• Dr Izhar Aziz

SLS: How it works

The development of Laser Selective Sintering or SLS technologies begins in the 1980s. When Dr. Carl Deckard and Dr. Joe Beaman of the University of Texas, in Austin, USA, develop the foundations of fusion technologies powder (powder bed fusion technologies). These technologies are capable of manufacturing with multiple materials from polymers to metals, thanks to the application of a laser. When referring specifically to SLS technology, we are especially talking about plastic polymers, mainly nylon. Although that has changed a bit in recent years. The development of new dust fusion technologies resulted in the creation of the DTM Corporation, currently part of 3D Systems. Where multiple companies have also specialized in powder fusion techniques, including Farsoon Technologies, specifically specialized in SLS. Selective laser sintering allows you to print functional objects without resorting to an intermediate binder or to an eventual assembly stage. Before printing, the object is designed using CAD software (Inventor, CATIA, SolidWorks, ProEngineer…). This model will later be sent to a printer in numerical format. Then, the printing is done layer by layer, from fused powders, thanks to the temperature generated by a CO2 laser.

An important issue when talking about a 3D SLS printer is to know what are the real benefits of using it compared to other 3D technologies. The key answer to this question is the strength and complexity of the parts that can be manufactured . Selective sintering of nylon powder (PA12) consists of manufacturing objects by the progressive fusion of powder particles, which by not using supports allows complex geometry to be used and techniques such as  topological optimization. To start the process and prepare the 3D SLS printer , the powder container and the construction area are first heated below the melting temperature of the polymer. The first layer of powder is discharged onto the construction platform. A CO2 laser then scans the contour of the next layer and selectively sinters (fuses) the particles of the polymer powder. The entire cross section of the component is scanned, so that the part is solidly constructed. When the layer is completed, the construction platform moves down and the material surface is coated again. The process is repeated until the whole part is complete. After printing, the pieces are completely encapsulated in the powder. This  powder container has to be cooled before it can be cleaned and post-processed . This can take up to 12 hours. Subsequently, the parts are cleaned with compressed air or other means of cleaning, and are ready for use or for further processing.

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