The aim of this study is to examine the formulation, process, and equipment conditions to obtain printable filaments for fused-deposition modelling three-dimensional printing (FDM-3DP) using Eudragit-S100 polymer, which is widely used in the pharmaceutical field and has a high glass transition temperature (Tg). 

The filaments were extruded by a modified simple single screw extruder. The influence of powder preparation processes such as pre-plastification, sieving, drying, and the formulation factors, such as types and amounts of excipients on the quality of filaments were evaluated. The mechanical properties of filaments were determined manually. Structural integrity and homogeneity of filaments and the printed tablets were demonstrated by SEM. Finally, the printability of the filaments was shown by producing the tablets using an FDM-3D Printer. 

When combining triacetin and citric acid, extrudable formulations with an adequate plastification were obtained. Magnesium stearate increased the output speed of the filament through the nozzle of the extruder. Furthermore, it was seen that simple modifications on the extruder and powder preparation process improved the printability of the filaments. A higher screw speed accelerated the output of the filaments while minimizing the filament diameter variability, which is a requirement for providing uninterrupted printing. 

In conclusion, the filaments containing Eudragit S100 were successfully and reproducibly printed into round-shaped tablets after modification of the extruder and improvement of the formulation development processes.