Extrusion Processing Conditions of Copper Fiber-Reinforced PLA Filaments: Influence of Extrusion System and Fiber Loading on Stability and FFF Printability

Polylactic acid (PLA) is widely used in fused filament fabrication (FFF); however, its limited thermal and mechanical performance restricts broader application. In this study, PLA was compounded with fine cut copper fibers to investigate the effect of metal fiber content on filament extrusion behavior, with a focus on melt flow stability and filament diameter consistency. Copper fibers with a diameter of 0.05 mm and an average length of 1.2 mm were incorporated at 5 - 60 wt.%. Filaments with target diameters of 1.75 mm and 2.85 mm were produced using two different extruders with real-time optical diameter monitoring, and processing parameters were optimized for each composition. All formulations were successfully extruded, although increasing fiber content resulted in greater sensitivity of filament diameter to processing conditions. Diameter variations of 1.5–2.0 mm and 2.7–2.9 mm were observed for 1.75 mm and 2.85 mm filaments, respectively. Pyrolysis analysis confirmed good agreement between intended and actual copper fiber contents. Among the filaments produced using the 3devo Composer 450 extruder, the formulation containing 5 wt.% copper fibers with a diameter of 2.85 mm exhibited the highest dimensional stability and was successfully printed using a commercial Ultimaker 2+ system. In comparison, the ARTME Desktop Filament Extruder produced filaments with more consistent diameters across the investigated composition range, and all formulations containing up to 40 wt.% copper fibers were successfully printed, demonstrating the improved printability achievable with this extrusion system.