SLA Stereolithography

Stereolithography was the first commercially available rapid prototyping technology and is the most widely used rapid prototyping process in the world today.  Stereolithography produces 3D rapid prototype parts a layer at a time by using the light of a solid-state laser to trace the cross sectional slice information of the 3D CAD data onto the surface of a container of liquid photopolymer.  These types of materials quickly solidify wherever the laser beam strikes the surface of the liquid.  Once one layer is completely traced, it's lowered a small distance into the container and a second layer is traced right on top of the first. The self-adhesive property of the material causes the layers to bond to one another and eventually form a complete, three-dimensional object that replicates the 3D CAD data.

Unlike the SLS rapid prototyping process, which requires no additional support structures, rapid prototype parts that have overhangs or undercuts must be supported during the SLA rapid prototyping process.  With today’s advanced software, support structures are automatically designed and fabricated right along with the object.  Upon completion of the rapid prototyping process, the object is elevated from the container, extracted from the prototyping machine and the supports are then removed.  The object(s) are then typically placed in a “light chamber” for additional photo curing.

Stereolithography (SLA) rapid prototyping generally is thought to provide better accuracy and surface finish than the other mainstream rapid prototyping technologies available today.  Over the years, a wide range of rapid prototyping materials with improved mechanical properties have been developed to further try and mimic engineering-grade thermoplastics.  There is a wide range of rapid prototyping materials available, but the expense and difficulty of changing out materials on this platform make it prohibitive for service bureaus to carry more than one or two different options.  SLA is also notable for the large object sizes that it is capable of producing.

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