Investigation of the effect of additive manufacturing process parameters on the fabrication of a 3D-printed talus bone prototype

<jats:p>Introduction. Additive manufacturing, and in particular fused deposition modelling (FDM), enables the fabrication of geometrically complex parts without dedicated tooling, which is especially valuable for patient-specific biomedical devices. The mechanical performance of polylactic acid (PLA) parts, however, depends strongly on the combination of printing parameters, and the available data on the joint influence of layer thickness, nozzle temperature, and material flow rate on the full set of strength characteristics remain fragmentary, which complicates process selection for anatomical prototypes. The aim of this work is to determine the optimum combination of FDM printing parameters for PLA parts that maximizes the integrated strength response, and to fabricate, using the identified settings, a full-scale patient-specific prototype of the human talus bone from computed tomography data. Materials and methods. A Taguchi L27 orthogonal array was implemented with three levels of layer thickness (0.1–0.3 mm), nozzle temperature (190–210 °C), and material flow rate (95–105%). Tensile strength and Young's modulus were determined in accordance with ASTM D638–22 on a universal testing machine at a crosshead speed of 5 mm/min; specific fracture energy (toughness) was measured according to ASTM D256–23 using a notched Izod pendulum impact tester. The significance of the factors was evaluated by analysis of variance (ANOVA), and multi-response optimization was performed by grey relational analysis (GRA). The geometry of the fabricated prototype was inspected on a coordinate measuring machine. Results and discussion. Material flow rate was found to be the dominant factor for tensile strength (contribution of 50.3 %) and for toughness (92.9%), whereas Young's modulus is governed primarily by layer thickness. The highest grey relational grade (0.853) was obtained at a layer thickness of 0.1 mm, a nozzle temperature of 210 °C, and a flow rate of 105%. The dimensional deviations of the fabricated prototype from the CT data did not exceed 0.2 mm, which confirms its suitability as a master model for the subsequent manufacture of an implant from a biocompatible material.</jats:p>