Abstract: Fused filament fabrication (Fused-filament fabrication, FFF) is one of the most widely used 3D printing technologies, and the bonding neck between the adjoining material filaments of FFF products has an important influence on its forming quality and mechanical properties, but the corresponding mechanism is not clear. Combining theoretical and experimental analysis, the effect of different layer thickness and extrusion width on the FFF parts' bonding neck is studied. Firstly, the theoretical model of the bonding neck is established based on the viscous sintering phenomenon of the extruded filament; The preparation of the samples is then completed, and the bonding neck of the samples is observed and measured by scanning electron microscope (SEM); Finally, the theoretical and experimental results are compared and analyzed, determining the influencing rule of the layer thickness and extrusion width on the built samples' bonding neck, and verifying the correctness of the theoretical model. The results show that increasing the layer thickness will increase the longitudinal bonding neck, but reduce the horizontal one; While for the extrusion width, the situation is in vise versa. In general, the FFF products' bonding quality is improved with the increasing layer thickness or extrusion width, and the mechanism is revealed. The research findings will provide theoretical reference and technical support for FFF technology in improving forming quality.

Key words: fused filament fabrication, layer thickness, extrusion width, bonding neck, theoretical model