The effect of annealing on the impact resistance of machine parts made using 3D-printing technology from polylactide

BACKGROUND: The 3D printing technology is rapidly developing, giving the opportunities for the manufacturing of parts with specified properties. However, the mechanical characteristics of materials obtained by 3D printing often do not meet the requirements for various applications, for example, agricultural machinery. Increasing the impact strength of materials produced by 3D printing is a relevant task for expanding their application. OBJECTIVE: Study of the effect of heat treatment (annealing) and 3D printing parameters (layer thickness, filling percentage) on the impact strength of the polylactide (PLA) samples. METHODS: An experimental study was conducted using the PLA samples made by 3D printing with variable parameters: layer thickness (0.15 mm, 0.20 mm, 0.25 mm) and percentage of filling (50%, 75%, 100%). The samples were annealed at a temperature of 80 °C for 2 hours. The impact strength was determined by the Charpy method using standard test equipment. RESULTS: 27 PLA samples were included in the study. Annealing significantly increases the impact strength of all samples. The dependence of the impact strength on the thickness of the layer and the percentage of filling was observed. The maximum impact strength (2.58 ± 0.12 J/cm2) was achieved with a layer thickness of 0.15 mm and 100% filling. Statistical analysis of the results performed using ANOVA (p 0.001) showed a significant influence of all factors on the impact strength. CONCLUSIONS: The results obtained demonstrate that annealing and optimization of 3D printing parameters (layer thickness, filling percentage) can increase the impact strength of materials obtained by 3D printing from PLA. The optimal parameters achieved in this study can be used in development of parts of agricultural machines with improved mechanical properties.