Using advanced additive manufacturing technology, researchers at the United Technologies Research Center and UConn have developed ‘smart’ machine components that alert users when they are worn or damaged.
The scientists also applied another version of the technology to make polymer-bonded magnets with complex geometries and arbitrary shapes, paving the way to new possibilities for manufacturing and product design.
The main factor to both innovations is the use of an advanced form of 3D printing known as direct write technology. In contrast to conventional additive manufacturing, which employs lasers to fuse layers of fine metal powder into a solid object, the direct write technology uses semisolid metal ‘ink’ that is extruded from a nozzle. The metal ink’s viscosity looks like toothpaste being pressed out from a tube.
This process enabled the UConn-UTRC researchers to form fine lines of conductive silver filament that can be embedded into 3D printed machine components while they are being created. The lines, which are capable of conducting electric current, serve as wear sensors that can identify damage to the part.
Here is how they function. Parallel lines of silver filament, each joined with a minute 3D-printed resistor, are fixed into a component. The interconnected lines become an electrical circuit when voltage is applied. As lines are fixed deeper and deeper into a component from the surface, each new line and resistor is allotted a progressively higher voltage value. Any damage to the component, such as abrasion or wear due to friction from moving parts, would cut into one or more of the lines, breaching the circuit at that stage. If more lines are cut, the damage is greater. Real time voltage readings allow engineers to evaluate potential damage and wear to a component without having to dismantle a whole machine.
To obtain a proper idea of how these micro sensors might be used, visualize them being embedded in the ceramic coating of a jet engine turbine fan blade. These blades are exposed to great physical forces and heat. A microscopic crack in the protective coating could possibly be disastrous to the blade’s performance, yet undetectable to the naked eye. With the embedded sensors, mechanics would be notified to any blade damage quickly so it can be looked into.
This changes the way we look at manufacturing. We can now integrate functions into components to make them more intelligent. These sensors can detect any kind of wear, even corrosion, and report that information to the end user. This helps us improve performance, avoid failures, and save costs.
Sameh Dardona, Associate Director of Research and Innovation at UTRC
The UConn-UTRC team was able to embed sensor lines that were merely 15 µm wide and 50 µm apart. That is a lot thinner than an average human hair, which is around 100 µm. This allows detection of very microscopic damage. Creating such a precise sensor is not easy. UConn associate professor of chemical and biomolecular engineering Anson Ma and a Ph.D. student from Ma’s Complex Fluids Laboratory, Alan Shen, measured and enhanced the flow properties of the silver-infused ink so that micron-sized lines could be consistently deposited without jamming the nozzle or causing extensive spreading after deposition.
Dardona from UTRC has applied for a patent for the embedded wear sensor technology.
The researchers also used direct write technology to develop novel components that have magnetic coatings or magnetic material implanted inside them. These polymer-bonded magnets can conform to any range of shape, and eliminate the need for individual housings in machines necessitating magnetic parts.
This opens up a lot of exciting opportunities. Imagine magnets that can take on different shapes and fit seamlessly between other functional components. Also, the resultant magnetic field that is created may be further manipulated and optimized by changing the shape of the magnets.
The magnet fabrication technique formulated by UConn and UTRC considerably enhances upon current manufacturing practices in other ways too. Current approaches for developing custom 3D-printed magnets depend on high-temperature curing, which regrettably decreases a material’s magnetic properties as a result. The researchers at UConn and UTRC discovered a way to sidestep that problem by applying low-temperature UV light to cure the magnets, just like how a dentist uses UV light to toughen a filling. The resultant magnets displayed considerably better performance than magnets made using other additive manufacturing techniques.
Magnets have a broad range of industrial applications, from generating electric currents in alternators to tracking the speed or position of moving parts as high-grade sensors. Embedding magnetic material directly into components could result in new product designs that are more aerodynamic, lighter, and efficient, Dardona says.
“This is a great example of collaboration between industrial research and academic research,” he says. “We always have new concepts that we’d like to try and explore. This collaboration allowed us to leverage the knowledge, expertise, and facilities available at UConn to help us address some of these technological challenges.”
The partnership also aids UConn. Shen, the Ph.D. student in Ma’s lab, served as a lead researcher on the two projects, creating, testing, and re-testing the new technology over the last three years.
These kinds of collaborations allow us to help companies like UTC develop new technologies that we know they are going to take to the next level. It’s also very rewarding for our students. Students involved in these projects are fully integrated into the research team. It’s not only great from a workforce development perspective; it also gives students a chance to work closely with professional engineers in a beautiful facility like UTRC.
More comprehensive information regarding the fabrication of the wear sensors can be found in an article in Additive Manufacturing. Details about the direct write production of polymer-bonded magnets have been reported in an article in the Journal of Magnetism and Magnetic Materials. Two UTRC engineers, Dustin Caldwell and Callum Bailey, also contributed to the study.
The study was made possible with the financial assistance from United Technologies Research Center and Connecticut Space Grant Consortium.