3D printing (3DP) additive manufacturing (AM) technologies are the future of rapid prototyping and small/big production lines for industry. There are several variations of this technology; however, there is one with extraordinary potential yet to be explored – selective laser sintering (SLS).
How SLS works
SLS involves powder sintering with infrared lasers in elevated temperatures, which helps the grains of the powder consolidate before being bound with the laser beam. Most SLS printers have a bed on which a roller spreads a thin layer of powder. This powder is then sintered according to the layers sliced from a 3D model file.
Afterwards, the platform moves down by a small increment and the process repeats until the last layer is formed. Next comes post-processing, which requires removing the model from the unsintered powder suspension and sandblasting. Unlike 3DP technologies such as fused deposition modeling (FDM), SLS can 3D print without any support structures for models with complex geometry due to models being suspended in powder.
The two main types of SLS printers are industry grade and benchtop. Industry grade are expensive while benchtop – such as Sinterit’s Lisa or Lisa PRO – are more affordable. The main differences are print volume, process automatization, and material range. Benchtop printers are ideal for academic research, rapid prototyping, and small serial production.
Materials for SLS 3D printers
The variety of materials used in SLS is broad – from different metal powders used in the automotive industry to polyamides and thermoplastic polyurethane (TPU) for the medical market. All powders can be altered for the specific application to achieve the desired mechanical properties.
SLS is a zero-waste technology: unsintered powder can be recycled for next prints. Its small refresh ratio (amount of fresh powder that must be added to maintain print quality) lets powders be reused with a fraction of new powder. However, some powders oxidize quickly and require a neutral gas atmosphere such as nitrogen to preserve the print quality. This solution is present in Lisa PRO, which has a nitrogen intake.