Measurement and Control of Serial Manipulator Robots for 3D Concrete Printing (2024-09)¶

3D Concrete Printing (3DCP) in many off-site manufacturing environments use serial manipulator robots as positioning devices due to their low relative cost, high working volume to footprint ratio, and ease of use. These devices are responsible for replicating the tool paths generated that translate a digital representation of a solid object into the precise location of deposited material in the physical world by material extrusion. Defects such as interfacial voids, which affect the mechanical performance of material and poor compliance of the external geometry are both well recognised quality issues that are a function of both the rheology of the material and the path of the extrusion nozzle. While there has been significant effort in understanding the rheology of the material, there has been far less, if any, published work exploring the effect of precision of the robotic positioning systems, which are known to exhibit positional errors statically and variable dynamic behaviour, on printed parts. This article addresses this gap by presenting methods and a case study assessment of a robotic system used for full-scale 3DCP. From a dataset of 1575 paths taken for a sample artefact, subtle changes in the control strategy of the robot are identified that cause considerable errors in the path completion time, the dwell time at corners, and the amount of positional overshoot. Finally, the relationship between these parameters and the geometry of printed parts is shown empirically on printed samples based on the RILEM TC 304-ADC test artefact.