My X1C started feeding filament to the extruder, failing to grab it, retracting, and repeating. Inside, the extruder gears were coated in gunk after about 18 months of use. Swapping them is easier than it looks and takes around 20 minutes.
The short version
- Symptom: filament reaches the extruder, isn’t gripped, retracts, repeats.
- Part: Bambu Lab’s hardened steel extruder gear assembly (fits X1C, P1P and P1S).
- Tools: screwdriver (an electric one helps), fine tweezers, a magnetic mat for screws.
- Time: about 20 minutes, then a load test to confirm.
Why hardened steel?
On the P1P and P1S, the hardened steel gears are also an upgrade: together with a hardened nozzle they let you print abrasive filaments like carbon fibre blends.
Step 1: Get the extruder out
- Home the printer and lower the bed for working room.
- Remove the toolhead front cover and unplug the cables (tweezers help; the small one has a latch). Pull by the connector, not the wires.
- Undo the two hotend screws, check it’s cool, and pull the hotend straight down.
- Unplug the extruder cable (the first time there’s a dab of glue to pick off) and remove the PTFE tube by pressing the collet.
- Undo the top and middle screws. Before the bottom screw, loosen the filament cutter screw and swing the cutter aside.
- Remove the bottom screw and pull the extruder assembly out in one piece.
Step 2: Swap the gears
- Undo the four screws on the top shell and lift it off. Don’t lose the bearing inside it.
- Loosen (don’t remove) the top screw to release the spring tension.
- Remove the driven gear (tap it out from behind if it’s stuck), then the active gear.
- Fit the new active gear, snug the top screw a little, check the bearing is in place, and fit the driven gear, rotating until the teeth mesh.
- Fully tighten the top screw, refit the shell (bearing and pin aligned) and its four screws.
Step 3: Reinstall and test
- Push the assembly back in, aligning its gear with the motor gear, and refit the three screws.
- Slot the filament cutter back into its track and tighten its screw. Check it still moves.
- Refit the hotend, reconnect all four cables, the PTFE tube and the cover.
- Power cycle, unload the old filament, then load one. If it extrudes cleanly from the nozzle, you’re done.
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