Volume-forming 3D concrete printing using a variable-size square nozzle

The 3D Concrete Printing (3DCP) process is rapidly developing worldwide, showing its ability to construct large-scale components or even a building. However, the current 3DCP process has found it hard to manufacture architectural components with detailed ornamentations and features on their surface due to the Fused Deposition Modelling (FDM) manner that generates fixed-width filaments. This paper introduces a novel Volume - Forming 3D Concrete Printing (VF3DCP) method applying a variable-size square nozzle to manufacture architectural ornaments. The VF3DCP process is described as to directly fabricate a variable cross-section volume during one-time work instead of an FDM accumulation process. A VF3DCP extrusion kit prototype featured by a steering module and a nozzle-varying module is developed. Functional relationships of four key process parameters for a trial material, including nozzle size, nozzle travel speed, material extrusion rate and toolpath curvature radius, are fitted by two process tests. Two case studies into the manufacture of an architectural carved pattern and a curved wall structure together validate a Voronoi Diagram-based skeleton line-segment algorithm for the single-path and multi-path toolpath planning of the VF3DCP process. The results show the potential of the proposed method in manufacturing architectural ornaments.