How to fix stringing and oozing in 3D prints

Updated June 2026 · 11 min read

Stringing — the fine threads of filament that span between parts of a print during travel moves — is one of the most common quality problems in FDM 3D printing. It happens when molten filament oozes from the nozzle during travel moves instead of staying retracted. The result is a print covered in thin plastic hairs that require post-processing to remove, or that break off and contaminate the print surface.

The good news is that stringing is almost always fixable through slicer settings. The bad news is that the wrong approach — blindly increasing retraction — can cause jams and under-extrusion. This guide covers the systematic approach to diagnosing and fixing stringing: understanding what causes it, which settings address the root cause, and how to tune them without creating new problems.

What causes stringing

Stringing has three root causes, and identifying which one applies to your situation determines the correct fix.

The first cause is insufficient retraction. When the extruder moves from one point to another without printing, it should retract the filament slightly to reduce pressure in the hotend and prevent oozing. If retraction distance or speed is too low, the filament continues to ooze during the travel move, leaving strings.

The second cause is excessive print temperature. Hotter filament is more fluid and oozes more readily. A print temperature that's 10–15°C higher than necessary will produce significantly more stringing than the same settings at the correct temperature.

The third cause is slow travel speed. If the nozzle moves slowly between points, it has more time to deposit oozing filament along the travel path. Fast travel moves minimize the time available for oozing.

The correct order of adjustments

Most stringing guides start with retraction, but temperature is often the more impactful adjustment. Start here:

Step 1: Reduce print temperature. Drop the print temperature by 5°C and print a stringing test (a simple two-tower test object works well). Repeat until stringing reduces or print quality degrades. For PLA, the optimal temperature for minimal stringing is often 195–210°C; many printers default to 215–220°C, which is unnecessarily hot for most PLA brands.

Step 2: Increase travel speed. Set travel speed to 150–200mm/s if it isn't already. Faster travel moves reduce the time available for oozing. Most modern printers handle 150mm/s travel without issues.

Step 3: Enable combing. Combing (called "avoid crossing perimeters" in some slicers) routes travel moves through the interior of the part rather than across open air. This means that any oozing that does occur happens inside the part where it's hidden, rather than across open gaps where it forms visible strings. Enable combing in your slicer before adjusting retraction.

Step 4: Adjust retraction. Only after the above steps, tune retraction. For direct drive setups, 0.5–2mm retraction at 25–45mm/s is the typical range. For Bowden setups, 4–7mm retraction at 40–60mm/s. Start in the middle of these ranges and adjust based on results.

Retraction settings by extruder type

Direct drive extruders require much less retraction than Bowden setups because the filament path is short. Too much retraction on a direct drive printer causes the filament to pull back past the melt zone, introducing air gaps that produce under-extrusion on the next print move. For direct drive, 0.5–1.5mm is usually sufficient; going above 2mm often creates more problems than it solves.

Bowden setups require more retraction because the long PTFE tube allows the filament to compress and spring back. 4–6mm is a reasonable starting range for most Bowden setups. The optimal value depends on the tube length, the filament material, and the hotend design. PETG in a Bowden setup often needs less retraction than PLA despite being more prone to stringing — this is because PETG is more elastic and over-retraction causes more problems.

Material-specific stringing behavior

Different filament materials have different stringing tendencies. PLA strings moderately and responds well to retraction and temperature tuning. PETG strings more than PLA and is more sensitive to over-retraction — PETG's higher viscosity means it doesn't retract as cleanly, and pulling too hard causes the molten PETG to string rather than break cleanly. The fix for PETG stringing is usually temperature reduction and faster travel rather than more retraction.

TPU strings significantly and requires a different approach — reduce retraction to near zero and rely on combing and fast travel to minimize stringing. Nylon strings moderately but the strings are often finer and harder to see. ABS and ASA string less than PETG at equivalent temperatures.

Wet filament strings more than dry filament. If you've tuned your settings and stringing suddenly gets worse, moisture absorption is a likely cause — particularly for PETG and nylon. Dry the filament before continuing to tune settings.

When stringing is acceptable

Some stringing is acceptable in many applications. For functional parts where appearance doesn't matter, minor stringing that can be removed with a heat gun or by hand is not worth extensive tuning time. The 30 minutes spent tuning retraction to eliminate the last few strings on a bracket that lives inside a machine is time that could be spent on more productive work.

For display models, figurines, and anything where surface quality matters, eliminating stringing is worth the tuning investment. A quick pass with a heat gun (carefully, at low heat) melts and removes most strings without damaging the print surface.

The settings that don't fix stringing

Increasing retraction beyond the optimal range causes under-extrusion and jams without eliminating stringing. This is the most common mistake in stringing troubleshooting. If you've increased retraction to 6mm on a direct drive printer and still have stringing, more retraction is not the answer — temperature and travel speed are.

Reducing print speed (not travel speed) does not help with stringing and often makes it worse by keeping the nozzle in one place longer. Reducing layer height does not affect stringing. Changing infill pattern does not affect stringing.

The three variables that actually fix stringing are temperature, travel speed, and retraction — in that order of impact for most materials. Work through them systematically, change one variable at a time, and use a dedicated stringing test object to evaluate each change before moving to the next variable.