Lasers, fusion, and SPACE: Julien Cohen curates Real Scientists

Real Scientists is donning the appropriate personal protective equipment (PPE) this week with Julien Cohen (@jul_coh), Lead Engineer at Eaton’s Additive Manufacturing Center of Excellence in Michigan, USA. His current work focuses on industrializing laser powder bed fusion for flight-certified aerospace hardware. This cross-disciplinary work blends particle and laser physics, heat transfer, fluid dynamics, precision machine design, and design engineering…which sounds pretty supervillain-y, which is exactly how we like things here at Real Scientists. Julien chatted to us about his work so far:

Welcome to Real Scientists! How did you get here?DSC06037
I was always curious about how things worked– destroying countless household objects in my childhood trying to figure out the internal mechanisms. Various childhood events (my grandfather giving me a random circuit board and telling me it could call Batman when I was 5), childhood reading (Hawking’s Universe in a Nutshell, Asimov’s Robots), and in general an internet/network-mediated childhood pushed me towards studying science.

How did you decide to focus on mechanical engineering?
I have always been interested in the intersection of the digital and physical world, and the link between data and matter (if you can even make that distinction, that’s a separate but fascinating discussion). For me, additive manufacturing is the cutting edge of how humanity is extruding digital creativity into physical reality.

What are you working on right now?
The process I’m currently working on is called Laser Powder Bed Fusion, or L-PBF (you’ll see it also as DMLS, SLM, DMLM, and a dozen other acronyms). Basically, we spread a very thin layer of metal powder, hit that powder with a laser to melt in into the previous layer in a highly accurate 2D pattern, and repeat those steps a few thousand times until we’ve built a bunch of metal parts. Using this method of “slicing” a 3D shape into many 2D layers, parts can be built with essentially infinite complexity.

Doing this once isn’t that hard. Anyone with a few $100k can go buy a machine, get laser parameters from the machine manufacturer, and start building parts. To do this process repeatably, robustly, with consistent quality, over many years, over dozens of machines, in industries regulated by the FAA/EASA or FDA, while hitting cost targets… this is the real challenge.

What do you want the public to know about your work?
Additive manufacturing (AM) is kind of a “wonky” field of work, in the same way that the majority of the general public doesn’t care about advances in CNC machining or investment casting… but these advances and their scientific bases are what make cars cheaper and safer, planes more efficient, computers use less energy, and rockets reusable.

AM is a key tool in the toolkit of the technologists working today to build our collective future.

What do you get up to outside work?
I’ve practiced Brazilian Jiu Jitsu for around 7 years, I cook extensively, photograph the outdoors/animals/night sky, and solo backpack in the wilderness as much as possible.

What does a perfect day off look like for you?
Morning Jiu Jitsu training followed by a delicious breakfast, read a book in a hammock, then meet up with good friends for a hike in the mountains and a live music show at night.


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