Real-time toolpath planning and extrusion control (RTPEC) method for variable-width 3D concrete printing

Extrusion-based 3D concrete printing (3DCP) is one of the most widely used methods for the digital fabrication of concrete material. For variable thickness components, inner cavity or in-ternal toolpath can occur when using constant-width filament. Printing with variable-width filament is a possible solution to reduce the inner toolpath and enhance the integrity of the components. However, the conventional open-loop control method requires pre-calibration of materials and extrusion equipment and relies on the fine control of the material properties and the stability of the pump system. This paper presents a variable-width 3DCP method using real-time toolpath planning and extrusion control (RTPEC). In this paper, the material requirement, extrusion system, and real-time control algorithm are discussed. A controlled experiment is performed to verify the feasibility of the algorithms and the real-time control system. The printing accuracy in the horizontal and vertical directions is analyzed by 3D scanning. The result shows better horizontal accuracy and surface quality by using the RTPEC method. The result is well within the tolerance of the building scale component and demonstrates the potential applications in 3D concrete printing of building scale components.