Dec 20, 2017 | By Benedict

GE is using a supersonic cold spray 3D printing system to fabricate large metal parts such as jet engine airfoils. The 3D printing system consists of two robotic arms, one of which holds the part while the other sprays it with a barrage of metal powder.

When GE revealed its monstrous ATLAS demonstrator 3D printer earlier this year, we didn’t think the meter-class power bed fusion machine would be beaten for size anytime soon—not least by GE itself. But according to a new report from the company, an unusual new additive manufacturing technique could result in larger metal parts than ever before.

Leo Ajdelsztajn and a team of scientists at GE Global Research are harnessing the power of cold spray, a technology that uses a supersonic nozzle to shoot a barrage of tiny metal specks at four times the speed of sound, to fabricate large metal parts such as functional components for the aerospace industry.

The cold spray system developed by the scientists uses two large robotic arms, one of which is responsible for holding a part while the other sprays the part via the supersonic nozzle. Working in tandem, these robots move together in a fully coordinated 12-degrees-of-freedom space, allowing them to move, tilt, and pitch in different directions.

The freedom of movement afforded by the twin robotic arms means the system can fabricate very large metal parts, while also enabling a higher level of intricacy, since the nozzle can effectively be sprayed from any angle.

It’s a huge leap for 3D printing. In Ajdelsztajn’s words, it means engineers are no longer “confined to a specific build volume or size,” since the robots, equipped with advanced machine learning software, are not contained within an enclosed printing area.

To demonstrate its power, the robotic system has already been used to 3D print an airfoil for a jet engine, marking a further milestone on GE’s already lengthy journey into aerospace additive manufacturing.

The futuristic project isn’t just about covering more cubic centimeters though. In fact, the intelligence inside the 3D printing system is vital to its effectiveness, since it allows the system to learn by analyzing the set of instructions followed each time a part is made. GE likens this practice-makes-perfect approach to artistry.

“Imagine painting the same picture 40,000 times per year,” says GE scientist Joe Vinciquerra. “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. By applying those changes in real time, the quality of every new painting increases.”

Cold spray, of course, wasn’t just plucked from thin air. GE has used the process before, but generally as a way to repair metal parts. In October, for example, GE Aviation company Avio Aero used cold spray to repair a gearbox on the GE90, the world’s most powerful jet engine.

It’s easy to see why the technique was chosen to fix the aviation component. When the supersonic nozzle fires metal powder at the part, the tiny pieces land with such force that the solid particles start behaving like liquid, forming an atomic diffusion bond. The liquid-like metal can then form a new layer on top of the damaged area, which makes the process ideal for restoring worn-out sections of a component without changing its mechanical properties.

But when GE successfully repaired the GE90 gearbox, it was already looking ahead to new possibilities: namely, using the cold spray method not just to add fresh layers to existing parts, but to fabricate new parts from scratch.

And now that GE has appropriated cold spray as a unique form of 3D printing, Adelsztajn—sticking with the art analogy—says the technique is “a different brush in the painter’s kit.”

“One way in which we are building our additive toolbox is by looking at how each additive technique balances the others,” he adds. “An artist wouldn’t limit themselves to one color of paint and one size brush.”

The GE scientists say this new cold spray approach could have exciting applications in aviation, energy, and elsewhere.

Posted in 3D Printer

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