Abstract
Large-scale 3D printing of polymer composite structures has gained popularity and seen extensive use over the last decade. Much of the research related to improving the mechanical properties of 3D-printed parts has focused on exploring new materials and optimizing print parameters to improve geometric control and minimize voids between printed beads. However, porosity at the microstructural level (within the printed bead) has been much less studied although it is almost universally observed at levels of 4 %-10 % when using fiber reinforced materials. This study introduces a vacuum-assist approach that minimizes internal porosity by removing ambient air from the interstitial space between pellets in the hopper and acts as a negative pressure vent for gases that evolve during the initial stages of single-screw extrusion. Vacuum-assisted extrusion was able to reduce porosity below 2 % across a wide range of processing parameters, moisture content, fiber reinforcements, and printing platforms. Specifically, when printing on a large-format extruder (Strangpresse Model-30), the vacuum-assisted extrusion reduced internal porosity by 35–75 % compared to conventional non-vacuum extrusion, and only pores with length scale > 2 microns are affected. The success of this approach prompted the design of a patent-pending continuous vacuum hopper relevant for large-scale 3D printing on commercial systems.
| Original language | English |
|---|---|
| Article number | 104612 |
| Journal | Additive Manufacturing |
| Volume | 97 |
| DOIs | |
| State | Published - Jan 5 2025 |
Funding
The authors gratefully acknowledge support from the Composite Core Program (CCP 2.0), supported by Vehicle Technology Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy. A portion of the research was also sponsored by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office, under contract DE-AC05\u201300OR22725 with UT-Battelle, LLC. This material was also based upon work supported by the National Science Foundation under Grant No. 2055529. Feedstock materials used in this work were provided by TechmerPM, TN, USA. The authors acknowledge the assistance of Dilworth Parkinson of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02\u201305CH11231. Authors also thank Dr. Segun Isaac Talabi and Brittany Rodriguez for assisting in vacuum-assisted LFAM prints. The authors gratefully acknowledge support from the Composite Core Program (CCP 2.0), supported by Vehicle Technology Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy. A portion of the research was also sponsored by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. This material was also based upon work supported by the National Science Foundation under Grant No. 2055529. Feedstock materials used in this work were provided by TechmerPM, TN, USA. The authors acknowledge the assistance of Dilworth Parkinson of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. Authors also thank Dr. Segun Isaac Talabi and Brittany Rodriguez for assisting in vacuum-assisted LFAM prints.
Keywords
- 3D printing
- Fiber reinforced
- Large format
- Microstructure
- Porosity
