Casting for Battle
Whenever Army troops stationed around the world move from one site to another, a great deal of waste material is often left behind. Everything from plastics, rubbers, paper and wood to various metals and chemicals have to be either dealt with by the local community or incinerated in a massive, noxious, open burn pit. But battlefield metalcasting could change that picture forever in the future.
A team of foundry experts and students, headquartered at Worcester Polytechnic Institute (WPI), are exploring the concept of a mobile foundry, where replacement parts could potentially be cast at the point of need on the battlefield using just about any scrap metal that’s on hand––operating inside a fully-equipped ISO shipping container with a probable working footprint of 12 by 17 ft., according to the team leader.
Under the direction of the Army Research Laboratory, the work is funded with a grant awarded by the Strategic Environmental Research and Development Program (SERDP), a cooperative between the Department of Defense, the Department of Energy and the Environmental Protection Agency that seeks ways to improve processes that support objectives of all three government bodies.
The researchers are building on an existing Army model that’s already in the field: The Expeditionary Lab (aka Ex Lab), which is a mobile, self-contained manufacturing unit housing 3D printing, a sewing machine and electrical capabilities inside a shipping container that’s easily moved to bases around the globe.
Today, the Army ranks the foundry project at a low technology readiness level, focused purely on research of what can be done in a lab setting. Progress over two years has been considerable, despite the mandated laboratory shut-down for most of 2020. Due to the interruption, the team was granted a deadline extension of July 2022. At the end of April, the team gave their annual review presentation to a Government Technical Committee panel, providing a thorough status of the team’s achievements to date.
The core research group is comprised of:
Principal Investigator and WPI Engineering Professor Jianyu Liang.
Advanced Casting Research Center Founding Director Diran Apelian, the former Alcoa-Howmet Professor of Mechanical Engineering at WPI who is now Distinguished Professor at University of California Irvine’s Department of Materials Science and Engineering.
Rick Sisson, George F. Fuller Professor of Mechanical Engineering, who is an expert in steel metallurgy and the heat treating of steel.
Brajendra Mishra, a recycling expert who is head of WPI’s Materials and Manufacturing Program. He is the Kenneth G. Merriam Professor of Mechanical Engineering and director of: Manufacturing & Materials Engineering, the Metal Processing Institute and the NSF Center for Resource Recovery & Recycling (CR3).
From Waste to Value
Repurposing waste metal is one of the key drivers of the project as the military works toward greater environmental sensitivity and decreasing its impact on the local community where troops are based.
“Imagine the fumes from those burn pits ... not to mention the environmental hazards associated with them,” said materials engineer Marc Pepi, the Army Research Laboratory’s lead for the Solid State Additive Manufacturing Team—he spearheaded the Statement of Need proposal that got the mobile foundry idea rolling. “I thought, ‘Let’s try to put those scrap materials to good use by adding a new capability. It just seems like the right thing to do, the conscientious thing to do.”
Pepi, a member of the Office of the Secretary of Defense’s SERDP and Environmental Security Technology Certification Program (ESTCP) Weapons Systems & Platforms Technical Committee, said the Army Research Laboratory has separately explored how to recycle some plastics and turn them into filament for 3D printing machines.
Using atomic emission spectroscopy (AES), laser-induced breakdown spectroscopy (LIBS), and X-ray technology––in downsized, portable devices––the SERDP researchers are proving they can take virtually any unidentified scrap metal, sort it, identify its composition, and create a process for casting a part in a very compressed workspace.
“The idea is to create value out of waste,” said Apelian. “With certain technologies that were developed in the recycling center we founded at WPI 12 years ago [CR3)], we have techniques where we can identify what [the metal] is––and if you know what you’ve got, then you can blend them so you have the right composition for a casting.”
Recycling doesn’t stop with the metal, said Liang. Because the team is presently focused on the use of investment casting for the mobile foundry application, even the ceramic shells can be crushed into environmentally safe material or recycled as construction material. While she hasn’t ruled out sand casting in future experiments, Liang said investment casting was chosen as the initial process due to its rapid production and because it requires minimal post-processing and machining.
The Merits of Speed
Not surprising, they’ve got the process down to a science. Today, the Army sends hunks of random scrap steel and aluminum to the SERDP team, which then produces finished parts using an existing CAD file design. The streamlined process is expedited by 3D printing a wax pattern, which takes about a day. Using shells for investment casting, molds are then easily made.
The accelerated speed at which an on-location part can be cast means the Army’s “logistical tail” is shortened––and less transportation to get the part where it’s needed reduces the carbon footprint. Even more significant, rapidly producing a part onsite could make the difference between “limping back home and getting back in the next battle,” Pepi said.
“You really can’t put a cost on readiness, but something like this could definitely improve our operational readiness. In fact, readiness is the Army’s No. 1 priority. We wouldn’t have weapon systems idle, waiting for a part that might get there in six months––hopefully, we can just make one at the point of need and put [a vehicle or weapon] back in service until the actual part arrives.”
Technology Draws Students
The high-tech aspects of the mobile foundry research made it easy to recruit WPI students to work on the project. Beyond the OES characterization, additive manufacturing and simulation modeling and design, Liang said AI, machine learning and the collection and analysis of data have also been incorporated, which attracts future manufacturing engineers. Liang said she may even roll some robotics into the metal pouring, both for safety and consistency purposes. Students are also drawn to the project’s environmental goals of recycling and reusing resources.
“When you think about foundry operations, students don’t think it’s ‘sexy.’ Young people, nowadays, they’re not attracted to this industry and its past knowledge,” Liang said. “One thing that I’m really happy about is that through this project, because we are integrating all those modern technologies ... we have been able to attract three first-year engineering students from WPI to join our team. One of them, Lily Wolf, is going to continue over the summer to work with us. And another student, William Gunn, actually became so interested, he won the AIST [Association for Iron & Steel Technology] summer internship to continue to work in an industrial steel company. We’re all super proud and happy for him.”
Students are an important part of taking the mobile foundry research to the end zone by next summer. Liang has appointed a student team to think inside the box––that is, to work on the CAD design of the operation’s physical layout and how to ultimately get all the essential equipment efficiently arranged inside a shipping container.
A related key assignment on the table this year is completing a plan for the mobile foundry’s ventilation system, as well as fire protection to ensure worker safety. Liang said the team developed a ceramic cover for the induction furnace (which handles 5–50 lbs. of molten metal) and a reflective metal sheet to control and redirect radiation in the confined area. Researchers also installed floor protection in their lab. The student team is simulating and studying the management of heat distribution in the tight space within a trailer.
“When we’re designing the trailer, we’re hoping we will be able to install a different kind of venting and get the flow of the air and the flow of the heating as we need it,” Liang said. “The next big thing for us to work on is getting this design simulated––understanding the thermodynamics and the physical principles.”
Ultimately, the pinnacle component to the execution of the mobile foundry concept is the human operators. But it can take years to train people in the science of metalcasting, which begs the questions: Who’s going to make the castings, and how? The secret, said Pepi, is that Army personnel won’t be casting anything from scratch.
That’s because, concurrent with the team’s development and integration of processes, equipment and technologies, they have been constructing the beginnings of a database and computer models that will eventually comprise all or most of the designs for parts that could be in demand. She said generous collaboration and sharing of steel alloy data from the Steel Founders Society of America has greatly enhanced the development of the SERDP’s models. Steel accounts for about 60% of the total metal waste generated at a military base, according to Liang––aluminum represents over 30%, she said.
Liang envisions a casting team leader or “pilot” might receive about 30 hours of training, enough to competently do what the model instructs him/her to do. Tapping into the database to access the model for a required casting (replete with heat treating directions), Army personnel would follow a complete casting checklist––like an interactive recipe where the cook plugs in available ingredients and receives a formula adapted for what’s on hand.
“The end user doesn’t need to know how the model runs or what kind of principles the models are based on,” Liang said. “They just need to know, okay, this is the composition of the waste [metal] that I have, and this is the property I need, then they put all those into the model. The model tells you the ... steps, and they just follow what the model prescribes. They will have high confidence that the final product is going to be what they need.”
In situations where a new part has to be designed, Liang foresees the Army Research Lab, staffed with experienced manufacturing personnel, possibly supplemented with non-military metalcasting experts, could remotely accomplish the necessary simulation and design for patterns, molds and metal mixing, and provide a new “model” to the battlefield warfighters working in the mobile foundry.
In addition to putting casting directions at the fingertips of Army troops globally, building up a future military workforce that excels in metalcasting could be beneficial, Apelian added.
“This is where AFS comes in,” he said. “There probably should be some introductions to the folks who are involved in Aberdeen [Army Proving Ground in Maryland] and ARL [Army Research Lab] with AFS because, to me, the training and education is one of the first steps. I’m thinking to myself, you can have all the technology in the world, but you still have to have people who understand it.
“It’s all about metal casting, it’s all about controlling the liquid-solid transformation, at a different, smaller scale,” he continued. “The need to educate and train people is always the universal constant.”
As Liang, Apelian and their colleagues guide the SERDP project toward its 12-month countdown to completion, the future of the mobile foundry in the Army––and all the work that turned an idea into a real, compact casting operation––is uncertain.
Once the system and technology are transferred to the Army Research Laboratory, thus completing the goal of the SERDP to develop technology in a laboratory and to prototype it to scale, the next step, said Pepi, will be for the team to apply for funding from the Environmental Security Technology Certification Program (ESTCP). This would advance the mobile foundry into demonstration and validation, “Dem Val” in military lingo, the stage that precedes actual war-gaming or battlefield application. In the case of the mobile foundry, the plan would be to proof test it at the Army’s Rock Island Arsenal Additive Manufacturing Center of Excellence.
The caveat, Pepi added, is that only projects with a government sponsor can apply for ESTCP funding, and the competition for limited dollars is fierce among myriad other SERDP projects seeking life outside the lab.
“That’s the tough part about all these great SERDP projects,” he said. “A lot of them aren’t funded to move along, and it’s a shame, especially if the project isn’t picked up by an individual service. If we had unlimited funding, it would be awesome, but [money] ends up being the bottom line.”
For now, the work continues, and, as Pepi observed, “it’s all about the art of the possible.”
By winning the SERDP, this research team proved its competitive prowess; and with undeterred tenacity, they’ve demonstrated they can identify the composition of random scrap metal, expedite pattern-making and part casting, and scale the whole operation into a proverbial tin can––a feat Liang said she’s very proud of. Perhaps the future of the mobile foundry is bright, after all.