  In this paper a phase-field approach for structural topology optimization for
a 3D-printing process which includes stress constraint and potentially multiple
materials or multiscales is analyzed. First order necessary optimality
conditions are rigorously derived and a numerical algorithm which implements
the method is presented. A sensitivity study with respect to some parameters is
conducted for a two-dimensional cantilever beam problem. Finally, a possible
workflow to obtain a 3D-printed object from the numerical solutions is
described and the final structure is printed using a fused deposition modeling
(FDM) 3D printer.
