New US Army Research has revealed a new multipolymer filament designed for use with low-cost FFF 3D printers. The high tenacity filament is expected to help in the battlefield and produce business critical parts in a timely manner at a fraction of the cost of traditional parts. The study was featured on the cover of the April issue of Advanced technical materials.
Multi-thermoplastic filament
FFF is the most widely used 3D printing technology today due to its low barrier to entry and relatively low cost. However, parts made with FFF tend to have no mechanical strength, so their use is generally discouraged in high-level field operations where they are exposed to harsh combat conditions. U.S. Army research is aimed at overcoming the limitations of readily available filament and instead creating something as sturdy as the warfighters that will use it.
The researchers combined ABS and polycarbonate (PC) to formulate their novel filament. A 3D printer was used to create a solid preform that consisted of a lower temperature ABS shell and a higher temperature star shaped PC core. A thermal draw tower was then used to feed the solid preform through diameter and tension sensors and convert it back to filament. This newly drawn filament was returned as a starting material, but this time as a mixture of ABS and PC, which gave it superior mechanical properties. To complete the process, parts that were 3D printed from the new filament were annealed in an oven for 24 to 48 hours to completely fuse the layers together for additional structural integrity.
The 3D printed parts came out of the heat chamber with ductilities comparable to injection molded ABS parts and fracture toughness values 1500% (15x) higher than those of identical ABS geometries. The researchers concluded that PC infusion helped withstand heat-induced creep and maintain accurate part dimensions during the annealing process. The team hopes to reduce the glow time to four hours or less in the future.
3D printing the preform and drawing the filament. Image via US Army.
Additive manufacturing in the field
Dr. Eric Wetzel, co-author of the study, explains that the army wants to print parts on site to simplify logistics. Moving digital files and raw materials eliminates the need to lug around excessive physical parts. Unfortunately, the technologies for 3D printing high-strength parts in an expeditionary environment have not been practical. The printers are too big, use too much power to operate, are quite delicate in construction, and their raw materials require special storage conditions.
Jeff Wallace, mechanical engineer at the Army’s C5ISR Center at APG, adds, “The ability to additively manufacture parts from a high strength polymer using the FFF process at the field, division, and / or depot level is sure to become an option for warriors give the ability to make better temporary parts much faster – hours versus days or weeks – and at a significantly lower cost – often pennies versus ten dollars. “
Wallace sums it up, “Soldiers also improvise as needed and often find their own design solutions to the problems they face. Offering a higher strength polymer material that can be used in the desktop printers they have access to gives them the opportunity Immediate innovation to temporarily solve a larger number of delivery and design challenges. Your designs would then be sent to the appropriate engineering support activity for evaluation. “
Dr. Eric Wetzel demonstrates the thermal drawing process. Photo via US Army.
For more details on the study, see the article entitled ‘Robust, additively manufactured structures, made with double thermoplastic filaments‘. It is co-authored by Kevin Hart, Ryan Dunn and Eric Wetzel.
The U.S. Forces has long used additive manufacturing to manufacture parts and conduct research for their field operations. Earlier this year, tThe US Army announced that it would work towards it Development of its supply chain Support the integration of additive manufacturing. More recently, the army began using the University of Delaware for 3D printing High temperature composites with a Roboze ARGO 500 3D printer.
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The picture shown shows the 3D printing of the preform and drawing the filament. Image via US Army.
