This article introduces a novel computer-aided procedure to design optimised coated structures with precise shell thickness control using the Smallest Univalue Segment Assimilating Nucleus operator and a novel augmentation-projection technique. Structures with heterogeneous sections, or coated structures, combine two different materials for the nucleus and the shell, which are generally chosen so that the material in the infill is lighter and the material in the coating is stiffer, which in this work are supposed homogeneous. Solving the interface problem requires material properties interpolation equations that consider three material phases, accurate placement of the coating over the base material, and precise control over the coating's thickness. The formation of the coating is controlled by the Smallest Univalue Segment Assimilating Nucleus, an edge detection operator developed in Digital Image Processing. The coating's thickness is controlled by an innovative methodology consisting of the projection of an augmented contour field, which is shown to create a constant thickness coating around the material domain. The optimisation problem is solved with the Sequential Element Rejection and Admission method. The validity of the procedure has been verified by solving various numerical application examples.

This work presents a computational procedure for direct integration of Topology Optimization and Additive Manufacturing (AM) technologies for compliant mechanisms design. Many topologically optimized geometries present manufacturing problems derived from the lack of self-supporting capacities and require sacrificial support material for 3D printing. The proposed strategy introduces a novel overhang constraint to control the amount of sacrificial support material required for additive manufacturing of compliant mechanisms. This overhang constraint is defined as the ratio between the value of self supported contours and the total amount of admissible and inadmissible contours, and is computed by an edge detection algorithm known as the Smallest Univalue Segment Assimilating Nucleus, that analyzes the geometry of the model for locating contours and computes their inclination and orientation. The proposed algorithm has been implemented as part of a software for computer aided design and several benchmark examples have been used to demonstrate the capacities of the approach.