Check the temperature before the retraction
On a direct-drive machine the stringing fix looks backwards from Bowden: the correct retraction is short, and the most common mistake is over-retracting until the filament clogs. Before you turn the retraction dial, check the nozzle temperature — it is the one setting that usually clears PETG hairs on these extruders.
Why direct drive is easy to over-retract
The Prusa Knowledge Base stringing and oozing article names two causes: nozzle temperature too high, and retraction settings that do not fit the machine. Direct-drive extruders (MK2.5/S, MK3/S/+) have the gear right at the nozzle, so the retraction that works is short.
Settings to change
Every number below is from the Prusa Knowledge Base stringing and oozing page.
- Retraction length — on direct-drive machines keep it at a maximum of 2 mm. Going longer pulls molten filament up into the cold zone and can cause clogs. (Prusa KB)
- Nozzle temperature — lower it 5–10 °C and re-test; this alone often clears PETG stringing. (Prusa KB)
- Retract on layer change — leave it on so the nozzle retracts before a travel move. (Prusa KB)
- Lift Z — lower values improve stringing, but disabling lift can cause the nozzle to collide with the part. (Prusa KB)
- Minimum travel after retraction — preset is 1 mm; raising it speeds the print but increases oozing. (Prusa KB)
- Rule out moisture — a spool that has gathered moisture will string a lot; Prusa suggests trying a different (dry) spool before changing settings further. (Prusa KB)
Confirming it's gone
Begin from the PrusaSlicer factory preset for your PETG and test one change per print. Use a small cylinder or a part with a visible seam, and watch for the over-retraction signature: a gap at the start of a line, or hollow tops. If the hairs are gone and the lines start clean, the setting is right; if you see those gaps, the retraction (or the temperature drop) went too far, so back it off.