Mechanical properties of fused filament fabricated PEEK for biomedical applications depending on additive manufacturing parameters.

DESIGN: of experiments was employed to investigate the combinations of 3D-printing parameters for Polyether ether ketone (PEEK) with a fused filament fabrication (FFF) process and to quantitatively evaluate the quality of 3D printed parts. This research was conducted using a newly developed FFF 3D printer and PEEK filament. Standard PEEK parts were 3D printed for bending and compression tests. Based on the Box-Behnken design, a three factors based experiment was designed using the Response Surface Methodology (RSM). Nozzle diameter, nozzle temperature and printing speed were involved. The density and dimensional accuracy of these printed parts were evaluated, and the bending and compression tests were conducted. The nozzle diameter was found to be the most significant parameter affecting the bending and compression performance of the printed PEEK samples, followed by printing speed and nozzle temperature. The highest accuracy in sample width was obtained with a 0.6 mm nozzle while the most accurate diameter was obtained with a 0.4 mm nozzle. A combination of a 0.4 mm nozzle diameter, 430 °C nozzle temperature and printing speed of 5 mm/s was beneficial to get the densest samples and therefore the highest bending strength; a reduction of internal defects was achieved with a 0.2 mm nozzle, a higher nozzle temperature of 440 °C and slower printing speed leading to better bending modulus. The best compression properties were achieved with a 0.6 mm nozzle, with relatively low influence of the other parameters. Different parameter combinations have been found to obtain optimal mechanical properties. Optimized parameters for better dimension accuracy of small additively manufactured PEEK parts were also achieved depending on the shape of the specimens.