The flow sensor has triggered

The Ultimaker S5 and the Ultimaker S3 feature a flow sensor in the feeder. The flow sensor is utilized during printing and it measures how much filament has passed through the feeder. It can detect forward movement and retractions. It is utilized to detect an end of filament in the pro bundle, or to detect for example under-extrusion.

How the flow sensor works

As the filament passes through the feeder, the flow sensor triggers a type of reading. This reading is material specific, and can be correlated to the expected filament steps.

There is an expected amount of filament flow during printing. This flow is determined by the print core size, the filament type and the created g-code. There is an allowed deviation from the expected flow, which can compensate for occasional slippage of the feeder, for example on soft materials such as TPU. 

However, if the deviation of the measured flow from the expected flow is too much, the flow sensor will trigger and a warning will be displayed.

Note: The flow sensor is always disabled for the first 2 printed layers of a print job.

What to do if you are encountering this error

Most often, this flow sensor triggers due to under-extrusion. This can occur because:

  • There is filament grind somewhere along the system. Check the filament, and if necessary remove the grounded down filament
  • There is a degraded / carbonized material in your print core. Clean the print core.
  • The filament is not good quality. This can happen for example after a material absorbs too much humidity from the atmosphere.

If the error is persistent and blocking your print job:

Try switching the flow sensor off. This may lead to print quality issues if there truly was under-extrusion in the system caused by problems in the extrusion train. Furthermore if you are using an Ultimaker S3, or a standalone S5, end of filaments will not be detected.

Alternatively, please get in contact with support. To best be able to help you, please provide as much detail as you can about your print job, including preferably the print job file, materials used, and whether its a single or dual print job. 


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