It’s Not Just Science’

SEAPOWER MAGAZINE 01 JUN 17 – Edward Lundquist
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Additive manufacturing has grown beyond gimmickry and entered the mainstream of modern manufacturing. That’s why the Navy is leveraging the experience and expertise of its own world-class experts and facilities at systems commands, warfare centers, research labs, shipyards and repair facilities — even on ships — to meet uniquely naval needs.

Referred to as AM and frequently thought of as 3-D printing, it’s much more than that. AM is an umbrella term involving seven different processes and many materials. It involves successive layering of materials such as plastics and metals in the form of liquid, powder, paper or sheet material, and includes a variety of processes from vat photopolymerization, material jetting, binder jetting and material extrusion to sheet lamination, stereolithography, powder-bed fusion and directed-energy deposition.

The result is an ability to produce or manufacture things that could not be made with traditional subtractive methods.

Ben Bouffard, branch lead for additive manufacturing at Naval Surface Warfare Center (NSWC) Carderock, Md., Division, said AM technology is not new, and the Navy has been using it for a long time to create molds, jigs and tooling fixtures to help make existing processes more efficient. But that is changing.

“We’re transitioning from those indirect applications — from printing a tool that helps you make a part — to printing the actual part itself,” Bouffard said.

When it comes to making parts for submarines, ships and aircraft, the materials, processes and results must be consistent, and the end-product certified for use on the specific platform.

Norfolk Naval Shipyard in Portsmouth, Va., has significant experience using AM. Maria Williams, a nuclear engineer at the shipyard and lead for the yard’s additive manufacturing subcommittee, said submarines have a much higher standard than can be met with the current state of AM technology. But AM is being used to make models, prototypes and tools.

“You won’t see 3-D-printed parts on the submarine we’re working on, but they will be involved in what you do see,” she said. “3-D parts will be used to get that ship ready for sea.”

The Navy’s vision is to be able to make parts that are out of stock, out of production, or were made by companies that no longer exist. The cost of contracting for the manufacture of very small quantities of such items can be orders of magnitude greater than the part originally cost. In some cases, AM could be used for urgent temporary repairs.

“We could make noncritical parts that might be good enough,” Bouffard said. “They probably wouldn’t last long, but it might get them through.”

3-D printers and software can be inexpensive, which makes experimentation and creativity affordable. Resourceful Sailors onboard the aircraft carrier USS Harry S. Truman found that the clasps for their $600 hand-held radios were constantly breaking. They created a replacement part onboard — dubbed the “Tru-Clip” — using 3-D printing that cost about 10 cents each.

“When we can make parts on demand, when we need them, that will have a direct impact on readiness,” Bouffard said.

“The Navy and Marine Corps envision using the technology in forward-deployed operational settings, whether that be in the desert or afloat, wherever we need to use it,” he said. “So we need more robust equipment that can handle those environments.”

That environment is one of the challenges. Most AM processes require clean and stable work areas. Ships operate at sea, with the salt air, moisture and pitching and rolling. So the Navy is studying how those factors affect the AM process at sea. But the environment can be an advantage.

“Additive manufacturing allows us to come up with different ways to make some of the assets we use today,” said Dr. Ryan Kincer, a materials engineer at NSWC Panama City, Fla.

Panama City is experimenting with adjustments to the “recipe” to make disposable unmanned underwater vehicles that eventually dissolve in seawater.

“We can change the amount of polyhydroxylalkinate added to the material to degrade faster or slower, de – pending on how long we want it to last. We don’t need to recover it because the cost is so reasonable,” Kincer said.

Unlocking the Constraints

The method by which products have traditionally been manufactured dictates how they are designed and maintained. The manufacturing processes used can limit how fast you can build and test a prototype. That, in turn, affects how a company can innovate and turn a new idea or concept into a reality that is ready for market.

Finished products that used to be made at a factory and shipped to a customer might now be more affordably printed on demand at the point of use by the customer.

“Additive manufacturing unlocks the constraints, and offers new ways to design, distribute and service products. It allows an industrial system that gives you complete process control, and allows you to connect a continuous digital thread from concept to finished part. It’s not just a toy or a tool for experimentation,” said Aaron Frankel, senior director of marketing for manufacturing engineering software products at Siemens PLM Software, Plano, Texas.

Siemens, for example, offers a system that integrates design, planning and construction that is fully compliant with manufacturing operating systems.

Frankel said there are many disconnected applications for specific engineering specialties. Different computer-aided design and engineering systems, print software and printers can be made to work with each other, but something may be lost in translation.

“If we convert files from one software to another, we disconnect the digital thread and can lose fidelity, and the ability to manage the workflow,” he said.

There are challenges. Parts milled from forgings have different qualities than printed parts made from metal powder.

“We’re seeing deformation of printed parts based on different thermal properties. We need to compensate for that in the design,” he said.

Frankel said broken or damaged parts can be digitally scanned to produce a model and then print the repaired part.

“You don’t need outside tooling,” he said.

Machined parts remove metal from a block to shape a part, so the part is limited by the shape of the block. AM removes that restraint allowing the manufacture of shapes that cannot be done using conventional machining techniques.

Dr. Daniel Henkel is research manager for additive manufacturing and materials at the Commonwealth Center for Advanced Manufacturing (CCAM) near Petersburg, Va., an industrial applied research center. According to Henkel, some parts are so complex, such as those with very fine or non-linear internal channels for cooling or fiber connectivity, they are sometimes impossible to machine, but easy to do in AM.

“In just one build, we can make custom components or entire assemblies that can’t be done any other way,” he said.

CCAM works with five Virginia universities. One of the recent efforts is researching the corrosion of additive parts, an important factor in a marine environment.

“We’re working with the University of Virginia’s Center for Electrochemical Science and Engineering, which is doing research with the Navy on corrosion of additive parts,” Henkel said.

He said the university does not currently have the AM capability.

“We’re going to do the additive manufacturing part of the project here at CCAM, and they’re going to do the corrosion testing. We don’t know how these materials are going to corrode,” Henkel said. “It’s a different grain structure and chemistry. We don’t know if they will corrode similarly to conventional wrought metals.”

Science and Technology

Dr. Julie Christodoulou is director of the Naval Materials Science and Technology Division in the Sea Warfare and Weapons Department of the Office of Naval Research (ONR).

“We don’t make widgets. We transfer technology to the widget makers,” she said.

Christodoulou manages a portfolio of science and technology programs trying to solve complex problems with naval applications. For example, she said the Navy is interested in novel conformal heat exchangers, because there’s no reason, other than manufacturing limitations, to make them in rectangular blocks.

“AM opens a broader design space so we can make better use of the space available to us. It might have some benefits to us in very tight spaces that are common in military systems. The design has to be approached in a different way because we’re no longer constrained by traditional manufacturing technologies and processes. Understanding what we can control and how we can control it is as important as simply building it,” Christodoulou said.

ONR has also been working on very compact, high-efficiency fuel cells for a number of applications.

“When you try to demonstrate a new system in a laboratory environment you need to make your own parts. For our fuel cell, the titanium bipolar plate has a very complicated internal flow path, which was best made by additive. The team made it in a couple of different variations and generations to find what worked best and then demonstrated on the Ion Tiger small long-endurance UAV [unmanned aerial vehicle], developed by the Naval Research Lab,” she said.

Additionally, Christodoulou said there is a great deal involved in qualifying the materials, processes and systems used in additive. And it’s important to build confidence into the process, and make it more predictable. That calls for real-time sensors and better predictive tools to ensure that during a build, the result will have the desired properties, “so that we know what it is we’re going to have at the end.”

According to Christodoulou, during each AM build different alloy compositions, heated to different temperatures over different amounts of time, and with different cooling rates depending on the part dimensions, alter the microstructure of the finished material.

“We are conducting research on the compositional and process changes that can be made to the more well-established alloys to deliver the microstructures and properties we desire. It’s not going to be used for everything,” she said. “In some cases, the only way to produce something that can perform a function with the correct form and fit, and do it elegantly, is with a traditional method.

“It all comes down to the economics of the process and the properties that are needed,” Christodoulou said. “Sometimes the business case is very compelling.”

Not Just Science

“I have world-class experts in many fields, from energetics, radar propagation or missile control, to chemical and biological warfare defense, electronic countermeasures and naval architecture,” said Rear Adm. Tom Druggan, commander of the Naval Surface Warfare Center in Washington (NSWC). “We have experts working on AM at all of our centers.”

Druggan sees AM as a way to make special or otherwise unobtainable parts for deployed or remote units.

“If I had a 3-D printer, and the right technical data package that would allow me to manufacture it, I could have that part on the ship in hours instead of days or weeks. That’s operationally significant, and a huge enabler,” he said.

Druggan said the Navy’s warfare centers are engaged with developing standards and certifying parts.

“What happens if a 3-D-printed part is installed and it fails and someone gets hurt, or pieces of equipment go bad? What are the standards that are required? NSCW Corona [Calif.] is looking at how we characterize the requirements of the machine itself to make them eligible for Navy use. It won’t be tomorrow, but eventually you’ll see this start to enter the fleet ships as an operational enabler,” Druggan said.

“It’s not just science,” he said. “It’s an emerging engineering application that adds value to the Navy.”