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.