Process parameter modeling for the fabrication of functionally graded materials via direct ink writing

The direct ink writing (DIW) technique utilizing a single-screw mixing exhibits the capability of fabricating functionally graded materials (FGMs) featuring continuous gradients. Nevertheless, the vast array of parameters involved in the printing process and the absence of standard values and suitable matching relationships between individual parameters are factors that negatively impact print quality. This, in turn, hampers the potential application of FGMs across a multitude of fields. Thus, the primary objective of this study was to devise a process parameter model that can facilitate the setup of additional control parameters. To this end, the parametric model was constructed on the basis of the correlation between volumetric flow and pressure in each zone, and took into consideration all structural parameters of the prototype and material property parameters. Moreover, the digital image processing was employed to analyze and compare the printing results of FGM samples fabricated using different screw speeds across three groups. The analysis revealed that for stacking quality, deviations from the optimal screw speed resulted in understacking or overstacking. Furthermore, unsuitable screw speeds led to inconsistencies between the printed material information and the expected results.