Select Laser Sintering
Beaman and Deckard developed Selective Laser Sintering (SLS) process at the University of Texas at Austin. In the SLS process, a layer of powder is deposited on a support and leveled by a rolling device. A laser beam scans a two-dimensional pattern on the deposited powder layer to sinter the powder layer. After sintering of a layer, a new layer of powder is deposited in the same manner. Successive powder deposition and laser scanning then builds a 3D part.
In the first three years of commercial use, the SLS process was used primarily to produce durable nylon-based prototype and patterns for making silicone rubber molds. Rubber molds are used to vacuum cast durable plastic prototype parts from liquid urethane or epoxy systems.
The direct production of nylon-based parts is generally economical when a limited number of parts is needed. The vacuum casting is attractive when more parts are required, particularly if the parts are larger. While nylon-based and cast prototype parts are useful for some level of functional evaluation, it is necessary to have prototype parts made with the production material and process if more rigorous testing and analysis are required.
As a result, there has always been a great deal of interests in using Rapid Prototyping (RP) processes to produce durable prototype molds for injection molding plastic parts. A plastic pattern is first made by a RP process and then converted to a mold using a secondary process. While these options have some attraction, particularly as the quality of RP patterns has improved, they all suffer from limitations associated with fabrication time, accuracy, durability, stairstepping, or a combination of these factors.
Therefore, the SLS process has since been developed to fabricate metallic, plastic, ceramic, and composite functional parts. SLS now uses two processes, namely, indirect and direct SLS processes, but continuing research promises greater advances in overcoming the limitations and further improving the SLS process.
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