Curling and Drooping Overhangs: Cool, Angle and Tune Pressure Advance

A print that looks crisp on flat walls but turns into a frayed, lifted mess the moment a roof slopes outward is almost always a cooling and geometry problem, not a broken machine. Curling and drooping overhangs happen because the freshly extruded plastic on an unsupported edge stays soft long enough for it to either sag under gravity or shrink and lift as it cools unevenly. Fix the airflow, respect the angle, and tune one extrusion setting, and those edges come back clean.

Quick Answer

Run your part-cooling fan at 100% over overhangs, keep unsupported angles at or below 45 to 50 degrees from vertical, and slow the outer wall to roughly 15 to 25 mm/s. Curl is poor cooling plus too steep an angle, so cooling and angle are the two levers that matter most before you touch anything else.

Why overhangs curl and droop

Every overhang layer is partly hanging in mid-air, anchored only to the layer below. Two things go wrong. Drooping is gravity winning while the plastic is still molten, so the edge sags downward instead of holding its shape. Curling is the opposite force: as that thin lip cools and contracts, it pulls upward and lifts, and on the next pass the nozzle can clip the raised edge, which compounds the roughness layer by layer.

Heat is the common thread. The hotter and slower the plastic stays at the edge, the more both effects show up. That is why a print can look perfect on the bed-side walls and fall apart only where the geometry leans out.

Cool harder and slow down

Part cooling is your strongest tool. Set the fan to maximum over overhanging regions and print without an enclosure for PLA, since trapped heat keeps the lip soft. If you suspect your fan is underpowered or aimed poorly, a better-ducted cooling setup makes a real difference, and you can browse fan and printer upgrades through the popular printer accessories on the Evetech bestsellers shelf to sharpen airflow.

Pair cooling with a small temperature drop. Knocking the nozzle down 5 to 10 degrees within your filament's safe range lets each edge firm up faster. Then slow the outer perimeter to around 15 to 25 mm/s so the plastic has time to set before the next layer lands on top of it.

Respect the angle and tune pressure advance

Most FDM machines print overhangs cleanly up to about 45 degrees from vertical. Push past 50 to 60 degrees and even good cooling struggles, so either add support, reorient the model, or design a chamfer instead of a sharp lip. Lower layer heights also help, because thinner layers expose less unsupported area per pass.

Pressure advance (called linear advance on some firmware) controls how the printer manages pressure in the nozzle on speed changes. Dialled in, it keeps extrusion even as the head slows into an overhang, which stops the slight over-extrusion blob that makes a curled edge worse. Calibrate it with a test tower and change one value at a time so you can see what each step does. If you want a stronger machine that handles fine detail more predictably, compare current models in the desktop 3D printer range at Evetech.

Frequently Asked Questions

What overhang angle can I print without supports?

On most FDM printers, up to 45 degrees from vertical prints cleanly. Between 45 and 60 degrees quality drops and you need strong cooling, and beyond that you usually want supports or a redesign.

Does a hotter nozzle make curling worse?

Yes. A higher nozzle temperature keeps the edge molten for longer, giving it more time to sag or lift. Dropping the temperature a few degrees, within the filament's rated range, helps the edge solidify sooner.

Will pressure advance alone fix bad overhangs?

No. Pressure advance refines edge crispness once cooling and angle are already sorted, but it cannot rescue an overhang that gets no airflow or exceeds the printable angle. Treat it as the finishing tune, not the first fix.

Why does only one side of my print curl?

That side likely gets less direct fan airflow, or it faces the steepest overhang. Check the fan duct aim and consider rotating the model so the worst overhang sits where cooling is strongest.