FDM
Fused deposition modelling, or FDM for short, is a material extrusion method of additive manufacturing where materials are extruded through a nozzle and joined together to create 3D objects. In particular, the “standard” FDM process distinguishes itself from other material extrusion techniques, such as concrete and food 3D printing, by using thermoplastics as feedstock materials, usually in the forms of filaments or pellets.
A typical FDM 3D printer, therefore, takes a polymer-based filament and forces it through a heated nozzle, which melts the material and deposits it in 2D layers on the build platform. While still warm, these layers fuse with each other to eventually create a three-dimensional part. Scalability is one of the most significant advantages of FDM 3D printing. Unlike resin 3D printers, FDM printers can be easily scaled to any size because the only constraint is the movement of each gantry.
Print quality is not only about the looks. The mechanical performance also counts here, and FDM offers a great value for producing strong and durable functional parts, especially when compared to fragile resin 3D prints. FDM 3D printing is also very versatile because the print quality can be sacrificed in favour of speed and even sturdiness, making it an excellent tool for producing both pleasing aesthetic parts and more functional, tough ones. Though already mentioned, the flexibility and availability of different FDM materials also play an important role here. A single FDM 3D printer can produce parts with entirely different properties and appearances just by changing the type of filament.
SLA / DLP
Resin 3D printing is the process of curing a liquid plastic with light. It’s one of the oldest forms of 3D printing and still produces some of the best quality prints with an unmatched level of detail. While an array of technologies and machines are utilized in resin printing, two of the main ones are stereolithography (SLA) and digital light processing (DLP). These two types achieve the same goal in different ways. Simply put, the main difference is that SLA uses a laser light source to cure the resin, while DLP uses a projection system with LED lights
Among 3D printing processes, SLA and DLP are typically seen as the technologies capable of reaching the highest standards in terms of part complexity and precision. Both rely on the use of light, typically in the UV region of the spectrum (365-405 nm), although some printers use visible light to cure the photosensitive resin. In simple terms, the laser or projector draws an image in the resin that makes the liquid harden. Before we talk about how the resin is cured, it’s worth discussing what resin is.3D printing resin is typically composed of epoxy or acrylic and methacrylic monomers that polymerize and harden when exposed to light. This process is called cross-linking. As light shines on the resin vat to create specific shapes or patterns that make up each layer, a solid object is built up. Depending on the particular resin, its characteristics can vary greatly from soft and rubbery to very hard or high-temperature materials.
MJF/SLS
Multi Jet Fusion (MJF) and Selective Laser Sintering (SLS) are industrial 3D printing technologies that belong to the powder bed fusion family. Both processes build parts by thermally fusing (or sintering) polymer powder particles layer by layer.
The main difference between these two technologies is their heat source. SLS uses a laser to scan and sinter across each cross-section. MJF, on the other hand, dispenses an ink (fusing agent) on the powder for absorbing infrared light. The printer then passes an infrared energy source over the build platform to fuse the inked areas. Essentially, MJF combines SLS and Binder Jetting technologies.
Multi Jet Fusion parts will have a finer feature resolution of 0.020 in. (0.51mm) compared to 0.030 in. (0.762mm) for SLS. Although, it should be noted that SLS has better small feature accuracy of ±0.001 (0.0254mm) over ±0.004 in. (0.1016mm) for MJF. If a smooth surface finish is a requirement, MJF will be a better choice than SLS. Secondary operations are often recommended for both processes if surface finishes are crucial to your application. SLS will provide you with a broader range of options with multiple nylons as well as a TPU for elastomeric prototyping and polypropylene to get flexible, lighter-weight parts for demanding environments. Also, SLS parts can be dyed a variety of colors. Currently, Multi Jet Fusion offers parts built in PA 12, but you can also get the more rugged PA 12 40% Glass-filled Black for stronger parts. Note that these parts come off the platform as grey but can be dyed black for improved cosmetics.
