Measurement of Forces Generated during Robotized Additive Manufacturing Process Using Pellet Extruder

Robotic additive manufacturing using pellet extrusion has gained significant scientific interest and industrial maturity. Increased part dimensions, reduced production time, and lower raw material costs are the main advantages of this process. This development has led to a strong demand for improved control and understanding of the process and of multiple phenomena occurring during fabrication. Consequently, process monitoring has received considerable attention, as it enables better understanding and detection of anomalies and their origins during manufacturing, allowing for immediate correction when possible or for more in-depth post-process analyses. Several studies in the literature have focused on monitoring parameters such as extrusion temperature, layer height, and printing speed to investigate their effects on final part quality and mechanical performance. In the present study, the objective is to quantify the forces applied to the deposited material during robotic additive manufacturing by pellet extrusion. This is made possible using a six-component force sensor, which allows the measurement of forces and moments along the three directions (X, Y, and Z). Following data acquisition, the results allowed understanding of force variations throughout the fabrication cycle and their correlation with the different stages of the manufacturing process. A single layer curve was explained with the corresponding peaks of each segment of the trajectory. It was found that at rounds there are peaks in Z forces due to the fact that, at the rounded sections, there is a slight accumulation of material, as the robot’s travel speed decreases while the material flow rate remains constant. This therefore results in higher applied forces. Consequently, it was observed that from the third layer onward, forces along the Z direction were almost no longer detectable. These measurements aim to facilitate the detection of manufacturing defects through unexpected force variations and to relate these observations to the final mechanical properties of the fabricated parts.