SLS 3D Printing was developed in the 1980s by Carl Deckard and Dr Joe Beaman, a professor at the University of Texas at Austin. The technology utilises a range of materials such as plastics, metals, glass, ceramics, and various composite material powders.
MaterialNylon is a synthetic thermoplastic polymer which is the common material used by SLS printers. nylon 12 (PA12). is one of the common type of material use and overall it has the following qualities;
Nylon 12 comes in the form of powder and some SLS printer uses dual powder such as coated powders for instance Nylon with a mixture of aluminide, carbon, or glass are developed to optimise the printed part to have higher strength, stiffness, or flexibility. only the powder component between the two with ower glass transition point is sintered, binding both components.
There are ranges of Nylon to choose such as Nylon PA12, TPU, PA 11, PA6 depending on which will have material properties that will fit the project.
SLS 3D printing process has the following applications such as robotics, special machinery, jewellery & watches, IoT devices, sports equipment, consumer products, architectural models, drones, footwear, medical devices, electronics housing, medical devices, sculptures, orthopaedic technology, education, jigs and fixtures, promotional items, with a continuous expansion of use every day.
On top of the platform in the build chamber, the printing process begins by dispersing powder in a thin layer followed by a preheat of powder to a temperature below the melting point of the raw material which makes it easy for the laser to raise the temperature of specific regions of the powder bed it traces the model to solidify a part. The laser then scans the cross-section of the 3D model providing heat to the powder below or right at the melting point of the material, fusing the particles into one solid part .on the other hand the unfused powder provides support to the part during printing and eradicate any need for extra support structures unlike support in FDM and SLA printers. In the build chamber, the platform lowers by one layer normally between 50 to 200 microns and the process repeated till the print is complete. When the print is complete the inside the build chamber needs to cool down as well as the outside the printer to ensure optimal mechanical properties and avoid warping in parts. The Post-processing for SLS prints involves removing the part from the build chamber, separated, and cleaned of excess powder. The powder can be recycled, and the printed parts can be post-processed again by media blasting or media tumbling hence, making SLS one of the least wasteful manufacturing methods.
Begins with using CAD Software to design the 3d object followed by STL or OBJ file export and import into a slicing software whereby print setting is adjusted, orient and arrange models in an optimized way, estimate print times, and slice the digital model into layers for printing. After this step, the software directly via wireless or cable connection sends the printer’s instruction to start printing.
The workflow varies depending on different SLS printing systems for instance traditional SLS systems require extensive training, tools, and physical effort to prepare and maintain. While some other system workflow is simple, efficient with modular components to enable nonstop printing and end-to-end powder handling.
After the machine is instructed to print SLS Printers can take hours to days to print depending on the size, density and complexity of the printed part.
When the prints complete there has to a time to allow a cooling-off outside and inside of the machine which takes up half of the print time.
Post-processing requires less time for SLS Prints compared to other 3D printing technologies as it is easily scalable and has a consistent result for the finished prints as it does have supports attached to them at the end instead only access powdered needs to be cleaned using compressed air or a media blaster.SLS 3D prints have a grainy finish but media blasting or media tumbling ensure smooth surfaces and even more, the parts can be spray painted, lacquered, electroplated, and coated to achieve different colours, finishes, and properties, for example, water tightness (coating) and conductivity (electroplating).
SLS printing has a dimensional tolerance of ± 0.3% and a lower limit of ± 0.3 mm and is the most accurate process resulting in high resolution and is great to produce complex geometries. Although SLS is better than FDM there is a probability that the layers will not cool at the same rate hence warping may occur especially for larger-scale objects and leaving the powder to fully cool down is one of the solutions.
The SLS printers come in different types whereby the main differentiators are the type of laser, the size of the build volume, and the complexity of the system and they all use a different approach in controlling the temperature dispensing powder and depositing layer.SLS printer has to control the powder and the unfinished part with 2 °C during the three stages of preheating, sintering, and storing before removal to minimize warping, stresses, and heat-induced distortion.
Traditional Industrial SLS 3D Printers is characterised by high-power use of single or multiple lasers and the environment has to be inert containing gases such as nitrogen to prevent oxidization and degradation of the powder hence, in this case, it is necessary to have air handling equipment such as HVAC etc requiring at least 10 m² installation space. The prices range around $100,000.
Fuse 1: The First Benchtop Industrial SLS 3D Printer is a cheaper SLS system emerging however some consequences comes with the costs such as ower part quality and complex, manual workflows resulting from the lack of post-processing solutions which became limiting for use in industrial and production contexts.