The 3D Concrete Printing technology (3DCP) has developed fast in the past few years. Compared to conventional construction method, the 3DCP technology offers an advantage in speed and cost. However, the surface of a structure from 3DCP technology requires post-finishing processes as the direct outcome suffers from low quality surface finish problem, such as jagged surface and staircase effect. This study aims to improve the surface finish quality in 3DCP using a developed novel variable-geometry nozzle that can directly control the extrudate geometry during the printing process at every layer. The nozzle assembly features an adjustable nozzle outlet geometry that can be controlled along the process. The mechanism requires a slicing algorithm to determine the extrudate geometry at every layer based on the designated printed structure. The corresponding algorithm was also developed and will be presented in this paper. Subsequently, the functionality of the proposed method was validated with a case study of manufacturing a structure with curved outer-surface geometry (an arch).

在过去的几年中，3D混凝土印刷技术（3DCP）取得了快速的发展。与传统的构造方法相比，3DCP技术在速度和成本上具有优势。但是，3DCP技术的结构表面需要进行后期加工，因为直接结果会遇到低质量的表面光洁度问题，例如锯齿状的表面和阶梯效应。这项研究旨在使用已开发的新型可变几何形状喷嘴提高3DCP的表面光洁度，该喷嘴可以在印刷过程中直接控制每一层的挤出几何形状。喷嘴组件具有可调的喷嘴出口几何形状，可在整个过程中进行控制。该机制需要切片算法，以便根据指定的印刷结构确定每一层的挤出物几何形状。还开发了相应的算法，并将在本文中介绍。随后，以制造具有弯曲的外表面几何形状（拱形）的结构的案例研究验证了所提出方法的功能。