A study of variation in the cross-sectional areas of thermoplastic filaments on lattice structures manufactured by fused filament fabrication

Abstract

This research was focused on developing a method to control the width of extruded filaments, to have a controlled structure of the infills of 3D printed products manufactured by Fused Filament Fabrication (FFF). Different parameters and their effect on the width of extruded filaments in FFF were studied. The materials used were three thermoplastic filaments: polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polycarbonate (PC). The extruded filament widths were measured using optical characterization and analyzed using statistical analysis. Two different approaches were followed. First, an experimental one, in which the effect of the extrusion temperature, the feed rate, the layer height, the fan power, and the bed temperature on the width was studied. A factorial design of experiments was performed using the previously mentioned parameters, in which different combinations were made to obtain the experimental data and perform a regression analysis that explains and predicts the width of the filaments after extrusion. A second approach was done to obtain an empirical model that predicts the die-swell of the filament when it is extruded. To obtain this model, two different mathematical models were selected from the literature. The first model explains the pressure inside a nozzle, considering the rheological properties and parameters of the FFF process. The second model predicts filament die-swell after extrusion, considering extrusion pressure, extrusion temperature, printing speed, and nozzle diameter. In the end, an empirical model was done by adapting the pressure model to the die-swell model and it was possible to obtain the values that could give a controlled thickening considering the extrusion temperature and adjusting the printing speed.