Stops Extruding Mid-Print
Fix extrusion that stops randomly partway through a print — check for heat creep, an empty spool, or a jam that developed after the print started.
Use this guide when extrusion starts normally and then stops while the nozzle continues moving. Note what happened immediately before the failure: the spool stopped, the drive clicked, a head changed, or power was interrupted. That observation determines the next check.
Stop or pause the failed job before diagnosing it. Layers already missed during the failure cannot be restored simply by restarting extrusion.
Choose the First Check
| Observation | First check |
|---|---|
| Filament pulled taut or spool stopped | Tangled spool or restricted path |
| Sensor says loaded but nothing reaches the head | Broken filament in the tube |
| Clicking and a worn section of filament | Grinding Filament |
| Failure after a period of normal printing | Hotend cooling, chamber conditions, and a developing blockage |
| Failure immediately after changing heads | Material loaded in the newly active head |
| Extruder motor no longer moves | Web Interface errors and support |
Record the affected head, elapsed printing time, material, nozzle temperature, chamber conditions, and any messages before restarting.
1. Check the Spool and Path
Confirm that filament remains on the spool and it can turn freely. Look for crossed turns, filament trapped beneath another wrap, or a spool binding against its holder.
Follow the guide tube to the extruder. A sensor reports material at its own location; it does not prove a continuous piece reaches the head. If filament broke beyond the sensor, the printer may continue moving without a runout indication.
Use Filament Breaks Inside Tube to clear broken pieces and correct the cause. Do not force fresh filament into a path that may still contain fragments.
2. Inspect the Drive and Hotend
Check for filament dust or a worn section near the gears. If present, use Grinding Filament, remove damaged material, and correct the feeding resistance before reloading.
If the upstream path is clear:
- Check that the hotend heatsink fan operates as intended. This is the fan cooling the hotend's cold side, not simply the part-cooling fan.
- Compare chamber conditions with the material profile. Follow Hotend Filament Jamming for heat-creep diagnosis.
- Select the affected head and use its standard loading/extrusion macro, or the temperature in the printer-specific material profile.
- Once actual temperature is stable, test a small manual extrusion.
- If feeding still fails, inspect the nozzle and heatbreak using Under-Extrusion.
Do not repeatedly force the drive against a blockage. After nozzle or heatbreak replacement and reassembly, follow Auto Calibration before printing again.
3. Check a Runout-Triggered Head Change
On V4, the setting is Web Interface > Macros > System > Settings > Filament Runout > 2nd Tool Backup. It controls automatic continuation with the other tool after filament runout. The firmware labels this feature under development and requires the same filament in both tools and completed auto-calibration.
To inspect the current setting without changing it, enter echo global.filamentBackup in the Web Interface > Console: true means enabled and false means disabled. The saved setting is in System > user > variables > FilamentBackup.g. The macro's Enable/Disable dialog does not show the current state.
To change the setting while the printer is idle, run 2nd Tool Backup and select Enable or Disable. Check the confirmation in the Console, then query the value again. Do not enable automatic continuation unless both heads are loaded with the same filament and ready to print. On V2/V3, verify whether your firmware provides this feature; the V4 path and variable above may not be available.
Check which head is active and whether the left head actually contains material. Confirm feeding from that head with its normal loading procedure. Do not assume the presence of a second head means it is prepared to continue the job.
If the macro or variable is unavailable, or the head-change behavior is unclear, send support your printer version, firmware version, configuration details, and event messages.
4. After a Power Interruption
For normal shutdown, keep the printer powered through its standard hotend cooldown. Loss of cooling while the hotend is hot can contribute to a blockage.
After an interruption, reheat using the loaded material's profile and verify manual extrusion before attempting another print. If feeding has not recovered, inspect for a blockage. Restored flow alone does not establish that an interrupted part can be resumed accurately; check the printer's recovery state and whether layers were missed.
Verify the Result
Run a short test under the conditions that previously failed. Check steady spool movement, uninterrupted extrusion, and the absence of new grinding. If failure previously took longer to develop, a brief successful purge is not sufficient evidence; observe the next print through that interval.
Record the Diagnostic Results
If the motor does not move or failure returns with a clear path, contact support before repeated feeding attempts. Record elapsed time, active head, cooling observations, error messages, and whether manual extrusion worked after reheating so the conditions can be reproduced.
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