and high-performance alloys are in greater demand as OEMs strive to reduce
weight in new aircraft, such as the Boeing Dreamliner 787. Content of titanium
in the Dreamliner is 15 percent, by weight.†
But the high cost of mill products and machining are major obstacles in
providing cost-effective planes. Many parts are machined from solid mill
products, and many others are made from closed-die forgings or castings. As a
result,long lead times needed for die design and fabrication create
is no doubt that additive manufacturing will replace some of the traditional
manufacturing practices," says Greg Morris, CEO and chief operating officer of
Morris Technologies, a Cincinnati-based company that was the first in North
America to acquire Direct Metal Laser Sintering (DMLS) technology, one of
several additive manufacturing processes. "There is tremendous opportunity for
the aerospace industry to cut costs and to become more efficient."
engineering scientist Blake Slaughter has studied additive manufacturing
systems and says that: "We have a huge task ahead of us, but we need to begin
somewhere." Boeing's Commercial group has already used additive manufacturing
to produce metallic, non-structural interior components.
also commented on Boeing's interest in the new approach at a meeting held by
the Edison Welding Institute in Ohio to kick off a consortium where OEMs are
joining forces to share testing and other data. Participants at the meeting
included representatives from GE Aviation, Lockheed Martin, the Air Force
Research Lab., Boeing, Honeywell, Oak Ridge National Lab., NASA, Pratt &
Whitney, Rolls-Royce (aircraft engines) and Northrup Grumman.
goal of the consortium, the first of its kind in the U.S., is to advance the
manufacturing readiness levels of additive processes.†
industries, researchers, technology providers and government agencies are
independently working to develop and implement additive processes," says Chris
Conrardy, vice president of technology and innovation at EWI. "The consortium
will create a forum for these groups to prioritize needs and coordinate
programs to advance key technologies through to implementation," he says.
manufacturing is a term that emerged from the rapid prototyping business where
CAD-driven lasers are used to create three-dimensional components from plastic
and metal in multiple, tiny layers. Those systems are now being adapted for
low-volume production, and are already widely used for dental applications and
assembly fixtures. One example is DMLS, which works with some nickel materials
and titanium as well as cobalt chrome alloys.
aircraft industry wants to take the concept a few steps farther and has brought
in some additional manufacturing approaches. These include other bulk
deposition systems, such as electron beam welding (which has a faster build
time than DMLS) and cold spray. Also in play are feature deposition systems
such as electron beam free-form fabrication (EBFFF or eBAM); laser-additive
manufacturing (LAM), which would be best suited for small, intricate features;
and plasma transferred arc solid free-form fabrication (PTA-SFFF).
candidate part at Lockheed Martin is a flaperon spar on the F-35 stealth
fighter. A flaperon controls the roll or bank of an aircraft. Analysis showed
considerable cost and lead time savings with the electron beam process compared
to forging. Most of the savings come in reduced materials costs, one of the
huge payoffs for the aircraft industry. Pieces produced by additive processes
are close to net shape, and only require minimal machining.
Fodran, program manager at Northrup Grumman, estimates the "buy-to-fly" ratio
for conventional manufacturing routes at a range of 10-20:1. The buy-to-fly
ratio is the mass of material that is required to machine a part compared to
the mass of material in the finished part. Northrup-Grumman analyses show that
buy-to-fly ratios for additive systems offer a 35-45 percent cost reduction in
comparison to alternative traditional manufacturing options.
DMLS process developed by EOS begins by sintering a layer of 20 micron
(0.0008-inch) powder onto a steel platform. They are then melted with a
high-powered, tightly focused laser to create dense three-dimensional parts.
The platform then lowers by 20 microns, and a fresh layer of powder is swept
over the previously sintered layer. Several high-performance metal alloys
(including nickel and titanium) created with this method are available now and
more are under development.
have made parts with additive manufacturing that could not have been made with
any other manufacturing technology," Morris says. The company expects to go
into series production in the next year or two on parts that previously would
have required multiple cast or machined components welded together to achieve
the same functionality as a single part made with additive manufacturing.
Details are confidential.
additive manufacturing processes are better suited for other types of aerospace
parts, particular larger parts - such as aircraft frames - and parts that don't
require complex features.
engineers fear that commercially available additive manufacturing technologies
may not be sufficiently productive, reliable, cost-effective or capable of
producing components of the sizes, alloys or properties needed by the aircraft
of our understanding of fatigue performance is based on surface finishes of
wrought or cast processing," says Boeing's Slaughter. "These processes
inherently have better surfaces than most of the deposited technologies at
their current maturation."
posed this question to the EWI meeting: "Can we compensate for the surface
finish with increased component bulk? Sure. Can we develop reliable inspection
methods? Possibly. Does the increased component weight make sense over the life
of the platform?"
Northrup Grumman's Fodran also says it's imperative to
develop a materials properties' database that includes static and dynamic data.
Another important issue is that deposited structures carry large amounts of
residual stress or distortion, or both. Also, traditional modeling techniques
are not applicable.
ASTM Committee F42 on Additive
Manufacturing Technologies has been established to set standards. Subcommittees
are in place for test methods, processes, materials, design and terminology.
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