Additive manufacturing opens up new prospects at CERN

Additive manufacturing opens up new prospects at CERN

Lightweight, robust, complex parts produced using additive manufacturing (3D printing) are proving their worth in the accelerators

Video explaining the process of 3D printing for metal pieces at CERN. (Video: CERN)

For four years now, the Mechanical and Materials Engineering group in the Engineering department (EN-MME) has been using a metal-additive manufacturing machine (also known as a 3D printer) to produce geometrically complex parts.

The advantage of additive manufacturing lies in the production of lightweight, seamless, multifunctional components. This process is proving itself in the aerospace and medical industries, where its use has skyrocketed. Until now, however, it has not been widely used in the field of particle accelerators, where unique specifications have to be met. For ultra-high vacuum, cryogenics and radiofrequency cavities, in particular, CERN produces and characterises components that need to meet very specific requirements and may require the use of rare materials like niobium. 

The additive manufacturing technique adopted by CERN is selective laser melting: metallic powder is melted successively, layer by layer, using a laser beam. The laser’s trajectory is set using a three-dimensional model. The layers of powder are deposited and melted over and over, up to thousands of times, until the object takes shape.

This process makes it possible to conceptualise and design parts that until now would have been difficult, if not impossible, to manufacture. Selective laser melting results in robust parts of complex shapes, which include features such as cooling channels (as illustrated below in a radiofrequency spiral load for CLIC). The process requires relatively little raw material while preserving good mechanical properties. This is shown in the case of beam wire scanners, which have to be light but rigid.

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The spiral load serves to dissipate the electromagnetic power of the radiofrequency cavities in the CLIC project’s X-band testing facility (Xbox). Additive manufacturing makes the part compact while still incorporating cooling channels (shown in orange on the 3D image). (Image: CERN)

Although this technology has been tried and tested with common materials, such as aluminium and titanium alloys and stainless steel, additive manufacturing involving rare materials such as niobium, a superconducting element that is used throughout the radiofrequency cavities of CERN’s accelerators, is relatively uncharted territory. A development programme has been under way for several years and has produced promising results with some of the first components, like the HOM couplers below. Nevertheless, there are still challenges to overcome, related in particular to the purity of the materials, the roughness of the surfaces and the high dimensional precision that these parts require.

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This HOM coupler prototype made of niobium has cooling channels going right down to the point of the hook, where the electromagnetic fields are intense. (Image: CERN)

In addition to the metal-additive manufacturing machine, CERN also has a plastic 3D printer, which is used by the Magnets, Superconductors and Cryogenics group (TE-MSC) to produce parts from plastic resin (mainly epoxy) using stereolithography, a technique that involves using a laser to harden the liquid resin. The applications of this technique include making radiation-resistant parts and high-voltage electrical insulation for the detectors, as well as many moulds and prototypes.

Additive manufacturing is set to continue making inroads into the world of accelerators. By expanding the range of possibilities offered by conventional technologies, this new tool is likely to help resolve many technical challenges posed by future projects, such as the Future Circular Collider (FCC).

For more information about metal additive manufacturing, contact Gilles Favre; if you’re interested in plastic resin parts, write to Sébastien Clément.

 

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Plastic 3D printed coil holder for the electronic components of the PS particle beam acceleration system (right, white parts) and thermally insulated optical reflector for superconducting magnet position monitoring system (Image: CERN)