Above: Dr. Eric Wetzel demonstrates dual-polymer 3D printing filaments at the U.S. Army Research Laboratory at Aberdeen Proving Ground, Maryland/Image Credit: EJ Hersom
US Army scientists are on the brink of pioneering a Dual-Polymer 3D printing technology that is not only cutting edge but at the same time battlefield-friendly to help Soldiers quickly swap out broken plastic components with durable 3D printed replacements.
In the past, troops have either lugged replacement parts around or ordered them from warehouses thousands of miles away, only to wait weeks for them to arrive.
But with dual-polymer 3D printed parts — developed by scientists at the U.S. Army Combat Capabilities Development Command Army Research Laboratory, or ARL — Soldiers could be a few clicks away from swapping out broken pieces and heading back to the fight within hours.
According to Dr. Eric Wetzel, ARL’s research area leader for Soldier materials, “We’re crossing a threshold where low-cost, easy-to-operate and maintain printers will be proliferated on the battlefield — and able to produce engineering parts of very good quality with short turn-around times.”
He added, “In order to do that, we need printing technologies that can print parts that are accurate geometrically and have mechanical properties that are sufficiently robust to survive conditions in battle.
The Dual-Polymer 3D Printing Technology
Above: Dr. Eric Wetzel explains the Dual-Polymer 3D Printing Technology/Video Credit: The U.S. Army/YouTube
Until this point, 3D printing technologies that produce mechanically robust parts have required printers and print technologies that are not suitable for austere environments, while the printers suitable for austere environments produced poor-quality parts.
That’s where the ARL scientists decided to pitch in and developed a cutting-edge filament capable of being used in off-the-shelf, low-cost 3D printers to produce mechanically strong, battlefield-ready parts.
According to Wetzel, “Conventional polymer filaments for 3D printing are made up of a single polymer. Our innovation is that we’ve combined two different polymers into a single filament, providing a unique combination of characteristics useful for printing and building strength.”
Above: The preform is made from a combination of Acrylonitrile Butadiene Styrene (ABS) & Polycarbonate (PC)/Image Credit: EJ Hersom
The dual-polymer 3D printing filament combines Acrylonitrile Butadiene Styrene (ABS), with Polycarbonate (PC). A critical design feature of the filament is that the ABS and PC phases are not simply mixed together, a common approach for creating blended polymers. Instead, a special die-less thermal drawing process developed by ARL is used to create an ABS filament with a star-shaped PC core. Once coupled, the filament is used as feedstock in a desktop fused-filament fabrication, or FFF, printer to create 3D prints with a heavy-duty ABS/PC meso‐structure.
FFF printers work with a heated nozzle that emits thin layers of melted plastic, similar to molten glass. The filament is deposited onto a print bed, one layer on top of another until it forms the 3D printed part. In order to fabricate a unique part, the nozzle, print bed, or both move while the hot plastic streams down.
After the solid bodies are initially printed, they are put in an oven to build strength. During this annealing process, the deposited material layers fuse together while maintaining their geometry and form. This stability is caused by the higher temperature resistance of the built-in framework.
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“The second polymer holds the shape like a skeleton while the rest of it is melting and bonding together,” explained Wetzel.
He continued, “Through a series of filament design trials, we were able to identify that the star-shaped PC core provided a superior combination of part toughness and stability compared to other arrangements of ABS and PC in the filament.”
“Manufacturing at the point-of-need provides some exciting possibilities,” Wetzel said. “In the future we can imagine Soldiers deployed overseas collaborating with engineers in the United States, allowing new hardware concepts to be designed and then sent as digital files to be converted into physical prototypes that the Soldiers can use the same day. This paradigm shift could allow us to innovate at a much higher speed, and be keenly responsive to the ever-changing battlefield.”
Current filaments, traditionally consisting of a single thermoplastic, produce parts that are brittle and weak, and deform excessively during the annealing process. The Army wants reliable and durable parts which the new method provides. The new filament samples will soon be distributed to Army transition partners and based on the feedback, the ARL will ramp up production of the material.
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