Physik | Technik
Luca Dalbosco, 2004 | Davos Dorf, GR
Additive manufacturing offers many new possibilities. However, how can one reuse the waste accumulating from failed prints, support structures or similar? Most 3D-printers which process thermoplastics, use a filament as the raw material. In order to reuse materials, the waste would need to be molten and extruded into a filament first. This process of melting further deteriorates the material’s quality. Furthermore, expensive equipment is needed. A pellet 3D-printer could directly process plastic pellets as well as shredded plastic waste. This helps saving precious materials and thus also money. In addition, not every material is offered in filament form. Especially in science, the use of exotic or newly developed materials can be necessary. As a pellet extruder can process the plastic in its raw form, a wider spectrum of materials is available. In the scope of this thesis, such a pellet extruder was developed, built and tested. The machine can be mounted onto most desktop 3D-printer motions systems and is able to process plastic pellets. Further improvements are needed to make the machine more reliable as well as to enhance the overall print quality.
The goal of this thesis was, to design and build an extruder which can be mounted on most desktop FDM 3D-printer motion systems in order to convert it from printing with filament to printing directly with pellets. Furthermore, the machine should not only run reliably and print with decent quality, but also be completely reproducible.
In terms of research, the main focus was on books and scientific papers. As, with the available resources, there wasn’t much information to find on small scale extruders, bigger extrusion systems e.g., for injection moulding were used as inspiration. Once built, the prototypes were tested as thoroughly as possible. For this, the motion system of a low-cost desktop 3D-printer was used. Furthermore, multiple scientists and professionals in the additive manufacturing sector were interviewed. In order to design the different components of the machine, as well as to test them using thermal simulations, the CAD software «Autodesk Fusion 360» was used.
In the time of 1.5 years, two prototypes of a pellet extruder were designed, built and extensively tested. The machine was tested using a 1.2mm nozzle, which worked well. However, there are still some clogs in the system. The machine is tuned to a certain degree where it can be used just like any other FDM machine. This is not only in terms of the workflow with it but also with the possible geometries which can be manufactured. A pellet extruder also allows to process shredded plastic waste (e.g., from previously failed prints) as well as using additives like pigments, carbon- or glass fibres and many more with the base material. However, this couldn’t be tested yet due to time constraints. Additionally, the variety of useable materials is wider, as every thermoplastic is produced in the form of pellets.
While the machine works well with large nozzles, it still has to be tested with smaller nozzles. This should drastically improve print quality and precision. Also, further optimisation is required in order to make the machine more reliable. Further tests are to show, whether the machine is able to homogeneously mix in additives. The developed system shows that it is possible to convert an existing 3D-printer to print with plastic pellets. However, the development of a suitable machine is very complicated. As the workflow with this pellet system doesn’t differ from the one with standard fused filament fabrication machines, it would be easy for companies or private users to adapt parts of their production. The motion system used for testing was not optimal and no permanent solution. For industrial or professional use, a sturdier motion system would be required.
Overall, it can be concluded that it is possible to convert most FDM machines to directly process plastic pellets. A suitable addon/replacement extruder system was developed and could be sold as a conversion kit. Thus, the initial goal of this thesis was definitely reached. However, the project is far from complete. The development will be continued to make the machine more reliable and increase the overall print quality. Also, the mixing of additives remains to be tested.
Würdigung durch die Expertin
Bei der additiven Fertigung (3D Druck) werden häufig Kunststoff-Filamente als Rohmaterial eingesetzt. Diese Filamente müssen in einem vorgelagerten Schritt zuerst (z.B. aus Pellets) hergestellt werden. Das schränkt die Materialauswahl ein und erschwert das Recycling. Dieses Problem löste Luca Dalbosco, in dem er einen herkömmlichen 3D Drucker um einen selbst entwickelten Pellet Extruder-Kopf erweiterte, mit dem direkt Pellets gedruckt werden können. Mit grosser Begeisterung setzte er seine Ideen erfolgreich um und entwickelte von Grund auf eine funktionierende technische Lösung.
Sonderpreis «I-FEST²» gestiftet von der SJf-Trägerschaft
Schweizerische Alpine Mittelschule Davos, Davos-Platz
Lehrer: Lutz Behne