Supports (3D Printing)

On FDM, an overhang above roughly 45° from vertical starts to droop because there is nothing under the new layer to hold it up. On resin printers, almost every part needs supports because parts hang upside down from the build plate and gravity pulls unsupported features off.

The slicer detects overhangs and generates support structures — tree-like branches in modern slicers, or simple grids in older ones. The support touches the part at small contact points so it peels away cleanly.

Supports are unavoidable for some shapes (a T, an inverted bowl, an outstretched arm). For everything else, you can usually eliminate them by reorienting the part on the build plate. That saves print time, material, and post-processing.

Tree supports (PrusaSlicer Organic, Bambu Tree, Cura Tree) touch the part at fewer points than grid supports, leaving cleaner surfaces. Soluble supports (PVA, BVOH) on dual-extruder printers dissolve in water and leave no marks at all.

Bridges — short horizontal spans between two walls — usually do not need supports. Up to 30–50mm, FDM bridges across air with surprisingly clean undersides. The slicer's overhang detection sometimes flags bridges as needing support; you can override.

SLS, MJF, and other powder processes do not need supports — the unfused powder holds the part up.