Dense 3D-packing algorithm for filling the offset contours of a new printing process based on 3D plastic droplet generation

In this paper a new slicing method for filling an arbitrary polygon with 3D-balls for a 3D plastic droplet generation process is presented. The work principle of the 3D plastic droplet generation is to squeeze the plastic material through a nozzle, out of which small hardened balls are formed and based on the contour and infill algorithm the 3D objects filled with plastic droplets are layer-wise created. Zigzag lines and the Shrinking contours infill strategies, used in the most slicing software of the similar rapid prototyping process Fused Deposition Modelling (FDM) are applicable in this case as well, but do not take advantage of utilising droplets. In the proposed algorithm, each of the slices with contour polygons is intersected with a constant fixed 3D densest sphere formation. Those spheres, which are within a polygon of a certain slice, are forming printed droplets. The droplet placement is by applying this algorithm predefined and completely controlled. Moreover, the holes within a slice, as well as between the slices are minimised and regularly scattered. In the experiment the density of a cube filled with droplets with three different infill strategies (Zig-zag, Shrinking contours and the dense 3D packing) is measured and the dense 3D packing method results in the highest density. This method leads to achieving the goal of producing the 3D objects with fine surface quality and sufficient stability.