How does 3D printing work and what are its main technologies?

The main technologies differ either in the material they use for printing or in the way the layers are created. The price of printing, availability and use in practice (or perhaps even at home) also depend on this. Basically, they all work on the same principle – adding material in certain layers until the resulting 3D object is created. We will analyze the most fundamental and most used of them in a little more detail.

SLA, DLP a LCD

Stereolithography (SLA) technology is considered one of the first 3D printing methods ever. It was created on the basis of a patent from the eighties of the last century and was also used in the very first commercial 3D printer. It is also still a very widely used technology and is the second most used technology for home printing after FDM.

SLA works by gradually curing a liquid polymer with the help of UV laser radiation – in layman’s terms, it could be said that it is several types of resin that react when in contact with light. Everything is then just about the correct setting – the laser shines through the individual layers only in predetermined places (and for a precisely predetermined time, often within a few seconds), and they then harden and thus form the final product. Thanks to this, it is one of the most accurate 3D printing methods ever, as it is capable of creating even layers with a height of several hundredths of a millimeter.

DLP works similarly, but uses a projector instead of a beam, thus lighting the entire layer at once. LCD then, as the name suggests, uses an LCD display, and thus works practically the same as DLP.

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There are two variants, in one the printing surface is completely submerged to the bottom of the container with polymer and gradually moves up as the beam from below hardens the individual layers (see picture), in the other, on the contrary, it gradually dips down and the beam acts from above.

Prusa, Anycubic, Creality, or even Elegoo can be included among the most famous brands of 3D printers mainly for households, small businesses and schools with SLA technology. Their prices are often in the order of thousands to lower tens of thousands, but it is advisable to purchase a hardening and washing station (also priced in the order of a few thousand), which will remove excess material and increase the hardness of the resulting model. In practice, they are used, for example, in dentistry.

DMLS a SLS

Other laser-based technologies are very similar to DMLS (Direct Metal Laser Sintering) and SLS (Selective Laser Sintering), which use it to melt/sinter a powder (instead of a liquid). In this technology, the laser is precisely focused on an even layer of powder, and thanks to the heat conductivity, the new layer is well connected to the previous ones. DMLS is used for sintering powdered metals – titanium, aluminum, steel, nickel and others, while for SLS, nylon (with various additives), polystyrene, but also ceramics are most often used.

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The advantage is that the unbaked powder can often be sifted and reused, but the disadvantage is the need to clean the entire printer in a very complicated way if the material needs to be replaced, and of course also the high cost of acquisition. However, it is widely used for the creation of various prototypes that already have some functionality – other options would be much more expensive.

You will only meet these printers in an industrial environment and their price ranges well above 100 thousand crowns. But their popularity is still rising.

FDM/FFF

The most well-known and currently the most widespread 3D printing technology among do-it-yourselfers is undoubtedly FDM (Fused Deposition Modeling), sometimes also called FFF (Fused Filament Fabrication). The meaning of these two abbreviations is slightly different in the original sense, but today they are often used as synonyms. This technology melts a plastic string (filament) at different temperatures (according to the exact type and brand) and applies (extrudes) it in layers onto the substrate.

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Most often we now encounter printers that move the print head upwards to create the third dimension (height), but some printers move the pad instead. Although the basic material is plastic, the exact types differ significantly in their properties, quality and price.

We probably encounter this technology most often today. Not only is it widely used in companies, but thanks to its relatively low price, it is also often purchased by various scientific and medical facilities, schools and, last but not least, ordinary households. The price of such a printer will vary according to the requirements of its user, most often it ranges within several tens of thousands of crowns.

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Among the most well-known manufacturers for home use, we can include, for example, Prusa (Czech printers, modified model in the picture), Bambu Lab, Creality, Anycubic, Snapmaker, or even Voron kits (for assembly). However, many of these brands also produce printers working on other principles and do not focus only on FDM/FFF technologies. Professional printers have been manufactured since the nineties by the company Stratasys (which patented the FDM technology at the time), or 3D Systems.

And more…

Among other, but technically very similar technologies, we can include, for example, WAAM, which works with metals and layers them on top of each other, similar to FDM, but individual layers are welded. It is mainly used to create more complex or hard-to-reach metal models and is widely used, for example, in the aviation industry – it saves not only the price but also the material and thus the weight of the result, which is definitely an important factor in this industry.

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Another such specific technology is 3DCP, which was created thirty years ago and is used for the construction of buildings and their parts. Similar to FDM, it layers a self-hardening material on top of itself, but uses a powder like DMLS/SLS to create it, which is mixed with a liquid binder (instead of using a laser).

We could go on, but basically every other technology is just a small offshoot of some of the ones we’ve already imagined. Next time we will focus on choosing a printer and materials for beginners.