PETG Stringing: The Settings That Actually Fix It
PETG stringing is the trade-off for a material that’s tough, chemical-resistant, and sticks to itself almost too well. Those fine hairs between towers aren’t a defect—they’re PETG doing what PETG does. The fix isn’t one magic setting. It’s a small set of adjustments working together: retraction to relieve nozzle pressure, temperature to reduce oozing, travel moves to break threads, and wipe or coasting to clean up the last residue. Change them in the right order and the hairs mostly disappear without sacrificing layer adhesion.
Why PETG Strings More Than PLA (and Why That’s Actually a Good Sign)
PETG has higher melt viscosity and higher surface tack than PLA. When the nozzle moves from one printed area to another, the molten PETG doesn’t snap cleanly. It stretches into a thin fiber and stays attached to both the nozzle and the print. That’s the string.
This is annoying, but it points to the main reason people print PETG: the material sticks extremely well to itself. Good layer adhesion and stringing come from the same sticky behavior. If you tune PETG until it never leaves a single hair, you can also over-cool or under-extrude it enough to produce weak layers. The goal is to reduce strings to the point where a quick pass with a heat gun or fingernail removes them—not to chase a flawless surface at the cost of part strength.
| Behavior | PLA | PETG |
|---|---|---|
| Melt viscosity | Lower | Higher |
| Surface tack | Low | High |
| Typical stringing | Low | Moderate to high |
| Tuning priority | Basic retraction | Retraction, temperature, travel, wipe/coasting |
| Risk if pushed too cold | Brittle layers | Weak layer adhesion, skipped extrusion |
Retraction: The First Dial to Turn
Retraction relieves pressure inside the melt zone. When the print head finishes one area and prepares to travel, firmware pulls filament back a set distance. That reverse motion lowers pressure at the nozzle tip so molten PETG doesn’t keep oozing out behind the nozzle.
For PETG, the usable window is wider than for PLA, but over-retracting is a real failure mode. Pull back too far and you can introduce air into the melt zone, create a void at the start of the next extrusion, and on some hot ends promote heat creep because molten filament spends longer near the cold zone. You get missing seam lines or a partial clog instead of cleaner prints.
| Extruder type | Retraction distance start | Retraction speed start |
|---|---|---|
| Bowden | 4–7 mm | 30–45 mm/s |
| Direct drive | 0.5–2 mm | 20–35 mm/s |
Retraction Distance
Start Bowden setups at 4 mm and direct drive extruders at 0.8 mm. Print a small stringing test, then increase Bowden retraction by 0.5 mm or direct drive retraction by 0.2 mm at a time if heavy strings remain. Too much distance causes gaps at the start of the next line, weak seams, and eventually heat creep or jams. The right distance is usually the smallest one that reduces strings from heavy cobwebs to fine, breakable hairs.
Retraction Speed
Typical effective retraction speed for PETG is 25–50 mm/s. Bowden machines often need the higher end because the long filament path has some slack, while direct drive extruders usually work well between 20 and 35 mm/s. Too slow and the retraction doesn’t interrupt oozing fast enough. Too fast and the extruder gear can grind a notch into the filament, especially if tension is high or the hot end is partially resistant. If you hear a thunk or see filament dust around the extruder, reduce retraction speed before changing anything else.
Temperature: Hot Enough to Flow, Cool Enough to Stop Oozing
Nozzle temperature drives oozing more directly than any other setting. If PETG is too hot, it remains fluid at the tip and strings even with aggressive retraction. If it’s too cold, it stops stringing but may not bond to the previous layer. Typical PETG range is 230–250 °C, but not all PETG is the same. Start at the filament manufacturer’s midpoint or 240 °C, then run a temperature tower from 225 °C to 250 °C in 5 °C steps.
Examine the tower carefully. Lower temperatures should reduce fine hairs but may produce duller surfaces, rougher layers, or separated strand lines. Higher temperatures should look shinier and stronger but hairier. Pick the lowest temperature that still gives clean layer lines and strong bridging between tower pillars. If you hear the extruder clicking or see under-extrusion at 225 °C, stay higher.
A temperature change affects retraction behavior, so set temperature before retraction calibration. A stringing test printed at 250 °C will mislead you into raising retraction distance more than needed, which then jams or under-extrudes at a lower temperature. Cool first, then tune retraction.
Travel Speed: Move Fast, Break (Fewer) Hairs
High travel speeds help because the move happens before the thin strand has time to cool and stiffen. A fast snap across open air stretches the molten PETG until it thins and breaks, leaving less material attached to the part. If travel is slow, the nozzle drags a hot, viscous string and lays it down like a hair across gaps.
Set travel speed to 150–200 mm/s or higher if your machine can handle it. But travel speed alone isn’t enough if acceleration is low. On a bedslinger with default travel acceleration around 500 mm/s², the nozzle may never reach 150 mm/s on a short 20 mm hop. Raise travel acceleration to 1000–1500 mm/s² and, if firmware exposes it, set travel jerk or square corner velocity to around 8–12 mm/s to preserve speed through short segments.
Don’t go so high that the printer shakes the print loose or leaves ringing marks on vertical walls. A rigid CoreXY machine can usually handle more aggressive travel than a loose bedslinger. If you see ghosting or layer shifts, back travel acceleration down before changing anything else.
Wipe and Coasting: The Extra Tricks That Clean Up the Rest
Wipe and coasting address the residue retraction and temperature can’t fully eliminate. They’re finishing tools, not replacements for the first settings.
Wipe moves the nozzle a short extra distance along the printed part before travel. This can scrub the tip against already-printed infill or the outer wall to break a forming string. Start with a wipe distance of 0.4 mm. If your slicer separates wipe locations, prefer wiping on infill rather than the visible outer wall—an outer-wall wipe can leave a slight scar on the surface.
Coasting stops extrusion slightly before the end of a line, letting residual nozzle pressure finish the segment. For PETG, start with a coasting volume of 0.02–0.04 mm³ and increase if you see blobs at seam points. Too much coasting leaves gaps or under-extruded seam corners. Coasting works best after retraction and temperature are already dialed in, not as a first resort.
Drying: The Setting That Isn’t in the Slicer
PETG absorbs moisture from the air, and wet filament strings far worse than dry filament. The water in the filament turns to steam in the melt zone, expanding and forcing extra material out of the nozzle. If you’ve tuned every slicer setting and still get persistent fine hairs, the filament itself is likely the problem.
Dry PETG at 60–65 °C for 4–6 hours before printing. A dedicated filament dryer works, but a food dehydrator or even a heated bed with a cardboard box cover can do the job. Store PETG in a sealed container with desiccant after drying. If a spool has been sitting out for a week in a humid room, expect stringing to return regardless of slicer settings.
The Tuning Order That Actually Works
The order matters. Changing settings randomly leads to chasing your tail. Follow this sequence:
- Dry the filament. Eliminate moisture as a variable first.
- Set temperature. Print a temperature tower and pick the lowest temperature that still gives good layer adhesion and surface quality.
- Set retraction. With temperature fixed, tune retraction distance and speed on a stringing test.
- Set travel speed and acceleration. Raise travel speed and acceleration until strings break cleanly or the printer shows signs of shaking.
- Add wipe and coasting as finishing touches. Use small values to clean up what’s left.
If you’re still fighting persistent overhangs curling up alongside stringing, the cooling setup may need attention—Overhangs Curling Up: PLA & PETG Cooling Fixes covers that separately.
When to Stop Tuning
A PETG print with zero strings is a PETG print that’s probably under-extruded or too cold. The realistic target is fine, wispy hairs that break off with a fingernail or disappear under a heat gun in two seconds. If you’re spending more time tuning than a quick post-processing step would take, you’ve passed the point of diminishing returns. Print the part, hit it with a heat gun, and move on.
