Effects of printing speed and temperature on the extrusion-based 3D printing of pelletized polymers

Abstract

Large-Format Additive Manufacturing (LFAM) has expanded the use of pellet-fed extrusion systems for large-scale polymer processing. However, insufficient understanding of extrusion parameter interactions may lead to dimensional instability and degradation of material properties. This study investigates the influence of process temperature and screw speed on the extrusion behavior of pelletized polymers, aiming to provide a foundation for LFAM process characterization. Controlled experiments were conducted using a vertically oriented, customized pellet extruder with three polymers (ABS, PLA, and PCL). Filament diameter, extrusion pressure, mass flow, and volumetric output were measured to assess process stability and dimensional consistency. Thermal characterization was performed using Differential Scanning Calorimetry (DSC) to determine glass transition temperature (Tg), melting temperature (Tm), and degree of crystallinity (Xc). The results indicate that a screw speed of 20 rpm provides stable extrusion conditions for all tested polymers without significant dimensional deviation. For ABS, optimal extrusion behavior was observed at 190 °C, while 180 °C resulted in incomplete melting and 200 °C suggested possible thermal degradation. PLA exhibited improved dimensional consistency at 170 °C, whereas lower temperatures led to reduced density due to insufficient melting. PCL showed favorable extrusion characteristics at 70 °C, although handling and solidification were challenging due to its low melting temperature. Overall, the findings establish correlations between thermal and kinematic parameters and extrusion performance, providing fundamental insights to support parameter optimization in pellet-fed LFAM systems.