The maximum angle (measured from the vertical) at which a surface can be printed without supports; beyond this limit the layer has insufficient support from the layer below.
An overhang exists when part of a layer extends beyond the layer below without support. The critical angle depends on how each process deposits or cures material. FDM relies on the cooled previous layer as a shelf; at 45° each new bead rests 50% on the previous bead and 50% on air: the practical limit. SLA has no solid shelf: uncured resin offers almost no support, so the limit drops to 30°. SLS is self-supporting (powder bed acts as support) and has no overhang angle limit. DMLS uses a powder bed too but high thermal gradients cause distortion above 45°.
Re-orient parts so critical surfaces face up or within the support-free angle. Use teardrop profiles for horizontal holes to eliminate overhangs. Split complex assemblies at natural overhang lines. In DMLS, minimise support volume by orientating overhangs to 45° exactly: each support requires post-process CNC/EDM removal.
Cooling performance affects FDM overhang limits significantly: with active part cooling, high-performance printers can reach 60°–65°; without cooling, even 30° droops. SLA users often under-support because the model appears solid on screen; trust the slicer's support analysis. Do not confuse angle from vertical with angle from horizontal: the rules here use angle from vertical.
Related terms: Maximum Bridge Length, Minimum Wall Thickness, SLA Drainage Holes for Hollow Parts
| Theme | geometry |
|---|---|
| FDM | <= 45 deg: 45° from vertical is the widely accepted FDM self-support limit. Beyond 45° each new layer overhangs more than 50% of its width, causing sagging and surface defects. |
| SLA | <= 30 deg: SLA resin layers cure in liquid and have less self-support than FDM; 30° from vertical is the safe limit before suction forces and resin weight cause delamination. |
| DMLS | <= 45 deg: DMLS metal powder has no binding at 45°+ overhangs: the melt pool loses support from the powder bed and the solidified slice sags or falls into powder. |
| Also called | overhang limit, support-free angle, critical overhang angle |
| Source | Wiki/tech/fdm-fff.md, Wiki/tech/sla.md, Wiki/concepts/support-generation.md |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert