Impact of infill strategy and process parameters on selectivity and performance of PLA structures obtained by 3D printing

In recent years, fused deposition modeling (FDM) techniques have become essential for the future of additive manufacturing. One of the main challenges is to identify the optimal printing parameters that enhance the quality, productivity, and durability of the resulting structures. Although hardness is critical for mechanical strength and wear resistance, it has been little studied in polylactic acid (PLA) structures. This study addresses this gap by evaluating the impact of FDM process parameters on microhardness using design of experiments (DOE) tools. Factors such as filling strategy, extrusion temperature, and layer count were analyzed. Response surface methodology (RSM) and ANOVA analyses were employed to develop a decision-support strategy. Vickers microhardness was measured for various PLA samples under different 3D printing conditions. In this context, by correlating structural homogeneity with microhardness, a performance index was established to maximize microhardness while minimizing heterogeneity. The study identified optimal printing conditions: a ZIGZAG filling strategy, an extrusion temperature of 230 °C, and four layers, each with a thickness of 0.2 mm. These conditions allowed for an increase in the microhardness of PLA structures by up to 400%, with a microhardness variability of less than 16% (more homogeneous PLA structure).