3D printing has become a key manufacturing method in modern production, yet the process remains complex due to material melting, extrusion behavior, and numerous interacting technical parameters. The final geometry and dimensional accuracy of printed parts are highly sensitive to factors such as material properties, printing settings, and machine precision, often leading to defects when parameters are not optimized. This study investigates the influence of four major FDM printing parameters - nozzle temperature, printing speed, printing angle, and infill percentage - on the shrinkage behavior of Polylactic Acid (PLA), one of the most widely used polymers for technical components. Each parameter was examined at three levels using a Taguchi L27 orthogonal array, resulting in 27 experimental conditions. For every condition, five specimens were fabricated, and each specimen’s length was measured at three positions to determine the average shrinkage value. The Taguchi method was applied to evaluate shrinkage through the signal-to-noise (S/N) ratio, yielding an optimal S/N value of 26.0206 with the corresponding optimal parameter set: nozzle temperature 210°C, printing speed 80 mm/s, printing angle 90°, and infill density 100%. ANOVA results further confirmed that nozzle temperature, printing angle, and infill percentage significantly affect shrinkage, while printing speed has a comparatively minor impact. The ranking of factor influence from highest to lowest is: printing angle, nozzle temperature, infill density, and printing speed. This study provides a systematic and practical optimization framework for minimizing shrinkage in PLA 3D-printed products, offering valuable guidance for enhancing dimensional accuracy and manufacturing quality in the additive manufacturing industry.