Experimental analysis and optimization of the influence of layer height, infill pattern, and nozzle temperature on tensile strength, hardness, and relative density of FDM-PLA prints

Abstract The study explores the influence of layer thickness, infill pattern, and nozzle temperature on tensile strength, hardness, and relative density of FDM printed specimens of polylactic acid (PLA). Eighteen different sets of parameters were explored during the study, including two layers of thickness (0.1 and 0.2 mm), three different infill patterns (concentric, rectilinear, and octogram spiral), and three nozzle temperatures (210, 220, and 230 °C). The tensile test was done following ISO 527-2, the hardness test according to ASTM D2240, and the measurement of relative density was done using the Archimedes principle. From the results, it can be observed that the effect of layer thickness is significant where samples of 0.1 mm exhibited tensile strengths of 35–49 MPa compared to samples of 0.2 mm with tensile strengths of 34–48 MPa. The highest tensile strength was exhibited by concentric infill pattern due to its continuous load-bearing capacity, followed by rectilinear while the lowest was recorded by octogram spiral infill pattern. There was a significant correlation between the tensile strength and relative density ( r = 0.89, p < 0.001), and it reached its maximum at a value of 99 %. Analysis of the failure showed that rectilinear pattern had ductile failure, while octogram spiral pattern failed by delamination.