Effect of 3D printing process parameters on surface and mechanical properties of FFF-printed PEEK

Fused filament fabrication (FFF), as one of the most commonly used additive manufacturing (AM) technology, draws lots of attention in fabrication of polymer-based materials because of its simplicity and relatively low-cost. Recent advances in FFF printing enables fabrication of high-temperature and high-performance polymeric materials such as polyether ether ketone (PEEK). The objective of this work is to evaluate the effects of different process parameters of FFF printing on mechanical and tribological properties of PEEK polymers. The properties of interest include surface mechanical properties measured through indentation and roughness tests as well as bulk mechanical properties defined by tensile tests. We used the Taguchi method along with the analysis of variances (ANOVA) to determine the process parameters with the most significant effect on the outcomes. The process parameters of interest are nozzle temperature, platform temperature, infill percentage, layer height, and print speed. Nozzle temperature and layer height were the process parameters that significantly influenced the resultant roughness as well as the elastic modulus measured via indentation test (Nozzle temperature: p = 0.001, contribution = 36.1 % & p = 0.008, contribution = 41.9 %; layer height: p < 0.001, contribution = 41 % & p = 0.026, contribution = 29.7 % for roughness & elastic modulus measured by micro-indentation, respectively). There were no process parameters significantly affecting hardness and creep. For the bulk mechanical properties measured by tensile test, such as elastic modulus, yield strength, ultimate strength and modulus of resilience, infill percentage (p < 0.001 for all the measured properties), platform temperature (elastic modulus: p < 0.001, contribution = 8.9 %; ultimate strength: p = 0.024, contribution = 5.5 %), nozzle temperature (elastic modulus: p = 0.013, contribution = 3.5 %; ultimate strength: p = 0.041, contribution = 3.9 %; modulus of resilience: p = 0.034, contribution = 18.2 %) and layer height (elastic modulus: p = 0.005, contribution = 5.9 %; ultimate strength: p = 0.026, contribution = 4 %) were among the factors that show the most significant effect. Our results suggested that through an accurate control of FFF process parameters, this simple yet affordable three-dimensional (3D) printing technology can be utilized to fabricate PEEK polymers with desired mechanical and tribological performance.