Continuous contour-zigzag hybrid toolpath for large format additive manufacturing

Large format additive manufacturing (LFAM) has witnessed rapid development in recent years and facilitated digital fabrications of geometrically intricate structures. However, there has been limited research on toolpath optimization tailored for LFAM. This paper presents a novel framework to generate a globally continuous toolpath for both solid and partial infill designs in LFAM. For solid infill, outward contour and double offset schemes are used to generate smooth curves as the primary volume-filling paths; the remaining unfilled areas are covered by extending zigzag lines from the closest contours. Subsequently, a contour layer-wise connection is carried out based on the depth-first-search algorithm to formulate a globally continuous path. A post-processing step is also presented to optimize the coverage and curvature of the toolpath design. The concept is extended for partial infill settings by trimming and joining rectangular grid lines. Compared with other state-of-the-art methods in the literature, the proposed algorithm is superior in delivering better print quality, fewer sharp turns, and enhanced fabrication efficiency. Finally, two interesting experiments demonstrate how LFAM of topology optimized structures can benefit from the proposed continuous toolpath: topology optimized table printed from thermoplastic polyurethane (TPU) and topology optimized chair printed from 3D concrete printing (3DCP).