RE tools quickly turn parts into data for aerospace manufacturers
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EWhile aircraft manufacturers struggle to keep up with orders for
new planes, more aero component-makers are stepping in to supply parts
they've never supplied before. But making parts requires data, and
often current data or even prints don't exist, especially for older
aerospace components that have undergone undocumented changes. In these
cases, the only option is to reverse-engineer a current part and
capture its dimensions, and for this work, 3-D laser scanning stands
out as a particularly useful tool.
"There's a lot of reverse engineering [RE] that goes on in the
aerospace industry," says Giles Gaskell, director of business
development, NVision Inc. (Wixom, MI). A particular target area for RE
has been replacement parts for aircraft engines. Engine manufacturers
may sell an engine for not much more than it costs to make, and then
look to profit from selling spare parts down the line, Gaskell
explains. "People have seen that opportunity and thought, 'if we can
make spare parts, then we can make all the profits without having to
make the engine in the first place.'"
The kinds of parts these manufacturers are reproducing and selling
do not fall under patent protection, he says. Thus, this kind of
duplication is generally an open secret among aerospace manufacturers:
"It's not something they can do under the table, because the parts do
have to be approved by somebody-you can't just stick any old junk on an
airplane and expect to get away with it."
Aero manufacturers of all sizes look carefully at the competitors'
parts they might want to start producing, says Dan Jeanloz, application
engineer for the Brown & Sharpe service division of Hexagon
Metrology Inc. (North Kingstown, RI). "They buy the original
manufacturer's part and ask us to reverseengineer it so they can create
a model and start making that part as an aftermarket part." This is
especially true for lucrative parts that are definite money-makers.
Part-duplication is just one of many reasons for performing RE, says...
Recent improvements in 3-D scanning have enabled more of this RE to
be done in aerospace and other industries. "On the hardware side,
there's something for everyone," says consultant Todd Grimm (T.A. Grimm
& Associates Inc.; Edgewood, KY). For instance, laser scanners
range in price from $2500 to well over $100,000, depending on the
user's needs. The key challenge now is educating more users, Grimm
observes. "People have a lot of misperceptions about 3-D scanning, and
many don't even know the right questions to ask."
In this process, scanners acquire massive amounts of point-cloud
data quickly. By comparison, a CMM with an analog scanning-probe head
allows less speed, though more accuracy. With a laser scanner, "you get
a lot of data quickly, but your accuracy is 20-50 µm," says Jeanloz of
Brown OC Sharpe. "With the analog head on a CMM, your accuracy is 3-4
µm, so it's a big difference."
However, the speed of laser scanners can't be ignored, says Brian
Gudauskas, application engineer for Hexagon's Romer Inc. (Wixom, MI).
"Reverse engineering in the past was done with touch probes [roughly
1-2 points per second], and in the recent past with analog scanning
probes [roughly 150-400 points per second]." At 20,000 points per
second or more, "laser scanning now offers the ability to get mass
quantities of points for a low cost in time and money."
Recently, Romer's ScanShark 5V laser-scanning probe was updated to
capture 458,000 points per second, making it nearly twenty times faster
than the previous version. Increasing speeds this high could, at some
point, be seen as overkill, but Gudauskas argues that higher numbers of
points at higher densities are better to have than not. "When scanning
first and post-processing later, you don't want to be missing
anything."
Scanner accuracies are also expected to improve, says Michael
Raphael, president and chief engineer, Direct Dimensions Inc. (Owings
Mills, MD). "Some of the newer 3-D scanner systems can capture large,
complex shapes such as aircraft wings, tails, and complex fairings-in
single setups, with near-CMM accuracies and significantly higher
point-spacing resolutions." Accuracy is improved by combining
positioning systems with hand-held laser line scanners, allowing
untethered contour scanning of larger shapes.
One specific project example was the scanning of all of the major
structural components in the belly of a 40-yearold BAC 1-11 commercial
airliner, says Raphael. To help the client incorporate a new radar
system, technicians scanned the dimensions and positions of stringers,
frames, brackets, clamps, skins, and fittings. "All of this raw
information was then converted into a detailed 3-D CAD solid model in
SolidWorks."
Turbine-blade scanning demonstrates the importance of choosing the
right tool for good RE in aerospace. Blades can be lucrative parts to
manufacture both in aerospace and in the power-generation industry,
where they can be sold for tens of thousands of dollars, says Dan
Jeanloz. In aircraft engines, blades need to be replaced relatively
often, given the heat and wear they're exposed to.
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