Abstract

Fused filament fabrication (FFF) is a widely used additive manufacturing method in which the process forces within the hotend play an important role in terms of print quality and speed, particularly in high-throughput applications. This work reports on the influence of filament diameter, melting zone length, and nozzle set temperature on the process forces and the maximum achievable volumetric flow rate. Experimental measurements were carried out using a test rig that integrates a load cell to capture the resulting forces, complemented by non-isothermal numerical simulations. The results show that increasing the melting zone length reduces process forces and increases the attainable volumetric flow rate at high feed rates, as the filament has more time to melt. However, the effect depends strongly on filament diameter. For a diameter of 2.85 mm, extending the melting zone leads to a monotonic increase in the maximum achievable flow rate across the entire investigated range. For a diameter of 1.75 mm, an optimum is observed at an intermediate melting zone length, beyond which additional flow resistance outweighs the benefit of improved melting and thus reduces the attainable flow rate. When normalizing for the maximum transferable extruder force, the smaller filament diameter consistently yields superior throughput performance. The simulations reproduce the experimentally observed trends well and support the interpretation that throughput is limited by the competition between heat-transfer-controlled melting and viscous pressure losses.

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