To improve the product quality of polymeric parts realized through extrusion-based additive manufacturing (EAM) utilizing pellets, a good control of the melting is required. In the present work, we demonstrate the strength of a previously developed melt removal using a drag framework to support such improvement. This model, downscaled from conventional extrusion, is successfully validated for pellet-based EAM—hence, micro-extrusion—employing three material types with different measured rheological behavior, i.e., acrylonitrile-butadiene-styrene (ABS), polylactic acid (PLA) and styrene-ethylene-butylene-styrene polymer (SEBS). The model’s validation is made possible by conducting for the first time dedicated EAM screw-freezing experiments combined with appropriate image/data analysis and inputting rheological data. It is showcased that the (overall) processing temperature is crucial to enable similar melting efficiencies. The melting mechanism can vary with the material type. For ABS, an initially large contribution of viscous heat dissipation is observed, while for PLA and SEBS thermal conduction is always more relevant. It is highlighted based on scanning electron microscopy (SEM) analysis that upon properly tuning the finalization of the melting point within the envisaged melting zone, better final material properties are achieved. The model can be further used to find an optimal balance between processing time (e.g., by variation of the screw frequency) and material product performance (e.g., strength of the printed polymeric part).

To extend the diversity of commercial materials relevant for fused filament fabrication (FFF), the relation of nozzle temperature and layer thickness with respect to final product mechanical performance is examined for the less studied group of (co)polyesters, considering tensile and impact strength and microscopic imaging. It is demonstrated that with limited polymer degradation, one can focus on increasing the layer height (from 0.1 to 0.3 mm) by tuning of the contribution of inter-layer welding, whereas with significant degradation, a lower layer height (0.1 mm) is needed to exploit the contribution of intralayer welding for which a higher nozzle temperature (e.g. 260°C) is beneficial. The relevance of degradation is studied by both melt flow index and rheological analysis. The study ultimately provides the best FFF parameters for three commercial copolyesters and highlights the competition of inter-and intra-welding as a key microscopic material design strategy.