As additive technology gains importance in aerospace innovation, it offers compelling opportunities to revolutionize critical elements of the aerospace workflow. From design to certification and to production, AM helps companies unlock innovation and maximize efficiency while maintaining the high levels of quality required for aerospace applications.
Dr. Michael Shepherd, Vice President Aerospace and Defense Segment at 3D Systems offers insights.
Better RF satellites
The satellites used in aerospace today are incredibly complicated systems of systems, making their design and production challenging. Plus, they must receive signals from the Earth that are weak, process them, and then retransmit them to somewhere else at light speed.
In addition, space is an incredibly harsh environment. Satellites undergo tremendous thermal cycling and radiation exposure, they are in a vacuum, and there’s not a whole lot of power to work with. Finally, they need to last about 10 or 15 years.
While people have been making telecommunications satellites for decades, the market is very active now. There are a number of manufacturers developing RF satellites. And those designs not only need to perform well, but they also need to be cost-competitive in that market.
Additive is one of those technologies that “takes the handcuffs off from a design perspective,” says Dr. Shepherd. “It lets you optimize the designs for efficiency, but it also brings some really positive things to the table in terms of the logistics or supply chain side of things.”
From a materials perspective, the most challenging part of a passive RF device’s life is during the launch phase. The materials a designer selects, particularly from an additive perspective, must be strong enough to get to orbit and be compatible with the additive manufacturing process.
“We typically see, aluminum, silicon, tin, magnesium, or a legacy casting alloy often chosen, says Shepherd. “We’re starting to see quite a bit of interest in Scalmalloy. It’s a high-strength aluminum material that is free of many of the additive manufacturing extreme challenges that you see with some of the other high-strength aluminum alloys. Sometimes titanium is used. Titanium’s a little bit more expensive and you have to, maybe for like Ka band applications, you have to maybe do some surface treatment, silver coating and things like that to get the surface conductivity back. But structurally, it’s very efficient.”
Benefits of using additive manufacturing
AM is a powerful tool. Shepherd finds two general categories benefit from the improvements that you get with AM—efficiency and performance, and the supply chain.
Historically RF designers were limited by the geometries available through conventional subtractive machining. With additive, structural components are shifting to more organic-looking shapes. Software such as topology optimization and generative design can create these organic shapes but it takes additive production to make them.
The smooth, complex contours are useful in the RF space, especially with filters and the organic cavities that can be used to improve filter performance.
Anything that goes into space benefits from technology that reduces weight and size. Such efficiencies reduce launch costs, which still can cost $5, $10, even $20 thousand dollars per kilogram.
Additive helps designers get “really aggressive with unitization, combining multiple parts made with traditional manufacturing into maybe a single part,” says Shepherd.
“There was one filter that we worked on with Airbus where we combined, I think 39 parts into a single part,” continues Shepherd. “The final design weighed 50% of what the conventional design weighed. So, a tremendous benefit there. You also get rid of a lot of interfaces through unitization–the combining of the parts. And in RF, you’re really looking to minimize the signal losses. So, each interface between the different components needs to be carefully prepared, assembled, and tested. And all these different interfaces take up space, add weight, and cost a lot of time and money, and require highly skilled, smart people to pull it all off.”
Unitization reduces parts count way down, it reduces the number of vendors you have to work with, and it reduces associated shipping.
“And if you’ve ever been involved with this stuff, these very expensive, complicated pieces of hardware going back and forth between the vendors, the cost and drama and time that goes with all of that can really add up in an unhelpful way on a complicated system like a satellite,” says Shepherd. “With additive, you can get the major components ridiculously fast. I come from an aerospace background. And sometimes these systems take years and years to come together. Now, some of our customers, they’re printing large complicated satellite parts, a half-meter cubed in a few days on our factory 500 systems. It’s really kind of breathtaking how fast the process is.”
As a reference, previously, the time involved in making satellite parts was extensive. One part might have dozens of pieces to it. Engineers often used a Gantt chart to lay it all out and the time involved was often months.
Even though additive parts often require additional finishing steps, the overall level of effort and time involved to get to the delivery of a final part is much lower.
Expanding into more aerospace applications
Additive manufacturing is another tool in the toolbox for aerospace engineers. But it is an incredibly powerful tool that offers not just the design advantages, but also supply chain benefits. Engineers are still working through some of the limitations of using additive parts for flight critical, load-bearing components. It’s not that it has not been done, it has, but it is not easy. As understanding and experience increase and mature with additive manufacturing, it will be moving into more aerospace applications.
Shepherd’s background is in behavior and life prediction. He’s a fracture mechanics person, viewing technology through the perspective of how fast things would break. From a structural integrity perspective, regarding additive technology, “we know how to make parts that won’t break, even doing the toughest jobs.”
While metallurgy is a bit different with additive manufacturing, when done properly with materials that are compatible with the process, material properties are in the same ballpark as forged equivalent materials. But it’s important to understand the failure mechanisms and do all of the design math.
According to Shepherd, additive technology offers incredible value now. Most of the components that are on an aircraft are not necessarily critical load bearing structures. With the big-bone parts, the really critical primary structures, engineers need to think about what the best tool in the toolbox is.
“And if it’s additive manufacturing, I think it is in some cases, you just have to be diligent and you have to go through a building block type approach to make sure you understand all the ins and outs of the process and the ultimate properties of the metal, or composites, or in some cases polymers that you’re going to get in the end. But a lot of times the big bones are still metal.”
What’s in store for AM?
For Shepherd, he sees increased adoption of additive manufacturing, new innovative materials that will add additional capability to both metals and polymers.
“At 3D Systems, we specialize in photopolymers and there are exciting innovations that we’re bringing forward with stereolithography and our DLP processes. And those let you get really fine features that are useful. Traditionally, stereolithography has been thought of as for making prototypes, but we’re starting to develop photopolymers that are useful for final production parts. You can use the parts and they’re going to last in the environment. Also, other properties like flame retardancy, and so on.
“It’s an exciting time to be in additive. And if you like jets like I do, seeing all the new applications and seeing the creativity that’s facilitated with additive, it’s just a really exciting time to be involved in the space.”