Abstract
Fused Filament Fabrication (FFF) involves depositing material layer-by-layer to create a
three-dimensional object. This method often demonstrates high mechanical anisotropy in the
printed structure, leading to a drop in the material strength of the part when comparing structures
along the deposition plane (X/Y-Axis) versus across layers in the build direction (Z-Axis). Initial
efforts to improve anisotropy led to the development of the Z-Pinning process, where continuous
pins are deposited across layers in the Z-Axis. Z-pinning has demonstrated significant gains in
toughness and inter-layer strength, particularly in fiber-reinforced materials. However, this
process can also create flaws in the structure that increase in severity and frequency as the pins
grow in length and diameter. To mitigate this, a penetrating nozzle has been developed that
extends a fine-tipped extrusion nozzle deep into the pin cavity and simultaneously extrudes
material as it retracts. This study investigates the printability of the penetrating nozzle for simple
geometries and evaluates the resulting Z-pinning mesostructure. As a result of this study, the
prototype penetrating nozzle design was analyzed and built. Through a pressure driven flow
analysis it was determined that the penetrating nozzle extruder can not only flow extrude
filament. After a transient thermal simulation it was found that after a pause of 15 seconds
resume printing with no drop in heat at nozzle exit.
