Screw extrusion-based additive manufacturing of PEEK

Polyether-ether-ketone (PEEK) has high mechanical strength, thermal performance, and biocompatibility, and is widely used in biomedical and chemical engineering applications. However, to date there are no guidelines for the building of a 3D printer for highly viscous materials, e.g., PEEK. In this paper, a screw extrusion method was developed to overcome the existing problems of the filament-feeding method. Excellent flow stability (<3% variation) and high printing speed (up to 370mm/s) for PEEK printing were achieved. Highly reproducible mechanical tests of the printing products were demonstrated with 96% of the bulk material strength for the first time. Furthermore, an exchangeable printing head was built to cover both line- and plane-printing needs to widen its applications and improve printing surface quality (up to 0.945nm in Ra). All printed material had a more brittle character in comparison with the bulk material and the post annealing process was found to have no significant effect on the mechanical strength. Additionally, porous artificial intervertebral cages with controllable size and distribution were manufactured to demonstrate potential applications.