Small details melting or curling: fixing overheating

This guide covers overheating of small features: needle tips, small towers, pins, thin spires and the top of anything that narrows to a point. It walks through the layer-time and cooling settings in Bambu Studio, PrusaSlicer, OrcaSlicer, Cura and Simplify3D, and what Polymaker, Prusa and Bambu Lab say about fan speed by material. It's a different problem from these, so check you're in the right place:

What does overheating look like?

Simplify3D's example is a pyramid whose top "was not able to cool quickly enough to retain its shape." Polymaker describes the same thing on any part that "comes to a point," which gets "a melted, very ugly look to it." Bambu Lab shows a cone printed fast with the part cooling fan not working next to one printed with stock settings and the fan on.

Small layers can also curl. Polymaker's curling article says this "can mimic what looks like warping, but rather than the part warping off of the build plate, the individual layers seem to be warping upward." It adds that the fixes are "nearly the exact opposite" of the ones for warping. If the part is lifting off the bed, read our warping guide instead.

Why do small layers overheat?

Simplify3D's explanation: if each layer prints very quickly, "you might not allow enough time for the previous layer to properly cool before you are trying to deposit the next layer of hot plastic on top of it." It adds that "even with a cooling fan, you may still need to decrease the printing speed for these small layers."

Polymaker's version is that "there is not enough time for a layer to cool before the next hot layer is laid on top of it." Its fixes come down to two things: "increase the time that the layer has to cool, or increase the rate at which the layer cools."

Bambu says larger models "are not usually affected by this, as it takes longer to print a layer and there's enough time for it to cool down."

Step 1: Check the part cooling fan

Bambu Lab calls the part cooling fan "the most common reason for overheated layers and droopy prints." On its printers, it says to turn the fan on from Bambu Studio under Device, Part cooling fan, set it to 100% and confirm it spins.

• If the fan spins, Bambu says "the issue is related to the printing profile and settings you have selected for your print."
• If it doesn't, Bambu lists a faulty part cooling fan, a bad wire connection to the fan, or something related to the tool head board.

Polymaker's curling guide also says to "confirm fan functionality before extended prints." Its cooling guide says to aim the fan duct at the extruded material, not the nozzle.

Step 2: Give each layer more time

This is the main fix for small details. Every slicer below can slow a short layer down so it takes at least a set number of seconds. The names and defaults differ.

The defaults come from each slicer's source at the version shown. Printer and filament profiles can set their own values, so check the number your profile shows before you change it.

Bambu Studio

Bambu's auto cooling page says the cooling settings are on the Filament Settings page. "Slow Printing Down for Better Layer Cooling" reduces speed "to ensure the single-layer print time is no less than the target time (defined in the Max Fan Speed Threshold)." Bambu says this "is particularly effective for sharp spires, small details, and other areas requiring ample cooling." The Bambu Studio source tooltip says it "can improve the cooling quality for needle and small details."

Bambu's melted prints page gives the minimum layer time as an example of 4 seconds and says: "If you have problems with overheating layers, it's best to increase the Layer Time with a few extra seconds."

There's a floor. Bambu says that once the speed reaches "Min Print Speed," the printer "will maintain the minimum print speed and will not slow down further," even if the layer is still too short. Its example uses 4 seconds and 20 mm/s. The source default for Min print speed in Bambu Studio 2.08.02.61 is 10 mm/s.

"Don't Slow Down Outer Walls" keeps outer walls at full speed. Bambu says this helps with glossy or silk filament, but it also means the outer wall isn't slowed to meet the layer time. Bambu doesn't say to change it for this problem, but if small details still melt with it on, it's worth testing a print with it off.

PrusaSlicer

Prusa's cooling article puts these under Cooling thresholds in the filament settings. "Slow down if layer print time is below" means that if a layer is estimated below that many seconds, "the print move speed will be slowed down to extend the duration to this value." "Enable auto cooling" must be on for the fan and speed to change during the print. It defaults to on in PrusaSlicer 2.9.6.

"Min print speed" (default 10 mm/s in PrusaSlicer 2.9.6) is the floor. Prusa warns that "printing at extremely low speeds for extended periods of time could lead to problems such as heat creep," and that raising it too high may "partially invalidate the minimum layer time." See our heat creep guide if extrusion fades on long, slow sections.

PrusaSlicer 2.9.6 also has a "Cooling slowdown logic" setting. Its tooltip says "Consistent surface" first tries to keep the first two perimeters at speed, while "Uniform cooling" (the default) "slows down all print features, including the first two perimeters."

OrcaSlicer

The OrcaSlicer wiki says "Slow printing down for better layer cooling" makes sure the final layer time "is not shorter than the layer time threshold in Max fan speed threshold," and that "this can improve the quality for small details." "Min print speed" is the lowest speed it slows down to. Like Bambu Studio, it has "Don't slow down outer walls," which keeps external perimeters from being slowed down to meet the minimum layer time.

Cura

Cura 5.13.0's "Minimum Layer Time" (in the Cooling settings, default 5 s) "forces the printer to slow down, to at least spend the time set here in one layer." "Minimum Speed" (default 10 mm/s) is the floor, because slowing too much makes "the pressure in the nozzle" too low.

Cura says layers "may still take shorter than the minimal layer time if Lift Head is disabled and if the Minimum Speed would otherwise be violated." "Lift Head" (off by default) lifts the head away and waits out the rest of the time. Polymaker suggests combining Minimum Layer Time with Lift Head, and says a 3 to 5 second minimum layer time "proves effective for most materials."

Simplify3D

In Edit Process Settings, on the Speeds tab, the "Speed Overrides" section slows down small layers "to ensure they have enough time to cool and solidify before printing the next layer." Simplify3D's example is layers that take less than 15 seconds, and it calls this "a vital feature for combating these overheating issues."

Step 3: Print more than one copy

Simplify3D calls this "a simple, yet very effective strategy." With two objects on the plate, "the hot nozzle will need to move to a different location on the build platform to print the second part, which provides a short relief for your first part to cool down." In Simplify3D, use Edit, Copy and Paste, or import a second object.

Polymaker calls it "a preferred method if the model you are printing is quite small," and notes there's no oozing from pausing, because the print head keeps moving. The drawback, Polymaker says, is wasted material if you only need one. Simplify3D says the second object doesn't have to be a copy: you can "import a second object that can be printed at the same time."

Step 4: Set fan speed for the material

More fan helps small details in some materials and hurts others. Bambu says "PLA usually needs as much cooling as possible, while other filaments like ABS and ASA need less cooling."

PrusaSlicer 2.9.6's "Keep fan always on" tooltip says it's "Useful for PLA, harmful for ABS." Prusa says the setting is typically on for most materials "with the exception of ABS, ASA, PC, and some flexibles." Polymaker also notes that turning the fan up has a drawback with "a material that cannot be rapidly cooled, such as Polycarbonate." Its other two fixes, minimum layer time and extra copies, don't rely on the fan. In Simplify3D, fan speed setpoints are on the Cooling tab of Edit Process Settings.

The fan also changes with layer time. In PrusaSlicer, Prusa says the Max fan speed is used when a layer is below the "Slow down if layer print time is below" value. In Bambu Studio and OrcaSlicer, the fan is interpolated between a Min and a Max fan speed threshold by layer time. Bambu's example: 10% at 30 seconds and 80% at 3 seconds. Cura's "Regular/Maximum Fan Speed Threshold" (default 10 s in Cura 5.13.0) does the same between Regular and Maximum Fan Speed. Check that your maximum fan speed is high enough for the material.

Step 5: Lower the nozzle temperature

Simplify3D says that if you're already using a fan and still see overheating, try "lowering the print temperature by 5-10 degrees," but "be careful not to lower the temperature too far," or the plastic may not extrude. Polymaker suggests reducing temperature, "especially if printing at low layer heights on small nozzle diameters," and says to stay within the maker's range.

Bambu ties temperature to speed. Its example: PLA is set to 220 °C in Bambu Studio for the default speed, and if you use the Silent speed setting, "you might want to set the hotend temperature to 210C."

Cura 5.13.0 can do this per layer. "Small Layer Printing Temperature" will "gradually reduce to this temperature when printing at reduced speeds because of minimum layer time."

Step 6: On Bambu printers, set speed in the slicer

Bambu says setting the speed higher with Sport and Ludicrous "on small models doesn't increase the part cooling performance," and that "when the print speed is increased using these options, more cooling is required." It recommends "adjusting the print speed settings in the slicer, instead of adjusting them from the screen options."

Other things to rule out

• Very thin layers. Polymaker says thinner layers "exhibit reduced rigidity," which makes curling more likely, and suggests a higher layer height or print speed.
• Supports on small angled features. Polymaker recommends supports at 55° and above for PLA, and says ABS and ASA need them at 45° and above "due to cooling restrictions." Our overhangs and bridging guide covers overhang cooling.
• Wet filament. Polymaker says curling that remains after other changes "indicates potential filament hydration." See our wet filament guide.

A sensible order

1. Confirm the part cooling fan spins at 100%.
2. Check your slicer's slowdown for layer cooling is on, and raise the minimum layer time a few seconds.
3. Add a second copy, or another part you need, to the plate.
4. Set fan speed for the material.
5. Lower the nozzle temperature 5 to 10 degrees, staying within the filament's range.
6. Try a thicker layer height, then supports for small angled features.

Change one thing per print and note the result.

Checklist

• Small features melt but large parts print fine.
• Part cooling fan confirmed working.
• Slowdown for layer cooling turned on.
• Minimum layer time raised by a few seconds.
• Minimum print speed not set so high it cancels the layer time.
• "Don't slow down outer walls" off if outer walls still melt.
• Two or more copies on the plate.
• Fan speed suits the material.
• Nozzle temperature at the low end of the filament's range.
• Lid or door open for PLA in an enclosed printer.

How this guide was checked

This is a research-based guide. We haven't printed these tests for it. Every cause, setting name, menu location and default comes from the Simplify3D, Bambu Lab, Prusa Research, OrcaSlicer, UltiMaker Cura and Polymaker sources listed above, retrieved on 2026-10-12. Defaults are from Bambu Studio 2.08.02.61, PrusaSlicer 2.9.6 and Cura 5.13.0 source files. Read more in our editorial standards.

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