Design for Additive Manufacturing
Handling Anisotropy in Additive Manufactured
/ 3D Printed Components
Advances in process and materials have launched a revolution in additive manufacturing. This has broken the link between design complexity and manufacturing cost, opening new possibilities in geometric freedom. Once considered only for visualisation and prototyping, additive manufacturing is now practicable for structures in safety critical applications such as aerospace.
However, from a structural viewpoint, additive manufactured materials do not behave the same as their machined billet or cast counterparts. Even for an identical alloy, the manufacturing process weakens the structure in certain directions. Engenuity’s testing and analysis approach not only avoids in service failures but also optimises designs to make the most of the new possibilities in 3D printing.
ARE ADDITIVE MANUFACTURED PARTS ANISOTROPIC?
It is common for additive manufactured parts to show anisotropy in all mechanical properties, including strength, stiffness and fatigue life. This is caused by the intrinsic directionality of AM processes. When setting up parts for manufacture, often the designer will choose to orientate the parts to fit the most on a single run, or for surface finish. However, this orientation is critical to the structural performance of the design and should be considered from the concept stage of design development.
The graph below shows that under a moderate 20MPa cyclic stress, the part will handle 1,000,000 cycles in the X direction but only 3,500 cycles in Z. Without considering the anisotropy as part of the design process the part will either fail early or weigh more than is required for the application.