One of the most interesting and challenging aspects of precision machining aerospace parts is when we get to work on projects for spacecraft. Most people dream of spaceflight, and while we may never actually get to experience that ourselves, many parts we manufacture are orbiting our pale blue dot.
One such project we had the privilege of working on was a reaction wheel for an aerospace company that manufactures satellite components.
This company came to Coastal Machine and Supply by way of recommendation from a sourcing company. They had been in search of an ITAR-registered manufacturer, specifically an AS9100-certified machine shop, capable of precision machining aerospace components for research and development and low-volume production.
Other machine shops had turned down this project due to the requirements and low volume of parts. However, according to the sourcing company, Coastal Machine and Supply is “the go-to for the complex, crazy stuff” — and they’re totally right.
The Challenge: Precision Machining Aerospace Parts with Tight Tolerances and Symmetrical Features
If you’re not familiar with reaction wheels, these are used to turn spacecraft with 3-axis attitude control in a zero-gravity environment. It does this by rotating at a high speed, using inertia to create enough force to turn the spacecraft with incredible accuracy.
The reaction wheel that this aerospace company designed was intended to be used within a large satellite, and as such, the reaction wheel itself was also large, with a 16” diameter. In fact, we discovered that this was one of the largest reaction wheels ever put into production for a commercially made spacecraft!
While the size of the reaction itself didn’t pose a challenge for us — we excel at precision machining large parts — the precision of the features was another story.
Achieving a Precise TIR on Cylindrical Features Without Grinding
The reaction wheel was designed with two bosses on each end, and these had to have a total indicator reading (TIR) — the measurement of a part’s flatness or, in this case, roundness — within .0002” to .0004” of each other.
Normally, tolerances like this wouldn’t be much of an issue, as we would work with a reliable grinding vendor to laser-balance the reaction wheel for weight and achieve the required TIR of the bosses. However, because of the cost and the timeline this would add to production, this wasn’t an option for our customer. Additionally, due to the part’s application and the extreme precision it required, our grinding vendor simply didn’t want to touch it.
That left us with no choice — we’d just have to do what we do best, precision machining, and do it very accurately.
Putting in the Work: Precision 5-Axis Machining with Complex Fixturing
To machine this reaction wheel and its features with extreme precision, we needed to leverage our knowledge of geometric dimensioning and tolerancing (GD&T) to ensure that the TIR of the bosses would be within spec while maintaining all the other datums of the part.
Since the reaction wheel needed to be machined on all sides, using our 5-axis mill was the natural choice. However, because laser-balancing wasn’t an option to achieve precise symmetry, we developed complex fixtures to position the 6061 aluminum stock in such a way that the reaction wheel could be machined with one setup. This eliminated the risk of tolerances being out of spec due to repositioning.
After 25 hours of machine time, our 5-axis mill had completed machining the reaction wheel. Verifying the accuracy of the part’s geometries using our coordinate measuring machine (CMM), we were pleased with the results — everything was in spec, including the bosses.
To complete the manufacturing process, we applied a high-quality chem film to protect the reaction wheel from corrosion while it’s here on Earth and ensure a long operational life in orbit.
Achieving Success: Enabling Attitude Control for Satellites
Manufacturing this reaction wheel is something we are incredibly proud of. Not only did it allow us to put our aerospace CNC machining capabilities to the test for manufacturing critical satellite components, but manufacturing parts for spacecraft is — well, it’s just a really cool thing to do.
In total, we manufactured six reaction wheels for this customer, and soon these complex parts will be orbiting Earth and enabling precision attitude control for large satellites.
While there currently aren’t many spacecraft that require reaction wheels of this size, when the SpaceX Starship comes out of development, it will allow a far greater number of large satellites to be launched into Earth’s orbit. With the rapid advancements in space technologies, we are excited about the opportunity to manufacture more reaction wheels of this size — or maybe even larger — in the not-too-distant future.
In the meantime, we’ll be busy precision machining aerospace components for other applications, so if there’s a “complex, crazy” part that you need, just reach out and let us give you a quote. We enjoy a challenge.
