A1 and A1 mini: wet filament, how to spot it and how to dry it (not on its bed)
Checked against the official documentation from Bambu Lab.
Technology: FDM · Brand: Bambu Lab · Symptoms: Strings between parts (stringing), Blobs and zits on the surface, Layers split apart (delamination) · Updated on 5 November 2026
Symptom
On the A1 or A1 mini the filament has absorbed moisture: prints show bubbles, strings and oozing, holes or a rough surface, and parts are weaker. It gets worse the more humid the room is and the longer the spool has been left out.
Likely causes, from most to least likely
- Filament absorbs moisture from the air; inside the hot nozzle the water vaporises at once, the plastic expands and extrudes erratically.
- A spool stored open, without a sealed container, or left out for a long time in a humid room.
- Very moisture-sensitive materials (PA, PC, TPU or carbon or glass fibre filled), which also warp or clog the nozzle when damp.
Checks to tell which one it is
- Watch the filament leaving the nozzle: if it bubbles, or the print has strings, holes and a rough surface, it is probably wet.
- Think how long the spool has been out of its bag and how humid it is: the longer and the more humid, the worse.
- Check the material: TPU, PC and PA must always be dried before use.
Before you start
Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.
Step-by-step fix
Dry it outside the printer
The A1 and A1 mini are open-frame and Bambu Lab states they cannot be used to dry filament on the bed, as its enclosed printers can. Dry it in a filament dryer or a forced-air oven with Bambu Lab's values: PLA Basic or Matte at 50 °C, PETG at 60-65 °C and TPU at 70 °C, for 8 hours. Check first that the spool can take that temperature.
Check: Prints no longer show bubbles and the surface comes out smooth.
If that does not fix it: If it is the same with dry filament, check the filament profile and its temperature in Bambu Studio.
Store it sealed right after drying
When drying finishes, store the spool in a sealed container or bag with desiccant and use it soon: left out, it absorbs moisture again.
Check: The spool keeps printing well over the next days.
If that does not fix it: Dry it again before the next print.
Dry sensitive materials first
Always dry TPU, PC and PA before printing them. With PLA and PETG, Bambu Lab recommends drying them if you do not know how they were stored, especially for parts where the finish matters.
Check: Parts in those materials come out without bubbles or weak layers.
If that does not fix it: Dry for longer or check the dryer temperature.
Prevention
- Keep spools in a sealed container or bag and take them out only to print.
- If you do not know how a spool was stored, dry it before a part where the finish matters.
Still not fixed?
Tell usi3d's AI about your case: choose your printer, describe what you see and add photos if you like. It proposes checks step by step, with their sources.
Printers it applies to
The Bambu Lab A1 family: A1 and A1 mini.
Official sources
This guide summarises the official documentation linked here:
- Filament Drying · Bambu Lab
- How to Avoid Nozzle Clogs · Bambu Lab
This guide is general information: usi3d has summarised it from the official documentation linked here, and it may not match your model, its version or its firmware. If in doubt, follow the manual and the support of your printer's manufacturer. You decide what you do with your machine, and working on it may affect its warranty.