Integrating short carbon fibers into polymers for extrusion-based three-dimensional printing represents a promising strategy for developing high-performance mechanical components. This study investigates the interplay between manufacturing parameters and environmental conditions to enhance the predictability of carbon fiber-reinforced Polylactic Acid performance through a multi-response optimization approach. Addressing a critical gap in the literature through the systematic inclusion of five environmental covariates within a full-factorial framework that has not been previously reported for fiber-reinforced Polylactic Acid composites. By combining this experimental design with a custom Python-based backward elimination algorithm, the study evaluates the effects of layer thickness, printing temperature, and printing speed. Analysis of variance reveals a peak Ultimate Tensile Strength of 52.09 MPa with 0.08 mm, 240 °C, and 20 mm/s; an elongation of 0.046 mm/mm with 0.08 mm, 210 °C and 20 mm/s; a top surface hardness of 75.15 with 0.1 mm, 240 °C, and 70.1 mm/s; and a bed surface hardness of 77.38 with 0.14 mm, 240 °C, and 20 mm/s. Furthermore, chamber temperature significantly improves interlayer thermal fusion, and surface hardness is maximized near the print bed due to prolonged thermal consolidation. Conversely, increased layer thickness constrains geometric precision, negatively impacting dimensional accuracy. These findings underscore the necessity of strictly controlling both manufacturing and environmental factors to optimize mechanical and dimensional properties, highlighting the material's potential for demanding engineering applications.
