Rheological approach for an additive manufacturing printer based on material extrusion

Commercially available grades of poly(lactic acid) (PLA) and acrylonitrile-butadiene-styrene (ABS) were printed in different shapes using an additive manufacturing (AM) printer based on material extrusion (ME). It is known that the quality of a 3D printed sample is closely connected to the rheological properties of the polymer matrix. However, some printing parameters, such as the feed rate and the print speed, might not be determined only by equipment design as usually reported in the literature. Instead, the thermal and rheological properties of the polymers should be carefully considered. The focus of many studies has relied on optimizing the specific properties of an ME printer through the adjustment of the printing parameters. Still, few researchers have shown how the rheological behaviour of a material can affect its final properties. Therefore, this paper would like to answer satisfactorily some recurring questions with clear practical importance, which is related to the fact that some materials have better print quality than others do and about the feasible margins for increasing the print speed according to the characteristics of a polymeric material. Thus, in this work, rheological characterization of the resins was conducted and it was detected that the processing condition for a specific thermoplastic is highly dependent on its rheological behaviour. A method of mass flow conservation was presented for determination and consideration of the rheological characteristics when selecting an appropriate process parameter for the additive manufacturing system. It was found that even a small recovery strain resulting from the characteristic morphology of ABS could provide lower layers' roughness and good printing quality to the 3D printed samples. Thus, the main goal of this work was to evaluate the importance of the rheological properties of common thermoplastics used in extrusion-based process on the controlling of a 3D printer and on the final printing quality.