Experimental and Numerical Investigation of the Extrusion and Deposition Process of a Poly(lactic Acid) Strand with Fused Deposition Modeling

Abstract

In the last decade, Fused Deposition Modeling (FDM) has gained popularity for allowing the fabrication of pieces with complex shapes. The final quality of the pieces is strongly linked to the shape, size and surface finish of the strands deposited successively, which themselves depend on the printing parameters and extruded material properties. In this work, we present an experimental characterization of an extruded and deposited single strand of Poly-Lactic Acid (PLA), by means of high-speed visualization of the bead region between the substrate and the nozzle, where the molten polymer is still in liquid phase. A Computational Fluid Dynamics (CFD) model proposed in literature, and, based on isothermal and viscous flow assumptions, is validated with this data in terms of strand height and meniscus shape. The characteristics of the printed layer are also confronted to the measurements of the solidified strands by microscopy, with a good agreement. The focus on high printing speeds allows extending the conclusions of previous studies. Regarding the surface finish, the roughness patterns detected on the printed strands are correlated to the velocity fluctuations of the printing head. The CFD model does not capture those thickness variations, however, due to not accounting for solidification.

The Effect of a Phase Change on the Temperature Evolution during the Deposition Stage in Fused Filament Fabrication

“…PLA, a partially crystalline polymer, is biodegradable (compostable) and has low melting temperature but has limited thermal stability [14]. The performance of these two materials for 3D printing has been assessed [15][16][17][18], particularly in terms of dimensional accuracy [19,20], surface roughness [21], mechanical performance [22] and emission of volatile organic compounds (VOC) [23,24]. For the 3D printing of a compact omnidirectional wheel, Rubies and Palacín [25] observed that when using 100% infill density, PLA yielded a better mechanical performance than ABS.…”

Dimensions of the deposited strand in the material extrusion process: Experimental and numerical investigations

“…By performing optical microscopy measurements, Serdeczny et al [5] assessed the strand geometry found by Comminal et al [4]. Based on a volume-of-fluid method, Gosset et al [6] performed numerical simulations of strand deposition. The temperature is assumed uniform.…”

Modeling crystallization kinetics for selective laser sintering of polyamide 12

“…Simulation for additive manufacturing (AM) of polymers represents a field of high research activity covering several approaches, such as extrusion methods [4,11,29] or selective laser sintering (SLS) of polymers [1,3,10,[22][23][24][25]28]. For an overview of additive manufacturing using polymers we refer to [5][6][7]19,27] and references therein.…”

“…Comparison of the model corresponding to Equation (8) (𝜔 = 1) and the modified model from Equation(11) (𝜔 = 𝜔(𝜗)) in terms of the accumulated released heat for a given temperature field. At a fully crystallized state, the accumulated released heat matches the total energy released during the exo-thermal reaction, that is, Δh 𝛼 , indicated by the red line.…”