Printing Setup and Sample Size Influence on the Mechanical Performance of Polylactic Acid Obtained by Material Extrusion

Material extrusion additive manufacturing was introduced in many industries due to some relevant features such as the capability to process complex geometries and internal microstructures, application of material combinations, low volume production, faster product development cycle and waste reduction. However, this technique also exhibits some drawbacks like highly restricted printable materials and a generally low mechanical performance. The wide variety of processing parameters combined with the influence of complex lattice structure, quality bonding and heating-cooling periods along the building cycle indicates that an extensive mechanical characterization should be performed to warrant the in-service success of 3D printed parts. This study aims to investigate the effect of material extrusion setup, raster pattern and specimen size on the tensile, flexural and fracture behavior. The experimental performance showed that the ductility (strain at break reduction of 50%) was drastically limited with large sample dimensions. Printing setup and raster patterns exhibited a marginal influence on tensile performance. Each test revealed different dependencies with printing parameters, particularly under flexural loading conditions. A coarse printing setup, promoting a reduction of build cycle times, combined with bidirectional patterns looked like a promising way to improve the mechanical performance of 3D printed parts.