Modeling of the chemical finishing process for polylactic acid parts in fused deposition modeling and investigation of its tensile properties

Fused deposition modeling has become one of the most diffused rapid prototyping techniques, which is widely used to fabricate prototypes. However, further application of this technology is severely affected by poor surface roughness.primarily due to staircase effect. It is necessary to adopt post-treatment operations to improve surface quality. Chemical finishing is typically employed to finish parts in fused deposition modeling. The purpose of this paper is to provide a universal finishing method or solution for FDM parts made up of PLA, and to represent the evolution of surface topography between adjacent layers during the chemical finishing operation by building a geometrical model of the deposited filament. Case study was used to validate the proposed model by an experimental observation using a 3D laser scanning microscope. The comparison between theoretical computed values and observed data shows a significant reliability by means of statistical analysis. Subsequently a number of specimens are tested to determine the changes in tensile properties of fused deposition modeling parts building in different orientations. The results show that the horizontal build directions have little influence on the tensile strength. And, untreated specimens of polylactic acid show brittle behavior due to the inherent material properties. Because of the thin transparent film formed on the appearance, the tensile mechanical properties of specimens after chemical finishing are obviously changed, with the result that the tensile strength reduces by 63% and elongations at break improve by 50%. This chemical finishing not only decreases the roughness of parts manufactured in fused deposition modeling significantly, but also improves the toughness of polylactic acid parts. (C) 2016 Elsevier B.V. All rights reserved.