A grammar-based algorithm for toolpath generation: Compensating for material deformation in the additive manufacturing of concrete

In architecture, AM technologies have been used for rapid prototyping since the early 1990s. However, using AM for automated building construction represent a revolution for the industry that requires modeling the complex relationships between materials, printing system, and designs. An important aspect of research in this area is the deformation of concrete during printing and how it affects shape accuracy and structural stability of the printed geometries. A previous experimental study proposed a series of equations to predict material deformation for a specific concrete mix. This study incorporates these equations in a shape grammar-based algorithm to decompose complex geometries into simpler ones, slice the simpler geometries, and generate compensated toolpaths. The algorithm was implemented in Grasshopper, a Rhino plugin, and it can be used as a 3D slicer specifically for 3D printing concrete purposes. The slicer is validated with two printing experiments, involving a simple and a complex shape. The algorithm can be extended to other material mixes by developing similar experimental studies and incorporating the resulting equations.