Fused filament fabrication (FFF) is one of the most widely used rapid prototyping or additive manufacturing (AM) technologies based on the extrusion deposition process. In this process, a semi-molten thermoplastic is extruded and deposited along a prescribed road onto a build platform. Later, the extruded thermoplastic bonds to neighboring materials as it solidifies to create a 3D-printed object. The FFF process is a complex, multi-step, and multi-physics phenomena.<br/>This research aims to understand the flow instabilities that may arise during the deposition of a single road in a FFF process and to predict the shape of the printed strand, particularly where local acceleration around sharp turns may lead to high-stress concentration at the nozzle outlet. A 3-dimensional model based on the finite element method (FEM) is carried out using COMSOL Multiphysics. In this numerical model, the molten thermoplastic is considered an incompressible non-Newtonian fluid as a function of temperature and shear rate. Different transfer phenomena (energy and momentum equations) are incorporated with the generalized Maxwell equation to describe the viscoelastic behavior of the polymer melt. Our current model tracks the moving interfaces by using both level set and phase field methods. Simulations of this two-phase system suggest a relationship between velocity profile, residual stress evolution, and axial temperature profile leading to new insights into the melt flow behavior and geometry of the printed road as a function of printing parameters.

Numerical simulation of extrusion-based additive manufacturing in order to predict flow instabilities of a single deposited polymer melt

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.