Tech Briefs Magazine - October 2021 - 56

SPINOFF
ost automated machinery is still
only affordable to large manufacturers
that can make major investments
and expect long-term savings. While ro -
bots take up more of the factory floor,
they're generally segregated from their
human colleagues due to safety concerns
- largely oblivious to their surroundings,
they're strong and dangerously clumsy.
In the mid-1990s, two Northwestern
University professors patented an alternative
concept under a new term: cobots.
Collaborative robots, designed to cooperate
with humans, would be smaller,
smarter, more responsive, and more
aware, with tighter self-control. In the
years since, leaps in artificial intelligence
and sensors have made these cobots a
reality but cost still prevents their widespread
adoption. The biggest cost drivers
aren't always the advanced software and
sensors - it often comes down to rudimentary
gears.
M
Flexsplines are thin, flexible, cup-shaped gears
integral to the strain wave gears common in
robotics. The flexspline on the right was injection
molded from metallic glass in a cheaper,
simpler process. (Credit: NASA)
lubricants every time it prepares to start
rolling, using up about a quarter of the
discretionary energy that could otherwise
be used for science.
NASA has worked with specially engineered
materials called bulk metallic
Pasadena, CA-based Amorphology
hopes to drop the price of cobots with
advances originally made for robots that
were never intended for human interaction:
NASA's planetary rovers. Gears on
NASA's rovers are made of steel, which is
both strong and wear-resistant. But steel
gears need liquid lubrication and oils
don't work well in frigid environments
like the lunar or Martian surface. So,
NASA's Curiosity rover, for example,
spends about three hours warming up
glass, or amorphous metals. These metal
alloys can be rapidly cooled from liquid
to solid before their atoms form the crystalline
lattice structure that is common to
all other metals. Instead, the atoms are
randomly arranged like those of glass, giving
the materials properties of both glass
and metal. Depending on their constituent
elements - often including zirconium,
titanium, and copper - they can
be very strong and because they aren't
crystalline, they're elastic. Most compositions
also form a hard, smooth ceramic
oxide surface. These properties together
afford gears made of some amorphous
metals a long lifetime with no lubrication.
Spinoff is NASA's annual publication featuring
successfully commercialized NASA technology. This
commercialization has contributed to the development
of products and services in the fields of health and
medicine, consumer goods, transportation, public safety,
computer technology, and environmental resources.
Metallic Glass Gears Up for Cobots, Coatings, and More
A bulk metallic glass could slash prices of collaborative robots and lead to advanced
3D-printed metals.
Amorphous metals have a property
that makes them attractive for gears on
Earth: low melting point. Together with
their native strength and the fact that
their volume hardly changes upon solidifying,
bulk metallic glasses are easy to
use in injection molding, which can dramatically
reduce the cost of making
parts like gears.
The most difficult, expensive gear component
to machine from a steel block is
one of the most common in robotic arms:
the flexspline, an extremely thin-walled,
flexible cup with a toothed rim. This is
the centerpiece of a strain wave gear
assembly, which offers better precision,
higher torque, and lower backlash than
other gear sets. This eliminates positioning
errors that would be compounded in
https://spinoff.nasa.gov/metallic-glass-gears http://www.techbriefs.com http://info.hotims.com/79418-936
Tech Briefs Magazine - October 2021

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