Selective Laser Sintering printing is a method of printing high performance parts. A laser beam is used to melt (sinter) particles of material together, layer by layer. Some of these machines are capable of even printing metal or high-impact Nylon. When used to print metal parts the process is referred to as Direct Metal Laser Sintering.
SLS machines are used for prototype parts, large production runs and printing materials that other machines simply cannot handle. These machines have reasonable accuracy, comparable to an Fused Filament Fabrication printer. They print everything from engine parts to medical implants and prosthetics.
How SLS Machines Work
Carl Robert Deckard and Dr. Joe Beaman invented SLS printing in the mid-1980s, patenting the invention in 1989. SLS machines operate by the same software principles as other 3D printers, namely that a user takes a 3D model, slices it into layers and has those layers converted into machine movement code.
However with an SLS machine the movement is directing a high powered laser beam, which is used to trace each layer onto a bed of power. The laser beam melts the powder together, forming the part. The powder bed is lowered, a new layer of powder is added and the process repeats.
What about support material? SLS machines do not have any. Instead, the unfused powder acts to support parts. This makes it able to print some shapes that even other 3D printers can’t handle without internal supports. This also means that parts can be stacked one on top of the other inside the print area, which enables SLS machines to create many parts in a single print.
The SLS Process
- The Powder Feeder dispenses additional material onto the Build Platform.
- The Recoater takes this powder and pushes it across the Build Platform, creating an even flat layer of powder. Extra powder is pushed into the Overflow Bin.
- The Recoater retracts and the Laser Scan System at the top of the machine begins tracing the layer on the top layer of the powder.
- Once the layer is completed, the Build Platform drops down to allow for a new layer to be recoated and the process repeats.
Why should you use SLS?
- You need to create hard-wearing, watertight parts that resemble injection-molded/mass manufactured parts.
- You have a large volume of parts that you need to print cheaply.
- The design makes it difficult or impossible to remove support material.
- You need high strength but also a reasonably good surface quality.
- You want to create end-use parts.
- You want your prototype to have the same strength, material and a close finish to the final part.
When would something else be better?
- You are financially constrained; SLS parts are much more expensive than other options.
- You do not need the materials or strength characteristics that an SLS printer offers.
- Extremely fine details and smooth surfaces are required.
- You need a desktop printer; SLS machines are often the size of a refrigerator laid on its side – or larger. They are coming down in size but they have not reached the level of Fused Deposition Modeling (aka FFF) or Stereolithography machines.