|Sean Johnson, TD, used Fermilab’s 3-D printer to make this model of a strand of Nb3Sn wire, which he then spray-painted. Photo: Steve Krave, TD|
In 2008, Mauricio Lopes, an associate scientist in the Technical Division, started to build a model of a helical solenoid out of cardboard in order to prove a design concept. The process was painstakingly slow: In a week, he and Miao Yu, a mechanical engineer from TD, had finished only four rings. So Lopes thought of a solution for finishing such a model in a fraction of the time: a three-dimensional printer.
By October 2009, the Technical Division had its printer, a refrigerator-sized device housed in the Industrial Building Complex that spits out plastic renderings of computer models. The process takes anywhere from a few minutes to a few days, depending on the size and complexity of the object being printed.
“You can try things really fast,” said Steve Krave, a mechanical engineer. “You can have something made over the weekend, and so you can try building something and see how it works in real life instead of spending hours and hours trying to analyze every little thing.”
“And it’s much less labor intensive,” Lopes added.
Since Lopes first printed his helical solenoid model, the Technical Division has found a variety of uses for 3-D-printed pieces, including helping with winding coils for superconducting magnets. As coils are wound around a cylindrical surface, technicians need to control the shape of the magnetic field at the end of the coil in addition to alleviating stresses in the cable.
To do this, they use U-shaped end pieces, which traditionally have been ordered from machining vendors outside the lab, a process that can take about a month. With the 3-D printer, an end piece can be printed right in the lab, allowing for multiple iterations of the piece if changes need to be made.
“A lot of analysis and a lot of fabrication effort goes into making this curved surface,” said Rodger Bossert, a mechanical engineer. “Being able to turn around these parts quickly and cheaply is a huge advantage.”
Because forming the coils requires higher temperatures than Fermilab’s 3-D printed parts can withstand, the printed shapes are used in trials. The final shapes are made of metal—sometimes from off-site 3-D printers. This allows TD to experiment with different designs. The printer, for example, can build notches into the U-shaped end pieces, allowing them to compress and expand.
It works much like a two-dimensional printer in concept: Instructions are created on a computer and sent to the printer, which then produces a physical replica of what you see on the computer screen. But instead of printing ink on paper, it prints melted plastic onto a flat surface, with a melted resin used as a support structure. Once the printing is complete, the water-soluble resin can be broken and washed off, leaving behind only the plastic, allowing for objects with multiple parts, like working gears, to be printed in their entireties instead of being assembled in individual pieces.
“With machining, you have to drill holes and cut things away,” Krave said. “What’s really cool about 3-D printing is that you can build all sorts of complicated structures at once.”
|A modified end part that was 3-D printed off-site sits in the foreground, with a traditional, machined part in the background. Photo: Steve Krave, TD|