An analytical model experimentally validated for density prediction in Arburg Plastic Freeforming

Arburg Plastic Freeforming combines pellet-based feedstock with droplet-wise deposition, offering material flexibility while posing challenges for maintaining repeatable high-density fabrication at increasing printing speeds. An analytical model for part density prediction is proposed here. It is derived from mass conservation and an ideal tangential droplet-placement assumption, yielding a density formulation expressed as a function of process velocity and geometric parameters such as Drop Aspect Ratio and layer thickness. First, a preliminary droplet-chain characterisation on polycarbonate was conducted to assess the mismatch between the slicer-idealised pixel geometry and the actual droplet morphology, thereby selecting a representative operating condition for the second experimental activity. Then, cubic specimens (10×10×10 mm3) were printed by varying the tangential speed from 0.35× to 4×, showing close agreement between the extruded and deposited volumes. Density measurements follow the predicted trend within a bounded operating window of the investigated velocity range. At higher printing velocities, variability in shutter oscillation frequency alters droplet spacing and introduces uncertainty in the achieved density. By accounting for measured frequency deviations and propagating their uncertainty within the analytical framework, the proposed approach helps identify operating conditions that support an informed trade-off between printing velocity and density requirements. This provides practical guidance for process setup and highlights the limits of reproducibility under high-throughput conditions, supporting informed industrial adoption of Arburg Plastic Freeforming.