Fused Deposition Modeling (FDM) is classified as the most commonly used 3D printing process due to its low cost, wide range of material selection, and high accuracy. As an additive manufacturing method, FDM selectively deposits a melted plastic material layer by layer to produce a 3D object according to a geometry defined by a CAD model. The 3D printing process parameters, including infill density, printing speed, and printing orientation, have a huge effect on the mechanical properties of the 3D printed parts. Thus, finding the optimum 3D printing parameters is a very significant task that enriches the FDM 3D printing process, resulting in 3D printed parts with augmented mechanical performance. The present study investigates the effects of the FDM injector’s nozzle diameter and printing path direction (raster angle) on the mechanical properties of the nylon/carbon fiber composite 3D printed parts. The two targeted parameters are optimized through experimental tests on the elastic and flexural strength. Their impact on the nylon/carbon fiber composites’ microstructure is also explored deploying Scanning Electron Microscopy (SEM). The findings provide a comprehensive understanding of the mechanical performance of nylon/carbon fiber composite 3D printed parts. In addition, inspecting the internal microstructure of the materials, especially at the interface zone between the nylon and carbon fiber, provides an explanation of the material composites’ failure mechanism under various loads.

This study investigates experimentally and statistically the influences of the Machining Parameters (MPs) and environments on the surface roughness (Ra) of Polyamide 6 (PA6) during the turning operation. The experiments were conducted using a lathe machine, carbide cutting tool, and roughness tester. The statistical approach was implemented using Taguchi Experiment Design (TED) and Analysis of Variance (ANOVA). The parameters and their values were: cutting velocity (VC) of 125, 200, and 250 m/min; feed rate (FR) of 0.05, 0.1, and 0.15 mm/rev; and cutting depth (DC) of 2, 4, and 6 mm. The environments used were: dry (D), compressed air (A), and air-water mixture (A+W). The research aimed to improve the cutting surface quality of PA6 based on the R criterion. The results revealed that the FR is the most influential factor on R compared to other factors. The effect percentages on R were 61%, 15%, 13%, and 11% for FR, Machining Environments (MEs), DC, and VC, respectively. The optimum combination has been achieved based on an FR of 0.05 mm/rev, air with water, a DC of 2 mm, and a VC of 125 m/min, providing a minimum total average surface roughness (Ra) of 1.2 μm for PA6. The study demonstrates that an optimum combination can enhance the cutting surface quality, reduce the machining costs, and provide a pathway for producing high-performance PA6 components.