Design and Use of a Penetrating Deposition Nozzle for Z-Pinning Additive Manufacturing

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.