3D-printed explosives

Scientists can additively manufacture ceramics, glass, and polymers, among other materials. So why not explosives? In 2016, the High Explosives Science and Technology group at Los Alamos National Laboratory started to explore this possibility. Fast forward to today, and the group members are designing and producing explosives that are often safer and more effective than those made through traditional methods.

Research and development (R&D) engineer Adam Takeshita explains that the process is called direct ink writing. “That’s when you push a paste through a nozzle, and the paste is deposited layer by layer into a formation that hardens,” he says.

Producing explosives this way opens up a range of possibilities that are tricky, if not impossible, to replicate with traditional production methods. Scientists can create complex internal lattices and structures that influence the explosive characteristics of each build. The way an explosive is printed affects how it detonates.

“The design and safety implications of this research and technology may transform the function and production of high explosive parts throughout the nuclear security enterprise,” says scientist Alex Mueller.

As with any additive manufacturing device, the way in which an object is printed has to be programmed into the printer. “The machine doesn’t know what to do, so you have to tell it what to do,” Takeshita says.

To achieve the enhanced print fidelity of complex parts, however, the team requires more control over the process than what standard 3D printers offer. The 3D printer used for printing explosives uses the typical x, y, and z axes for movement and also has two rotational axes, which allow for more fluid movement to create more complex designs. A large part of Takeshita’s job is creating toolpaths that direct the movement of the printer in a coding language called G-code.

“The machine interprets the code, and it will tell all of the axes to move in a coordinated way,” Takeshita explains, “including what speeds to print at and how fast to move.”

Developing the explosive material for the printer has also been a challenging process. Chemists in the group eventually created an explosive material with a toothpaste-like consistency that can be extruded through the printer nozzle. The material is also ultra violet (UV) curable—shining a UV light on it causes it to harden and thus hold its shape.

Takeshita and his colleagues work closely with the people or organizations requesting an explosive design. “It can take a lot of time and conversation to develop a design to meet their needs,” he says.

Some builds can take up to a year, depending on how many design iterations the team has to go through. But most simple designs can be produced in a matter of days. Once an explosive design is printed, the team tests the design to ensure it behaves as anticipated. For any unexpected responses or failures, the team heads back to the drawing board to iterate on the design.

Although the team has been largely successful in developing both 3D-printed explosives and the appropriate toolpaths, Takeshita admits there’s still plenty of room for improvement. “There are any number of things that can go wrong,” he says. “Any day-to-day variation in formulation or process can lead to structural and performance changes."

Takeshita takes the challenges in stride, noting that the benefits of 3D-printed explosives outweigh the obstacles. “Lots of people do 3D printing in general, but explosives R&D is something pretty much only the national labs do,” he says. “And it might be part of the bias of working at Los Alamos, but I really do believe Los Alamos does it best.” ★