In early 2022, the Cold Operable Lunar Deployable Arm (COLDArm) project, led by NASA's Jet Propulsion Laboratory in Southern California, successfully integrated special gears into the robotic arm's components, according to 3D Science Valley's Market Watch. The robotic arm is slated for use in lunar missions in the next few years.
Integrated into COLDArm's joints and actuators, these bulk metallic glass (BMG) gears were developed through the game-changing project to develop bulk metallic glass (amorphous alloy) gears that can operate at temperatures below 280 degrees Fahrenheit (minus 280 degrees Fahrenheit). 173 degrees Celsius) extreme temperatures. In this issue, 3D Science Valley and Gu Friends come together to gain insight into how the development of technology promotes the progress of human beings' ability to explore the universe.
Start the commercialization process of 3D printed metallic glass
Amorphous metal (metal glass), also known as amorphous alloy, has both the advantages of metal and glass and overcomes their respective disadvantages. Such as glass brittle, no ductility. The strength of metallic glass is higher than that of steel, the hardness is higher than that of high-hardness tool steel, and it has certain toughness and rigidity. Therefore, people praise metallic glass as the "king of glass" that "cannot be broken or smashed".
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Amorphous metals combine many excellent properties, such as high strength, high hardness, wear resistance and corrosion resistance. These excellent properties make it have broad application prospects in aerospace, automobile and ship, armor protection, precision instruments, electricity, energy, electronics, biomedicine and other fields.
According to the ACAM Additive Manufacturing Center in Aachen, the development trend of 3D printing-additive manufacturing is towards a multi-dimensional deepening level, facing mass production applications, 3D printing breaks through the economic requirements of current applications, and extends to the application side. One development path is to implement products with more complex structures.
/ Self-lubricating gears for low temperature operation
The metal-glass gear alloys in the robotic joints and actuators of NASA's COLDArm project have a disordered atomic-scale structure that makes them both strong and elastic enough to withstand these unusually low temperatures. Typical gearboxes require heating to operate at such low temperatures. BMG gear motors have been tested and successfully operate at approximately -279 degrees Fahrenheit (-173 degrees Celsius) without heating assistance. This gear motor is one of the key technologies that enables the robotic arm to operate in extremely cold environments, such as during lunar nights.
One of four assembled robotic joints, including bulk metal glass gear motors for each joint of the COLDArm robotic arm
© Motiv Space Systems, Inc.
Each of the four joints containing the BMG gears will be tested after the arm is fully assembled, robotic joint testing will include dynamometer testing to measure torque/rotation speed and cryogenic thermal vacuum testing to see how the device will perform in a space-like environment application in. Once tested, the BMG gear and COLDArm cold-operable lunar deployable arm will perform future missions in the extreme environments of the Moon, Mars and ocean worlds.
© Motiv Space Systems, Inc.
The COLDArm project is funded by the Lunar Surface Innovation Program and managed by the Game-Changing Development Program of NASA's Space Technology Mission Directorate. Under NASA's Small Business Innovation Research Program, a company called Motiv Space Systems is leading the design and manufacture of the COLDArm arm and motor controller, which 3D Science Valley believes may usher in a new era of collaborative robotics applications.
/ High-precision gears and collaborative robots
In the mid-1990s, two Northwestern University professors patented a new term for an alternative concept: collaborative robots. Cobots designed to work with humans will be smaller, smarter, more responsive and aware, with tighter self-control and better manners. In the years since, leaps in artificial intelligence and sensors have made these "friendlier" robots a reality, but cost still hinders their widespread adoption.
However, the biggest cost factor is not always advanced software and sensors. It also boils down to some of the most basic machine parts: gears, for example, which are known to cost at least half as much as a robotic arm in the manufacture of some cobots.
Now California-based Amorphology wants to bring down the price of cobots, technology originally built for robots never used for human interaction (NASA's planetary rover).
Like most gears on Earth, the gears on the NASA rover are made of steel, which is strong and wear-resistant. But steel gears require liquid lubrication, and oil doesn't work well in cold environments like the surface of the moon or Mars. So, for example, NASA's Curiosity rover spends about three hours heating up the lube each time it's ready to start rolling, consuming about a quarter of its discretionary energy.
Metallic glasses (amorphous alloys) can be rapidly cooled from liquid to solid before their atoms form a lattice structure common to all other metals. The atoms are arranged randomly like glass, giving glass and metals their material properties. Depending on their constituent elements — which typically include zirconium, titanium, and copper — metallic glasses can be very strong, and because they are not crystalline, metallic glasses are elastic.
Most compositions also form hard, smooth ceramic oxide surfaces, which together provide gears made from some amorphous metals with long life without lubrication. This is very important to NASA because the gearbox can be run without lubricating it.
Currently, the Cold Operable Lunar Deployable Arm (COLDArm), co-developed by Motiv Space Systems for lunar missions, is expected to operate in temperatures as low as -290 degrees Fahrenheit using bulk metallic glass gear without the need to install a heat source.
Metallic glasses (amorphous metals) have another property, these alloys are designed to have low melting points, because to make metallic glasses, the alloy must be allowed to cool faster than it crystallizes. This low melting point, combined with their inherent strength and The fact that their volume hardly changes when cured can greatly reduce the cost of manufacturing parts such as gears.
However, the fabrication of metallic glasses (amorphous metals) is a challenging process, especially the formation of amorphous metallic glasses, which typically require above their melting temperature and rapid cooling to avoid crystallization. The manufacturing process requires extraordinary cooling rates and limits the thickness they can be formed into, as thicker sections are difficult to cool quickly.
The most difficult and expensive gear part to machine from a steel block is one of the most common in robotic arms: the flexspline, an extremely thin-walled flexible cup with toothed edges. This is the heart of a so-called wave gear assembly, and flexsplines offer better precision, higher torque and lower backlash than other gear sets. This eliminates positioning errors that can occur in robotic limbs with multiple joints.
A flexspline is a very strange looking gear, but it is the heart and soul of a precision robot. According to 3D Science Valley, this is where forming with amorphous metal can provide the greatest cost savings: the cost is about half the cost of machining a strain wave gear from steel.
/ Self-lubricating gears and metallic glass
Forming small high-performance planetary gears and strain wave gears became the core business initiative of Amorphology, which was founded in 2014. Through Caltech, the company has been awarded multiple patents for technology developed for NASA.
Amorphology isn't the first Caltech company to commercialize a metallic glass innovation, but it's notoriously difficult to create a startup based on a new material, according to 3D Science Valley's market understanding. Among the difficulties are the need to find a long-term market for the material, and bulk metallic glass (BMG) gears are a big step toward continued commercial success of BMG.
According to the market research of 3D Science Valley, in 2017, the California Institute of Technology obtained a patent for amorphous metal through additive manufacturing technology. It is worth mentioning that the inventor of the patent, Douglas Hofmann, is the founder of Amorphology.
The method of manufacturing amorphous metal at Caltech is: melting the surface of the first layer of metal alloy at high temperature; rapidly cooling the layer of molten metal alloy to solidify to form the first layer of amorphous metal; then proceed to the next layer on this basis processing. In this process, a "spraying technique" is applied to each layer, including methods such as plasma spraying, arc spraying, etc. The raw materials that can be used in "spraying technology" include: metal wire and metal powder. According to 3D Science Valley's market research, the "spraying technology" is DED direct energy deposition 3D printing technology.
/ Self-lubricating gears for low temperature operation
According to market research by 3D Science Valley, the commercialization of amorphous metals has become a hot topic in the metal additive manufacturing community in 2017. According to the market observation of 3D Science Valley, EOS has also invested in Exmet, an amorphous metal 3D printing start-up. Instead of the DED technology used, Exmet has an EOS M 290 metal 3D printer in its factory for the manufacture of high-performance amorphous metal parts.
According to 3D Science Valley’s market observations, Exmet has also cooperated with Heraeus to develop amorphous metal 3D printing technology, and Heraeus announced in early April 2019 that they manufactured through SLM (Selective Area Laser Melting) 3D printing technology of amorphous metal gears. Heraeus says it is the largest amorphous metal component in the world to date, and they are pushing the boundaries of amorphous metal manufacturing, opening up new design possibilities for amorphous metals in manufacturing. The 3D-printed amorphous metal gears developed by Heraeus use a topology-optimized structure, which can reduce the weight of the gears by 50% compared to traditional manufacturing processes. With SLM 3D printing, Heraeus redefines the limits of traditional technology in terms of the size and design complexity of amorphous metal gears, changing the design possibilities of this type of material.
According to the Institute of Physics, Chinese Academy of Sciences, China has achieved international attention on the basic scientific issues of metallic glass in the past 10 years. For example: the discovery and characterization of beta relaxation in metallic glasses, the rheological mechanism of metallic glasses, the phase transition in metallic glasses, the fracture criterion of metallic glasses, the physical interpretation of the fracture morphology of metallic glasses, the elastic model of metallic glasses, etc. Research. Over the past half century, metallic glass has developed into a material that is eagerly selected by high-tech such as aerospace and fashionable products such as mobile phones and laptop computers. As a new type of metallic material with glass, metal, solid and liquid properties, metallic glass has maintained many of the highest records of metallic materials, such as: so far, metallic glass is the strongest and softest metallic material, and the strongest armor-piercing It is the most easily processed metal material, the most corrosion-resistant metal material, and one of the most ideal micro- and nano-processing materials. Metallic glasses have the characteristics of heredity, memory, soft magnetism and large magnetic entropy, and are also model systems for studying some important issues in materials science and condensed matter physics.
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