printed a conformal sensor, antenna, and power and
signal circuitry directly onto the wing of a UAV. But,
Wolk said, the 3D printing process involves the melting of polymers and metals, and those high temperatures could pose problems for sensitive circuitry.
Naval Research Laboratory researchers are exploring
the combinations of materials — such as titanium and
ceramics, or plastics and metals. Imagine printing a functioning conformal antenna on the fuselage of a UAV, or
the circuit and battery for a sensor embedded on a helmet.
According to Alberto Piqué, of the laboratory’s
Materials and Sensors Branch, layers of circuitry can be
fabricated, with 3D conductive pathways generated by
laser printing of conductive nanoinks. The circuitry
and its components can be printed onto irregular
shapes without the toxic waste generated during traditional circuit board fabrication processes.
“We’re talking about an ensemble of technologies,
using direct-write techniques with existing AM tools,
and combining them in clever ways,” Piqué said.
With laser direct structuring, a 3D object with integrated circuitry can be fabricated from special doped
thermoplastic resins. Once the object is built by injection molding or FDM, a laser strikes its surface along
the circuit’s digitally rendered path activating nucleation centers on the plastic, which grow into the
desired conductive tracks after a metal plating step.
“Electronics have been traditionally placed onto 2D
circuit boards. Now we have the ability to create circuitry
on virtually any type or shape of material,” Piqué said.
On-Demand Stock Room
One value of AM is the ability to make small numbers
of urgently needed parts as opposed to restarting a production line.
“Another big benefit is if you move the point of production from the production line to wherever you have
the printer — this also can greatly increase speed. And,
even if you don’t have a perfect 100 percent replacement,
you might have a stand-in that can bring mission capability back to, say, 50 percent until you get that replacement,” said Lt. Scott Cheney-Peters, a member of the
Chief of Naval Operations’ Rapid Innovation Cell team
who has written about AM and disruptive technologies.
Could the Navy put an AM capability onboard a carrier so it could fabricate parts instead of carrying a
large inventory of spares? Wolk noted that making so
few parts means there are no test articles to make sure
the parts have the requisite properties. And what will
the process be to approve parts made on the ship?
“The Navy has specifications for everything,” she
said. “How do you make sure it meets the specs?”
“It’s not enough to be the right shape; it has to have the
right properties,” said Ashraf Imam, of the Naval Research
Lab’s Materials Science and Technology Division. “A gear
might be fabricated to the exact shape, but not have the
metallurgical properties to withstand constant use.”
There are safety issues, too. Metallic powders are
hazardous, and possibly even explosive. A moving ship
and molten materials can be a bad combination. Will
vibration and other environmental conditions affect
the printers themselves?
Using a higher resolution permits parts of smaller
size or more complexity, whereas using lower resolution allows items to be printed faster. Printing from
extremely complex digital models is not significantly
more expensive than it would be with traditional manufacturing techniques.
Cost Versus Complexity
Traditionally, the more complex an object, the more
expensive it was to make. However, with AM that is no
longer necessarily so.
“Cost is no longer a factor of complexity,” said Tim
Shinbara, technical director at the Association for
Manufacturing Technology, McLean, Va.
The all-3D-printed SULSA (Southampton University
Laser Sintered Aircraft) drone, and its descendant —
the 2Seas surveillance UAV, both made in the United
Kingdom by University of Southampton researchers —
feature a complex crisscross geodesic pattern in the airframe for strength. Such a structure would have previously been very expensive to produce.
There are a lot of AM success stories.
“Each industry has their poster child,” Shinbara said.
GE and Pratt and Whitney are making aircraft parts
such as turbine engine fan blades and injection nozzles.
WWW.SEAPOWERMAGAZINE.ORG 46 SEAPOWER / OCTOBER 2013
Naval Surface Warfare Center Carderock Division deliv-
ered a fabricated model of the hospital ship USNS Com-
fort Jan. 10, marking the first model to be created using
the new 3D printer. The model was used in Carderock’s
Anechoic Flow Facility wind tunnel.