WEAK OR SAGGING OVERHANGS
Overhangs sagging, curling up, or printing as fuzzy strings? This is a cooling and speed problem. Maximize cooling, slow overhangs, and reorient where possible.
⚡ 5–15 minbeginnerhigh confidenceoverhangscoolingspeed
Quick Fixes
Part cooling fan: 100% (PLA), 70-80% (PETG), 30-50% (ABS)
Overhang speed: 50% of normal print speed
Lower nozzle temp 5-10C
Reduce layer height to 0.16-0.20 mm
Add supports or reorient past 55-60 degrees
WHY THIS HAPPENS
Every overhang line is partially unsupported. The line below it doesn't extend all the way under the new line, so part of the new line hangs over open air. Surface tension and partial support from the previous line hold it in place - but only if the plastic solidifies fast enough. Hot, fluid plastic deposited over an unsupported edge has no choice but to droop or curl as it cools, because surface tension and gravity both pull the molten edge inward.
The critical variable is cooling power. A part fan at 100% on PLA can solidify the leading edge of an overhang line within milliseconds, locking the geometry before any sagging occurs. The same overhang at 30% fan stays molten long enough that surface tension distorts the edge into a curl. This is why PLA prints clean overhangs to 60-70 degrees while PETG and ABS struggle past 45-50 degrees - they tolerate less cooling.
Overhang speed amplifies the cooling problem. At 60 mm/s the nozzle deposits a millimetre of plastic every 17 milliseconds; cooling has barely started before more hot plastic arrives next to it. At 25 mm/s, each millimetre has 40 ms to firm up before a neighbour shows up. Slowing overhang moves to 50% of normal print speed gives the cooling fan time to win against gravity.
WHEN THESE FIXES FAIL
**If overhangs sag uniformly downward** - cooling is too low and/or speed is too high.
**If overhangs curl upward** - they're solidifying then warping due to differential cooling. Drop nozzle temperature 5-10C and ensure fan is at max for the filament.
**If only steep overhangs (>50 degrees) fail** - that's beyond your printer/filament limit. Add supports or reorient.
**If overhangs got worse after switching to PETG or ABS** - normal. These filaments tolerate less cooling and overhang less cleanly than PLA.
**If overhangs work on small features but fail on large ones** - the nozzle is moving too fast across the unsupported area. Slow overhang speed.
**If overhangs only fail in tall thin features** - cooling can't reach the small top surface effectively. Print taller features at lower speeds with maximum fan.
MOST LIKELY CAUSES
1
Insufficient cooling
high confidence
Overhangs need fast cooling so unsupported plastic solidifies before it sags or curls.
→ Set overhang fan to the highest stable value
→ Use 100% fan for PLA-style overhang profiles
→ Use separate overhang fan settings if your slicer supports them
2
Overhang speed too high
high confidence
Fast overhang moves do not give each unsupported line enough time to firm up.
→ Set overhang speed to 50% of normal print speed
→ Enable automatic overhang speed reduction
→ Reprint the overhang test at the slower overhang speed
3
Nozzle temperature too high
medium confidence
Hot filament stays soft longer and droops before it can support the next line.
→ Lower nozzle temperature by 5-10C
→ Reduce layer height to 0.16-0.20 mm
→ Add supports or reorient geometry past 55-60 degrees
WANT SETTINGS TUNED FOR THIS ISSUE?
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Generate SettingsWhat It Looks Like
Overhanging surfaces sag, curl upward, or print as a fuzzy stringy mess instead of a clean angled face.
Why It Happens
Every overhang line is partially unsupported. The line below it doesn't extend all the way under the new line, so part of the new line hangs over open air. Surface tension and partial support from the previous line hold it in place - but only if the plastic solidifies fast enough. Hot, fluid plastic deposited over an unsupported edge has no choice but to droop or curl as it cools, because surface tension and gravity both pull the molten edge inward.
The critical variable is cooling power. A part fan at 100% on PLA can solidify the leading edge of an overhang line within milliseconds, locking the geometry before any sagging occurs. The same overhang at 30% fan stays molten long enough that surface tension distorts the edge into a curl. This is why PLA prints clean overhangs to 60-70 degrees while PETG and ABS struggle past 45-50 degrees - they tolerate less cooling.
Overhang speed amplifies the cooling problem. At 60 mm/s the nozzle deposits a millimetre of plastic every 17 milliseconds; cooling has barely started before more hot plastic arrives next to it. At 25 mm/s, each millimetre has 40 ms to firm up before a neighbour shows up. Slowing overhang moves to 50% of normal print speed gives the cooling fan time to win against gravity.
What The Community Data Says
Based on 145 confirmed fixes from r/FixMyPrint, these are the causes ranked by how often they actually worked:
1. Part cooling fan too low - cranking to 100% (PLA) or to filament max (PETG 70-80%, ABS 30-50%) fixed most cases. Many users had reduced fan to fix delamination and inadvertently broke their overhangs.
2. Overhang speed too high - dropping to 50% of print speed on overhanging perimeters specifically (most modern slicers expose this) gave cooling time to work.
3. Nozzle temperature too high - dropping 5-10C produced firmer-on-deposit plastic that resisted sagging.
4. Layer height too tall - going from 0.28 mm to 0.16-0.20 mm reduced the unsupported overhang per layer and produced cleaner steep angles.
5. No supports on geometry past 55-60 degrees - users insisted their printer 'should' bridge it, but the real fix was adding supports or reorienting the model.
Data sourced from r/FixMyPrint - one of the largest 3D printing troubleshooting communities on Reddit. This represents real user-reported issues and community-confirmed fixes, not theoretical advice.
How To Diagnose Your Specific Cause
If overhangs sag uniformly downward - cooling is too low and/or speed is too high.
If overhangs curl upward - they're solidifying then warping due to differential cooling. Drop nozzle temperature 5-10C and ensure fan is at max for the filament.
If only steep overhangs (>50 degrees) fail - that's beyond your printer/filament limit. Add supports or reorient.
If overhangs got worse after switching to PETG or ABS - normal. These filaments tolerate less cooling and overhang less cleanly than PLA.
If overhangs work on small features but fail on large ones - the nozzle is moving too fast across the unsupported area. Slow overhang speed.
If overhangs only fail in tall thin features - cooling can't reach the small top surface effectively. Print taller features at lower speeds with maximum fan.
Fixes By Cause
Cause 1: Maximize part cooling
PLA: 100% always. PETG: 70-80% on overhangs (use slicer's overhang fan setting separately from main fan). ABS/ASA: 30-50% on overhangs only. PrusaSlicer/OrcaSlicer/Bambu Studio expose 'overhang fan speed' as a separate setting. Crank it.
Cause 2: Slow overhang perimeters
Set overhang speed to 50% of normal print speed. Modern slicers (PrusaSlicer, OrcaSlicer, Bambu Studio) auto-detect overhang segments and apply this slower speed only to those segments. Cura: enable 'Overhanging walls' speed reduction in experimental settings.
Cause 3: Lower nozzle temperature
Drop 5-10C to give freshly-deposited plastic less time fluid. PLA at 200-205C overhangs cleaner than 215C. PETG at 230C overhangs better than 245C - but watch for layer adhesion issues if you go too low.
Cause 4: Reduce layer height
0.16 mm layer height with 0.4 mm nozzle is the sweet spot for steep overhangs. Each layer overhangs less than the next, so visible aliasing decreases. The print takes longer but produces noticeably cleaner overhang surfaces.
Cause 5: Add supports or reorient
For any geometry past 55 degrees off vertical (or 35 degrees from horizontal), enable supports. Most slicers default to 50-55 degree threshold. Tree/organic supports leave less scarring than traditional grid supports. Or rotate the model to put the overhang on a face that prints upright.
Printer-Specific Notes
Bowden printers (Ender 3 family): Stock fan ducts are notoriously poor. Replace with a CR-Touch dual fan duct or printable upgrade like the Hero Me Gen 7 - dramatic overhang improvement. Keep fan at 100% for PLA without exception.
Direct drive printers (Bambu, Prusa MK4S): Strong fans built in. Bambu printers can do 70-degree overhangs reliably with default profiles because of their cooling design. Prusa MK4S has good cooling out of the box.
Enclosed printers (Bambu P1S, K1 Max): Hot chamber air reduces cooling effectiveness even at 100% fan. For PLA, vent the door to let cooler air in. ABS overhangs in an enclosed printer will be worse than open-air ABS - consider supports more readily.
Filament-Specific Notes
PLA / PLA+: Best overhang performance. Reliable to 60-65 degrees with good cooling.
PETG: Reliable to 45-50 degrees. Beyond that, add supports. PETG overhangs always look stringier than PLA overhangs even with optimal settings.
ABS / ASA: Reliable to 35-45 degrees. The narrow cooling tolerance limits steep overhangs. In an enclosure expect even less.
TPU: Surprisingly good overhang performance because TPU is flexible and doesn't crack from minor sagging. Reliable to 50-55 degrees.
PC: Poor overhangs - low cooling tolerance combined with high print temperature. Use supports liberally past 30-35 degrees.
How To Prevent It Next Time
Set overhang speed reduction (to 50% of normal speed) as a default in your slicer profile. Modern slicers handle this automatically per overhang segment.
Run an overhang test print (search Printables for 'overhang test') with each new filament to know your printer's reliable angle limit. Add supports above that limit instead of fighting it with settings.
Keep the part cooling fan duct intact and aimed correctly. A bent duct is the most-overlooked cause of bad overhangs on aging printers.
Get An Exact Fix For Your Setup
Use FixMyPrint to get fan speed, overhang speed, layer height and support angle threshold tuned for your specific printer and filament - based on what actually worked for similar issues in the community.
Go to /settings-generator to generate yours.
Recommended Slicer Settings
Related Guides
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Supports leaving ugly marks on overhangs and bridges? Fix Z-distance, interface layers, support pattern and switch to tree/organic supports for clean release.
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Rough or Pillowing Top Surface
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