Design considerations due to scale effects in 3D concrete printing

摘要

The effect of scale on different parameters of the 3D printing of concrete is explored through the design and fabrication of a 3D concrete printed pavilion. This study shows a significant gap exists between what can be generated through computer aided design (CAD) and subsequent computer aided manufacturing (generally based on CNC technology). In reality, the 3D concrete printing on the one hand poses manufacturing constraints (e.g. minimum curvature radii) due to material behaviour that is not included in current CAD/CAM software. On the other hand, the process also takes advantage of material behaviour and thus allows the creation of shapes and geometries that, too, can’t be modelled and predicted by CAD/CAM software. Particularly in the 3D printing of concrete, there is not a 1:1 relation between toolpath and printed product, as is the case with CNC milling. Material deposition is dependent on system pressure, robot speed, nozzle section, layer stacking, curvature and more – all of which are scale dependent. This paper will discuss the design and manufacturing decisions based on the effects of scale on the structural design, printed and layered geometry, robot kinematics, material behaviour, assembly joints and logistical problems. Finally, by analysing a case study pavilion, it will be explore how 3D concrete printing structures can be extended and multiplied across scales and functional domains ranging from structural to architectural elements, so that we can understand how to address questions of scale in their design.