Anycubic error 11511 (Extrusion / Feeding Abnormal) occurs on the Kobra 3, Kobra 3 Combo, Kobra X, Kobra S1, and Kobra S1 Max when the extruder system is unable to advance filament during a print job. On single-color models this usually points to a mechanical issue in the toolhead; on multi-color setups the ACE Pro color engine is a common failure point that prevents filament from reaching the printhead at all.

What the Error Means

The extruder drive gear must grip the filament firmly and push it through the PTFE path to the hotend at a steady rate. Error 11511 fires when this feed process is interrupted — the firmware detects that filament is not being extruded at the expected rate or cannot be pushed forward at all. Causes include a spool tangle preventing free feeding, filament diameter out of the 1.75 mm tolerance range causing the drive gear to slip, a partial nozzle clog creating backpressure the feeder cannot overcome, a kinked or blocked PTFE tube, or worn drive gear teeth that can no longer grip the filament. On Kobra 3 Combo and similar multi-color printers the ACE Pro hub must push filament several hundred millimetres through a Bowden tube to reach the hotend — any restriction along that longer path can trigger this error.

Step-by-Step Fix

1. Check the filament spool for tangles, knots, or crossed loops. An uneven wind that locks up the spool is a common but easily overlooked cause of feeding errors. Straighten any tangle and verify the spool rotates freely on its holder.
2. Measure the filament diameter at several points with digital calipers. It should be 1.75 mm ±0.05 mm. Filament wider than 1.80 mm or with irregular spots can jam the drive gear or PTFE tube.
3. On multi-color printers: manually feed each filament channel at the ACE Pro by pushing filament by hand through the Bowden tube to the printhead inlet. Each channel should advance smoothly with moderate hand pressure. Any channel that binds or stops indicates a blockage in that specific path.
4. Inspect the PTFE tube from the extruder to the hotend for sharp kinks, compression damage, or inner-wall buildup. Remove the tube, blow through it, and replace it if restricted.
5. Perform a cold pull to clear any partial clog in the nozzle: heat the hotend to printing temperature, then cool slowly to 90 °C while maintaining gentle pull pressure on the filament. Alternatively, use a nozzle cleaning needle to clear material from the melt zone.
6. Remove the extruder cover and inspect the drive gear teeth. If the teeth are ground down, packed with filament dust, or stripped on one side, clean them with a stiff brush or replace the extruder gear / extruder assembly.

Parts Required

• Replacement PTFE tube (cut to length for your model)
• Replacement extruder drive gear or extruder assembly (if gear teeth are worn)
• Digital calipers (for filament diameter check)
• Nozzle cleaning needle

If error 11511 recurs after clearing clogs and replacing worn extruder components, contact Anycubic support for further diagnosis.

Frequently asked questions

What does Anycubic 11511 mean?

Anycubic error 11511 (Extrusion / Feeding Abnormal) occurs on the Kobra 3, Kobra 3 Combo, Kobra X, Kobra S1, and Kobra S1 Max when the extruder system is unable to advance filament during a print job. On single-color models this usually points to a mechanical issue in the toolhead; on multi-color setups the ACE Pro color engine is a common failure point that prevents filament from reaching the printhead at all.

How do I fix Anycubic 11511?

Anycubic error 11511 means the extruder cannot feed filament during printing. Fix ACE Pro feeding issues, clogs, and worn extruder gears on Kobra 3, Kobra X, and Kobra S1.