Experimental Study of In-Process Heat Treatment on the Mechanical Properties of 3D Printed Thermoplastic Polymer PLA

Abstract

The scientific literature regarding additive manufacturing, mainly the material extrusion method, suggests that the mechanical characteristics of the parts obtained by this technology depend on a number of the input factors specific to the printing process, such as printing temperature, printing trajectory, layer height, etc., and also on the post-process operations for parts, which, unfortunately, requires supplementary setups, equipment, and multiple steps that raise the overall costs. Therefore, this paper aims to investigate the influence of the printing direction, the thickness of the deposited material layer, and the temperature of the previously deposited material layer on the part tensile strength, hardness by means of Shore D and Martens hardness, and surface finish by using an in-process annealing method. A Taguchi L9 DOE plan was developed for this purpose, where the test specimens, with dimensions according to ISO 527-2 type B, were analysed. The results showed that the presented in-process treatment method is possible and could lead to sustainable and cost-effective manufacturing processes. The varied input factors influenced all the studied parameters. Tensile strength tended to increase, up to 12.5%, when the in-process heat treatment was applied, showed a positive linear variation with nozzle diameter, and presented considerable variations with the printing direction. Shore D and Martens hardness had similar variations, and it could be observed that by applying the mentioned in-process heat treatment, the overall values tended to decrease. Printing direction had a negligible impact on the additively manufactured parts’ hardness. At the same time, the nozzle diameter presented considerable variations, up to 36% for Martens hardness and 4% for Shore D, when higher diameter nozzles were used. The ANOVA analysis highlighted that the statistically significant factors were the nozzle diameter for the part’s hardness and the printing direction for the tensile strength.

Experimental Study of the Tensile Behavior of Structures Obtained by FDM 3D Printing Process

“…However, the mechanical properties remain steady starting from the extrusion temperature of 185 • C. Additionally, it was observed that the print speed and the tested infill patterns had a negligible effect on the mechanical properties. However, the nozzle diameter has an effect on the mechanical parameter, as investigated by Tamas , ag et al [23]. They considered only the Cubic infill pattern (grid), and they added contours (covering walls) to the tensile specimens.…”

Effect of heat treatment on mechanical properties and dimensional accuracy of 3D-Printed black carbon fiber HTPLA

“…In addition, another study examined the effects of in-process annealing by manipulating printing direction, layer thickness, and temperature. The results indicate that heat treatment positively impacts tensile strength, while nozzle diameter and printing direction affect hardness [ 12 ]. The findings suggest the viability of in-process treatments for enhancing manufacturing processes, potentially leading to cost-effective and sustainable outcomes.…”

Innovative Strategies for Technical-Economical Optimization of FDM Production

“…Based on Taguchi analysis, it was highlighted that orientation angle and shell thickness notably impact ultimate tensile strength and moderately influence dimensional accuracy, with a focus on achieving optimal manufacturing outcomes. Similarly, in [ 16 ], the ANOVA analysis emphasized the nozzle diameter as the significant factor for a PLA 3D-printed part’s hardness, while for the tensile strength, the significant factor was identified to be the printing direction.…”