3D Printing 50 Polymer Stand-In Parts for Tokamaks at the PPPL & Elytt Energy

Of all the world’s things, a tokamak is one of the hardest, most complex, expensive and exacting ones to make. These fusion energy devices make plasma, and use magnets to channel it in order to create a fusion reaction. Essentially, a tokamak is an experiment to create a little mini sun here on Earth. The promise is an incredibly vast amount of energy reserves on tap. Tokamaks have been under development since the 1950s.

Within the US Department of Energy, the Oak Ridge National Laboratory (ORNL) and others have been working on the National Spherical Torus Experiment (the largest spherical tokamak in the US) at Princeton Plasma Physics Laboratory (PPPL) since 1999; this became the National Spherical Torus Experiment-Upgrade (NSTX-U) version in 2012. The system is a pilot for a spheroidal tokamak design which, if successful, could lead to pilot plants making energy commercially.

Now a 3D printed part is meant to be a stand-in for the all-important magnet component. The toroidal field magnet is currently being made in Spain by Elytt Energy, a specialized firm that makes magnets, flywheels, and power supply units for particle accelerators and tokamaks. Meanwhile, the rest of the tokamak is under assembly in Princeton. To sub for the magnetic coil, a polymer 3D printed part has been created. Measuring one meter by 60 centimeters, the prototype has been described as “the best money we ever spent” by NSTX-U project manager Tom Jernigan. The component helps the team correctly assemble and fit the rest of this super complex device in advance, mitigating delays. It’s also better that the team find any assembly problems now, rather than once they have the magnet in 2026.

NSTX-U project director Dave Micheletti stated that,

“The use of 3D-printed prototypes has been instrumental toward reducing risk and accelerating the schedule. It allows us to positively confirm that components will fit together and eliminates the risk of rework once final assembly starts. It’s saving both time and money.”

Of particular interest is the fit and assembling of 36 cooling coils at the top of the component. In total, this tokamak has 50 3D printed parts, like brackets, supports, and for electrical bus bars, which are used in a similar fashion. Other pre-assembly tasks include the fitting of thousands of tiles with extreme accuracy. Meanwhile in Spain, Elytt Energy also prototypes all of the main components of the magnetic coil during production. Once this is done, the coil can be shipped to the States and the final assembly can begin.

Using prototypes for final assembly has already been done for 3D printing in space, atomic energy, and even in window manufacturing. In extruded aluminum windows that can open and close in different ways, 3D printing has been used extensively. Here in the design phase, engineers want to check the ergonomics for clients, but also for the installers placing the windows in buildings and homes. For new models, custom jobs, complex projects, or custom facades, these processes are essential. For the window folks, finding out months from now that some national library somewhere can’t move forward to completion because your windows can’t be fit in like they should is a shock that they’d like to avoid. Likewise, in satellites and other high value assembly operations, any kind of experimentation with form and fit models that can play a role in assembly operations is welcome. Many clean room complex machinery assembly, or in high mix low volume operations, have also used 3D printed parts in this way. In all these cases, the part is expensive, but the timeline is the most expensive.

Not a lot of people talk about the uses of 3D printing for temporary or stand-in types of components. Usually, form and fit prototypes themselves are used widely and not discussed much either. Of that category, only very few components are actually meant to be stand-ins, while the rest of the thing is assembled. But, this is a very high return use of 3D printing. 3D printing can save oodles of money for people in very complex assembly operations. It’s good therefore for this team to showcase this use of additive in a high value way, as just a temporary part of a very complex thing.