The Oak Ridge National Laboratory which comes under the US Department of Energy took Additive Manufacturing to the next level by 3D printing the same kind of wheel as used by NASA for its robotic lunar rover. Through this step, US researchers have demonstrated how 3D printing technology could be used to make specialized 3D-printed parts required in space missions.
Using the existing NASA light-weight wheels design Volatiles Investigating Polar Exploration Rover, or VIPER, the space scientists created 3D printed wheels which would be used in NASA’s mobile robot plans to send it to the south pole of the moon in 2024.
The 3D-printed wheel is a prototype part of a rover that will look for ice and other potential resources in the lunar South Pole. The aim of this NASA space mission is to determine the origin and distribution of lunar water with the prospect of harvesting it to support life on the moon.
Although the 3D printed wheel developed by DOE’s Manufacturing Demonstration Facility (MDF), at ORNL, won’t be used for the actual NASA moon mission, it will help to analyse the design specifications of the VIPER. Scientists working in the project revealed that they have planned additional testing to validate the design and fabrication method used for 3D printing the wheels. Only then it can be used directly for space applications like Mars or lunar rovers.
Reducing waste and speeding up production in space missions
By creating 3D-printed wheels of rovers NASA scientists showcased how Additive Manufacturing reduces energy and materials waste in developing space missions. 3D printing also helped in reducing the lead time and achieving the design complexity and material properties required in such missions.
MDF is known for developing technology and using it in a range of fields like manufacturing, transportation and clean energy. In the fall of 2022, MDF researchers created the 3D printed rover wheel prototype using a specialized 3D printer with two coordinated lasers and a rotating build plate to selectively melt metal powder to achieve the designed shape.
The metal powder bed systems used for making the 3D-printed rover wheel operate by creating layers of powder over a stationary planet. A laser is used to selectively melt the layers prior to the lowering of the plate. This entire process is repeated simultaneously in a 3D printer which is large enough to hold a person, revealed Peter Wang from the laser powder bed fusion systems department at MDF.
Wang further explained how the 3D-printed rover wheel “dramatically increased the production rate with the same amount of laser power” as the “deposition occurs 50% faster“.
According to Wang, this is just “scratching the surface” in terms of what Additive Manufacturing can do and he thinks “the future of laser powder bed printing” lies in this, specially at large scale and in mass production.
So far the team has published a study regarding the 3D-printed rover wheel production and is analyzing the scalability of the technology for printing components like electric motors.
The 3D printer machine used by the scientists was unique to other 3D printers used in Additive Manufacturing but the key to the project’s success lies in automation and machine control. ORNL researchers developed a specific software to “slice the wheel design” into vertical layers. Then they balanced the workload between the two lasers to print evenly, ultimately achieving a high production rate. The scientists have used a computational technique for this purpose which they have applied for patenting.
Making way for better spoke patterns and locking
Brian Gibson from the ORNL research team termed the NASA project a “milestone” that ” propelled the 3D printing technology forward”.
“Made of a nickel-based alloy, the prototype wheel is about 8 inches wide and 20 inches in diameter – much larger than typical parts printed with metal powder bed systems. Making it required the ability to print small geometric features spread over a large work area. Additive manufacturing enabled greater complexity in the rim design without added cost or manufacturing difficulty”, Gibson explained.
Compared to this the VIPER wheels to be used in the actual mission requires multiple manufacturing and assembly steps. If this 3D-printed rover wheel prototype turns out to be as effective as the conventionally built VIPER’s 50-piece wheel rim is held together with 360 riveted joints, then future rovers could have single-printed wheel rims that takes only 40 hours to build.
Through 3D printing, the ORNL and NASA researchers could print precise design features, like angled sidewalls, a domed shape and wavy tread which increased the wheel’s stiffness. traditional fabrication methods can’t incorporate this in the present VIPER wheels. So 3D printing enabled complex spoke patterns and spoke locking features to the wheel in an easy and cost effective manner.
“A lot of these wheel features were put in just to highlight what you can do with additive manufacturing,” said NASA mechanical engineer Richard Hagen “It lets you easily implement design features that are hard to implement with traditional tooling or even a traditionally machined part”.
However, there are challenges to adopting 3D printing as the specialized 3D printer used by NASA can only process materials like nickel-based alloy which makes the 3D printed rover wheel 50% heavier than the actual aluminum VIPER of the same thickness.
NASA is planning to test the 3D-printed rover wheel in the rock yard of Johnson Space Center or in a giant “sandbox” of simulated lunar rocks and soil at a contracted test facility to evaluate its maneuverability, pivoting resistance, sideways slippage, slope climbing and other performance metrics.
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