Quick diagnosis
A matte, hairy or slightly rippled texture on TPU walls, worse at direction changes and thin features, that shows up even on a dry spool with belts that are already tight. If that description also fits a PLA or PETG print, start with Fix Fuzzy Skin instead. The causes here are specific to how flexible filament moves through an extruder, not the moisture, vibration or clog checklist that guide walks through.
Why TPU’s texture is a different problem
The general Fuzzy Skin guide already lists TPU as one of the materials most likely to pick up moisture, and that’s still true here. But a dry spool of TPU can produce a rough wall that a dry spool of PLA never would, because TPU is an elastomer and PLA is not. Fix TPU Stringing covers the same underlying fact from the stringing side: squeeze TPU in a drive gear and part of that force turns into stretch instead of movement, the same way a rubber band takes up slack before the far end moves. That stored elastic energy has to go somewhere, and on a wall it comes out as small, repeated inconsistencies in how much plastic actually reaches the nozzle tip, rather than the clean oozing or ringing a rigid filament produces.
That’s why starting from the generic guide’s checklist and simply swapping in TPU numbers tends to disappoint. The fixes below come from how flexible filament behaves in the extruder and on the bed, not from retuning the same five variables.
Cooling is doing more here than it does on PLA
Polymaker’s own slicer cooling guidance puts flexible filaments in a category by themselves: limited cooling, in the 0 to 30 percent range, to prevent nozzle jams and keep layers bonding properly. That’s a narrower band than almost any other material gets, and it cuts both ways. Too much fan and TPU’s already-soft layers cool before they can fuse into the one below, which reads as poor bonding more than as fuzz, but a wall with poor interlayer bonding also scatters light unevenly and looks textured rather than glossy. Too little fan on a thin wall, and the layer underneath hasn’t firmed up before the next one lands on it, which lets the new line squish and smear slightly instead of sitting cleanly, and that shows up as the same rippled look the general guide blames on vibration.
Start inside Polymaker’s 0 to 30 percent window rather than borrowing whatever fan curve your profile uses for PLA, and change it in small steps on a single test wall. Neither Prusa’s nor Bambu’s own TPU documentation publishes one universal number, because the right fan percentage also depends on wall thickness and print speed, so treat this as a starting range to tune, not a fixed setting.
A flattened or buckled filament path shows up as texture, not just strings
Bambu Lab’s own compatibility documentation is blunt about soft TPU grades: 95A, 85A, 83A and 80A grades are difficult to feed through a tube at all, and the company tells owners to keep the softest grades out of its AMS system entirely rather than risk a feeding failure. Elegoo’s filament wiki describes the same mechanism from the troubleshooting side, for materials as soft as or softer than TPU95A: the filament is prone to bending inside the extruder, producing something close to a plug rather than a clean jam, and the fix is to reduce extruder clamp force, raise the printing temperature slightly, and slow down, keeping speed under roughly 50 mm/s.
A full plug stops the print outright, so it’s easy to notice. A partial version of the same bending is easier to miss, because it doesn’t stop anything. It just interrupts the flow for a fraction of a second at a time, often right as the toolhead changes direction and the filament path flexes the most, and that shows up on the wall as a stutter in extrusion rather than a jam. If your rough texture seems to cluster near corners and direction changes rather than appearing evenly across a flat wall, that pattern points here before it points at vibration.
Give the layer time to set before the next one lands
Because the usual fix for a layer that hasn’t set yet, more cooling fan, is the same thing that hurts TPU’s interlayer bonding, the safer lever is time rather than airflow. A slicer’s minimum layer time setting (sometimes called minimum layer cycle time) pauses or slows the print when a layer would otherwise finish too fast for that filament to firm up, rather than relying on fan speed to force the issue. Printer forums report builds where increasing layer time, not fan percentage, cleared up a wavy texture on TPU walls that fan and flow tuning alone hadn’t fixed. No Bambu, Prusa or Polymaker document states a specific minimum-time number for TPU, so treat this as a lever worth testing and confirming on your own printer rather than a published spec.
Shore hardness decides how much of this applies to you
None of the mechanisms above apply equally across every TPU on the market. Bambu Lab ranks common grades from hardest to softest: 77D and 55D are hard enough to run through its AMS without issue, 95A down to 80A feeds directly but can still jam inside an AMS, and anything at 75A or softer is excluded from Bambu printers entirely in its own documentation. A harder grade like 95A behaves close enough to a rigid filament that a lot of the flattening and buckling described above barely applies. A soft 85A or 80A spool is where you’re most likely to see wall texture that traces back to the extrusion path instead of cooling or vibration. If a spool doesn’t list its Shore hardness, that’s worth tracking down before spending time on fan curves and layer time, since it changes which fix is actually worth trying first.
Fuzzy Skin TPU checklist
- Confirm the spool’s Shore hardness. 95A and harder behaves close to a rigid filament; 85A and softer is where extrusion-path texture is most likely.
- Set cooling fan within Polymaker’s 0 to 30 percent range for flexible filament rather than reusing a PLA or PETG fan curve, then adjust in small steps.
- On Bambu printers, keep 75A and softer grades out of the AMS and off the printer per Bambu’s own documentation; run 95A to 80A direct.
- If texture clusters near corners and direction changes rather than spreading evenly, suspect flattening or buckling in the extruder path rather than vibration.
- Reduce extruder clamp force, raise temperature slightly, and keep speed under roughly 50 mm/s if the filament is bending or plugging in the gear (Elegoo’s guidance for very soft filaments).
- Try raising minimum layer time before adding more cooling fan, since more fan is also what hurts TPU’s interlayer bonding.
- Rule out a wet spool before anything else if the texture looks more pitted than rippled. See Wet Filament Symptoms.
If the wall problem you’re looking at isn’t specific to TPU, or you’ve already ruled out everything above, the generic Fix Fuzzy Skin guide covers moisture, ringing, temperature and clogs across materials. For TPU’s other well-known symptom, stringing from the same elastic behavior described above, see Fix TPU Stringing.