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SLS (Selective Laser Sintering) – Process using a CO2 laser to sinter or fuse a powder
material. The laser traces the parts cross sectional geometry layer by layer. SLS creates
accurate and durable parts but finish out of machine is relatively poor.
The SLS method uses finely ground powders that are sintered by a laser to generate parts.
An SLS machine consists of the following parts: a feed piston, build piston, spreading
apparatus, CO2 laser, scanning device and an excess bin. All these components are kept
in a nitrogen rich build chamber to reduce the explosion risk associated with fine powders.
The build chamber is also heated to just below the melting point of the material to reduce
the energy needed by the laser to sinter the materials. The feed piston is used to measure
and feed powder that is spread over the build piston by a spreading apparatus. Once a layer
is spread onto the build chamber, a laser, controlled by a scanning device, sinters the
material together. After the first cross section is complete the feed elevator raises one
layer thickness and the build chamber lowers one thickness. The roller then spreads the next
layer of powder over the first cross section. The next cross section is then sintered. This
process is continued until the part is completed. Once the part is completed the part is
removed and any excess powder is blown off of the part. Unlike SLA and FDM, SLS needs no
support structures because the excess powder on the build piston acts as a support for any
The SLS method of rapid prototyping is a relatively quick method of creating accurate and
durable parts that can be used for many functional purposes. The drawback to SLS however
is that the parts have a rather porous surface finishes due to the sintering nature of the
technology. This can be a drawback for some applications and may require infiltrating with other materials to fill any voids.
The materials available for SLS are quite extensive. The method of local melting and
solidification allow many materials to be used. They include polyamide, glass filled
polyamide, elastomer, polystyrene, foundry sand, stainless steel and other polymers.
The color of parts depends on the material being used.