This article was originally published in Aerospace & Defense Technology Magazine.
Senior level military members are constantly evaluating risk and finding ways to articulate and mitigate risks on the battlefield. When it comes to new technology adoption and consideration, these same leaders must take a similar approach to justify spending taxpayer dollars and implementing new processes to improve operational outcomes.
3D printing, or additive manufacturing, has been investigated and researched by the U.S. military for decades and in 2021, the U.S. Department of Defense published the Additive Manufacturing Strategy* report, strategically focused on three key initiatives:
While 3D printing with polymers and metals has proven to be a major advantage for new product development and rapid prototyping, it's ineffective for on-demand manufacturing on a FOB (forward operating base) and in disaster relief scenarios. Installing and operating printers capable of producing reliable and production-grade metals is expensive, time-consuming, and oftentimes impossible due to facility restrictions and material handling requirements.
In order to explore the potential of 3D metal printing on U.S. Navy vessels, and at forward-deployed locations, the Naval Postgraduate School (NPS) in Monterey, California entered into a Collaborative Research and Development Agreement (CRADA) with Xerox. The agreement led to the installation of Xerox's ElemX Liquid Metal 3D Printer at the NPS campus, providing a unique test platform in a defense-focused, academic research environment. Operating with aluminum wire feedstock, the ElemX is engineered to be a safer option for deployable scenarios.
THE VALUE OF DEPLOYABLE ADDITIVE MANUFACTURING
Distributed and on-demand manufacturing is a key focus for the U.S. military as they seek to improve logistical challenges associated with overseas missions. Having immediate access to agile production equipment, such as additive manufacturing, enables sailors, soldiers, and specialists to quickly design and print solutions for a wide range of unforeseen problems. From an operational perspective, this eliminates bottlenecks typically associated with outsourcing or procuring parts.
That's why the U.S. Navy is looking into installation of the ElemX 3D printer on-board a Navy ship. This installation would be the first of its kind and an initial step toward resiliency and improved operational efficiency for the U.S. Navy.
The on-demand production of spare parts, custom tools, fixtures, and repair devices incentivizes sailors to think outside the box and develop quick, innovative solutions. Furthermore, instead of storing spare parts aboard the ship that may never be used, that space can be repurposed for other mission critical supplies. The vision is clear, but there are certain hurdles that must be addressed before the U.S. Navy outfits every ship with a metal 3D printer.
THE CHALLENGE OF ADDITIVE MANUFACTURING AT SEA
Other additive technologies have been considered but have yet to meet the required success criteria. Laser Powder Bed Fusion (LPBF) has always been a prominent additive technology due to its advancement in metals, such as tool steel, titanium, and other varieties of aluminum. However, it's not feasible to install one of these machines due to the material hazards associated with metal powders. Printing with aluminum wire has become the leading prospect due to it being a safer alternative and for its ease of use. NPS partnered with Xerox to advance the research in this area and develop a digital twin experience to properly test on-land and at-sea ElemX productivity and repeatability.
Once installed on a Navy ship, the testing would take place for the first full deployment, which is approximately six months. The goal is to test part repeatability in several sea states that a sailor could encounter to print, measure, and monitor equipment performance. The ElemX would be subjected to varying humidity levels, sea states, and other extreme environments associated with the ocean. For every part printed at sea (experiment), another would be printed at the NPS facility in Monterey (control) for element and metallurgical analysis. The digital twin experiment is intended to gain a greater understanding of the environmental effects of at-sea printing.
Although technical feasibility is an important measurement for the U.S. Navy, so is operational procedure and resource allocation. “Empowering sailors and marines to understand, own, and operate additive manufacturing is no easy task,” said Maj. Stephen Strieby, a USMC combat engineer and a Defense Systems Analysis student at NPS. “These men and women are trained for battle and may not have the luxury to learn new technologies or absorb the decades of tribal experience associated with additive manufacturing.”
ELEMX LIQUID METAL
Liquid metal is a solid freeform fabrication process for 3D printing metal parts. Individual molten droplets are accurately deposited onto a build substrate through a unique magnetohydrodynamics process using Lorentz forces, methodically jetting 250-micron droplets through a precise nozzle.
Using standard, off-the-shelf aluminum alloy wire feedstock, the ElemX can achieve nozzle melt temperatures above 800 degrees Celsius and can reach deposition rates up to 400 droplets per second. The onboard process monitoring system enables in situ monitoring and in process correction to ensure accurate and repeatable printing results.
Once the part is finished, the build plate is removed from the printer and quickly placed in a water tank. The thermal expansion mechanics of the differing metals allows the aluminum parts to immediately release from the build plate, with no sintering, de-binding, or additional steps necessary.
EVALUATING CONSISTENCY WITH CONFIDENCE
Ultimately, the U.S. Navy will measure every detail related to the quality of parts they are building and their confidence level will be determined through the digital twin experience. The data collected throughout this process will be priceless in terms of future considerations for the collective additive manufacturing industry. What is the maximum sea state level at which printing is possible/not possible? How will sea salt, humidity and vibration impact part quality and repeatability? How is quality defined for temporary and permanent 3D printed solutions?
The first trial of the ElemX completed with NPS was to determine the most commonly broken parts aboard a military vessel and print them in 4008 Al (A356). NPS identified multiple parts that were successfully printed and are currently being evaluated for onboard use. The most commonly replaced parts included ship valve handles, wrenches, valve stems, and light and fire suppression fixtures. These parts must perform as good or better than the originals in order to be considered for future deployment missions.
2022 AND BEYOND
Discussions have already begun to plan the installation of the ElemX aboard a Navy ship in the near future. From a research perspective, the data gathered will pave the way for further adoption and application. From an operational perspective, the U.S. Navy and Marine Corps are empowered to redefine the future of the military supply chain and maximize battlefield readiness with on-demand manufacturing that is safe, simple, and agile. The collective additive manufacturing industry will take another massive step toward full-scale adoption and set the bar for future technology advancements, ideas, materials and processes that help streamline the military supply and logistics chains.
In summary, the future of metal additive manufacturing at sea is quickly approaching. The U.S. Department of Defense has made AM a strategic focus and is embracing OEMs, partners and leaders to turn supply chain resiliency into reality. The intersection between defense, industry and research is once again proving how valuable collaboration can be to collectively improve the next generation of technology and innovation. Adopting a thorough and pragmatic approach to testing and implementation of the ElemX Metal 3D Printer will provide significant insights and data points for further development and utilization.
