Optical Process Control for extrusion-based Additive Manufacturing methods in construction

Additive Manufacturing (AM) provides many advantages when applied to the field of construction. However, due to the large scale of construction projects, time requirements for the printing process are also large, making AM processes susceptible to the influence of external variables. Accordingly, it is advisable to employ methods that can ensure the stability of the extrusion process. This study demonstrates a method to increase the reliability of extrusion-based concrete 3D printing processes through automated monitoring and controlled material extrusion process. In order to maintain a consistent width of the extruded material, a closed-loop optical process control system capable of tracking extruded layers has been developed. It utilizes a mounting system for the monitoring system (RGB camera) that can automatically rotate and moves relative to the printing nozzle and tracks the extruded filament. A computer-vision-based algorithm monitors the filament's width in real-time and continuously transmits the information to a PID controller regulating the material extrusion rate. Overall, the system can effectively track the extruded filament and adjust the extrusion rate based on the vision system, demonstrating significant potential in real-time process control applied in robotic construction.