Unlike FFF, SLA does not
require melt processing but liquid photo-reactive polymers which
can be cured by ultraviolet laser or other source. SLS is a technology
with very similar setup to SLA except that it uses laser with higher
energy than UV and prints from powder materials instead of liquid photopolymers. Neither SLA nor SLS has the degree of anisotropy
challenges as FFF does since the liquid photo-reactive polymers
used in SLA are crosslinked during printing and SLS creates a more
homogenous melt at the surface.