Selective Laser Sintering (SLS) technology can truly be called an additive manufacturing technology. Long used to build prototype parts early in the design cycle, increasingly it is used in limited-run manufacturing to produce end-use parts. It was developed and patented by Dr. Carl Deckard at the University of Texas in the mid-1980s under sponsorship of DARPA and patented in 1989.
SLS is a layer-based process, but instead of using a liquid, it works with a bed of thermoplastic, metal, ceramic, or glass powders. The laser selectively fuses powdered material by scanning cross-sections generated from CAD data. After each cross-section is scanned, the powder bed is lowered by one layer thickness and a new layer of material is applied on top. This process is repeated until the part is completed.
Each layer of fresh powder is slightly melted (sintered) together with the high-power pulsed laser. The imaging is vector-based, so it can be quite accurate.
SLS parts are typically very strong, and exhibit material properties that come close to the base material. Part density depends on peak laser power rather than laser duration. SLS machines tend to preheat the bulk powder material to make it easier for the laser to raise the temperature of the selected regions the rest of the way to the melting point.
This technology is an excellent choice for parts requiring strength and toughness. The weaknesses of SLS are its inability to do fine details and its surface roughness.
Some SLS machines use single-component powder, such as direct metal laser sintering. However, most SLS machines use two-component powders, typically either coated powder or a powder mixture. Depending on the material, you can achieve parts with up to 100% density, with material properties comparable to those from conventional manufacturing methods.
SLS does not require support structures because the constructed part is always surrounded by unsintered powder.
Because of the materials uses in SLS, the technology produces rugged, stable parts that do not lose their shape or post cure over time. (SLS) parts can be sanded, painted, plated, tapped, or even machined. Click here for a closer look at all available SLS machines.