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Where are the robot assistants we were promised?
For all the space that robots have occupied in the popular imagination for the last hundred years – and although the number of real-world robots has been growing for decades – most people’s interactions with them remain limited to a hands-free vacuum or child’s smart toy.
There are two main reasons for this, according to Glenn Garrett, Chief Technology Officer of NASA spinoff company, Amorphology – cost and safety. Most automated machinery is still only affordable to large manufacturers that can make major investments and expect long-term savings. And while robots take up more and more of the factory floor, they are generally segregated from their human colleagues due to safety concerns – largely oblivious to their surroundings, they are strong and dangerously clumsy.
In the mid-1990s, two Northwestern University professors patented an alternative concept under a new term – cobots (or collaborative robots) . Compared to traditional industrial robots, collaborative robots, which are designed to cooperate with humans, would be smaller, smarter, more responsive, and more aware, with tighter self-control and better mannered all around.
(Collaborative robots) is where the robotics industry is going. But if they cost $40,000, they are out of reach for non-industrial applications.
– Glenn Garrett, CTO, Amorphology
In the years since, leaps in artificial intelligence and sensors have made these “friendlier” robots a reality. Unfortunately, cost still limits their widespread adoption.
According to Garrett, the largest cost drivers for robots are not always the advanced software and sensors. Instead, it often comes down to some of the most rudimentary machine components – gears, which Garrett estimates account for at least half the cost of robotic arms.
Now, Pasadena, California-based Amorphology hopes to drop the price of cobots with advances originally made for robots that were never intended for human interaction – NASA’s planetary rovers (Figure 1, below).
Rovers Adapt to Martian Climate
Gears on NASA’s rovers, like most gears on Earth, are made of steel, which is both strong and wear resistant. But steel gears need liquid lubrication, and oils do not work well in frigid environments like the lunar or Martian surface.
Figure 1: NASA’s Curiosity rover spends about three hours heating up lubricants for its gears each time it sets out across Mars. To help future rovers save time and energy, NASA invested in bulk metallic glass for gears that require no lubrication. (Credits: NASA)
According to Doug Hofmann, Principal Scientist of the Materials Development and Manufacturing Technology group at NASA’s Jet Propulsion Laboratory (JPL), it is for this reason that NASA’s Curiosity rover spends about three hours warming up lubricants every time it prepares to start rolling. This process uses up about a quarter of the discretionary energy that could otherwise be used for science.
With an eye toward solving this and other materials-related issues, in 2010, JPL hired Hofmann, then a research scientist at California Institute of Technology (Caltech) with a background in materials science and engineering. NASA funded a new metallurgy facility at the Jet Propulsion Laboratory to explore alternatives for gears and develop new metal alloys.
Bulk Metallic Glass
From his days at Caltech, which manages JPL, Hofmann was familiar with an emerging class of specially engineered materials called bulk metallic glass, also known as amorphous metals. These are metal alloys that 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.
Figure 2: Most metallic glass alloys form a hard, smooth surface. This gives metallic glass gears a long lifetime without the need for liquid lubricants, making them appealing for NASA robotics that operate in cold environments, where lubricants need to be warmed before operations.
Depending on their constituent elements – often including zirconium, titanium, and copper – metal alloys can be very strong, and because they are not crystalline, they are elastic. Most compositions also form a hard, smooth ceramic oxide surface, and these properties together afford gears made of some amorphous metals a long lifetime with no lubrication (Figure 2, above).
According to Hofmann, it is the unique properties metallic glass alloys that makes them attractive to NASA. Metallic glass gears do not require liquid lubricants. Metallic glass gears can also operate in temperatures below minus 290 degrees Fahrenheit without requiringa heating source.
(The Flexplines) is a very strange-looking gear if you have never seen it, but it is the heart and soul of a precision robot.
– Glenn Garrett, CTO, Amorphology
Affordable Robot Parts
Amorphous metals have another property that makes them attractive for gears on Earth. The alloys used to make metallic glass have low melting temperatures.
Most high-strength metals have high melting points. They cannot be cast with molds because, in molten form, they would simply melt the mold. And steel needs to be rolled or forged to strengthen it, which also precludes molding. So, gears typically start as steel billets that are ‘machined’ – cut, ground, milled, and drilled – into their final shape. Tiny gears, like those for small cobots, are especially challenging – and costly.
Figure 3: Flexsplines are thin, flexible, cup-shaped gears integral to strain wave gears common in robotics. They’re typically cut, ground, and drilled from steel billets in a process that is long and costly. The flexspline on the right was injection molded from metallic glass in a cheaper, simpler process.
The low melting point of alloys used to make metallic glass, together with their native strength, and the fact that their volume hardly changes upon solidifying, makes bulk metallic glasses easy to use in injection molding. Injection molding 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. Flexsplines are extremely thin-walled, flexible cups with a toothed rim (Figure 3, above).
Flexplines are the centerpiece of what is known as a strain wave gear assembly (Figure 4, below). Strain wave gears provide better precision, higher torque, and lower backlash than other gear sets. This eliminates positioning errors which would be compounded in a robotic limb with multiple joints.
Figure 4: A strain wave gear converts the fast, low-torque rotation of an engine into slow, precise, forceful motion. As the oblong wave generator at the center spins, it deforms the flexspline around it, shown in red, which engages with the teeth of a fixed outer spline. The interaction causes the flexspline to rotate in the opposite direction of the wave generator, moving only two teeth for each turn of the motor. (Credits: Jahobr, CC0 1.0)
According to Hoffman, it is injection molding of strain wave gears with amorphous metals that promises the greatest savings. Injection molding costs about half as much as machining strain wave gears from steel.
Amorphology’s Business Plan
Molding small, high-performance planetary and strain wave gears became the central business plan for Amorphology, which Hofmann cofounded in 2014. Through Caltech, the company licensed several patents for technology he had developed for NASA.
Meanwhile, Hofmann and colleagues continued pursuing new materials for spacecraft at both the metallurgy lab and JPL’s Additive Manufacturing Center. A number of patents and technologies led Hofmann to found a second spinoff company focused on using amorphous metals in coatings, 3D printing, and other non-gear-related applications. Both were backed by the same venture capital group, and in 2020 they merged under the Amorphology name, combining about 30 patents and patent applications for the technology from JPL.
Amorphology’s first and largest customer is one of the world’s foremost manufacturers of strain wave gears. In addition, at least one other customer has hired the company to coat consumer electronics parts with metallic glass, making them more durable, indicating another market with immediate potential.
A Market Beyond Mars
Also in 2020, the merged company finished its move into a new, 13,000-square-foot manufacturing facility where about 15 people now work, mostly making and testing prototype pieces for small gear assemblies for several customers.
Amorphology’s first and largest customer is one of the world’s foremost manufacturers of strain wave gears. In addition, at least one other customer has hired the company to coat consumer electronics parts with metallic glass, making them more durable, indicating another market with immediate potential. Hofmann noted that gears that can operate without lubrication are also of interest to businesses like food manufacturing, where lubricants can become contaminants.
Meanwhile, many of the company’s other patents for JPL technology – all licensed from Caltech – are probably still years away from commercialization, although they are in fields that are gaining heavy interest. Among these are new alloys and advanced metal 3D printing technologies, from thermal spray additive manufacturing to ultrasonic welding.
NASA Technology Transfer
NASA has a long history of transferring technology to the private sector, and Amorphology is not the first company to commercialize innovations in bulk metallic glass from JPL and Caltech. But Garrett notes that creating a startup based on new materials is notoriously difficult. If lubrication-free gears or low-cost flexsplines find a long-term market, “that would be a huge step towards sustained commercial success for bulk metallic glass,” he said.
About the Author
Mike DiCicco is a longtime writer and Managing Editor for Spinoff, a publication of the Technology Transfer program in NASA’s Space Technology Mission Directorate. Spinoff profiles NASA technologies that have transformed into commercial products and services, demonstrating the broader benefits of America’s investment in its space program.
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