Correlação entre parâmetros de impressão 3D e a resistência mecânica anisotrópica de peças impressas em PLA

Abstract

Fused Filament Fabrication (FFF), better known as FDM© (Fused Deposition Modeling) is an additive manufacturing process (AM) by which a physical object can be created from a 3D model generated in the computer, through layer-by-layer deposition of half-melted plastic filaments. Once it is an efficient, durable and low-cost process, allowing the rapid prototyping of models and reducing the cost and design time ratio, it has been widely used in the industry for functional prototypes and low production volumes, since original patent break for FDM processes a large number of 3D printers have emerged in the consumer market, making this technology affordable and popular. However, parts produced by the FDM process have different characteristics compared to parts produced by traditional methods, such as plastic injection, especially with regard to mechanical properties related to stresses (tensile, compression, torsion and shear), due to the anisotropic nature of the process deposition. Because of this, it is important to identify and characterize the process parameters that have the greatest influence on the mechanical properties of parts manufactured using FDM. Many works have been carried out in order to determine the influence between the FDM process parameters and the mechanical characteristics of parts produced by this technology, but the vast majority of them analyze the longitudinal resistance caused by the direction and orientation of deposition of half-melted wires. The few works that address transversal anisotropy generally do so by simulating this anisotropy with specimens printed longitudinally and contemplate tests using ABS, a plastic very commonly used by the industry. In the last decade, a new plastic, PLA, has started to expand as a material used in 3D printers, especially printers for non-industrial use, as it is biodegradable and has other characteristics that make it more popular. This work try to figure out the relationships between the deposition properties (such as number of perimeters, percentual of filling, layer height and extrusion temperature) and the mechanical strength for tensile loads in the transversal direction of printed pieces, determining the contribution of these parameters and proposes a mathematical model to predict the resistance based on the geometry of the part, allowing the inclusion of printing parameters in its modeling. Tensile tests were carried out on a testing machine built especially for this research. To determine the experimental tests we use the factorial DOE methodology (Design of Experiment) to minimize the amount of experiments. Using analysis of variance (ANOVA) and the Taguchi method of analysis, we identified the Contact Area between the layers as the most relevant parameter in the tensile strength in the transversal direction of the printed layers, with a relevance of more than 95% over the other parameters studied. From the survey of relevant properties, new tests were carried out to determine the compromise solution between these parameters and the mechanical resistance of parts manufactured by FDM in PLA, suggesting a methodology to reduce the fragility of the parts due to transversal anisotropy.