Researchers at the Department of Energy’s Oak Ridge National Laboratory, in collaboration with NASA, are taking additive manufacturing to the next level and demonstrating the technology for custom parts by 3D printing a wheel similar to the design NASA uses for its robotic lunar rover. It is necessary for space exploration.

The additive manufacturing wheel is modeled after existing lightweight wheels on the Volatile Exploration Polar Exploration Vehicle, or VIPER, a mobile robot that NASA plans to send in 2024 to map ice and other potential resources at the moon’s south pole. The mission aims to help determine the origin and distribution of water on the Moon and whether sufficient amounts can be collected from the lunar surface to support the people living there.

Although the prototype wheel, printed in MDF at DOE’s Demonstration Factory, or ORNL, would not actually be used on a NASA mission to the moon, it was created to meet the same design specifications as the wheels made for NASA’s VIPER. Additional tests are planned to validate the design and manufacturing method before using this technology for future lunar or mars rovers or considering it for other space applications such as large structural components.

Additive manufacturing can enable complexity of design and custom tailoring of material properties while reducing energy consumption, material waste and lead time. MDF has been at the forefront of this effort, developing technology for a wide range of applications in the clean energy, transportation and manufacturing sectors for a decade. MDF researchers printed a prototype trip wheel at ORNL in the fall of 2022. A custom 3D printer used two coordinated lasers and a rotating work plate to selectively melt metal powder into a designed shape.

Typical metal powder bed systems work in stages: in a cabinet-size machine, a powder bed is scanned onto a fixed plate. The laser then selectively melts the sheet before the sheet lowers slightly and the process is repeated. Peter Wang, who heads MDF’s development of new thermonuclear laser powder systems, said the printer used for the prototype trip wheel was large enough for a person to fit inside and was unique in its ability to print large objects while the steps were simultaneous and continuous.

“This significantly improves efficiency at the same laser power,” he said, adding that deposition is 50% faster. “We’re just scratching the surface of what the system can do. I really think this will be the future of laser powder printing, especially at large scale and mass production.”

The wheel prototype, one of the first parts created by the system, demonstrates the value of interagency collaboration. “The NASA project has really moved the technology forward,” said Brian Gibson, a researcher who led the rover wheel project for ORNL, calling it a major milestone. “It was great to match capabilities with evolving needs, and the team was excited to prototype a component with applications for space exploration.”

Made from a nickel-based alloy, the prototype wheel is approximately 8 inches wide and 20 inches in diameter; this is much larger than typical parts printed using metal powder systems. Its production required the ability to print small geometric elements placed over a large work area. According to Gibson, additive manufacturing allowed for greater complexity in wheel design without added cost or manufacturing difficulty.

By comparison, VIPER’s four wheels, which will kick up moon dust next year, required many manufacturing processes and assembly steps. The rim of the VIPER wheel, which consists of 50 parts, is fixed with 360 rivets. The manufacturing process required complex and labor-intensive machining to meet demanding mission requirements.

If NASA tests prove the 3D-printed prototype is as strong as traditional wheels, future rovers could instead use a single printed wheel rim that ORNL took 40 hours to make. As part of the project, ORNL and NASA engineers also investigated precision design features such as angled sidewalls, domed shape, and wavy tread to increase the wheel’s rigidity.

These features are difficult to incorporate into existing VIPER wheel design using traditional manufacturing methods. Although it creates a more complex spoke pattern and spoke locking features on the rim, 3D printing has simplified the wheel design and reduced its cost, as well as making final assembly easier. Source