What is SLS 3D Printing?
Selective Laser Sintering (SLS) is a type of additive manufacturing, also known as 3D printing, used to create parts from 3D models. The two other most commonly known types also include FDM and SLA, although the list of technologies is ever expanding.
How it Works
SLS works by using a high powered laser to sinter powdered material, binding it together to create a solid object. The printer mainly consists of a build plate inside a box that is lowered down as the part is printed, a roller to spread on the powdered material, and a laser to sinter it. Imagine the box being empty with the build plate at the top of the box and a thin layer of powdered material on the build plate; this powdered material is spread over the build plate by the roller. The laser then fuses the powdered material in the cross-sectional shape of a 3D CAD model. The printer then moves the build plate down a layer, spreads another thin layer of powder over the top, and sinters that layer. One single layer at a time is printed and slowly builds the object up in thin layers.
Like all 3D printers, SLS printers use a 3D model to give the printer directions for making a physical object. Before sending an object to the printer, the 3D model is first sliced into thin layers which are used to create a program for the printer.
Here is a video from 3D Systems about the SLS 3D printing process:
The most common material used in SLS printing is polyamide plastic (nylon), although SLS printers exist which can also print in ceramic, glass, or metal.
Benefits of SLS 3D Printing
SLS printing is a very efficient type of 3D printing because the surrounding unsintered powder acts as support material for each successive layer. Most of the unused powdered material can then be used again in another print. Additionally, unlike FDM and SLA printing, parts can be nested on top of each other without negative effects to the surface quality.
This allows you to build incredibly complex shapes, because they’re just supported all the way around by powder as the object keeps dropping down in the build chamber.
SLS printed parts are almost as strong as parts created using normal manufacturing methods. They are fairly accurate as well; with accuracy usually in the range of +/- 0.002” per inch or +/- 0.015” in either axis, whichever number is greater.
Drawbacks of SLS 3D Printing
Plastic printed SLS parts have a clean and consistent surface finish, but it is kind of rough and grainy. Additionally, because the part is built up layer by layer, there is a visible layering effect on any printed part. This effect is fairly minimal, but definitely noticeable. SLS printers also have some limitations on how small of features and details can be printed, although it is sufficient for most prints.
Overall SLS printing is a great way to achieve consistently good prints regardless of the shape complexity.