Flow rate-dependent interlayer adhesion in FDM: a thermal and mechanical analysis

This study investigates the impact of material flow rate on the tensile properties of components produced via fused deposition modeling (FDM), also known as material extrusion (MEX). A comprehensive experimental plan was conducted using polylactide acid (PLA), varying nozzle diameter (0.4–0.8 mm) and layer height (37.5–62.5% of nozzle diameter) to achieve flow rates between 2.4 and 16 mm3/s. Infrared thermography was employed to analyze cooling rates during deposition, while tensile tests along the building direction assessed interlayer adhesion. The extruder’s energy consumption was monitored using a current sensor. Results reveal a complex interplay between material flow rate, thermal history, void dimensions, and mechanical behavior. Notably, smaller nozzle diameters (0.4 mm) produced components with small voids and high specific energy but short cooling times, while larger nozzles (0.8 mm) led to higher thermal inertia, longer cooling times, and larger voids. An intermediate nozzle diameter (0.6 mm) offered an optimal balance, resulting in improved tensile strength and elongation at rupture. This study highlights the critical relationship between process parameters, thermal dynamics, and mechanical properties in FDM, providing insights for optimizing print speed and component performance.