Selektives Laser Sintering SLS
How SLS works
The starting material in the SLS process is a fine plastic powder, which is applied in very thin layers (0.05-0.12 mm). After each layer, a high-precision laser scans the component contour and the powder is melted by the perfectly coordinated energy input. After the laser has covered the entire surface, the build platform lowers by exactly one layer thickness and the next layer of plastic powder is applied. This process is then repeated until all components have been 3D-printed by the laser, layer by layer. The entire build-up process in selective laser sintering can take several hours, depending on the size of the installation space.
As the fused components lie in the powder bed and the non-fused powder supports the components, no supports are required. As soon as the complete print job with all components has been printed, the components and the loose, non-fused powder between the components must cool down.
Schaltplan eines SLS-Druckers. Quelle: Hubs.
As soon as the complete print job with all components has been printed, the components and the loose, non-fused powder between the components must cool down. After a few hours, the build chamber will be at approximately room temperature and you can start to remove the excess powder from the printed components. However, the unmelted powder is not thrown away but reused. New powder is mixed with used powder in a mixer.
In selective laser sintering, a powder mixture is always used, which makes the process even more economical and produces virtually no waste. The typical plastics used in the SLS process are polyamides/nylons and elastomers, meaning that both rigid and flexible components can be printed. The most commonly used material in selective laser sintering is polyamide 12, which is characterized by very good tensile strength and rigidity.
Advantages of SLS
Due to its special mode of operation, selective laser sintering has a number of advantages over other additive and conventional manufacturing processes, such as milling or injection molding. Thanks to the layered construction method in SLS, the user has virtually no limits when designing components. There is no need to worry about bevels or undercuts, as these no longer play a role in the SLS process. Selective laser sintering also has a number of other advantages.
No tools or molds are required for the manufacturing process. The production of the tools takes several weeks and is very cost-intensive. This investment ties up your capital and weakens your cash flow. Especially in prototyping and for the production of small batches, tool-free production saves a lot of time and money.
The freedom of design in selective laser sintering leads to the possibility of so-called functional integration. This means that functional components such as snap-in hooks, air channels for vacuum grippers or hinges can be integrated directly into the component during the assembly process. This saves assembly steps and therefore time, money and potential sources of error.
Geometry adjustments are no problem in SLS. Due to the short product cycles, subsequent changes to components are no longer an exception. The next components can be manufactured according to the latest data status at the same time as the CAD model is changed. And as large stocks are avoided, there are no more old components in stock.
“Just-in-Time” and ‘Just in Sequence’. Two important concepts that are easy to implement in SLS. Production runs entirely according to demand and prevents large inventories that tie up capital.
The short production times significantly reduce the time-to-market, as each part can be printed and then tested in parallel with the component development. What used to be a months-long process is now implemented in just a few days.
Selektives Laser sintering: The Applications
Selective laser sintering is mainly used in the field of rapid prototyping. This means during the development of new components, early in the initial phase of creating the first prototypes and functional models. However, SLS is also increasingly being used for small series and the production of spare parts. SLS is a cross-industry technology that is used not only in the automotive industry and medical technology, but also in aerospace and mechanical engineering. The advantages of selective laser sintering are particularly important in the field of prosthetics and implants.
Materials
Selective laser sintering is mainly used to process polyamides and elastomers. We offer you a wide range of materials to achieve the right properties for every application.
PA 12
+GF/+CF
PA 11
+CF/-ESD
PP
TPU
70-90A
Alumide – PA 12 Aluminiumverstärkt
PPS (+GF), PEKK, PEEK
PA12 mit Flammschutz
Postprocessing in SLS
By nature, SLS components made from PA12 are white and have a relatively rough and open-pored surface. Both the color and the surface can be changed by post-treatment.
Coloring/Dyeing
The components are dyed in a color bath. This allows different colors such as black, red or green to be achieved. Exact colors according to RAL, for example, are not possible.
Varnishing:
SLS components are easy to paint in the color of your choice.
Surface finish:
We can finish the surfaces mechanically by grinding and polishing to your specifications.
Chemical smoothing:
A brief treatment in a chemical steam bath smoothes the surface and closes the pores. The result is then a smooth surface as in injection molding.
Shot peening:
In order to smooth the surface of the components and close the pores, there is the option of compaction blasting. This involves blasting the component with plastic beads.
Infiltrate:
Since SLS components are not watertight without post-treatment, it is possible to infiltrate the parts. After this process, the components are watertight.
Trowalizing:
In this process, incredibly smooth surfaces can be achieved and the components can even be polished.
