Concrete printing through lace pressing: Head, shoulders, knees and toes

3D concrete printing offers exciting possibilities for creating complex shapes without traditional formwork, but maintaining geometrical accuracy remains a challenge. Issues like early drying, gravity-induced stresses, and extrusion inconsistencies can compromise the quality of printed structures. This study explores the lace pressing technique, where the printhead stays in contact with the material to minimize deformation and improve precision. Through experiments, we identified three distinct zones within printed layers—shoulders, steady-state, and toes—each influenced by material yield stress, gravity-induced stresses, and layer pressing. Systematic variation of process parameters reveals the boundaries and characteristics of these zones. A theoretical model is introduced, incorporating dimensionless parameters, to predict the onset of plastic failure and deformation across these regions. The results not only validate the model but also highlight its potential for optimizing printing processes and retro-engineering material properties from benchmark prints. These findings contribute to advancing 3DCP by providing tools for more accurate builds.