Investigation of the Critical Overhang Angle in Fused Filament Fabrication Technology

In fused filament fabrication, overhangs are challenging because each deposited layer requires partial support from the previous layer. The frequently cited 45° guideline for unsupported printing originates from empirical practice and does not consistently represent process‐specific behavior. This study presents a comparative analysis of two thermoplastic polymers, PLA and PETG. Samples were produced with inclination angles between 5° and 85° at 5° increments. For each configuration, three wall‐deposition strategies, Inner/Outer (IO), Outer/Inner (OI), and Inner/Outer/Inner (IOI), were applied while other process parameters remained constant. The measurement of geometric conformity indicates that the IOI strategy extends the allowable overhang: conforming geometry was observed up to 25° from the horizontal for PLA and up to 30° for PETG. These thresholds fall well below the conventional 45° rule, demonstrating that the critical overhang angle is dependent on the material–strategy combination rather than on a universal limit. The IOI strategy proved most effective because partially solidified internal layers directly support the outer wall, enhancing surface stability and dimensional accuracy.