface of the resin.  A laser beam traces the cross-section of the model corresponding to that layer, which locally hardeneds the resin in the shape of the cross-section.  The elevator lowers the platform another layer thickness and the laser traces out the next cross-section of the model.  This process is repeated for the thickness of the whole model. The model is raised out of the vat and excess resin is allowed to drain off, leaving the 3D physical model.  A layer is sometimes refered to as a "slice".  Photo-sensitive resins used in SLA are usually epoxy based and tend to be brittle when hardened.
  Selective Laser Sintering (SLS)
  The selective laser sintering process is similar to the stereolithography process in that the model is built in layers ("slices").  A thin layer of heat-fusible powder, usually some type of thermoplastic, is spread across a platform.  Again, a laser traces the cross-section of the model, solidifying the cross-section.  The platform is moved down, a fresh layer of powder is applied, and the laser traces the next "slice".  Nylon is a typical powder material used in selective laser sintering.
  Laminated Object Modeling (LOM)
  Prototypes made with the laminated object modeling process are typically made of sheets of paper laminated (glued) together.  As in the other process, the model is built in layers and a laser is used to cut out the cross-section of the model.  The paper used in the process has a heat sensitive adhesive on one side.  The cross-section creation and laminating process is automated.  The part is built on an elevator platform and a continuous roll of paper is fed across the platform.  The laser cuts out the cross-section for that layer.  The new layer is heated to laminate it to the previous layer.  The elevator moves down one layer thickness and the paper roll indexes to an area of fresh paper.
  Fused Deposition Modeling (FDM)
  Like the other processes descibed on this page, models made using the fused deposition modeling process are made in layers.  Unlike the other processes, a laser is not used to produce the model layer cross-section.  Instead, a supply of the model material in the form of thin filament is heated and deposited directly on the elevator-controlled platform.  The machine traces out the cross-section of each layer to form a continuous stream of material.  The platform is lowered automatically after each layer.
  Prototype Casting

There is also the possibility to use the physical model as a pattern to make a low-volume mold.  One such common method is to make a silicone or polyurethane mold from a single rapid prototype model and casting a small quantity of polyurethane parts from that mold.

Bradley Beach Consulting - Monmouth County, New Jersey - (732) 859-7270