SLS (Selective Laser Sintering) is a rather exotic 3D printing process that few hobbyists can access. There are no consumer SLS 3D printers on the market, which means only corporations and well-funded makerspaces tend to have these machines. But SLS printing offers some unique advantages over other 3D printing processes that would benefit many hobbyists. To bring this technology to the masses, Tomas Starek is designing an affordable and open source SLS 3D printer called SLS4All.
SLS 3D printing works by shining a laser onto a bed of powdered material—usually some form of polymer, though metal SLS printers exist. The laser melts and fuses the powdered material, forming a solid. As with other forms of 3D printing, the layers build up to create a three-dimensional object. SLS printing offers two primary advantages over other processes: it works with materials not suitable for FFF (Fused Filament Fabrication) or resin printing, and the powder bed supports parts, thus making bridges and overhanging geometry a non-issue.
Moving a laser, either with galvo mirrors or a gantry setup, is trivial. Laser cutters already do this and a SLS printer just needs the added ability to keep the laser in focus in the Z axis. But an SLS 3D printer must also deposit a very fine layer of the powdered material onto the bed between every pass. It must do so without disturbing the printed part. The thickness of the new powder layer also has to be precise and consistent. The mechanism that handles that process, called the recoater, presents the biggest design challenge.
Starek's design is well on its way to overcoming that challenge. His SLS4All 3D printer already has a fleshed-out recoater mechanism based on a roller that rides along on standard hardened steel rods. The rest of the printer is made of a combination of T-slot aluminum extrusion, aluminum tube and channels, custom aluminum sheet, and 3D-printed plastic. To facilitate speedy printing, it utilizes a 5W 445nm laser diode paired with mirror galvos.
Most of the electronic components are common in the 3D printing industry. A BigTreeTech SKR 1.4 Turbo board controls the laser, galvos, and stepper motors (through TMC2209 drivers). It receives control commands from a Raspberry Pi 4 Model B (2GB) running Klipper software. A custom PCB handles some functions, such as thermistor readers and galvo signal processing. The AC heaters receive power through solid state relays and the DC heaters receive power through beefy 30A MOSFETs.
SLS4All is still in a work in progress, but Starek seems to be very close to the point where he can start running tests prints. As designed, the printer will have an effective print volume of 150 x 150 x 180 mm, which is large enough to be very usable. We can't wait to see this machine in action and are looking forward to SLS 3D printing finally making its way into the hobbyist segment.