Effects of extrusion speed and printing speed on the 3D printing stability of extruded PEEK filament

In fused deposition modeling (FDM) using polyether-ether-ketone (PEEK), the dimensions of extruded filaments are unstable and there is insufficiency dimensional agreement between the fabricated part and design model. The present study presents the effects of the extrusion speed and printing speed on the microstructure and dimensions of an extruded PEEK filament in 3D printing. The extrusion process characterization including extrusion force and extrusion resistance was measured for the understanding of the evolution of extrusion process with the increase in extrusion speed. The relationship between the extrusion speed and the diameter of the extruded filament was established by measuring the diameter of the extruded filament at different extrusion speeds in freeform extrusion. Furthermore, PEEK was stably printed in an experiment with increasing printing speed and it was revealed that the control algorithm that mathematically replaces the nozzle diameter with the diameter of the extruded filament is feasible and effective. During PEEK FDM, the melt pressure in the chamber directly affects the surface morphology and extrusion diameter of the extruded filament, and higher melt pressure is beneficial to reducing surface defects of the extruded filament. A fluctuating extrusion force is the main constraint on the stability of extrusion. The optimized control algorithm between the extrusion speed and the diameter of the extruded filament improve the stability of PEEK FDM and improves the dimensional accuracy and surface morphology of printed PEEK parts. Furthermore, this study could be applied to reveal the instability of extrusion and select a set of suitable printing parameters during FDM.