Bambu Lab Print Quality Problems: Fix Stringing, Layer Shifts, and Ghosting
The short version
- Stringing: dry the filament first, then tune retraction. PETG is sensitive to too much retraction.
- Layer shifts: prevent warping, check belt tension, and reduce speed.
- Ghosting and VFA: tune both belts to 110-120Hz, within 5Hz of each other.
- Most of these fixes cost nothing and need no new parts.
Quality problems are not the same as a broken printer
These problems are an ongoing frustration rather than a total failure. The printer runs, but the prints come out stringy, shifted, or marked with faint vertical lines. The cause is usually moisture, a setting, or belt tension, not a failed part. Work through the three problems below in order.
The fix, step by step
Wet filament is the number one hidden cause, so rule it out before you touch settings.
Moisture in the spool makes stringing worse no matter how well retraction is tuned.
Retraction settings are the fix for stringing once the filament is dry.
PETG is uniquely sensitive. Too much retraction can cause partial clogs.
A layer shift means something displaced the print mid-job. Three causes cover it.
A warped print that catches the nozzle can knock the layers out of position.
Belts lose tension over time, and loose belts let the toolhead slip.
High speed combined with resistance from the carbon rods can cause shifts.
Vertical fine artifacts are shadows or faint vertical lines on the print surface, caused by belt tooth resonance. They are common on CoreXY Bambu printers.
A smartphone frequency app can read the belt tone for you.
Tuning fixes most cases. Replacement belts are available from the Bambu store.
Official guide: wiki.bambulab.com/en/knowledge-sharing/common-print-quality-problem
Parts and supplies
You may not need any of these. If you do, here are the searches.
| Item | When you need it | Buy |
|---|---|---|
| Filament dryer | Stringing that persists on damp filament | Amazon search |
| Replacement belts | Only if belts are worn or will not hold tension | Amazon search |
Amazon search links. Check that parts match your printer model before you buy.
Avoid it next time
- Keep filament dry, since wet filament is the number one hidden cause of stringing.
- Check belt tension again if quality drifts or shifts start to appear.
- Change one setting at a time so you know which change worked.
Prints still not right?
Tell us the model, the filament, and what the problem looks like and we will point you to the likely cause.
Get a Free DiagnosisQuick answers
Why is my Bambu Lab print stringing?
Retraction settings are the main fix, and wet filament is the number one hidden cause. Dry the filament first, then tune retraction for the material. PETG is unusually sensitive: too much retraction can cause partial clogs.
What causes layer shifts on a Bambu Lab printer?
A warped print that hits the nozzle and displaces the layers, belt tension that has degraded, or speed set too high for the resistance of the carbon rods. Prevent warping, check the belts, and reduce speed.
What belt tension should a Bambu Lab printer have?
The target is 110-120Hz, with both belts within 5Hz of each other. A smartphone frequency app can measure it.
What is ghosting or VFA on a Bambu Lab print?
VFA stands for vertical fine artifacts. Belt tooth resonance shows up as faint shadows or vertical lines on the print surface. It is common on CoreXY Bambu printers, and belt tension tuning is the fix.
Do I need new parts to fix print quality problems?
Usually not. Most fixes are drying filament, changing settings, or tuning belt tension. Replacement belts are sold in the Bambu store if yours are worn.
Where is the official print quality guide?
Bambu Lab documents common print quality problems on its wiki at wiki.bambulab.com/en/knowledge-sharing/common-print-quality-problem.
Related: First layer not sticking, Nozzle clog and heat creep fix and AMS not feeding filament diagnostic. All guides are indexed at our Bambu Lab repair help page.