GE Global Research Developing Cold Spray Technology, Speeding Up Laser 3D Printing Processes

Cold spray technology involves metal powder fed through a supersonic nozzle, attached to a robotic arm, at high pressure and into a heated nitrogen or helium gas stream. Then, many tiny metal specks are fired at the surface of the part in question at four times the speed of sound, and the force of the landing causes the solid-state particles to behave like a liquid and form an entirely new layer, without changing the original mechanical properties. The process integrates artificial intelligence and robotics, and is often used for metal coatings or repairs. Earlier this year, engineers at Avio Aero, a GE Aviation company in Italy, used cold spray to repair a gearbox on the powerful GE90 jet.

But a team of scientists at GE Global Research, led by Leo Ajdelsztajn, aren’t satisfied with this 3D printing milestone, and are working to develop ways that cold spray, which is also known as 3D painting, can be used to build new parts, and not just fix existing ones.

Ajdelsztajn explained, “One of the advantages of cold spray as an additive manufacturing modality is that we are not confined to a specific build volume or size.”

Ajdelsztajn’s team have been developing the technology so it can work on a larger scale, adding in machine learning and a second robotic arm, which holds a part and moves it to a precise location so the first arm can spray it with powdered metal. The experimental design has already been put to work successfully building a jet engine airfoil.

The robotic arms are perfectly choreographed, moving together in a coordinated space with 12° of freedom, which means they can move up and down, forward and back, and pitch and tilt in opposite directions. But, if they don’t work in exact precision, the technique is not effective, and could even ruin a part. So the team reached out to GE scientist Joe Vinciquerra, who has also told us about his work exploring how to integrate machine learning and AI into manufacturing technologies like 3D printing, and he suggested making the robotic arms learn while they’re working, which means they will improve each time they make a new part.

“Imagine painting the same picture 40,000 times per year. Not every picture will be identically the same — even if a machine is doing it. Some will be better than others, and we can learn from those minute differences,” said Vinciquerra. “By applying those changes in real time, the quality of every new painting increases.”

According to Vinciquerra, the robots should improve over time, analyzing their given set of instructions after they make each part, which will limit future mistakes.

There are many different methods of additive manufacturing available, and GE Global Research has been working to speed up AM processes for a while now.

Bob Filkins, a senior principal engineer in Additive Technologies at GE Global Research, said, “One of the limitations of the technology today is that we can only print so fast.”

Most metal 3D printers weld extremely fine layers of powder – no more than the width of a human hair – with a 400 watt laser beam into finished parts. Filkins, who is one of GE’s Laser Masters, and his team believe that powerful lasers could be used to speed up the process, but currently, this would cause major consequences.

Filkins explained, “If we just arbitrarily took larger lasers and shot them at the powder bed, it would blow up.”

He believes that if 3D printers can use powerful lasers that are ten times more intense than the ones currently being used, parts could be built much more quickly, without compromising the design. His analogy centers around painting a room – a painter using a tiny paintbrush will take a long time to finish the room, though the work will be very precise. If the painter uses a roller instead, the job would be completed much more quickly.

Filkins and his team are actually developing 3D printing laser paint rollers, which basically equates to the shape of the laser beam hitting the metal powder having a more complex pattern. According to Filkins, expanding the footprint of the laser even a little bit will help – the extra wattage will add to the laser’s broader footprint, which will help it quickly cover more ground.

“Just consider that GE Aviation will be printing well over 200,000 fuel nozzles to meet their CFM LEAP engine orders. If we could print these parts 10 times faster, we would save 40 million build-hours,” Filkins said.

At formnext last month, GE Additive unveiled the first BETA machine developed for its Project A.T.L.A.S. (Additive Technology Large Area System) development program to develop the next generation of large additive machines. While 3D printing typically takes place in a confined space, the Project A.T.L.A.S. machine, designed to be the world’s largest metal 3D printer, can build parts as large as one meter along each axis, and increasing the speed of the machine is key.

Filkins said, “As the industry looks to scale in size of machines and parts being made, higher speeds are essential to keep build times feasible.”

The team should have a working prototype of the 3D printing laser paint roller sometime next year.

“In 60 years, laser technology itself has transformed so many industries and applications from surgery in the operating room to the internet itself. Now we have an opportunity to transform manufacturing as we know it, which is very exciting,” said Filkins.

In addition to laser modalities, GE Additive has also recently announced its intent to expand into binder jetting technology as the company continues to enhance its profile in metal additive manufacturing techniques.

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