Supports are the necessary evil of FDM — the scaffolding that lets you print overhangs steeper than ~45°. Done well, they snap off in seconds and leave clean undersides. Done poorly, they fuse to the model, leave craters, or fail mid-print and take the whole job down with them. This is the complete operator's guide to support strategy.
Use tree (organic) supports for figurines and organic shapes — less material, easier removal, smaller scars. Use normal (grid) supports for mechanical parts with large flat overhangs — flatter, more predictable interface surfaces. Always enable support interfaces at 0.20–0.25 mm gap. Set overhang threshold to 50° (not the default 45°) to support only what truly needs it.
The 45° rule is the standard heuristic: anything overhanging steeper than 45° from vertical needs support. But it's softer than that — modern slicers and quality cooling let many printers do 55–60° cleanly, and bridges (horizontal spans between two supported edges) print without supports up to surprising distances.
Normal supports build a vertical column from the bed (or a lower model surface) up to the overhang. They're predictable, work everywhere, and produce flat, even interface surfaces.
Tree supports grow branching, organic structures up to the overhang. They use less filament, print faster (no infill grid), avoid contacting vertical walls, and leave much smaller scars on the model. They're the default choice for figurines, art prints, and complex organic shapes.
If you're working with a complex model, expect 30 seconds to several minutes of slicing time for tree support generation. This is normal — the algorithm is solving a 3D space optimisation problem.
Support interfaces are a denser top layer (or layers) at the boundary between support and model. They give the model's overhang a smooth surface to print onto. Without an interface, the model bridges across the loose support pattern below, leaving an ugly scarred underside.
Modern slicers (PrusaSlicer, OrcaSlicer, Bambu Studio, Cura) let you click on the model and paint exactly where supports should generate, overriding the automatic detection.
The best supports are no supports. A few design tricks remove the need entirely: