Direct Simulation of Polymer Fused Deposition Modeling (FDM) — An Implementation of the Multi-Phase Viscoelastic Solver in OpenFOAM

Abstract

Among the many mature and commercial AM technologies, fused deposition modeling (FDM) is a popular technology commonly used for modeling, prototyping, and production applications. In this process, a filament thermoplastic material is fed into a liquefier chamber, melted to a liquid state, and deposited layer by layer through a nozzle to form the 3D part. As a result, part can be designed in a more freedom way, and fabricated quickly and rapidly to a desired shape. However, different combination of processing parameters may influence the final part quality greatly, which hinders wider application of this technique. In order to investigate the influence of processing parameters on the final part quality, a viscoelastic multi-phase solver is developed, with capability for dynamic meshing and based on OpenFOAM. The solver directly simulates the deposition process of FDM. By implementing this solver for different boundary conditions and geometry, we can evaluate the printed part quality for varied processing conditions. More importantly, the tool enables efficient optimization of the processing conditions for specified material parameters and desired print quality.

Experimental validation of a numerical model for the strand shape in material extrusion additive manufacturing

“…Comminal et al [53] developed a simplified twodimensional isothermal model of the deposition flow. The viscoelastic effects of the polymer melt were included in the twodimensional thermo-fluid model of Liu et al [54], developed in OpenFOAM, to investigate the impact of the printing speed and the external geometry of the nozzle on the deposition flow. A three-dimensional isothermal CFD model of the strand deposition was presented by Comminal et al [55], who investigated the effects of the printing conditions on the strand shape, under the assumptions of a Newtonian fluid.…”

Review on process model, structure-property relationship of composites and future needs in fused filament fabrication

“…Few parametric studies like the effect of nozzle geometry, printing temperature, and the time difference between bead-deposition were also conducted. 74 The results showed that a rectangular nozzle geometry with sufficient pause time and relatively lower print temperature (in this case, HDPE), a good bead spreading and good bead to bead bonding could be achieved.…”

“…Liu et al. 74 have developed a viscoelastic multi-phase solver with the capacity for dynamic meshing to model the FFF nozzle-extrusion using OpenFOAM © . This model also considers the multi-phase flow when the fluid is in direct contact with air and print platform.…”

“…The dynamic meshing capability is important to simulate the actual nozzle movement in FFF, which is not possible in any currently existing software. Liu et al 74 have developed a viscoelastic multi-phase solver with the capacity for dynamic meshing to model the FFF nozzle-extrusion using OpenFOAM ! .…”

“…Thus, it is necessary to model the complex viscoelastic relations associated with stresses. Xia et al 79 developed a viscoelastic bead deposition and solidification model like the ones presented by Liu et al 74 The model included the evolution of the conformation tensor and the viscoelastic stresses. The numerical simulation was based on front-tracking/ finite volume method, and the large variation in the material viscosity with temperature was solved using "implicit schemes" in the Navier-Stokes equation.…”