3D Printing, FDM Technology

SLS vs. FDM [Technology Review]

By TriMech on May 7, 2019

Choosing the right  3D printer for your prototypes or parts requires an understanding of the pros and cons of the different technologies available. Some 3D printers use technologies such as Fused Deposition Modeling (FDM), a layer by layer technology using multiple filaments to create a structure, while others use Selective Laser Sintering (SLS), a laser powered technology that uses a single filament material to create sturdy structures. Both FDM and SLS could create a strong structure, but it is important to understand how each technology can impact your 3D printing process.

How does SLS work?

SLS 3D Printed PartSLS is a type of additive manufacturing tool that uses a CO2 laser to essentially draw a solid structure by fusing together powdered material into one solid shape. The laser will gather the 3D description of a CAD file created in a software such as SOLIDWORKS. It is guided by the information from a CAD file converted to STL format. This creates a structure by continuously layering materials on top of one another, while any powdered material that wasn’t sintered acts a supportive structure. This process is repeated until the structure is completed.

Compared to FDM, SLS does need extra support structures because of the un-sintered powder that acts as such throughout the entire process.

SLS’s Strengths:

  • Affordable cost per part
  • Wide range of materials
  • Isotropic mechanical properties
  • Un-sintered powders act as a support, elevating negative draft and interior features problems
  • Good for multiple pieces of small sized with complicated geometry

SLS’s Weaknesses:

  • Not suitable for large flat parts. If used, the thin walls in large models may warp after cooling down
  • Parts with thin walls may not be printed due to the minimum 1mm limitation.
  • Sintered parts may differ from injected parts
  • SLS materials are not offered in colors
  • Running costs are high due to safety precautions. The room that the SLS machine is used in must be separated from the powder-handling room to prevent explosions. There must also be a consistent inert gas environment within the room and any personnel handling the machine must have additional safety training.

How does FDM work?

Antero FDM Printed PartFDM uses thermoplastic polymer materials to create a structure from an initial CAD file converted into STL format. The materials are in a filament form and one acts as the modeling material and the other as a support material. The process begins with the materials being fed through a nozzle to heat to melting point and is then moved in X, Y and Z directions. The process is repeated layer by layer with cooling in-between layers to bind touching layers until a structure is formed. 

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FDM’s Strengths

  • FDM does not include any flammable materials and there is no risk of explosion
  • Able to create complex geometries and structures
  • Simple post processing
  • Affordable pricing and cost-effective
  • Quick iteration
  • Wide range of materials

FDM’s Weaknesses:

  • Low dimension accuracy
  • Low resolution
  • Smoothing process is required to diminish layer lines.

If you’re looking to 3D print prototypes or parts using multiple materials and colors, TriMech recommends 3D printers that use PolyJet technology, such as the Stratasys J750.

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