3D Printing

Military-spec filament produces stronger 3D-printed objects

Military-spec filament produce...
The initial cylinder of material, which is itself 3D-printed (a), the thermal draw tower, which heats that material and draws it out (c), and a cross-sectional view of the resulting filament (e)
The initial cylinder of material, which is itself 3D-printed (a), the thermal draw tower, which heats that material and draws it out (c), and a cross-sectional view of the resulting filament (e)
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The initial cylinder of material, which is itself 3D-printed (a), the thermal draw tower, which heats that material and draws it out (c), and a cross-sectional view of the resulting filament (e)
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The initial cylinder of material, which is itself 3D-printed (a), the thermal draw tower, which heats that material and draws it out (c), and a cross-sectional view of the resulting filament (e)

While consumer-grade 3D printers may be adequate for making things like models or curios, they're not always up to the task of creating objects that stand up to real-world use. That could be about to change, though, thanks to a new printing filament.

Compact, inexpensive 3D printers typically utilize a process known as fused filament fabrication (FFF). This involves heating a plastic filament to its melting point, then extruding it through a nozzle. Successive layers of the molten plastic are deposited one on top of the other, forming a single solid object as they cool and fuse together.

According to US Army engineers, though, items printed in this fashion tend to be too structurally weak for rough-and-tough use by soldiers in the field. This is a shame, since if troops were able to carry small, cheap 3D printers with them, they could make parts and tools onsite as needed. And although there are printers that use non-FFF techniques to produce stronger objects, those machines are large and costly, making them impractical for field use.

Led by Dr. Eric D. Wetzel, researchers from the Army's Emerging Composites team set out to address this problem. They ultimately created a new dual-polymer filament that allows consumer 3D printers to produce much stronger items, utilizing their existing FFF hardware.

The material starts out in the form of a cylinder with a star-shaped polycarbonate core, that's surrounded on all sides by ABS (acrylonitrile butadiene styrene). Utilizing a proprietary device called a thermal draw tower, that cylinder is heated and drawn out into a thin filament.

Once that filament cools, it can be wound onto a reel and then used in an ordinary FFF 3D printer. Objects printed from the material are subsequently heated in an oven and then cooled, ensuring that the two polymers thoroughly fuse together.

In lab tests, such objects proved to be much stronger than those made from conventional filaments – in fact, they exhibited mechanical properties similar to those of identical items produced via commercial injection molding techniques. The material's annealing (heating and cooling) time currently sits at 24 to 48 hours, but the team hopes to reduce that figure to four hours or less.

The Army is now looking for industry partners who may be interested in commercializing the technology, for use beyond military applications.

A paper on the filament was recently published in the journal Advanced Engineering Materials.

Source: US Army Research Laboratory

5 comments
aki009
I have had great success with carbon fiber infused filaments.
paul314
I guess it all depends on your definition of small and cheap. Printers capable of using a composite filament like that under rugged conditions would likely be in the low four figures. (And take hours to print a objects of significant size.) They need high-temperature nozzles, heated printbeds, heated build chambers...

I can see how the annealing step would be important, because polycarbonate and ABS are typically printed at quite different temperatures and have different thermal coefficients of expansion. I wonder what temperature the composite gets printed at and how bad it smells...
Alex Hironaka
Neat approach, but kind of redundant. There have been blends of PC+ABS and PC+ASA for quite some time. Many of the newer 3D printers can print PC and some of the top tier ones can print in Ultem or PEI.
clay
Very interesting method of producing custom material properties at home.
Cody Blank
Awesome tech to make plastic things even harder to recycle.