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Size and print path effects on mechanical properties of material extrusion 3D printed plastics

ABSTRACT: Print conditions for thermoplastics by filament-based material extrusion (MatEx) are commonly optimized to maximize the elastic modulus. However, these optimizations tend to ignore the impact of thermal history that depends on the specimen size and print path selection. Here, we investigate the effect of size print path (raster angle and build orientation) and print sequence on the mechanical properties of polycarbonate (PC) and polypropylene (PP). Examination of parallel and series printing of flat (XY) and stand-on (YZ) orientation of Type V specimens demonstrated that to observe statistical differences in the mechanical response that the interlayer time between printed roads should be approximately 5 s or less. The print time for a single layer in XY orientation is much longer than that for a single layer in YZ orientation, so print sequence only impacts the mechanical response in the YZ orientation. However, the specimen size and raster angle did influence the mechanical properties in XY orientation due to the differences in thermal history associated with intralayer time between adjacent roads. Moreover, all of these effects are significantly larger when printing PC than PP. These differences between PP and PC are mostly attributed to the mechanism of interface consolidation (crystallization vs. glass formation), which changes the requirements for a strong interface between roads (crystals vs. entanglements). These results illustrate how the print times dictated by the print path layout impact observed mechanical properties. This work also demonstrated that the options available in some standards developed for traditional manufacturing will change the quantitative results when applied to 3D printed parts.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40964-022-00275-w.

SUBMITTER: Ai J

PROVIDER: S-EPMC8866044 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Extrusion-based 3D-printing is an easy-to-use, cheap manufacturing technique that could be used to produce tailored precision medicines. The technique has an almost unlimited versatility since a multitude of print parameters can easily be adapted. Unfortunately, little is known of the effect of these print parameters on the critical quality attributes of the resulting printlets. In this study, practical guidelines and means to adapt certain parameters in order to achieve the desired outcome (e.g., acceptable visual quality and flexible dosing) are stipulated for medical 3D-printing using a design-of-experiments approach. The current study aims at elucidating the effect of five print parameters (infill, overlap, number of shells, layer height and layer pattern) on the mechanical properties, dimensions, weight, porosity and dissolution characteristics of a fixed-size caplet consisting of Eudragit EPO (69.3%), Polyox WSR N10 (29.7%) and zolpidem hemitartrate (1%). In terms of the mechanical properties, 3D-printed caplets possessed anisotropy where the vertical compression strength and Brinell hardness exceeded the diametral strength. In general, all 3D-printed caplets possessed acceptable mechanical strength except for a small region of the knowledge space. Dimensional analysis revealed small, statistical significant differences between different runs, although the clinical relevance of this variation is likely negligible. The weight or dose of a caplet can be varied mainly using the infill and overlap and, to a lesser extent, via the layer height and number of shells. The impact on porosity was complicated as this was influenced by many factors and their interactions. Infill was the only statistically relevant factor influencing the dissolution rate of the current formulation. This study unravels the importance of the print parameter overlap, which is a regularly neglected parameter. We also discovered that small dose variations while maintaining the same dissolution profile were possible via modifying the overlap or number of shells. However, large dose variations without affecting the dissolution behaviour could only be accomplished by size modifications of the printlet.

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Size and print path effects on mechanical properties of material extrusion 3D printed plastics

Supplementary Information

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