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3D concrete printing (3DCP) structural components for construction assemblies are known for reduced material use and enhanced efficiency and design freedom. This article investigates the limitations in the geometrical and toolpath design of 3DCP structural components and presents an automated and comprehensive approach to their toolpath design and optimization. It exploits hierarchical geometric data structures and graph algorithms to achieve the following features: (1) By analyzing the overhang of toolpaths, the method offers quantitative criteria for determining the buildability of the components and predicting failure, thus assisting design decisions. (2) It provides toolpath offsetting and filleting methods that can enhance the dimensional accuracy of the print concerning layer line textures and overfills. (3) For branching and porous geometries, the method creates as-continuous-as-possible toolpaths with minimal stop-starts based on their topologies, thus reducing seam defects. (4) It converts the toolpath into efficient visualization meshes representing layer line textures and toolpath meshes compatible with finite elements analysis. The proposed method is implemented as a plug-in software within the environment of Grasshopper® for Rhino® to facilitate designers and engineers working with 3DCP. The effectiveness and versatility of the tool are demonstrated through the toolpath design and printing of four sets of examples. The tool reduces the number of toolpaths by 90% for a typical 80 mm nozzle and takes 0.21 s per meter of toolpath to slice, analyze overhang, generate continuous printing toolpaths, and visualize the print. 

This paper aims to advance the field of additive manufacturing by producing multimaterial objects with intricate topological features and polylithic material distribution through an integrated approach. First, we develop a Single-Nozzle Multi-Filament (SNMF) system equipped with active mixing to blend multiple filaments and deposit a programmable mixture. The system can also deposit gradient transitions between different materials within a single print. Second, we establish a numerical model to represent the material transitional behavior and validated it with experiments. The model enables the precise control of the material transitional interface to ensure high material fidelity. Third, we propose three strategies for designing and modeling multimaterial objects catering to different application scenarios, including image sampling, 2D discrete patches, and 3D surface division. The system’s capabilities were validated through six case studies designed and fabricated through the above approaches for distinct application scenarios, demonstrating the successful materialization of complex designs with multiple functionalities.