Home' Technology Review : January February 2012 Contents Feature Story 53
Todd Rockstroh, the GE consulting engineer who heads the effort.
The blade edge and the fuel injector will start appearing in engines
as early as 2013, and they will be integrated into full-scale produc-
tion runs in the thousands by about 2016.
Meanwhile, says Rockstroh, the company hopes to gain design
flexibility by using 3-D printing for more parts. When it recently
discovered that a stem in the fuel injector was subjected to exces-
sive levels of heat stress, a redesigned version came out of the
printer within a week. “Before, we would have had to redesign 20
different parts, with all the associated tooling,” says Rockstroh. “It
might not have even been possible.” And using 3-D printing to cor-
rugate the insides of some parts can reduce their weight by up to 70
percent, which can save an airline millions of gallons of fuel every
year. That prospect has GE looking for ways to print everything
from gearbox housings to control mechanisms. “We’re going on a
major weight-reduction scavenger hunt next year,” Rockstroh says.
Automobiles could similarly benefit from lighter parts, and the
University of Louisville’s Gornet notes that printing processes could
cut the weight of valves, pistons, and fuel injectors by at least half.
Some manufacturers of ultraluxury and high-performance cars,
including Bentley and BMW, are already using 3-D printing for
parts with production runs in the hundreds.
challenges to overcome
If it weren’t for the limitations of the technology, 3-D printing
would already be much more broadly used. “Speeds are atrociously
slow right now,” says GE’s Singh. Todd Grimm, who heads an
additive-manufacturing consultancy in Edgewood, Kentucky, esti-
mates that the time it takes to produce a part will have to improve
as much as a hundredfold if 3-D printing is to compete directly
with conventional manufacturing techniques in most applications.
That won’t happen in the next few years.
Another problem: for now, only a handful of plastic and metal
compounds can be used in 3-D printing. In laser sintering, for
example, the material must be able to form a powder that will
melt neatly when it is hit with a laser, and then solidify quickly.
The compounds that meet the necessary criteria can cost 50 to
100 times as much by weight as the raw materials used in conven-
tional manufacturing processes, partly because they’re in such low
demand that they’re available only from small specialty suppliers.
As demand increases with new applications, however, supplier
competition should pull prices down dramatically. And the list of
available materials is slowly expanding. GE is trying to use ceram-
ics, which would open up new possibilities in engines and medical
devices, among other areas.
Simple experience, too, will do much to improve the technology.
So far, manufacturers don’t have enough data to predict exactly
how a part will turn out and how it will hold up, or how production
variables—including temperature, choice of material, part shape,
and cooling time—affect the results. That can be frustrating, says
Singh: “3-D printing often ends up being a black art. A part is
made out of thousands of layers, and each layer is a potential fail-
ure mode. We still don’t understand why a part comes out slightly
differently on one machine than it does on another, or even on the
same machine on a different day.” For example, the layering process
tends to build up interlayer stresses in unpredictable ways, so that
some parts end up distorted. Porosity can vary within parts as well,
leading to concerns about fatigue or brittleness. That could be a
big problem in aircraft engines or wing struts. “We know how to
make the metals strong enough,” says Boeing’s Vander Wel. “But
we worry about the unpredictability. Can we repeat a result to get
100 parts that are exactly the same? We’re not sure yet.”
Even with these challenges, time is on the side of 3-D printing,
says Vander Wel, and not just because the processes are improv-
ing. Engineers are understandably reluctant to embrace a new
technology for critical parts when their deadlines and reputations,
not to mention the lives of people in airplanes, are at stake. “But
younger designers are adapting more quickly,” he says. “ They’re
not so quick to say, ‘It can’t be built this way.’ ”
Dav i D H. FreeDman , a S cience Jou r naliSt baSe D in boSton, wr ote ab out optoge n eticS
in tH e november/December 2010 iS Sue oF TR. HiS lat e St book iS WRong: Why ExpE RTs
KEEp Failing Us.
preSSing print the photo at far left shows an array of metal jet-engine
components printed at ge. in the middle is a microprinter that ge uses to
test new ways of building things out of ceramic materials. researchers are
using the machine to print the transducers used as probes in ultrasound
machines; they believe it might save time and money while improving
design. on this page (top) is a transducer made in the printer; at bottom is
the same part after being refined and finished in other machines.
Jan12 Feature 3D Printing.indd 53
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