Optimizing Parameters Affecting the Output Fibers of Thermoplastic Polylactic Acid Filament Machine Reinforced with Continuous Carbon Fibers

The fused deposition modeling (FDM) or material extrusion method is one of the most popular techniques for 3D printing. Given the challenges in producing 3D-printed parts with high mechanical strength and adequate surface quality, this study focuses on optimizing the parameters affecting the output fibers of a newly developed filament extruder, which has the capability of producing reinforced composite filaments. The optimization process involves evaluating parameters such as polymer melting temperature, filament collection speed, water bath temperature, and impregnation speed, and their effects on interfacial shear strength (IFSS). Statistical methods, such as design of experiments (DOE) and analysis of variance (ANOVA), were employed for this purpose. The results confirmed uniform impregnation of fibers and matrix through scanning electron microscope (SEM) images. It was also demonstrated that an increase in temperature does not necessarily lead to an increase in IFSS, and there is a risk of thermal degradation of the matrix. Moreover, low-viscosity melt can compromise geometric stability, indicating that temperatures above 230°C are not optimal for filament impregnation. Consequently, the optimal conditions for producing composite filaments with continuous carbon fibers and polylactic acid (PLA) resin were determined to be a melting temperature of 190°C, water bath temperature of 50°C, filament collection speed of 2 rpm, and impregnation speed of 1 rpm.