First steps of the melting of an amorphous polymer through a hot-end of a material extrusion additive manufacturing

Franck Pigeonneau (1) , Sarah Marion (2) , Lucas Sardo (3) , Thomas Joffre (4)

1 CEMEF - Centre de Mise en Forme des Matériaux
2 Mines Saint-Étienne MSE - École des Mines de Saint-Étienne
3 SC-Consultants - Sciences Computers Consultants
4 IPC - Centre Technique Industriel de la Plasturgie et des Composites

Nowadays, 3D printing by fusing filament is a widespread technology. Nevertheless, there are questions about how it works. In particular, the understanding of the melting of the filament in the printhead is not yet agreed upon. Bellini et al. [1] assume that the polymer is completely melted as soon as it enters the printhead. Osswald et al. [2] challenged this assumption by considering that melting only occurs when the polymer and the printhead walls are in contact. In the two previous works, the polymer melting remains practically axial. However, the printhead is heated along its entire length, which is ten times longer than the filament diameter. Therefore, the heat transfer is expected to be radial. To allow the filament to be inserted, the diameter of the print head inlet is larger than the filament diameter. Then, the following question arises: does the air gap between the polymer and the walls of the printhead persist during operation? To answer this question, numerical simulations were carried out. The polymer and the air are taken into account using the level-set method. The fluid mechanics equations coupled with heat transfer and implicit interface transport are solved using a finite element method. A transient regime is highlighted. For very short periods, the filament melting occurs when the polymer contacts the nozzle wall in the presence of the air gap. Subsequently, the air is expelled by the rise of the molten polymer along the walls of the printhead. For longer times a perfect contact between the nozzle walls and the polymer is established over the entire printhead. This transitional regime lasts only a few seconds. References: [1] A. Bellini, S. Güçeri, and M. Bertoldi. Liquefier dynamics in fused deposition. J. Manuf. Sci. Eng., 126(2) :237-246, 2004. [2] T. A. Osswald, J. Puentes, and J. Kattinger. Fused filament fabrication melting model. Addit. Manuf., 22 :51-59, 2018.

Mots clés: Additive manufacturing; numerical simulation; amorphous polymer

Domaines: Mécanique des fluides [physics.class-ph]; Génie des procédés

Franck Pigeonneau, Sarah Marion, Lucas Sardo, Thomas Joffre. First steps of the melting of an amorphous polymer through a hot-end of a material extrusion additive manufacturing. 38th International Conference of the Polymer Processing Society (PPS-38), May 2023, Saint-Gallen, Switzerland. ⟨hal-04105539⟩