In November 2016, when the Department of Defense (DOD) released its first Additive Manufacturing Roadmap, the document began with a sentence that has proven to be something of an understatement: “Additive manufacturing (AM), which includes the commonly used term ‘3D printing,’ is a rapidly growing and changing discipline.”

It’s been less than three years since then. While much of the world continues to think of AM technology as a convenient way to make sturdy plastic objects from 3D printers, military personnel at all levels have been pushing its limits far beyond what most imagined possible. Within that interval, these are just a few of the solutions produced by the military and its partners:

At the Oak Ridge National Laboratory, the Disruptive Technologies Laboratory of the Naval Surface Warfare Center produced the military’s first 3D-printed submarine hull, a 30-foot submersible hull inspired by the SEAL Delivery Vehicle. Compared to a traditional SEAL submarine hull, which costs up to $800,000 and takes three to five months to manufacture, the six carbon-fiber sections of the new prototype were built in four weeks and assembled at a cost of $60,000.

At the Picatinny Arsenal in New Jersey, at the facility now known as the Combat Capabilities Development Command (CCDC) Armaments Center, the Army unveiled a grenade launcher, the Rapid Additively Manufactured Ballistics Ordnance (RAMBO), a modified version of the older M203 launcher. RAMBO consists of 50 separate parts, each of which, except for the springs and fasteners, was built through an additive manufacturing process. The materials used for these parts include plastic, aluminum, and 4340 alloy steel.

Maintainers at Hill Air Force Base in Utah installed a 3D-printed bracket, made of titanium, on an operational F-22 Raptor. The corrosion-resistant part was used to replace an aluminum bracket in the kick panel of the aircraft cockpit. It was the Air Force’s first operational use of a metallic 3D-printed part on an F-22, and happened just months after the service’s Rapid Sustainment Office installed 17 printed parts, including both polymer and metal components, on a C-5 Super Galaxy aircraft.

With the use of a gantry-mounted concrete printer jointly developed by the Army’s Engineer Research and Development Center (ERDC), NASA, and Caterpillar, Marines, soldiers, and Navy Seabees built a 500-square-foot hardened living space – a barracks – in just 40 hours at ERDC’s Construction Engineering Research Laboratory in Champaign, Illinois. The printer is a joint Marines/Army initiative known as Automated Construction of Expeditionary Structures, or ACES. Months later, the 1st Marine Logistics group, with the help of the Marine Corps Systems Command, the Army Corps of Engineers, and Navy Seabees, used the ACES printer to build a functional concrete footbridge in 14 hours, the first 3D-printed bridge in the western hemisphere, at Camp Pendleton, California.

Titanium parts printed from powder and a laser provide researchers with high-strength, heat-resistant examples of the future of additive manufacturing

At the Institute for Soldier Nanotechnologies at the Massachusetts Institute of Technology (MIT), a research team supported by the National Science Foundation and the Office of Naval Research used additive manufacturing to produce soft, pliable nanostructures that can be manipulated when magnetized. The 3D-printed nanobots, which can be made to roll, crawl, jump, and grab, may someday be used as magnetically controlled biomedical devices.

Few technologies are as vigorously hyped throughout the military as additive manufacturing, for good reason: The ability to produce components on demand, at the point of need, will transform logistics, reduce material waste, and enable customization, all at a fraction of the costs and times involved in the manufacturing process that traditionally feeds military resupply and acquisitions.

AM is already being viewed as a possible alternative means of tackling problems unsolved by current budget levels: In the spring of 2019, the Navy’s Information Warfare Research Project Consortium issued a solicitation asking industry to use AM and innovative technologies to develop the Marines’ next amphibious transport, an item that was zeroed out of the most recent defense appropriation.

Such possibilities have serious implications for defense manufacturing: New designs can be prototyped and tested rapidly, without having to stand up production lines or create expensive tooling. In the future it may be possible for warfighters at forward outposts to print their own weapons, critical replacement parts, or even living quarters – but we’re not there yet. There are still a few hurdles to clear, both technical and organizational.

The Technology

The term “additive manufacturing” is used to distinguish the technology from more traditional “subtractive” methods, which form objects by cutting away from a piece of raw material and tooling it to achieve a finished product. While there are now several different types of AM, each forms an object in the same basic way: A programmed machine adds material, layer by layer, until a three-dimensional object is formed. The first 3D printing machines, produced in the 1980s, created objects out of thermoset polymers. Today’s machines can infuse these polymers with materials such as Kevlar, carbon fiber, and fiberglass, and also print objects made from a variety of materials including metals, ceramics, paper, food, and even living cells, introducing the possibility of printing human organs for transplant.

Initiatives such as the ACES program, which involves three military branches, NASA, and a private company, illustrate how the DOD achieves technical advances through collaboration. Innovations are made all the time by operational components such as the CCDC Armament Center, which owns more than 25 3D printers, including five contained within the mobile R-FAB system, a 3D printing lab in a shipping container. The R-FAB was recently deployed to U.S. Army Garrison Humphreys in South Korea, where machines have been used to print a number of replacement parts, mines, and mortar shells.

While these innovations are happening throughout the Defense Department, they are often nurtured by the military’s foundational research programs in additive manufacturing, conducted at the service branch corporate research laboratories – the CCDC Army Research Laboratory (ARL), the Naval Research Laboratory (NRL), and the Air Force Research Laboratory (AFRL) – often in collaboration with other service elements.

Marines from I Marine Expeditionary Force learn how to operate the world’s largest concrete 3D printer as it constructs a 500-square-foot barracks hut at the U.S. Army Engineer Research and Development Center in Champaign, Illinois

Much of this foundational research takes the form of exploring new materials, but as Dr. Joseph South, who leads the ARL’s AM-focused Essential Research Program, pointed out, it also involves investigating ways a process can be altered in order to produce different material characteristics. For example, by controlling the processing parameters in a laser powder bed fusion machine (LPBF) – a 3D printer that uses metal powder to build objects – a user can modulate the laser power and scan strategy to control the microstructure, and thus the strength and hardness, of the printed object. Team members in ARL’s Manufacturing Science and Technology Branch recently used a LPBF to produce an impeller fan used in the powertrain of an M1 Abrams tank. “That impeller was operating in an erosive environment,” said South. “As it spun at high speed, it sucked in sand, which wore away the blades. If I can control my process parameters, I could make the surface harder. That part would last longer in operation.” The new part may someday be printed in the field, or as needed, rather than loaded onto a truckload of spare parts adding to the logistical tail of an expeditionary force.

All of the service branches are working to develop a process for printing explosives, propellants, and pyrotechnics, which aren’t currently approved for AM applications. Impressive as the Army’s RAMBO grenade launcher is, the machines that printed it can’t simply extrude explosive material through a nozzle. Explosive powder in a binder can be 3D printed, but an inert binder often dampens the powder’s explosive force. “Obviously we like to have things go boom,” said South. “And if we can have more boom, the better. We’re leveraging our in-house polymer science and our explosive formulation expertise to start making the binder energetic – not just an inert binder, but energetic particles integrated into it, trying to make the binder itself have energetic content.”

It doesn’t take a lot of imagination to see how this application could go wrong, which is why a major focus for ARL and the other corporate laboratories is design science, the development of tools to guarantee each build meets specifications. “We already have the capability now, numerically, using these design tools, to say that if we build a propulsion system in a certain way, this is what the result will be in terms of performance. The next step is to experimentally validate the numerical tools.”

Ensuring that all is going as planned during an individual printing, however, is another task. ARL researchers are developing tools for in situ characterization – using techniques that train algorithms to flag defects as an object is being formed – and machine learning algorithms that will train different machines to correct lines of code in a build file.

“The last thing you want to do is build something and then at the end have it not be applicable to your process,” said South, “or not be applicable to the situation that you need it to be. Ultimately, the research is driving toward qualification.”

ARL research in additive manufacturing, like the programs at its counterpart corporate laboratories, is mostly aimed at the future, chartered for modernization – though it sometimes produces a solution, such as the impeller for the M1 Abrams, that can support the readiness mission of the Army Materiel Command, which stood up operations at its new Joint Manufacturing and Technology Center (RIA-JMTC) Center of Excellence for Advanced and Additive Manufacturing in the spring of 2019.