October 1, 2011  

Direct digital manufacturing

The industrial game changer you’ve never heard of

Two decades hence, the defense industry may look vastly different, thanks to shrinking Pentagon budgets, industrial consolidation and continuing globalization. But one of the most important factors may well be a technological breakthrough that few have heard of: direct digital manufacturing (DDM).

The defense industrial base we have today seems normal to us, but would seem quite different to anyone reflecting on the issue back in 1940, 1970 or even 1990.

As an example, for much of the 20th century, the modern defense industry was intertwined with the commercial industrial base. Companies like Philco built not only radios, refrigerators and the first televisions for suburban homes, but also computers for National Security Agency and the Navy.

But as the defense side became less commercial and more specialized, fewer and fewer military items had large production runs and the sort of lower unit costs common in the civilian space. (Rare exceptions include disposable sensors like sonobuoys and small-arms ammunition.) To put it another way, the defense industrial base used to be defined by firms such as Chrysler or Ford that had a foot in both defense and civilian sectors and were engaged in mass production. Today, most defense firms focus mainly on the defense customer and have a production model that looks more like Ferrari.

Underlying this shift were the tools that enabled production and then specialization.

In the 1950s, the Air Force and Army fostered the industry’s adoption of numerically controlled machine tools, lending these automated systems to contractors as part of a government-furnished equipment program. Driven by analog, then digital, computers, they transformed the heart of defense manufacturing from blue-collar work on the shop floor to white-collar design in the cubicle. The Internet has added its own twist; companies can now control virtual and distributed machine tool capacity.

Design techniques advanced as well. In 1969, NASA released Nastran. The first of many structural analysis software packages in use today, it helped launched simulation-based design. For the first time, entire structures could be designed and modeled for key performance parameters without full-size mockups. By the late 1980s, this technique was the norm.

Today, we stand poised at another critical turning point for manufacture and design — indeed, at the very intersection of these numerically controlled fabrication and simulation-based design trends.


DDM is the fabrication of components in a seamless manner from computer design to actual part in hand. Also know as “3-D printing” or “additive,” “rapid,” “instant,” “on-demand” manufacturing, DDM uses 3-D computer-aided design files to drive the computer-controlled fabrication of parts.

Unlike traditional machining methods, which involve working from a rough mold and then cutting away to achieve the desired complex shape, direct digital manufacturing creates the shape precisely and instantly, using additive fabrication.

DDM is commonly explained through the example of creating a coffee cup. An old-style craftsman might slowly shape a piece of clay by hand into a handmade mug. Designers and machinists in a factory would build a series of metallic molds and then create a series of tools to mill metal into the key components of the cup (handle, bottom, etc.), which would then be assembled on a production line, often through welding. By contrast, a DDM designer would create a digital 3-D model of the cup, then turn production over to the computer, which would digitally slice it into a stack of wafer-thin layers, print them out, and fuse them together.

In execution, the process is a bit more complex.

Other methods of printing include fused deposition modeling, which lays down liquefied plastic or metal through a thin filament that forms into the desired shape as it hardens; stereo-lithography, which uses ultraviolet lasers to cure photopolymer “resin” one layer at a time; and selective laser sintering, which uses a high-powered laser to selectively fuse powders of plastic, ceramic, glass and even metals such as titanium and aluminum into the desired 3-D shape.

It all sounds incredibly sophisticated, but any teenager with a crooked overbite or misaligned teeth has already seen the benefit of such technology. Instead of the old method of metallic braces and corrective retainers clumsily created out of putty, dental supply companies like Invisalign now use the stereolithography version of DDM to produce aligner trays for straightening teeth.

We are finally at the point where the design part of the weapons manufacturing process can be much more than a physical or digital replica of a part, previously useful only in a lost wax mold for “the real part.” It can now be an actual structural member.

Perhaps the biggest advantage of DDM is something the defense industry has not been known for over the last few decades: speed. The ability to design, simulate and test in the virtual world allows a much more rapid turnaround than traditional techniques. Now we can add in the ability to rapidly fabricate the real part or system using the same digital file. This also applies to any changes or improvements to a design, as the entire manufacturing line doesn’t need to be retooled for any small change or new Pentagon requirement.

DDM can more easily produce organic shapes than the linear ones commonly used in defense manufacturing. That promises to introduce more complex shapes and geometries — very important for energy efficiency and even stealth characteristics. Yet the lower energy demands and material waste mean lower manufacturing costs, thus producing savings that could get passed on to the Defense Department.

upending expectations

Just five years ago, there were little more than 50 commercially viable examples of 3-D printing. But the market is starting to take off, growing at a clip of up to 35 percent annually. It is becoming price-competitive with traditional manufacturing techniques, especially ones for typical defense quantities.

And in this arena, as with so many other past industrial breakthroughs, military support has been important. Among the projects supported by Defense Advanced Research Projects Agency and the Office of Naval Research are programs to manufacture superalloy airfoils — for example, the wings of fixed-wing aircraft and helicopter rotor blades — and work at Boeing for on-demand rapid manufacturing for certain nonflight critical hardware on military aircraft. Other DoD-supported research projects are poised to take DDM to the next technical level, such as efforts to develop ever-more sophisticated lasers and manufacturing systems, further work on industrial- and military-strength products, and efforts to make DDM work at an even more scalable level, including through the use of nanotechnology.

DDM’s impact thus might be felt in the area of components and parts, and interestingly enough, not just for new systems. Many military systems have been in service for decades — B-52s, A-10s, surface ships — yet spare parts often become hard to obtain. DDM can be used to produce these parts, which also turns our present thinking about niche firms and preserving existing markets on its head.

But the impact will not just be at the spare part or subcontractor level. In July, engineers at the University of Southampton displayed an innovative new aircraft. Using a laser sintering machine, they produced SULSA (Southampton University Laser Sintered Aircraft), a small, remote-controlled aircraft with elliptical wings like a World War II-era Spitfire. The entire structure including wings, integral control surfaces and access hatches was printed out. An operative aircraft had been designed in days and could be manufactured in minutes.

And so, as DDM advances, the model of production may largely shift from traditional design, testing and manufacturing to simultaneous creation of complex products. Moreover, it lowers the barriers of entry to innovative firms outside the defense space.

This future is bright for defense DDM, but not yet rosy. The technology can answer many needs, but unless the defense industry proves its interest in actually being innovative and the Defense Department proves its willingness to enable industry to take risks, DDM will simply be yet another technology whose research was initially paid for by the military, but where the military and defense industry end up behind the civilian sector in actual use and benefit — as happened in information technology. Take something like a wing actuator support for an F/A-18 fighter jet. Presently, DDM is not an option, not just because of capability but due to issues of process, safety and certification. Is an actuator support made using DDM as strong and reliable as one it will replace? Who decides, and what process is used to certify that it is? What incentive exists for a company that wants to explore that risk for the reward?

Where this becomes even more concerning is that, unlike the last century of defense design and manufacturing, DDM is not an area where the U.S. defense industrial base can claim to be technologically ahead. Foreign development is advanced, and many other nations’ processes to work through the “ilities” (reliability, safety, maintainability ) are simpler and much quicker. This is not just a concern when it comes to other states, but DDM may even become a game changer for adversaries ranging down to the insurgent level, who stand ready to gain design and manufacturing capabilities once limited to nation-state arsenals. 3-D printing bureaus and do-it-yourself rapid prototyping machines are located around the world. If a university team can already design and build a small aircraft for fun, so can someone with more nefarious purposes in mind.

The use of DDM will only grow in the years ahead and may well alter forever defense design, manufacturing and acquisitions. Over the next 10 to 20 years, we may see a shift toward real-time manufacturing of components on an “as needed basis,” with parts and even entire systems being designed and produced at the time of need and even at the location of use. This could lead to a defense industrial base that won’t just be more diverse in its structure, but also would be more responsive to the needs of the war fighter.

Still, a DDM future will happen only if we begin to work through the processes and procedures today. One hurdle is establishing the necessary certifications and testing regimes on both the industry side and within the acquisition community. The actions we take in the near term in establishing the ground work for DDM will largely determine whether the defense industrial base forges ahead in the 21st century, or falls behind.