An additive manufacturing-oriented structural optimization design method to eliminate sacrificial support

Additive manufacturing (AM) has significant advantages in fabricating complex structures designed by topology optimization (TO). However, AM is also well-known to be plagued by overhang issues, which are usually partially solved by adding a large amount of sacrificial supports during printing. This paper proposes an effective method to eliminate supports at the TO stage by incorporating overhang angle and minimum feature size constraints into the TO problem formulation along with the regular volume constraint. Being used to establish the overhang angle constraint, overhang angles in the structures with blurry boundaries in solid isotropic materials with penalization (SIMP) are estimated as the angle between the horizontal direction and the density contour which is fitted by extracting the density of the element at the structure boundaries. A density numerical relationship is constructed between adjacent elements in the horizontal direction to limit the generation of too small size features. Structures can directly be manufactured with no requirement of sacrificial support material right after the proposed TO process. The structural TO problem is solved by the method of moving asymptotes (MMA). Numerical examples and experiments are given to demonstrate the capacities of the presented algorithm.