3D printed copper parts help spaceships relax
The prospects for using copper as an additive manufacturing material are improving these days, thanks in large part to the exploits of the “Wild West space cowboys.”
This is Pavlo Earle’s colorful way of describing the pioneers behind developments in the commercial space flight industry. Copper’s thermal properties make it an essential ingredient in rocket propulsion systems, noted Earle, vice president of engineering at Sintavia SARL, a Hollywood, Florida-based company that designs and 3D prints components for space and defense systems.
Copper provides “very good heat transfer, so it’s good for cooling,” he said. “And rocket components need a lot of cooling.”
Sintavia recently announced the development of proprietary printing technology for GRCop-42, a copper alloy used by NASA and private spaceflight companies. The technology eliminates the need for hot isostatic pressing as a post-processing step, reducing production time, costs and complexity, according to the company.
Sintavia primarily uses Direct Metal Laser Sintering (DMLS), a powder bed smelting technique, to print copper parts. The company produces copper rocket thrust chamber assemblies for a number of customers. Most parts are large components installed in power packages that can take days or even weeks to produce. Cooling functions are built into the parts, which are difficult to manufacture in part due to their geometric complexity.
“Conventionally manufacturing these components would be very difficult and would require a lot more time and money,” Earle said, adding, “You can’t just machine a heat exchanger from a block of material. All the small parts have to be machined and assembled.
In addition to its thermal properties, copper offers good electrical conductivity.
“If you exclude precious metals, which are too expensive for most applications, copper is the metal with the highest thermal and electrical conductivity,” said Hal Zarem, CEO of Holo Inc., a Newark, Calif., additive manufacturer of pure copper parts. “So virtually all applications of copper are thermal or electrical. “
Pure copper printing
Holo’s PureForm printing process, based on digital light processing technology, involves printing copper in a binder and then sintering to remove the polymer. The process can produce pure copper parts with high thermal and electrical conductivity and fine characteristics, according to Arian Aghababaie, co-founder and president of Holo.
PureForm’s ability to produce fine features, combined with the inherent advantages of additive manufacturing such as maximizing design freedom, allows the technology to print complex copper structures that outperform copper parts made with processes. traditional manufacturing, Aghababaie said. Today, these parts are used to cool high power semiconductor devices and in radio frequency systems used by various industries.
According to Zarem, many devices contain large copper plates which, for the most part, do not require a special manufacturing process, but include a “complex part” suitable for 3D printing. “Customers come to us to print smaller portions of a copper system, and then they solder, solder or braze the 3D printed part into a larger assembly,” he explained.
In other cases, like the production of RF micro-inductor coils, the whole part is printed. “But both cases require the fine functionality and design freedom that our technology offers,” he said.
Regardless of the technology used to print copper, those undertaking the task should remember that copper will oxidize fairly quickly if exposed to oxygen or other elements in the environment. To prevent oxidation from ruining the copper powder, users should operate their systems in a pristine environment and be careful when storing and transporting materials, Earle said.
Although it is possible to print copper parts with a number of additive technologies, the right choice will depend on the application.
Aghababaie, for example, views Fused Filament Manufacturing (FFF) primarily as a prototyping technology, not as a production tool. Also, he said, FFF parts can experience delamination that negatively affects conductivity in the plane.
“There have been demonstrations of pure copper printing with these technologies, but not to the point where they can produce on a production scale,” he said.
As for electron beam melting and directed energy deposition (DED), Aghababaie described them as “generally fairly low resolution technologies” that produce parts with high surface roughness that can make them unusable in applications. electrical applications. This means that copper components made with these technologies will require considerable post-processing to be turned into functional parts.
DED is also insufficient compared to powder bed fusion when it comes to producing fine lines, Earle noted. He added, however, that DED can produce larger parts and require less time to produce parts.
He also pointed out that the reflectivity of copper makes printing difficult with laser processes like DMLS. “If you try to melt copper with a laser and it reflects back and [the material] does not absorb this energy, which makes it very difficult, ”he said.
The success of DMLS with copper depends on the particular process of dealing with reflectivity and other difficulties with the material. “We have developed proprietary parameters for our copper printing technology,” Earle said. “And we have achieved very good mechanical properties through a unique combination of handling, printing and post-processing steps. “