The classic process of FDM 3D printing consists of creating layers through the deposit of a molten material, usually in the form of plastic filament. Recently, however, a new way of using this manufacturing technology is emerging, moving away from the coils for the use of pellets or granules. 3D pellet printing is a 3D printing method that uses thermoplastics in the form of pellets to manufacture layer-to-layer parts. More and more companies are developing machines that work with this type of material, or even solutions adaptable to standard 3D printers to make them compatible with pellets.
Granulated plastics are granular materials obtained through what is known as furcelling. In the process, the materials, which can be chemicals, plastics, composites or minerals, are molded into the compressed form of pellets. These types of resources are primarily used for injection molding, although, as we have already mentioned, they are becoming increasingly evident in the world of 3D printing. It turns out that its use in the manufacture of additives is somewhat low compared to the number of filament coils that currently exist. Although this may seem paradoxical, since the filaments are made from pellets, and the use of pellets directly in printing would save an intermediate step throughout the process.
One thing to keep in mind is that pellets and filaments require different extruders to suit your printing needs. Unlike filaments, pellet extruders have an integral bowl, which gradually absorbs materials and pushes them into the melting zone. There, the pellets are softened to the desired consistency, after which the plastic is ejected through the nozzle and deposited on the printing platform. While the process may seem a little more complex compared to filament extrusion, it has a number of really interesting benefits that we’ll see below.
As for the main advantages of 3D printing in granulated plastic, we find a clear reduction in the final cost of parts due to the low cost of the material and the shorter manufacturing time. In this way, we obtain an ideal technology for the production of long series or large parts that would not otherwise be entirely profitable. Another positive point is the reduction of jams during the manufacturing process, since working with filaments is a common printing problem that we can find. Finally, the manufacture of additives with granules makes it possible to create multicolored pieces by combining plastic pellets with different colors on the same tray.
But what is particularly interesting when working with granules are the final properties that can be obtained. When using filaments, it is important to know that they do not have exactly the same physical and chemical properties as the raw material. In fact, when we manufacture a filament, the raw materials need to be heated, which in turn degrades its properties – the more we heat it, the more significant the degradation. We are then required to add additives to reduce this degradation. The result obtained is therefore quite different from the starting material. However, when working from the outset with granules, there is no need to go through these transformations, allowing users to bypass these degradations and get much closer to the chemical and physical properties of the plastic used in injection molding.
In terms of disadvantages, it is worth mentioning that 3D printing in granulated plastic is not currently as democratized as filaments, so the development of extruders adapted to these materials can be difficult to achieve. In addition, when creating pieces layer by layer, the pellets are not connected to each other as in the case of the filament, but are dispersed. This makes it less easy to control flow changes, which is required for the more complex parts.
The growing popularity of 3D printing in granulated plastic is encouraging many companies to develop their own manufacturing solutions. An example is the Spanish project Tumaker with its 3D granulated plastic printers adapted to the needs of each user, the American company Titan Robotics also gives users the opportunity to print with pellets on their Atlas printer. Will this new trend mean the end of filament bobines?