To print an FDM 3D model without supports, keep overhangs under 45 degrees (FDM’s self-support threshold—each layer can support the next) by designing or orienting the model correctly.
Shallow overhangs (under 45°) prevent molten plastic from sagging; steeper angles need supports because the previous layer can’t hold the weight. Rotate the model in slicer software to lay flat parts that would otherwise require supports, or use brims to improve bed adhesion for small bases.
Before printing, use your slicer’s overhang preview tool to check for angles over 45 degrees—adjust the model’s orientation or simplify the design if you find any.