Graphics Reference
In-Depth Information
Polymer SLS
Selective Laser Sintering (SLS) of plastics also uses thermoplastic just like FDM, but the
base material in this case is in powdered form. The fact that the object is taking form in a
bed of powder means that no support structures are needed for overhanging parts. Plastics
used with SLS are either semi-crystalline thermoplastics (for example PP, PE or Nylon) or
amorphous thermoplastics (for example PS or PC). Semi-crystalline polymers are heated by
the laser to over melting temperature, resulting in a fully molten powder layer. The density
will be close to full density and the mechanical properties will be close to those of molded
polymers, resulting in relatively strong parts. However a certain shrinkage of the material
might take place.
Amorphous polymers on the other hand are consolidated by heating above the glass trans-
ition temperature at which they are in a much more viscous state than semi-crystalline poly-
mers
. Since amorphous polymers soften gradually they are seldom as easy flowing as
semi-crystalline polymers, and therefore they have a lower degree of consolidation which
results in higher porosity and less strength, but also the shrinkage is less.
Although a wide range of polymers may be used in SLS processing, the materials have
mostly been limited to Nylon (Polyamide PA), simply because it works best with SLS.
Nowadays EOS offers PEEK and PS too, and 3D Systems offers around ten different SLS
materials with different characteristics, most of them are based on Nylon, such as: Duraform
EX (based on nylon 11), Duraform GF (glass filled), Duraform FR 100 (flame-retardant),
Duraform HST Composite (mineral fiber filled). There is also a rubberlike material made of
thermoplastic elastomer called Duraform Flex, a PS material for casting etc.
