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SLS - Selective Laser Sintering ( New ) ( Better ) 


Selective Laser Sintering ( SLS ) is similar in many ways to the stereolithography process but uses powder instead of a polimer fluid. The laser sintering machines lay down thin layers of powder - either plastic or metal - and then melt the powder particles while tracing out the required cross-section. After the cross-section is complete, another layer of powder is applied and sintered to the layer below. This process of sintering, re-coating and then sintering again carries on until the part is complete. Powder that remains unaffected by the laser acts as a support for the sintered part during the build process and is brushed off when the component is complete.




Unlike the stereolithography process, laser sintering relies on laser generated heat to bond material, rather than  UV radiation to cure material. As such, the process requires a much higher power laser, delivering some 50 W of power at the material bed for plastic parts and 200 W of power for the metal based systems. The current build envelopes vary depending on the machine. The DTM-2500 machine has a maximum part build area of 380x330x420 mm whereas the EOSINT S, which is a sand sintering unit mainly for the production of complex, polymer-coated, sand-sintered cores of the sand casting process (metal parts), has a working volume of 720x380x400 mm.


( Hague R.J.M. & Reeves P.E. Rapid Prototyping, Tooling and Manufacturing, volume 10, number 9, 2000, pg. 6-7 )


Selective Laser Sintering - ( Previous )

The selective laser sintering process is a thermal process that uses a laser to sinter (fuse) layers of powdered thermoplastic materials together to form solid 3D objects. The powder needs fine grains and thermoplastic properties so that it becomes viscous, flows, and then solidifies quickly. Its chief advantages revolve around material properties. A variety of thermoplastics such as poltcarbonate, nylon or glass-filled nylon.(Rapid Prototyping And Engineering Applications,Frank W. LIOU, CRC Press,2008,p. 271)
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FDM - Fused Deposition Modeling ( New ) ( Better )


Fused deposition modeling ( FDM ) is an extrusion-based rapid prototyping ( RP ) process, although it works on the same layer-by-layer principle as other RP systems. Fused Deposition Modeling relies on the standart STL data file for input, and is capable of using multiple build materials in a build/support relationship. FDM was developed by Stratasys, Inc. of Eden Prainrie, MN, in the early 1990s as a concept modeling device that is now used more for creating casting masters and direct-use prototyping.


The FDM systems have evolved through several models, beginning with the original 3D Modeler, a floor unit, and progressing through the various "desktop units", including the 1500, 1600, 1650, 2000, 8000, and Quantum. Basically, the 1500 through 2000 models are capable of building parts in the 10" x 10" x 10" range, whereas the 8000 and the Quantum can build 24" x 20" x 24" parts.


( Cooper Kenneth G. Rapid Prototyping Technology Selection and Application, pg. 60 )


Fused Deposition Modelling(FDM) (Previous)

FDM is a nonlaser filament extrusion process tahat utulizes engineering thermoplastics, which are heated from filament form and extruded in very fine layers to build each model from the bottom up. The model can be made from acrylonitrile, ABS, polycarbonate, poyphenylsulfone, and various versions of these materials. Furthermore, the models are tough enough to perform functional tests.(Rapid Prototyping And Engineering Applications,Frank W. LIOU, CRC Press, 2008, p.257)
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