Metallic glass is the gear for robots Friday, 02 December 2016

A team from NASA's Jet Propulsion Laboratory (JPL) in California is making gears out of bulk metallic glass (BMG), a specially crafted alloy with properties they say make it ideal for robotics.

"Although BMGs have been explored for a long time, understanding how to design and implement them into structural hardware has proven elusive," said project leader Douglas Hofmann.

"Our team of researchers and engineers at JPL, in collaboration with groups at Caltech and UC San Diego, have finally put BMGs through the necessary testing to demonstrate their potential benefits for NASA spacecraft. These materials may be able to offer us solutions for mobility in harsh environments, like on Jupiter's moon Europa."

Hofmann says metals have an organised, crystalline arrangement but if you heat them up into a liquid, they melt and the atoms become randomised. If they are then cooled rapidly enough (about 1,000 degrees Celsius per second), you can trap their non-crystalline, 'liquid' form in place.

This produces a random arrangement of atoms with an amorphous, or non-crystalline microstructure, giving them their common names, amorphous metals or metallic glass. Since they were originally developed in 1960, metallic glasses have been used to manufacture everything from mobile phones to golf clubs.

BMGs have low melting temperatures allowing parts to be cast using injection-molding technology, similar to what's used in the plastics industry, but with much higher strength and wear-resistance.

They also don't get brittle in extreme cold, a factor which can lead to a gear's teeth fracturing. This is what makes them attractive for the kinds of robotics done at JPL.

"Being able to operate gears at the low temperature of icy moons, like Europa, is a potential game changer for scientists," said Peter Dillon, program manager in JPL's Materials Development and Manufacturing Technology Group.

"Power no longer needs to be siphoned away from the science instruments for heating gearbox lubricant, which preserves precious battery power."

[Gears made from bulk metallic glass don't get brittle in extreme cold. Photo: JPL]