Laser Sintering (LS)

image of Explanation of the technology laser including characteristics, materials, machines, vendors, applications and process chain. image of Explanation of the technology laser including characteristics, materials, machines, vendors, applications and process chain.

Synonyms

Selective Laser Sintering, SLS

Process description

A thin layer of plastic powder is selectively melted by a laser. The parts are built up layer by layer in the powder bed. Read more

A laser sintering machine will coat a layer of plastic powder onto a build platform, which is melted by a laser (or multiple lasers). The build platform will then be lowered and the next layer of plastic powder will be laid out on top. By repeating the process of laying out powder and melting where needed, the parts are built up in the powder bed.

Laser Sintering does not require any support structures. The built parts are sustained by the loose plastic powder. The entire build volume can therefore be filled with several parts including stacking and pyramiding of parts, which are then all produced together. The process chamber is preheated and under a protective gas environment.

Advantages / disadvantages

Laser sintering can manufacture parts in standard plastics with good mechanical properties. There is a constantly growing set of materials available. However, parts do not have exactly the same properties as their injection molded counterparts. Read more

The technology manufactures parts in standard plastics with good mechanical properties. A constantly widening set of materials is available. For small lot sizes, laser sintering is price competitive and often the cheapest solution.

Laser sintering parts do not have exactly the same properties as their injection molded counterparts. Especially in regards to surface finish.

Application areas

  • Prototypes are built by laser sintering in standard materials for form / fit and functional testing
  • Support parts (jigs, fixtures, helps) are produced
  • Small series parts are manufactured in standard materials

Characteristics / restrictions

  • Maximal build envelope: 550x550x750 mm3
  • Minimum feature size: 0.15 mm
  • Typical tolerance: +/-0.25 mm (can be improved through post-processing)
  • Minimum layer thickness: 0.1 mm

Characteristics are only indicative, as there are different types of machines available.

Process chain

When planning the build, the entire build volume can be utilized and filled with parts. Orientation of the parts has an impact on the mechanical properties. Laser sintering parts can be further processed in order to improve tolerances and surface finish. Read more

Pre-build planning

The production of parts is planned in a build preparation software. One or several parts are placed in the build, using the digital 3D files (typically in the STL file format). These can be arranged to fill the entire volume of the build envelope.


Post-processing
  • Removal of build envelope: The build envelope is removed from the machine
  • Remove powder: Parts are broken out of the powder cake. Afterwards excess powder is removed from the parts by sand blasting. This is usually straight forward, however might require some extra effort for parts with complex geometric features (e.g. trapped powder)
  • Post-machining: Parts might be selectively post-machined in order to fulfil critical tolerances.
  • Surface finish: Often, parts need to be further processed to improve surface finish by removing material (e.g. polishing, grinding, peening) or by adding material (e.g. painting, coating). Functional coatings are also possible (EMC, anti-bacterial etc.).

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