Study of samples geometry to analyze mechanical properties in Fused Deposition Modeling process (FDM)

Abstract

Parts manufactured by Fused Deposition Modeling (FDM) present anisotropic properties, which have influence in tensile test results. In this paper, test samples of Polylactide (PLA) are manufactured by FDM according to geometries defined in UNE-EN ISO 527-2:2012 and ASTM D638-14:2014. Manufacturing parameters as wall thickness, orientation of building wall lines, and orientation of infill pattern have beeen studied. A nomenclature to define manufacturing direction of sample is also developed. Stress concentration can modify obtained results in tensile test, and it could be due to geometrical discontinuities, pressure points and thermal shock. Standard and no standard geometries have been evaluated to test FDM process. In order to avoid premature sample failure by stress concentration, different strategies have been developed: manufacturing samples with a rectangular geometry, an annealing treatment and to manufacture the samples as union of different parts. Last strategy has allowed to reduce stress concentration zones and to improve tensile strength values.