Error- filament tangled or spool stuck, but spool is OK

Bambu Lab A1 Series Troubleshooting
1

Greetings, colleagues!

I’ve looked through the topic and used the search, but couldn’t find anything similar.

Bamboo Lab A1 (not AMS) printer, which I’ve been using for a year. It has printed approximately 15 kg of PLA, and everything was fine. Yesterday, after changing the spool, the new filament was loaded normally, and the extrusion process for cleaning the old and filling with new filament was completed.

I started printing, and during the preliminary calibration stage, the printer started showing an error saying that the filament was tangled in the spool or stuck in the tube. The print head automatically moved to the right, cut the filament, and moved to the left above the waste container. The print was paused, and the head stay heated.

I checked the spool—everything was fine, it rotated smoothly, and I found no obstacles. I pressed on the display that the problem was resolved and printing could continue. The printer re-loaded the filament, extruded a blob as during flow calibration (and I monitored it—the flow was smooth and quite voluminous, the filament fed from the spool without issues), smoothly moved the head to the right, and again cut the filament and displayed the same error.

I changed the filament spool to another one that I had already printed with, but the same result. I rebooted the printer—initialization passed without errors, but when starting a print, as soon as the preparation process begins, the head moves to the very back of the table, where it makes the first calibration touches, after which it should clean the nozzle on the plate—it immediately returns back, cuts the filament, and displays an error.

I removed the PTFE tube and plastic filament guide, fed the filament directly into the extruder—no changes. During filament testing during loading, the filament pulls well with noticeable force, no need to push it. The loading process completes without errors. But when starting a print—that’s it, an error—the filament is tangled on the spool, and filament feeding is stopped.

I disassembled the extruder—everything visually clean, but just in case, I thoroughly wiped the notches on the wheel, assembled it, started it— no result, same error.

I changed the nozzle to a new original one— no result, same error.

I haven’t run calibration yet; I don’t think it’s about the bed leveling…

What else could it be? Is the extruder motor acting up? I can take a photo of the error code, but perhaps it’s a known issue, and the experts will immediately guess?

2

It is possible you have something stuck in the head somewhere.

Try this guide and follow the steps. If the blockage is there, it will help you clear it out.

You may have a small piece of filament broken off in the mechanism, it doesn’t often occur, usually due to brittle filament or sometimes, just because.

Good luck.

3

Thank you Malc!
Head extruder was completly disassembled and checked. Nothing was inside. And filament comes in and out fine. I’'ll check later with switch off tangle sensor

4

Double check the ptfe tubing. Unhook it from the toolheads pneumatic coupling and make sure the metal teethies haven’t “bitten completely through it”. If those metal hooks end up in the plastic it can read like a snag