There are numerous technologies catering to various applications in 3D Printing. The most commonly used technologies are Selective Laser Sintering (SLS), Stereolithography (SLA), and Fused Filament Fabrication (FFF). To elaborate the varied nature of 3D Printing processes, here’s an article that gives detailed insights and compares the different 3D Printing technologies: SLS vs SLA vs FFF, thereby giving a cue as to what to expect from each of them and how they fare in comparison with each other.
Note:  FDM which stands for Fused Deposition Modeling is a proprietary technology by Stratasys. Whereas, FFF which is colloquially WRONGLY referred to as FDM, is a Desktop version of FDM. FDM Vs FFF Difference
Following are some of the distinguishing parameters for SLS vs SLA vs FFF:

  1. Method:

    The primary distinguishing factor in all the aforementioned 3D Printing technologies is the method of 3D Printing process and the energy source. SLS technology consists of a bed of powder material, build platform, a laser and a recoater. The laser scans and sinters the powder based on the input part geometry. Then the platform goes down by an amount equivalent to one layer thickness value. The recoater then moves the new layer of material in its place. The laser scans and sinters the new layer of powder material, and the platform goes down again and this process continues till the entire part is fabricated bottom-up. Watch the video below.

    On the other hand, SLA technology consists of a vat of photopolymer resin material, a UV laser, and a recoater blade. The resin material is cured (hardened) using a UV laser source. Then a new layer of resin is deposited in place using a recoater blade, and the process repeats itself until the entire part is fabricated. Watch the video below.

    FFF is a filament-based technology. A typical FFF setup consists of a material filament, a build platform and an extruder-nozzle assembly. The material enters the extruder in the form of a solid filament where it is heated and melted to a temperature of about 200˚C. The nozzle then deposits this semi-liquid material on the build platform. After depositing a layer of material, the platform goes down by an amount equivalent to one layer thickness, to pave way for a new layer of material to be deposited. This process repeats itself until entire part is fabricated bottom-up. The working of FFF is fairly similar to that of FDM so the video attached below should come in handy in understanding the working principle.

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  2. Nature of Material:

    The material used in SLS technology is in powder form, whereas the one used in SLA technology is a highly viscous resin (liquid) material. In FFF technology, the material is in the form of a solid filament wound around a spool.

    Nature of materials used: SLS (L), SLA (C), FFF (R)

  3. Accuracy:

    If you are dealing with engineering applications, this is one of those parameters that you may be most interested in. Accuracy is different from part resolution. Accuracy is the degree to which the manufactured part accurately conforms to the input 3D CAD design. Based on our experience we have observed that, the part accuracy in SLS technology is (+/-) 200 µm; the part accuracy in SLA technology is (+/-) 150 µm; the part accuracy in case of FFF technology is anywhere between (+/-) 300 µm to 400 µm.

  4. Multiple Parts:

    In SLS technology, you can fabricate multiple part models in one single build by nesting the parts throughout the bed volume. Whereas in SLA and FFF technology, multiple parts can be fabricated at a time, provided all the parts fit into one single horizontal plane. Although in case of FFF technology, it is highly recommended that only one part be fabricated at a time owing to the nozzle traverse distance and temperature gradients. Thus SLS is the most scalable 3D Printing technology, leading to a shorter lead-time for multiple part quantities.

    SLS (L), SLA (C), FFF (R)

  5. Layer thicknesses:

    Layer thickness is the resolution in Z-axis. Finer the layer thickness, better the surface quality, but more time is required to fabricate the parts and thus higher the cost, and vice-versa. The industry standard layer thickness is SLS & SLA technology is 100 µm. There’s no standard layer thickness is FFF technology. It differs from one service provider to the other. Thus, one should definitely enquire the layer thickness while printing the part in FFF technology. Invariably, the FFF layer thickness is anywhere between 180 µm to 300 µm. Chizel operates FFF technology at 140 µm. Just for your reference, a human hair is about 75 µm in size.

  6. Support Structures:

    For any overhanging feature or an unsupported part geometry, support structures will be generated in SLA and FFF technology. The removal of supports may leave burr marks on the surface. Thus usually, these parts are post-processed. But in SLS technology, since the unsintered powder itself acts as support, there is no support structure generation. Thus SLS technology can truly exploit the potential of 3D Printing by catering to intricate & complex part geometries with utmost ease.

  7. Surface Finish:

    Since SLS is a powder-based process, the parts have a grainy surface finish owing to the powdery nature of the material. SLA parts have a smooth surface finish, whereas, owing to the process characteristics and larger layer thicknesses, FFF parts have a rough surface finish. Due to larger layer thicknesses, the parts have distinct layer marks on the surface. That’s not the case in SLS and SLA technologies unless the part has a curvature, in which case the layer marks are visible, as is the case in any 3D Printing technology.
    SLS (L), SLA (M), FFF (R)

Summary: SLS vs SLA vs FFF

We hope that this article was helpful and that it will assist you in making informed decisions while dealing with 3D Printing technologies in future.
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