Selective laser sintering (SLS) is another example of an Additive Manufacturing process and type of 3D printing method. This technology uses a laser to selectively join powdered plastic to build full three-dimensional (3D) objects, layer by layer.
S.L.S. 3D printers need three main parts to do this; a powder bed, a powder delivery system that rolls powdered plastic onto the bed and a laser that turns the powdered plastic into solid plastic layers.
Before SLS 3D printing starts, the machine heats up all the powdered plastic to soften it. This makes it easier and faster for the laser to turn the softened powdered plastic, into a liquid plastic that hardens instantly to make a solid plastic layer. In the first step of SLS 3D printing, the powder bed is lowered by a small amount and a layer of softened powdered plastic is rolled out onto it from the powder delivery system. The laser then draws a pattern on to the powder bed and the pattern hardens instantly, making the first layer.
Then, the powder bed is lowered again by the same amount as before, and a new layer of softened powdered plastic is rolled out onto it from the powder delivery system. The laser then draws another pattern on top of the first layer, creating a second layer. This new second layer hardens instantly and joins to the first layer. This layering process happens again and again until a full 3D object is created.
Unlike in FDM and SLA (you can find out more about these in the Lexicon), 3D objects printed by an SLS 3D printer aren’t printed with ‘supports’. This is because the 3D object is always surrounded and supported by the powdered plastic. It is also important to know that in SLS 3D printing users cannot print out closed, empty 3D objects because a hole is needed to remove the powdered plastic once the object is finished. However, SLS creates smooth looking and polished objects.