A fully automatic non-planar slicing algorithm for the additive manufacturing of complex geometries

The aim of this work is the implementation of a novel non-planar slicing algorithm, capable of combining traditional planar layers with non-planar ones. The geometry to be reconstructed will consist of an inner volume made of planar layers, and an outer shell made of non-planar layers. Both planar and non-planar layers are in turn constituted by an outer region, the shell, and an inner region, the infill. The outer non-planar shell gua-rantees an enhancement in the aesthetic properties and electro-mechanical behaviour of the printed objects, as well as a better adhesion when directly built onto a complex geometry. The algorithm was tested on three different three-dimensional models usable for aerospace, electronics, and biomedical applications showing robust results. An experimental validation was carried out by using a 5-axis robotic printer equipped with an extrusion-based printing unit. Different structures combining planar and non-planar paths were printed onto complex substrates, as well as into a bone defect that was completely regenerated following the proposed approach. The comparison between our method and the existing non-planar slicing methods revealed several advantages such as the capacity to generate both top and bottom non-planar surfaces, the possibility to manage complex concave/undercut structures, as well as the option to directly register the planned printing path on the receiving substrate in the working environment. To ensure proper and easy use, a graphical user interface was also created.