Efficiency Manipulation of Filaments Fusion in UV-Assisted Direct Ink Writing

This study systematically investigates the ultraviolet-assisted direct ink writing (UV-DIW) process, focusing on the influence of critical parameters, including UV intensity, the ratio of printing speed to ink extrusion rate (vP/vE$v_{P} / v_{E}$), and relative nozzle height (H/h), on filament fusion and structural morphology. The rheological behavior of photosensitive resin ink is analyzed, revealing that UV irradiation induces a fluid-to-solid transition critical for shape retention and structural integrity. The results demonstrate that UV intensity plays a pivotal role in controlling filament fusion, with insufficient curing causing filament sagging and excessive fusion, while higher UV intensities improve structural fidelity. Additionally, printability (Pr), calculated from cross-sectional analysis, is used as a quantitative metric to assess filament fusion quality and structure preservation. Parameter phase diagrams are developed to visually map the relationships among printing variables, providing a framework for optimizing UV-DIW conditions. The successful fabrication of dense solid blocks without filament interfaces highlights the potential of UV-DIW for producing high-quality, defect-free 3D structures. This work provides valuable insights into parameter tuning, paving the way for advanced applications in manufacturing, biomedical engineering, and material science.