How to Fix 3D Print Stringing and Oozing: Retraction & Temperature Tuning

Stringing is the cobweb of fine plastic hairs that stretches between separate parts of a print — between the letters of a name keychain, the ears of a cat figure, or two earrings printed side by side. It rarely ruins a print structurally, but it makes a finished piece look messy and adds clean-up time to every job.

The good news is that stringing has a short list of causes, and they can be tested one at a time. This guide explains what is physically happening in the nozzle, then walks through a tuning order that fixes the vast majority of cases: dry the filament, lower the temperature, tune retraction, and finally adjust travel moves.

What actually causes stringing

Molten plastic in the hot end is under pressure. When the print head finishes one part and travels to another, a small amount of that plastic keeps leaking out of the nozzle. As the nozzle moves away, the leaking plastic is pulled into a thin thread that cools in mid-air and stays behind as a string.

Anything that increases pressure or makes the plastic runnier makes stringing worse: a nozzle temperature that is too high, filament that has absorbed moisture (water turns to steam and pushes plastic out), long slow travel moves, and retraction settings that do not pull the filament back far enough before travelling.

Stringing vs oozing vs blobs

Stringing leaves thin hairs between parts. Oozing leaves small drips or dribbles where the nozzle paused or started a new layer. Blobs and zits are small bumps on the outer wall where each layer starts or ends. They share the same root — uncontrolled flow — so the fixes below help all three, although blobs also respond to seam settings such as “aligned” or “rear” seam placement.

Step 1: Dry your filament first

Moisture is the most overlooked cause of stringing, especially with PETG and TPU. Wet filament often crackles or pops as it prints, leaves a rough or bubbly surface, and strings no matter how retraction is tuned. Before you change any setting, dry the spool.

PLA can be dried at about 45–50°C for 4–6 hours; PETG at 60–65°C for 4–6 hours; TPU at 50–55°C for 4–8 hours. A dedicated filament dryer is the easiest option, and storing spools in a sealed box with silica gel prevents the problem coming back. Our guide to drying and storing filament covers this in more detail.

Step 2: Lower the nozzle temperature

Hotter plastic is runnier and leaks more easily. Print a temperature tower — a test model that changes temperature every few millimetres — and look for the lowest temperature that still gives good layer bonding and a glossy, even surface. Many slicers, including PrusaSlicer, OrcaSlicer and Bambu Studio, include a built-in temperature tower calibration.

As a starting point, lower the temperature in 5°C steps. Going too low causes weak layers and under-extrusion, so stop when the surface turns dull and rough or layers can be split apart with a fingernail.

Typical starting temperatures and retraction (direct drive)
Material	Nozzle temp	Retraction distance	Retraction speed
PLA	200–215°C	0.5–1.0 mm	30–45 mm/s
PETG	230–245°C	0.8–1.5 mm	25–40 mm/s
TPU (95A)	220–235°C	0–0.5 mm (often off)	20–25 mm/s
PLA (Bowden)	200–215°C	4–6 mm	35–45 mm/s

Step 3: Tune retraction distance and speed

Retraction pulls the filament back a short distance before a travel move, relieving pressure in the nozzle. Direct-drive printers, where the extruder sits on the print head, need only a short retraction — usually under 1.5 mm. Bowden printers, where the extruder pushes filament through a long tube, need more, typically 4–6 mm, because the tube compresses and stretches.

Print a retraction test (two or more thin towers spaced apart) and change one value at a time. Increase distance in small steps (0.2 mm for direct drive, 0.5–1 mm for Bowden) until the strings disappear. Too much retraction can pull molten plastic up into the cold part of the hot end and cause clogs, so do not keep increasing it once the strings are gone.

Pressure advance and linear advance

Modern firmware such as Klipper (pressure advance) and Marlin (linear advance) predicts nozzle pressure and reduces flow before the head slows down. When calibrated, it reduces oozing at corners and the ends of lines and often allows shorter retraction. Bambu Lab printers calibrate a similar value automatically. If your printer supports it, calibrate it before fine-tuning retraction.

Step 4: Optimise travel moves

The shorter and faster the travel, the less time the nozzle has to leak. Raise travel speed if your printer can handle it (150–300 mm/s is common), and enable “avoid crossing perimeters” or “combing” so the nozzle travels over the inside of the part, where any strings are hidden by the next layer.

Wipe moves, which drag the nozzle back over the just-printed line before travelling, also help. Z-hop lifts the nozzle during travel to avoid knocking the part, but it can increase stringing slightly; leave it off unless the nozzle is catching on the print.

Cleaning up what remains

A few fine wisps are normal, especially with PETG. A quick pass with a heat gun or hair dryer on its hottest setting shrinks thin strings away in seconds — keep it moving so the part itself does not soften. Larger strings can be snipped with flush cutters or removed with a hobby knife.

For prints where clean results matter, such as gifts or items for sale, it is worth arranging parts on the plate so travel moves are short, and printing multiple small objects one after another rather than all at once (“print sequence: by object”) if your printer has the clearance.

Quick Checklist

Dry the filament before changing settings
Print a temperature tower and use the lowest good temperature
Tune retraction distance in small steps, one value at a time
Calibrate pressure/linear advance if available
Raise travel speed and enable avoid crossing perimeters
Remove remaining wisps with a quick pass of hot air

Frequently Asked Questions

Why does PETG string more than PLA?: PETG stays soft and sticky over a wider temperature range and absorbs moisture faster. It almost always strings a little; drying it, printing at the lower end of its range and slightly slowing retraction speed gives the cleanest results.
Can a worn nozzle cause stringing?: Yes. A worn or partially clogged nozzle changes how plastic flows and can leave strings and blobs. Nozzles are inexpensive; if tuning stops helping, replace it.
Should I turn retraction off for TPU?: Often, yes. Flexible filament compresses in the extruder, so long retractions cause jams. Use zero or very short retraction, slow travel and dry filament instead.
Does print speed affect stringing?: Print speed matters less than travel speed. Faster printing usually needs a slightly higher temperature, which can increase stringing, so retune temperature if you change speeds significantly.

Stringing is a flow-control problem, and it yields to patient, one-variable-at-a-time testing. Start with dry filament, find the coolest temperature that still bonds well, then tune retraction and travel. Once dialled in, write the values into a filament profile so every future print starts clean.