Additive Manufacturing Processes Powder Bed Fusion

Powder Bed Fusion


Powder Bed Fusion is a versatile Additive Manufacturing technology. (also called LS, Selective Laser Sintering, Sintering but most commonly is still called SLS). A fine 40-micron powder layer is spread out on a printer by a roller or a knife. A laser then moves around hardening the powder in certain places. A new layer of material is then applied. Loose powder, usually made of PA 12 (polyamide 12, Nylon), supports the layers above. At the end, parts are sieved out of the build, a loose block of powder. The resulting loose powder can be partially reused.


Parts made with SLS are strong, tough and detailed but with a rougher porous structure. Porosity means that SLS parts absorb dust and moisture and performance of parts may degrade over time with some UV effects felt as well (typically UV degradation with SLS is far less strong than with SLA but greater than with FDM parts). SLS is not good at making flat parts but very good at delivering thousands of parts per day in high yield applications. SLS parts have been used to produce hundreds of thousands of surgical guides and millions of parts for consumers. The technology is also very versatile and predictable. Due to this it is used a lot by service bureaus. Along with FDM, it is the most suited for end use parts for consumers. Since the machine has to heat up and cool down it does take longer to get your SLS part than with FDM but with SLS you can make many more parts per build.


EOS, 3D Systems have traditionally been the players in the space but now newer startups are bringing the technology to the desktop. SLS is a good technology for manufacturing but the material choice is much more limited than with FDM. SLS relies a lot on polyamides and specifically on PA 12 while few other grades are available. There are glass filled and carbon filled materials however and also materials such as PP.


Advantages:

  • High Yield
  • Strong, tough, detailed parts.

Disadvantages:

  • Porosity
  • Higher up-front investment than in FDM or SLA.

Main uses:

  • Surgical guides for dental and orthopedics
  • Service bureaus