How to Fix Drooping Overhangs

An overhang is any part of a model that extends outward with nothing solid underneath. Because FDM printing builds layer by layer, Bambu Lab's wiki notes that unsupported material tends to sag or deform under gravity. Droopy, rough or curled undersides are the result.

Why overhangs sag

Prusa describes the core problem: once melted plastic leaves the nozzle it is no longer under precise control, and when printing overhangs or bridges the plastic must freeze in place as soon as possible or it will sag. Fixes therefore fall into three groups: give the plastic something to rest on (supports, orientation), make it easier to freeze (cooler, slower, more air) or reduce the unsupported distance.

Quick reference

1. Look at the angle and add supports

Bambu Lab defines the overhang angle as the angle between the sloped surface and the heatbed. Its rule of thumb is that below 45 degrees supports are recommended, and above 45 degrees none are needed, though the other settings below can still improve quality. Do not confuse this with the "overhang threshold" setting, which measures the proportion of an extrusion line left unsupported. Learn how the options differ in supports explained.

2. Try rotating the model

Prusa's bridging guide gives the best solution as changing orientation until the troublesome overhangs or bridges disappear, because the surest way to avoid droop is to have no unsupported area. That is not always possible, but check before you generate supports.

3. Lower the nozzle temperature

For steep overhangs, Bambu Lab suggests a slightly cooler nozzle, because when overhang speed is slow the plastic then needs less cooling. For PLA it says other-layer temperature can go down to about 205 degrees C with the overhang cooling fan at 100%. For other filaments, check the filament's recommended range and lower by about 5 to 10 degrees C if needed. For third-party filament, Bambu Lab suggests printing a temperature tower. These figures come from Bambu Lab's own filament and printers, so use them as a starting point only.

4. Slow down on overhangs

Either lower the overall print speed or turn on slowing for overhangs. Bambu Lab says overhang speeds are generally set between 10 and 60 mm/s, with larger unsupported areas needing slower speeds. Slicers expose this as a "slow down for overhangs" option. Prusa's slicer also has a separate bridge speed. More on how speed affects quality is in print speed vs quality.

5. Add cooling

Prusa's cooling article explains that fans are the main tool to freeze plastic. In its slicer you can set a higher bridge and overhang fan speed than the normal print, and a dynamic fan option scales the fan by how much of the extrusion overlaps the layer below. Prusa notes that with some materials more cooling can worsen warping or layer separation, so tune per filament. Bambu Lab says to confirm the part cooling fan and auxiliary fan actually work during the print.

Bambu Lab also says opening the front door and lid can improve cooling for PLA, PETG and TPU, but is not advised for high-temperature filaments, which may then warp or have weak layers. See enclosed vs open-frame printers for how enclosures change this.

6. Treat bridges separately

Flat spans between two supports are bridges, not slopes. Prusa recommends a lower bridging flow, lower bridge speed, and optionally a support island halfway across a long bridge. Our poor bridging guide covers this.

Material notes

Prusa lists "poor bridging and overhangs" as a con of PETG, so budget for supports and strong cooling with it. See PETG vs PLA for the wider trade-offs.

If you add supports and they then fuse to the underside, this guide to supports stuck to the print covers the Z distance and interface settings.

Confirm the fix

Print an overhang test with steps at increasing angles, change one thing at a time and note the angle where the underside turns rough. That angle is your printer's practical limit for that filament.