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

Date

2022

Authors

Bales, Brenin
Walker, Roo
Pokkalla, Deepak
Kim, Seokpum
Kunc, Vlastimil
Duty, Chad

Journal Title

Journal ISSN

Volume Title

Publisher

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 filament will flow through the penetrating nozzle as the system pressure drop of 9.3 Mpa is less then the minimum critical pressure of 12.07 Mpa. Additionally, it was after a transient thermal simulation, it was found that after a pause of 15 seconds the system can resume printing with no drop in heat at nozzle exit. This means the additional length of the penetrating nozzle, will not cause any clogs during any pauses in filament flow.

Description

Keywords

LCSH Subject Headings

Citation