The Automatic Material System reports a feed fault or the spool stops advancing during a load or mid-print color change, leaving the toolhead starved.
These are the failure paths we see most often on the Bambu Lab AMS for a not feeding condition. Likelihood reflects field frequency; First Check is what you can do remotely before sharing logs.
| Cause | Likelihood | First Check |
|---|---|---|
| Spool brake too tight or filament wound under a previous layer (bird's nest) | High | Pull the spool and check it spins freely; look for filament trapped under the roll |
| PTFE kink or debris at the AMS inlet or toolhead transition | High | Inspect the tube path and the four-way hub for resistance when pushing filament by hand |
| Filament buffer arm stuck or spring disengaged | Medium | Move the buffer arm by hand and confirm it returns smoothly |
| AMS motor skip from wet or brittle filament | Low–Medium | Check the filament for snapping and note the humidity of the spool |
Work through these in order. Each step is something you can perform and report back on without opening the enclosure or swapping parts.
Note the slot number and the precise message (e.g. 'filament stuck' vs 'feed interrupted'). The wording tells us whether the fault is at the spool, the hub, or the toolhead.
Remove the spool and confirm it turns on the holder without drag. If the brake is too tight or filament is wound under itself, re-spool loosely and re-seat it centered on the hub.
With the AMS open, push filament by hand through the PTFE to the toolhead. Resistance at a specific point localizes the kink or debris so we can target it.
Cycle the filament buffer arm fully out and in. A stuck arm desyncs the load sequence; resetting it clears false 'not feeding' states.
Re-run the slot load from the screen and record where it fails. Send the on-screen step and any clicking sound timing to the specialist.
AMS feed faults are mechanical at the spool or pneumatic at the tube junction — rarely electronic. A short video of the buffer arm and the hub during a failed load is the fastest way to pinpoint it. Cross-reference the broader collections: Feed / load failure · Multi-material feeding.
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No. The feed motor is not user-serviceable and opening it voids the path we can guide. We resolve feeding through spool, tube and buffer adjustments.
Sometimes. Brittle, moisture-loaded filament snaps under feed tension. We assess the spool condition remotely and advise drying before swapping parts.
We do not ship parts. We identify the exact tube section to replace and the part number, but fulfillment is yours.
Share the slot error and a clip of the buffer arm. We guide a clean reload and tell you exactly which tube to swap if needed.
Submit Your Case Connect With SpecialistsWe do not perform hardware repair, we do not replace parts, and we cannot promise a 100% resolution. Our role is limited to remote diagnostic and step-by-step guidance based on the information, photos and logs you share.
When the blockage is past the AMS, at the hotend instead.
Another 3D printer thermal fault with a different remote path.
Full 3D printer troubleshooting collection.