Analysis of the Carreau Model Mixed Mechanism with a Stir Shaft in Color FDM Printing

Conventionally, fused deposition modeling (FDM) 3D printing allows for multiple color printing, but it is limited to only various monochromatic colors. Consequently, the effect of progressive color transition cannot be reflected. To produce the progressive 3-D color printing effect, the only solution is to implement stereolithography technology, which is particularly expensive. There-fore, the aim of this paper is to develop a color mixing mechanism to be incorporated into an FDM 3D printer, which is relatively inexpensive. The underlying idea is to pre-mix the color so that the FDM 3D printer can produce a progressive color printing effect. Three conceptual color mixing mechanisms are designed, i.e., a triangular stirring shaft, a rectangular spoiler stirring shaft, and a spiral blade stirring shaft. The mixing process is modeled based on the non-Newtonian fluid theory, in which the Carreau model is used to simulate the motion of pseudoplastic fluids in FDM 3D printing under forced mixing. The resulting mixing ratio produced by all the designs is computed, which inspires the integrated design of rectangular spoiler stirring shaft and the spiral blade string shaft. Subsequently, the axial velocity of the mixed-color fluid, which increases from inlet to outlet, is verified. The integrated design is then fabricated and incorporated into the FDM 3D printer, and the progressive color printing effect is practically demonstrated.