PETG stringing: diagnose and fix it step by step

1. Check that the problem is stringing

Prusa's stringing guide identifies nozzle residue as another possible contributor. Cleaning methods depend on the hardware; do not scrape a hotend or its wires with improvised tools.

2. Restore a known profile

Before tuning, confirm the selected printer, nozzle diameter, PETG filament profile, and build plate. Recheck settings imported with someone else's project. Save a copy before returning to the manufacturer's standard profile.

Write down the spool brand and product name, slicer version, profile, and any hardware changes. “PETG” is not a complete description of a formulation. If the issue started after changing a nozzle, spool, or project, that is a useful lead rather than proof of the cause.

For the basic selection and preview workflow, see Prusa's first-print instructions. Our compatibility finder covers PLA and PETG on Prusa Smooth PEI, Textured, and Satin sheets; other plates require their own guidance.

3. Investigate moisture before extensive tuning

Filament can absorb moisture, which may affect surface quality and extrusion. Rough surfaces or bubbling can support that suspicion, but stringing alone does not prove the spool is wet. Compare with the same spool's earlier results if you have them.

Read the filament maker's drying instructions, including time, temperature, equipment, and spool limits. Do not apply one brand's recipe to every PETG blend. Prusa's drying guide, for example, distinguishes Prusament material settings and different spool constructions.

A container with desiccant helps with storage; it is not a substitute for the specified drying process. Household ovens may fluctuate or fail to hold a low enough temperature. Use equipment suitable for the maker's procedure, then store the spool as directed.

After drying, repeat the saved test with unchanged print settings. Record the drying conditions and result before deciding whether another adjustment helped.

4. Test nozzle temperature within the approved range

An excessively hot nozzle can contribute to stringing. Use the filament maker's range and a compatible profile as the boundaries for a temperature check. If testing a lower temperature, keep the model, speed, cooling, and retraction unchanged. Compare the printed walls as well as the strings.

A cleaner-looking gap is not a complete success if the part develops poor layer bonding or extrusion problems. Prusa's PETG guidance describes a tradeoff between temperature and bonding between layers. The coldest possible setting is therefore not a universal target.

If you use a temperature tower, confirm the sliced instructions actually change temperature at the intended heights. Labels on the model do not perform those changes. Prusa documents layer-based temperature changes for advanced users; a supported calibration workflow avoids guessing at custom commands.

5. Check retraction without copying another printer

Retraction briefly pulls filament back before a travel move. Retraction length and speed are separate controls, and a Bowden system can need different settings from a direct-drive extruder. Start with your machine's preset instead of a value taken from an unrelated printer.

Use the slicer's supported calibration procedure if further adjustment is needed. Change one setting, print the same test, and inspect both the gap and the point where extrusion resumes. Excessive retraction can introduce new printing problems.

OrcaSlicer's retraction reference explains the controls and their tradeoffs. Check whether filament-level overrides are replacing the printer profile's values before comparing attempts.

6. Inspect the travel paths

In the slicer preview, display travel moves and look at the gaps that collect threads. A model with many separated features gives the nozzle repeated opportunities to cross open space.

PrusaSlicer's Avoid crossing perimeters option changes travel routing and can reduce stringing, with a possible increase in printing time. It does not eliminate every crossing. Other slicers may use different names and behavior.

Keep lifting and collision-avoidance settings at the supported baseline while testing. A shorter route is useful only if the toolhead can follow it safely. Treat travel routing as a separate experiment after addressing the material and profile.

7. Run a small comparison you can repeat

Choose a short model that reproduces the unwanted threads. Keep its size, orientation, plate position, and spool the same. Use this comparison plan:

1. Baseline: save the project and photograph the untouched result.
2. One change: write down the setting or material-treatment change before printing.
3. Same view: photograph the same gap under similar lighting. Note strings, wall defects, and extrusion restarts before removing anything.
4. Decision: keep the change only if the overall result improves; otherwise restore the baseline.

Download the print log and put photo filenames in the notes. Distinguish observations such as “fewer threads across this gap” from conclusions such as “the spool was wet.” A single better result can be worth repeating before adopting new settings.

When to stop changing settings

If a standard profile and correctly prepared material still give poor results, collect the project file, printer and hotend details, filament product, photos, and your change log for manufacturer support. Mention recent maintenance or component changes.

Before a longer PETG project, revisit PLA versus PETG to check whether the material suits the part. Use the cost calculator to compare test-job estimates. Replacing equipment is not the next step until you have evidence that it addresses the problem.