When an overhang curls into the nozzle, locate the first failed section before changing the profile. Use the current model, filament and cooling setup for a small comparison, altering one setting at a time. That gives the next print a question to answer.
Check the shape and the preview
Identify exactly where the defect starts. Distinguish an unsupported overhang from a bridge spanning two supports. Check the sliced preview for the toolpath, support and speed used at that point.
Make the test small while retaining the geometry that caused trouble. Keep its orientation, layer height and filament consistent, and save the failing baseline before changing anything. Work through shape and preview first, then the cooling hardware, then the profile comparison below. That is an order for isolating causes, not a claim that every curled edge has the same most likely cause. Changing cooling, speed and temperature together would leave a better-looking edge without a clear explanation.
Inspect the cooling hardware
Check the part-cooling fan and duct using the printer's instructions. Remove an obstruction only with the machine in the prescribed safe state. Do not move a duct nearer a hot nozzle or add a fan without checking the machine design.
Prusa's bridging guidance[1] identifies cooling, speed and bridge flow as relevant controls. A bridge recommendation is not automatically an optimal overhang profile for every material.
Tune within the material profile
Begin with the printer and filament maker’s supported profile. Try a modest cooling change or lower overhang speed, then inspect layer bonding as well as the outline. Give a 100% fan setting the same scrutiny on PLA or PETG before keeping it for the part.
If testing temperature, remain within the material and printer limits. Save each trial separately and note the actual change. Reject a cleaner-looking sample if it no longer has the integrity needed for the part.
Inspect short layers separately
Check the slicer’s cooling controls and per-layer time estimate separately from overhang speed. Prusa’s documented cooling controls[2] explain that automatic cooling can change both fan speed and print speed; the slowdown also has a minimum-speed limit. A high minimum speed can leave a short layer shorter than the requested layer-time target. Read the resulting behavior in the slicer before assuming that entering more seconds creates that much cooling time.
As a separate trial, compare a second copy of the same test if the nozzle returns to one tiny area too quickly. Treat the extra model as a change in the print sequence, not proof of a universal cooling cure. Confirm travel and clearance in the preview before printing, then compare the original troublesome section and the integrity of the part.
Keep the layer-time trial separate from the fan trial. Prusa warns that cooling can worsen warping or layer separation with some materials, and extremely slow printing can introduce problems such as heat creep. A cleaner overhang is useful only if the rest of the part remains acceptable; retain the supported material profile as the baseline rather than borrowing a universal fan percentage or time target.
Change geometry when tuning is not enough
Consider reorienting the model, reducing an unsupported angle or adding support. Keep the functional requirements in view: a decorative edge and a loaded bracket do not have the same acceptance criteria.
Record the material, printer, geometry and successful settings together, then repeat the test. Keep that result with the part's profile so the next print can start from a combination you have checked under the same conditions.
