Shell Wall: Coupling Non-Planar Robotic 3D Concrete Printing & Topology Optimization

Shell Wall demonstrator is the first lightweight, structurally reinforced freeform concrete wall ever 3D printed. This innovative wall system features a geometry optimized to support its load case, with material distributed in a hierarchical grid of curved ribs ranging in diameter from 65 to 150 millimeters. The non-load-bearing areas between these ribs are just 6.5 to 8 centimeters deep, enabling the sandwiching of insulation between two concrete shells that are only 2.5 millimeters thick. The fields of concrete between the ribs are domed to increase stability and minimize material usage. Shell Wall weighs only 160 kilograms – a 72% reduction in weight compared to a conventional, solid concrete wall of equivalent size.

This research develops non-planar 3DCP for the production of topology-optimized building parts, which entails features such as multiple tubular branching with varying diameters, interconnection between tubular and ultra-thin surface geometry, sharp overhangs. 

The project focuses on the 3D printing of lightweight concrete walls as this is the commonly used element in the current 3DCP but with no emphasis on material reduction. Materially and structurally optimized wall’s where load points are local rather than distributed all along the length will reduce the concrete consumption, improve the overall structural performance, lower the weight of the building, and ultimately reduce the building’s embodied carbon footprint. Additionally, according to the demand of industry and expediting real-world application, the research is set to eliminate the use of accelerators which can increase the potential of cracking and reduce the strength of the material.

Firstly, a geometrically informed non-planar toolpath method based on the geometry of the design has been developed. Geometrically Informed Non-Planar toolpath (GINP-toolpath) is a curved or spiral path for the printing head to follow rather than straight lines. Secondly, a geometrically informed variable material deposition method (GIV-material deposition) has been employed to regulate the amount of material dispensed during the printing process in reference to the nonplanar toolpath. GIV-material deposition refers to a technique that will regulate the amount of material being deposited along the toolpath based on the shape of the parts being printed and the relativity of the GINP-toolpath.