Implementation and virtual assessment of a non-uniform cylindrical slicing algorithm for robot-based additive manufacturing

Robot-based additive manufacturing (RBAM) is an additive manufacturing (AM) technology powered by robotic manipulators. The material is deposited from a nozzle onto an initial surface, adding successive layers on top of each other and pouring it along multiple directions (multiaxial deposition) thanks to the dexterity of robots, often of the anthropomorphic type. Furthermore, it is possible to manufacture layers of non-uniform thickness, thus obtaining non-parallel and non-planar layers. In particular, RBAM can be implemented to realize revolved parts with protruding portions. Cylindrical or conical slicing algorithms have been devised to process the sub-volumes, reducing the number of layers and the need for support structures. In this context, the paper presents a novel algorithm for non-uniform cylindrical slicing that processes sub-volumes connected to a cylindrical shape. The specific contribution of the work is an algorithm that moves from a curved slicing to increase the adhesion between the central body and the first layer, and it relaxes the curvature in the subsequent layers, arriving, if possible, at a planar slicing. The algorithm considers robots' intrinsic constraints on movements. Planar paths are better approximated than non-planar ones since they prevent the robot from constantly changing the nozzle angle, thus increasing the overall quality of the printing. The algorithm is applied to four test cases and compared with other slicing approaches using numeric indices, objectivating its strengths and limits.