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Seville researchers develop novel technique of composite filament manufacturing

Printing tests on the final composite magnetic filament.  Photos on the University of Seville.

Researchers from the University of Seville, Spain has developed a new process for making highly customizable composite filaments for the FFF 3D printing process.

The process uses pellet-like polymer capsules filled with magnetic additives. Using a 3devo Composer 450 filament manufacturer – a single-screw desktop extruder – the team was able to produce a special composite filament from the capsules that has an even distribution of additives and excellent printability properties.

Printing tests on the final composite magnetic filament. Photos on the University of Seville.

Formulation of filaments for FFF

Filaments and materials in general can be further functionalized with additives – particles that are embedded in the base matrix and add strength or some other desirable property. In the case of polymer filaments, achieving a very uniform additive dispersion can significantly increase homogeneity and maximize mechanical properties throughout the material. This usually requires several extrusion cycles with a twin screw compounder in order to really use the entropy effects.

While the cyclic method is effective, it is often impossible without special production equipment that a research laboratory may not always have available, let alone the time it takes to spend multiple extrusion runs. As a result, materials studies are sometimes limited to the compositions and filler concentrations offered by commercial companies – a potential impedance to science.

PLA capsules and steel powder

The first part of the Seville study involved the formulation of the new particle-filled capsules. The scientists used commercially available PLA pellets to 3D print a grid of open hollow capsules (almost like an ice cube tray). The team then filled each capsule with soft magnetic maraging steel powder before the lids were closed with PLA lids and sealed with acetone. The result: a range of highly customizable PLA pods filled with magnetic powder.

Printing and filling the capsules.  Image via the University of Seville.Printing and filling the capsules. Image via the University of Seville.

Then it was time to extrude the newly developed capsules to make the final filament. Since the capsules were completely sealed, the risk of the magnetic additive building up and being retained in certain places in the extruder was eliminated. The PLA shells reached the melt zone of the extruder in one piece so they could maintain their filler levels throughout the process.

SEM image of the magnetic steel in the PLA matrix.  Image via the University of Seville.SEM image of the magnetic steel in the PLA matrix. Image via the University of Seville.

X-ray tomography imaging of the resulting filament indicated that the batch had produced a smooth and continuous composite material with a uniform magnetic powder distribution. The researchers cite the need for a single extrusion run on a relatively inexpensive single screw extruder as the main advantage of the process. Despite the lack of industrial resources, the team continued to be able to create a predictable and reproducible filament composition and intends to expand research to other polymer matrices and additives.

X-ray tomography showing the even distribution of the steel in the PLA matrix.  Image via the University of Seville.X-ray tomography showing the even distribution of the steel in the PLA matrix. Image via the University of Seville.

For more details on the study, see the article entitled ‘Novel process for the production of functional composite filaments for additive manufacturing on a laboratory scale‘. It is co-author of Á. Díaz-García, JY Law, A. Cota, A. Bellido-Correa, J. Ramírez-Rico, R. Schäfer and V. Franco.

Multi-material composite filaments have grown in importance in recent years as the technology used for printing has advanced. Earlier this month 3D printer manufacturer RIZE debuted his new very durable RIZIUM fiberglass filament for use with its FFF 3D printers. The fiber-reinforced material has high dimensional stability and rigidity and is mainly intended for the manufacture of large parts.

Elsewhere, the U.S. Army has gone a step further and reinforced one polymer filament with another polymer filament. The high strength material has a Polycarbonate core and an ABS shelland is designed for use with low cost extrusion printers.

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The picture shown shows the X-ray tomography of the evenly distributed steel in the PLA matrix. Image via the University of Seville.

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