Filament Not Detected
Prusa 3D Printer
Severity: MinorWhat Does This Error Mean?
Filament Not Detected means the filament sensor does not see filament passing through it. The filament may actually be out, the sensor may be dirty, or transparent filament may not trigger the optical sensor. Check the filament path and clean the sensor.
Affected Models
- Prusa MK4
- Prusa MK3S+
- Prusa Mini+
- Prusa XL
Common Causes
- Filament spool is empty
- Filament broke between the spool and extruder
- Filament sensor dirty or obstructed
- Transparent or very light filament not triggering the optical sensor
- Sensor cable loose
How to Fix It
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Check if the filament is actually present in the sensor.
Look at the filament path. If the filament broke or the spool is empty, load new filament.
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Clean the filament sensor.
Dust and filament shavings can block the optical sensor. Blow compressed air through the sensor.
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For transparent filament: disable the sensor or use opaque filament.
Some optical sensors cannot detect clear or translucent filament. You can disable the sensor in Settings > Filament sensor > Off.
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Check the sensor cable connection.
Make sure the sensor cable is plugged in to the mainboard.
Frequently Asked Questions
Can I print without the filament sensor?
Yes. You can disable the sensor in the menu. You just will not get automatic pause when filament runs out.
Does the MK4 sensor work with all filament colours?
The MK4 uses a different sensor type than the MK3S+. It generally works better with transparent filaments, but very clear filaments can still cause issues.