Robert N. Yancey PhD, Vice President – Additive Manufacturing, Altair
Prashant P. Hiremath, Senior Application Engineer, Altair Engineering Inc
Additive manufacturing or 3D printing is a process of making three dimensional solid objects from a digital file, which allows for organically oriented designs that are structurally efficient and not subject to typical manufacturing constraints. Additively manufactured components, however, are found to be generally weaker in Z-direction/axis which is the printing direction. With some additive manufacturing methods, the Z-axis direction can exhibit strength knockdowns of 30-40%.
Topology Optimization generates structurally efficient concepts that utilize the manufacturing flexibility of 3D printing. Usually, this optimization is done without regard to manufacturing constraints. However the Z-direction/axis weakness inherent in additively manufactured components is very significant and must be considered.
To investigate this issue a simple 3D cube is constrained at three edge points and point loads are applied at the corners. A topology optimization problem is defined with minimize mass as objective and with varying directional stress constraints. The material is modeled as isotropic. The effect of including directional stress constraints on the resulting topology and mass are studied. Using Euler rotation angles, the axis system is rotated and directional stress constraints are applied in the rotated axis to study its effect on the mass of the resulting topology.