Simulations of fused filament fabrication using a front tracking method

Fully resolved simulations are used to study a few aspects of fused filament fabrication. The simulations are done using a finite-volume/front tracking method where the governing conservation equations are solved for the air and polymer flow in a rectangular cuboid using a fixed structured grid and the interface is tracked using connected marker particles. The nozzle is modeled as a moving source for mass and heat. The viscosity of the polymer depends on the shear rate and the temperature, and once the polymer cools down and the viscosity is high enough, it is effectively solid. The effects of the control parameters are examined for the construction of three objects: an inverted cone, a “bridge”, and a rectangle formed by parallel filaments. The results show that the shape of the objects depends sensitively on the control parameters. We find that an inverted cone, built with partially overlapping filaments, requires the polymer to quickly become very viscous for a stable shape, that parallel filaments need to be spaced closely for the formation of a large contact area and we show how the sagging of a freely suspended filament depends on the injection temperature.