Print-Path Design for Inclined-Plane Robotic 3D Printing of Unreinforced Concrete

The paper details the computational toolkit for print-path synthesis and execution that was used in the physical realisation of an arched, bifurcating, unreinforced masonry footbridge spanning 16 m, composed of 53 3D-printed concrete blocks. The printed concrete filaments of every block were placed in layers that are orthogonal to the expected, compressive force flow, resulting in the need for non-parallel, inclined print-path planes, thus also resulting in non-uniform print-layer heights. In addition, the bridge’s global structural logic of stereotomic masonry necessitated the precise coordination of the interface planes be- tween blocks. Approximately 58 km of print path, distributed over 7800 inclined layers, were generated and coordinated such that the resulting print paths meet printing-related criteria such as good spatial coherence, minimum and maximum layer thickness, infill patterns etc. We describe a schema based on Function Representation (FRep) for inclined-plane print-path generation, and its full implementation for practical and large-batch production. We also implement specific extensions to generate the infill print paths typically needed in 3D concrete printing.