3D-Printing Channel Networks with Cement Paste

Internal cavities or channels have the potential to enhance a component’s insulation capacity, allow for fluid transport and heat exchange, and/or reduce material use without structural disadvantages. However, extrusion-based 3D-printing of built-in cavities or channels with cementitious materials has remained challenging due to several limitations, including the lack of support materials, early-age deformations, and slicing algorithms that exclusively generate layered toolpaths parallel to build plate. The objectives of this research were to identify opportunities to 3D-print mm-scale internal channels with cement paste and develop an accessible, high-throughput workflow for designing and printing components with channel networks. The research examined channel stability by considering channel design variables, including channel diameter and channel inclination, and proposes the use of angled planar toolpaths to increase the stability of the 3D-printed channels. Our new parametric modeling script (Grasshopper, Rhinoceros) rapidly models the filament geometry, identifies its unsupported sections, and, from those, indicates the degree of channel stability. The samples were 3D-printed and evaluated on channel stability using fluid flow analyses and micro-CT imaging. The developed Grasshopper-based design workflow [1] offers new opportunities for extrusion-based 3D-printing of cementitious components with internal channels. It allows for rapid 3D-modeling of complex internal channel networks (of various types, and with the option to apply Murray’s law), toolpath angle optimization for channel stability, and automated g-code generation. The workflow capabilities were demonstrated by 3D-printing several designs with complex 2D channel networks inspired by biological vascular systems.