Sep 13 2002
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Besides cost and quality, time-to-market is becoming a more and more critical factor for the success of a product. A key contributor to product development cycles is the time required to make prototypes. Moreover, in markets where customers are expecting individually customized components, considerable time and cost can be involved in making tools or molds.
Rapid Prototyping (RP), also called Solid Freeform Fabrication (SFF) is useful to overcome these issues. Overall, the processes develop complicated shapes through additive processes, creating components without the application of tools.
Commercial selective laser sintering (SLS) is the most sophisticated laser fusion method. The feedstock used in this process is a thin ceramic layer coated with a thermoplastic binder.
A laser beam scans the surface, outlining the regions to sinter, fuse the polymer, and bond the particles. The rest of the layer remains as loose powder. The layer is lowered to apply an additional loose powder layer. Then, using the laser, another layer is processed, bonding it to the first layer.
The process is repeated until the green state component is created. The component is subsequently processed by conventional processes, as soon as the binder is burnt out. It is considered that SLS can be used to process any material that can be densified by conventional sintering methods, for example, SiC, Al2O3, and Zr composites.
Selective Laser Sintering
Lasers with a higher power (greater than 50 W) can be employed to sinter powders straightaway without the need for a polymer binder. Although Al2O3-B2O3 composites and WC-Co powder mixtures have been produced using this method, the density was just 70% theoretical and post-treatment sintering was still required.