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

Anne Gosset,Ana Ares-Pernas,Juan Carlos Becerra Permuy,Marcos Lema,María José Abad López,David Barreiro-Villaverde

doi:10.3390/polym12122885

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.

Highlights

Fused Deposition Modeling (FDM), known as Fused Filament Fabrication (FFF), is an additive manufacturing (AM) technique that relies on the extrusion of a molten material through a moving nozzle
It is interesting to note that the contact angle, θ, between the liquid interface and the substrate (Figure 11) is very large. θ is determined from the tangent to the interface at a distance of about 10–15 μm from the substrate, as illustrated in Figure 11 in the meniscus
This paper presents an experimental and numerical study of the extrusion and deposition of a single strand of Poly-Lactic Acid (PLA) by FDM

Summary

Introduction

Fused Deposition Modeling (FDM), known as Fused Filament Fabrication (FFF), is an additive manufacturing (AM) technique that relies on the extrusion of a molten material through a moving nozzle. The strands deposited on top of each other conform the shape of a three-dimensional object This technique was initially used for prototype making, the improvements reached during the last decade in terms of process control and material development have led FDM to become a major technique for the production of finished parts. Like any additive manufacturing technique, FDM has undeniable advantages regarding the fabrication of complex shaped pieces, minimizing the waste of material as no machining is required. It allows for the production of small series of pieces, with a remarkable flexibility for switching from one product to another. In desktop 3D printers, the feedstock is a filament which is forced into a liquefier, and its role is to melt the material at an adequate temperature for its extrusion through a small diameter round nozzle (a few tenth of millimeter)

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