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.

Most automated machinery is still only affordable to large manufacturers that can make major investments and expect long-term savings. While robots 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.

Pasadena, CA-based Amorphology hopes to drop the price of cobots with advances originally made for robots that were never intended for human interaction: NASA’s planetary rovers.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 lubricants every time it prepares to start rolling, using up about a quarter of the discretionary energy that could otherwise be used for science.

(Left) The planned Dragonfly rotorcraft-lander, which will explore Saturn’s moon Titan, could benefit from metallic glass gears that can operate in extreme cold. (Right) NASA’s Curiosity rover has to spend about three hours heating up lubricants for its gears each time it sets out across the planet’s surface. To help future rovers save time and energy, NASA has invested in bulk metallic glass for gears that require no lubrication. (Credit: NASA)

NASA has worked with specially engineered materials called bulk metallic 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.

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 a robotic limb with multiple joints.

This is where molding with amorphous metals promises the greatest savings — it costs about half as much as machining strain wave gears from steel. Molding small, high-performance planetary and strain wave gears became the central business plan for Amorphology, whose first and largest customer is one of the world’s foremost manufacturers of strain wave gears. Meanwhile, many of the company’s other patents for NASA technology include new alloys and advanced metal 3D printing technologies.

Read this article and other NASA Spin-Offs at NASA.gov .


Tech Briefs Magazine

This article first appeared in the October, 2021 issue of Tech Briefs Magazine.

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