British defence company BAE Systems have developed a new technique which reduces the distortion in 3D printed metal parts, potentially leading to making large components strong enough to use in aircraft.
Metal parts used in aircraft have to be manufactured to exacting specifications to ensure they do not contain any defects in the metal which can lead to component failure. The new technique uses an already established process of ultrasonic “peening” that is applied to each 3D printed layer before the next is laid. This relives the stresses in the component and improves the material’s microstructure.
3D printing is currently use to make small, less critical, components such as hinges, but problems exist when making larger components such as wings. As the 3D printed material cools internal stresses can build up will lead to problems with fatigue.
“As the material contracts it creates residual stress that is locked into the part,” said Andy Wescott, a senior research scientist at BAE’s Advanced Technology Centre, “This can manifest as distortion but also affects the mechanical performance.”
Ultrasonic Impact Treatment (UIT) is applied to the material after each layer is 3D printed and melted into shape by a laser and left to cool. The process is repeated for each layer until the final object is completely printed.
The hardware required for the UIT system can be robot controlled and is light enough to be easily added to an additive manufacturing system. The process can be tightly controlled so that each layer can be treated, or every fifth layer if required, without a significant additional time factor.
BAE Systems have already used the technique to 3D print metal parts that are up to 1m in length which also feature complex shapes. They are working towards optimizing the process for prototype parts but are not the first to use 3D printed metal parts in aircraft. Chinese aircraft manufacturers are moving towards using 3D printed titanium parts in their aircraft. To protect their investment BAE Systems have applied for patents for the UIT process and the associated hardware system.