ADDITIVE MANUFACTURING is the magazine devoted to industrial applications of 3D printing and digital layering technology. We cover the promise and the challenges of this technology for making functional tooling and end-use production parts.
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NOVEMBER 2017 Additive Manufacturing CHECK THIS OUT 64 By Stephanie Hendrixson Additive manufacturing (AM) is a natural pairing for design optimization, enhancing the ability to build high-performance parts. However, the size lim- itations and cost of metal 3D printing can make it less than ideal as the pro- duction technology for these parts. A recent project undertaken by Autodesk leveraged the advantages of AM in redesigning an airplane seat, but paired it with a traditional manufacturing method: investment casting. The goal of the project was to produce an airplane seat frame lighter than the original design but just as strong. With Autodesk's Netfabb soft- ware, research scientist Andreas Bastian created a seat frame design with an organic-like lattice structure, to be manufactured in aluminum. This design could have been produced with metal 3D printing, but the cost of this process combined with the part's size led researchers to look elsewhere for a manufacturing method, eventually landing on investment casting. Like 3D printing, investment casting enables complex geometries that wouldn't be practical to machine or manufacture with other methods. This is possible not through building parts layer-by-layer, but by casting parts in single-use molds that are destroyed in order to remove the parts. Investment casting offers expanded material options over AM, and better economics at scale. It also has the advantage of maturity. Whereas additive manufacturing is relatively new, casting is well-understood and widespread engineering expertise exists. For the investment casting process, Autodesk worked with Aristo Cast, a foundry located in Michigan. At the foundry's suggestion, Autodesk changed the material for the plane seat from the typical aluminum to magnesium for additional weight savings. Using Netfabb software, researchers ran the simulations for the part in the new metal and confirmed its properties. Though not used as the manufacturing technology, 3D printing did play a role in creating the casting patterns. The Aristo Cast team used the updated 3D model to 3D print positive molds of the lightweighted seat frame in plastic resin. These patterns were then coated with ceramic to create a negative mold. Once the ceramic shell hardened, the plastic was heated and vaporized away, and the mold was ready to be used for casting. At 766 grams, the resulting cast magnesium plane seats are 56 percent lighter than con- ventional aluminum seats weighing 1,672 grams. Design optimization accounts for 30 percent of the weight reduction, while the magnesium material makes up the remain- ing 24 percent. Though this project only produced small quantities of seats, researchers say it proved to be a viable process that could scale up to 160 seats every two days. Au- todesk estimates replacing the traditional seats with the magnesium ones could result in significant jet fuel savings and a reduction in CO 2 emissions from planes. The seat frames remain a research project for now, but Autodesk says it was successful in demonstrating the power of combining Autodesk's generative design ca- pabilities and 3D printing technology with casting. The same combination could also be used in automotive, medical devices, industrial equipment and other applications. For another example of the pairing of AM and casting—with molds and cores 3D-printed from sand—see the cover story on page 52. Aerospace Project Pairs 3D Printing with Investment Casting Andreas Bastian, research scientist for Autodesk, balances the lightweight airplane seat frame he designed. The frames were manufactured using a combination of 3D-printed patterns and investment casting in magnesium. The airplane seat frames were cast in magnesium, reducing the weight of the original aluminum frames by 24 percent.