Selective Laser Sintering, usually shortened to SLS, is an industrial 3D printing process that builds solid parts from a fine nylon powder rather than a spool of filament or a vat of liquid resin. Inside the machine a laser scans across a heated bed of powder, fusing the tiny particles together exactly where the part needs material, and once a layer is complete a roller or recoater spreads a fresh coat of powder over the top so the laser can draw the next slice. Repeat that thousands of times and a durable nylon component grows one thin slice at a time, completely buried in the surrounding powder.
The fact that the loose powder around each layer holds it in place is the single most important thing to understand about SLS, because it means the process does not need the support structures that filament and resin printing rely on. That changes how you design parts, what geometry you can build, and how much finishing work the part needs afterwards. We run SLS from our main warehouse in Perth as part of our MJF & SLS printing service, alongside other powder and filament processes.
Inside the build chamber
Before the laser even starts, the machine preheats the whole powder bed to a temperature just below the melting point of the nylon. This is clever, because it means the laser only has to add a small amount of extra energy to push each point over the line and fuse it, which keeps the process fast and the temperature of the part stable throughout the build. Stable temperature is one of the big reasons SLS parts come out with consistent mechanical properties no matter where they sit in the chamber.
A typical layer is around 0.1mm thick, and because the parts are supported by powder rather than printed structures, a single build can be packed with dozens or even hundreds of parts nested closely together in three dimensions. The full block of fused parts and surrounding powder is known as the cake, and it has to cool down slowly and evenly before anything can be touched, which protects the parts from warping as they come back to room temperature.
From powder to finished part
Once the cake has cooled, operators break it open and carefully lift each part out of the loose, unfused powder that surrounds it. The parts are then bead blasted, a process that fires fine media at the surface to remove the last clinging powder and reveal a clean, even, matte finish. For a lot of functional jobs the parts are ready to use at this point, which is part of why SLS lead times stay short compared with processes that need extensive hand finishing.
Where appearance or sealing matters, the parts can go on to be dyed, vapour smoothed or coated. Black dye is especially popular because it gives a professional, uniform look that hides the natural texture of the nylon, while smoothing or sealing helps a part resist liquids and look closer to an injection moulded product.
How SLS differs from filament and resin
It helps to see SLS next to the processes people meet first. FDM printing needs printed supports under any overhang, and SLA printing gives fine detail but more brittle parts that also need supports. SLS sits apart because the powder bed supports everything for free, so the geometry is far less restricted.
That is why SLS tends to win for tough, functional nylon parts. If you are unsure which process fits, send the model through with a get a quote and we will recommend the route.
Why people choose SLS
SLS is the process people reach for when they need genuine functional strength, freedom to build complex shapes, and a clean surface with no support scars to grind away. It happily covers everything from one off prototypes that have to survive real testing through to short production runs of end use parts, and it scales sensibly because so many parts fit in one build.
- No support structures, so complex shapes and undercuts print freely.
- Strong, slightly flexible nylon with good impact resistance.
- Excellent for nesting many parts densely in a single build.
- Consistent properties that suit functional testing and end use parts.
- A clean matte finish straight off the machine with no support marks.