FFF, SLA, SLS: Comparing Three 3D Printing Technologies
Over the years, 3D printing has evolved exponentially: from a niche technological process for hobbyists to an increasingly frequent and reliable asset in companies’ production processes. Nowadays, thanks to this technology, different industrial sectors can benefit from a drastic reduction in costs and production times, and achieve supply chain optimization.
The benefits are many and in one article we have listed the three advantages of additive manufacturing. However, it is necessary to explain the different technologies on the market, which can be distinguished by the method of material layers generation. We will therefore analyze the three main ones:
The simplest and most cost-effective technology is Fused Filament Fabrication (FFF). It is widely used in the additive manufacturing world and shows a different process than that of CNC machines. The latter generates a large amount of waste material, whereas FFF technology uses only the material needed to produce the component.
Indeed, the creation of an object involves the use of a spool typically of filament thermoplastic material, whose diameter is usually 1.75 mm or 2.85 mm. The material passes through the nozzle which, as it heats up, extrudes and deposits the material on a print bed which solidifies upon cooling. The extruder deposits the material filament following trajectories and instructions given by a G-code, which is generated by slicing software. The latter recreates the object by completing a layer, which will then be followed by a lowering of the print bed until the next layer is created. All of this is repeated until the component is completed.
It is important to know that no post-processing is needed and that the FFF 3D printing tolerance can vary from 0.05 mm to 0.5 mm. This technology offers the opportunity to customize the filling of the desired component, leading to a reduction in the use of material, costs, and printing time. In addition, FFF 3D printers offer a great variety of print volumes: it will therefore be possible to create large components, using inexpensive biodegradable materials. So, we can find a wide range of printable materials, including ABS, PLA, PET-G and Nylon, as well as carbon-filled polymers and superpolymers such as PEEK and ULTEM.
SLA, or Stereolithography, is a technology that, through layer-by-layer photopolymerization of liquid resins, allows the creation of a solid object. In favor of the process, an ultraviolet laser is used to solidify the resin until the finished component is created. Before the process, the resin is deposited evenly in a tank and the object is generated upside down on a bed which, during the process, moves along the Z-axis of the printer until print completion. To obtain the end-component, the print is immersed in solvents to remove resin residues and is processed in a UV oven with a curing process for the resin polymerization.
The components created through this process have an excellent surface finish compared to other objects printed with other 3D additive processes. SLA technology proves to be ideal for obtaining good surface roughness, thanks to the lower cross-section of the laser compared to the nozzle used in FFF 3D printers.
Stereolithography, however, involves high material costs due to the lower availability of photopolymers, making this technology less flexible. The component post-processing is necessary and the resin, being a toxic substance, must be handled with care and disposed of by specialized agencies, increasing processing costs.
Source: 3D Printing Media Network
Selective Laser Sintering (SLS) 3D printers use a CO2 laser to melt the powders and create a finished component. In the printing chamber, the powder is deposited in layers and the laser fuses the powder particles of the material to generate a solid object. Furthermore, not sintered powder acts as structural support, allowing to print very complex geometries. When the component is completed, the second phase of the process begins, which involves cooling for the stabilization of the printing material and powders recycling. The latter, specifically, requires the use of a particular suction system, as well as extreme precision. This is because incorrect powder recycling can damage the following prints and the 3D printer itself.
This technology allows to obtain components with excellent mechanical properties and allows a wide choice of materials to be used: indeed, it ensures the melting of both plastic and metal materials. However, long post-processing is required both to obtain a smooth finish, since the finished component is porous and rough, and to prepare the 3D printer for the next print.