Campbell, CA

Over the past four years, Enrique Enriquez, president of KW Micro Power, has worked in pursuit of his company’s goal: a microturbine generator roughly the size of a microwave oven that can crank out more power than systems ten times larger. He ran into some major roadblocks while attempting to manufacture one of the device’s key components and considered scrapping its design and starting over; however, he found the SupportFree metal powder-bed 3D-printing technology from VELO3D that got him back on track for a commercial launch by early next year.

Enriquez met Zach Murphree, vice president of technology partnerships at VELO3D, who reviewed the design, which was named the “spaceship.” Murphree built the part for Enriquez and helped him improve it significantly. The component is a titanium disc roughly 10" in diameter and 4" tall, whose interior contains a complex labyrinth that channels exhaust gases far more efficiently than conventional systems. It is the heart of KW Micro Power’s turbine technology.

It was also the system’s Achilles heel. Until he connected with VELO3D, Enriquez was unable to find anyone willing to make it for him and was turned down repeatedly by 3D-printing service bureaus and machine builders. It wasn’t until he discovered a company willing to work with him on his project. “I was talking to a friend of mine there about the problem, someone very knowledgeable about 3D printing, and explained that everyone was telling me it was impossible,” said Enriquez. It was then suggested that he speak with VELO3D.

The challenge no one else would take on was the microturbine’s internal channels. Most additive manufacturing technologies, and especially those that print metal, require a series of scaffold-like supports to keep the workpiece from drooping and warping during the build process. Though expensive and time-consuming, it’s accepted industry practice to machine or grind these supports away post-build. This can’t be done with small internal features — something that the spaceship is full of.

VELO3D came back with a test piece and then offered to take the design much further. A few weeks later, a redesigned spaceship was delivered that leverages every feature needed to keep the design functional, but at the same time is built around the bare necessities. Looking forward to a 2020 commercial launch, Enriquez is planning a selection of prototypes and already has interest from two companies, one in the drone business and the other in the directed-energy (laser/microwave) business.

Before (above) and after (below) images of a shrouded impeller illustrate how VELO3D eliminates the need for supports (in red) during the 3D-printing process.

VELO3D was founded five years ago by people who are from the semiconductor industry, according to Murphree, “so the initial focus was on developing a process with that same high level of control. We also wanted to produce a machine that’s able to print parts and features that nobody else can. This was the genesis of our Sapphire 3D-printer and its Flow build software.”

There are several key differences between Sapphire and other metal powder bed printers. The first is its SupportFree technology that provides the ability to print near-horizontal surfaces without supports; most printers can’t print features support-free if less than 45 degrees from level. This helps fulfill 3D printing’s mantra of “unlimited design freedom” for Sapphire-produced parts. There’s also a non-contact recoater that virtually eliminates build crashes and contamination that may occur when a traditional recoating blade drags across the top of a burgeoning workpiece.

The VELO3D Sapphire printer includes closed-loop melt-pool control, feature-specific processing, and a non-contact recoater, all of which help to reduce internal stresses in metal 3D-printed parts.

Another significant difference is the use of feature-specific processing. Where most machines use the same laser power, traverse rates, and other build parameters across an entire part layer — and often for the whole build — Sapphire can apply more than 20 geometry-dependent “recipes” to specific sections within each layer. The result is less metallurgical stress, greater part accuracy, and faster build times. And to make sure that all is going according to plan, Sapphire comes standard with advanced metrology to assure quality and reduce variability.

Said Murphree, “We can precisely define how much energy is applied anywhere within the build, which is a large part of the reason why we’re basically support-free. We’re able to calibrate and align the lasers at each layer if that level of precision is necessary. There’s also the enhanced atmosphere control, the quantitative metrology behind the powder bed and recoating system — there are many significant architectural differences between our system and others that allow us to operate within this extremely small process window.

VELO3D was able to print the perfect spaceship on the very first try. “Instead of doing four iterations over six weeks, we might deliver the first iteration in one week, as we did for KW Micro Power,” Murphree said.

On the left is a cross-section of a stator ring. The red areas indicate deformation during the 3D-printing process. The part on the right shows how VELO3D’s Flow software predicts and eliminates this deformation.

Software has a significant role in the fight for higher print yields. VELO3D’s Flow™ software simplifies print preparation while preserving design intent. It accurately simulates the entire build, analyzing, displaying, and correcting for potential deformation long before the laser ever lights up. Similarly, its composer function optimizes each layer, detecting part geometries and applying the feature-specific processing methods described earlier. The outcome is typically first part, good part.

With the spaceship, this would have been practically impossible, even if the other additive providers hadn’t turned away from the project. That’s because the Ti-6Al-4V alloy Enriquez chose for his microturbine component can be a challenge to work with.

“Thanks to all the internal stresses that typically build up with laser sintering, titanium likes to crack — in the worst case, the part essentially tears itself to pieces or rips itself away from the substrate that you’re printing it on,” Murphree explained. “And the bigger the part, the worse it gets. In 3D-printing terms, the spaceship is relatively massive. We knew this going into the project and built in some additional time but our ability to manage the stress inherent to printing large Ti parts was clearly demonstrated with that successful first print.”

Said Enriquez, “With small engines like mine, efficiency is hard to achieve, and I knew I would have thrown much of that away if I’d had to adopt a more traditional design. But to be honest, I never expected that VELO3D could pull it off. I’m delighted to say that I was wrong. Not only did they print my spaceship, they made it even better. It’s 37% lighter than when I started, the performance is better due to reduced stresses, it’s clearly manufacturable.”

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