Aerospace & Defense Technology - June 2022 - 22

Manufacturing & Production
new technologies or absorb the decades
of tribal experience associated with
additive manufacturing. "
ElemX Liquid Metal
Major Stephen Strieby, a USMC combat engineer, shows off a 3D-printed metal part typical of those that
might one day be made at sea. (Image: Courtesy of Xerox)
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
22
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
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ADT Feature 5 - Manufacturing 0622_2.indd 22
Intro
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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,
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Aerospace & Defense Technology - June 2022

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