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In this study, the effects of multiple printing parameters on the screw pull out force of PLA samples produced with a 3D printer were investigated statistically. Based on the Taguchi L27 orthogonal array, tests were carried out at different levels of printing speed, printing temperature, infill density, build plate temperature and infill pattern factors. Experiment results were assessed at the 95 % confidence level with analysis of variance, main effects and interaction graphs. Thus, the effects of factors and some two-way interactions on the screw pull out force and the levels that give the optimum response are determined. Accordingly, it is obtained that only the printing temperature, infill rate, infill pattern and printing temperature-fill rate factors and interactions are significant; It is also found that the infill density has the highest effect on the holding force with 55.08 %, followed by the printing temperature (18.62 %), printing temperature-infill density (12.19 %) and infill pattern (4.03 %). Finally optimum pull out force is predicted at the second level of printing speed (A2= 50 mm/s), third level of printing temperature (B3= 230 ° C), third level of infill density (C3=100 %), third level of build plate temperature (D3=80 ° C) and the first level of infill pattern (E1= Grid) as 1885.89 N. In 3 confirmation experiments performed at these levels, an average pull out force of 1993.33 N is obtained and it is determined that the result was within the specified confidence interval. Thus, the optimization made is of sufficient accuracy. [ABSTRACT FROM AUTHOR]

In the last century, polymer materials such as polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyethylene terephthalate glycol (PET-G) are widely used in many industrial fields due to being light, cheap, sustainable, and providing enough strength for engineering applications. Although plastic materials are mostly manufactured by the extrusion method, the 3D printing method is also taking the attention of researchers in the last decade because of its advantages over traditional methods. When the literature efforts about 3D printed polymers are examined, it can be seen that they are mostly focused on mechanical performance-determining processes such as tensile, compression, and threepoint bending. In this performance, the effect on layer height on the drop-weight impact behavior of 3D printed PET-G samples with fused deposition modelling (FDM) was examined at the various ambient temperature of 20°C, 40°C, and 60°C besides determining the hardness and tensile strength of the specimens. The results show that a maximum average hardness value of 69,4 Shore D was obtained at the specimen with layer height of 0,4 mm. It was determined that as the layer height value increased, the hardness values of the structures increased and the tensile strength values decreased. Besides, it can be stated that the layer height plays a more important role in the energy absorption amounts of the parts than the test temperature. Lastly, according to macroscopic and microscopic detections, no cracks were observed in the samples with a layer height of 0.4 mm, while it was determined that cracks were formed extending from the center to the corners in the samples with a layer height of 0.1 mm and 0.2 mm. [ABSTRACT FROM AUTHOR]

In this study, it was aimed to experimentally compare the mechanical properties of the traditional honeycomb structure, which is one of the cellular structures with its own specific area of use with its features such as lightness and load absorption, and the new generation re-entrant, chiral and hybrid structure (re-entrant + honeycomb) with negative Poisson behavior. In this context, standard test samples with honeycomb, reentrant, chiral and hybrid structures were produced with fused deposition modelling (FDM) under optimum conditions by using PLA material and different geometric parameters. Tensile and compression tests, hardness tests and surface roughness measurements were carried out with the specimens that were additively manufactured. According to the results, it was determined that the direction of the unit cells in the cellular structure and the rib thickness affect the energy absorption properties of the cellular structures. While the tensile and compressive strengths of the cellular structures increased with increasing rib thickness, the average Ra value and hardness value were measured as 14 μm and 75 Shore D respectively. Although negative Poisson ratio was observed depending on the amount of deformation in re-entrant, chiral and hybrid structures, positive Poisson behavior was observed in honeycomb structures. [ABSTRACT FROM AUTHOR]