UltiMaker S series printers and Factor 4 feature a filament flow sensor. The flow sensor is active during printing and measures how much filament is passing through the feeder. It can detect forward movement and retractions. The flow sensor readings are used to detect end-of-filament situations and severe under-extrusion.
On S series printers, the flow sensors are inside the feeders, just below the feeders' grip wheels. On Factor 4, which features a direct extruder, the flow sensors are located inside the feeder module in the print head.
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 print settings. There is an allowed deviation from the expected flow. This can compensate for occasional slippage, for example, on soft materials such as TPU 95A.
However, if the deviation of the measured flow from the expected flow is too much, the flow sensor will trigger. This can lead to the following scenarios:
- ER65: If the S series printer is set up with a Material Station, or on Factor 4, an extrusion problem can cause the ER65 warning message. This is an indication of insufficient extrusion and could mean that the print core is (partially) blocked. Learn more about this warning message here: ER65 - Extrusion problem detected
- Automatic spool change: Also on S series printers with a Material Station or on Factor 4, if no material movement is detected (in combination with decoupler readings), it is likely that the material spool is empty. If another spool of the same filament is available in the Material Station, the printer will automatically change to the new spool. Learn more about spool switching here: Automatic filament switching
- Material appears to be empty: On an S series printer without Material Station, the print will pause if insufficient or no extrusion is detected. The display will show a message that there is a problem with one of the materials; the material spool could be empty. The same behavior can occur on printers with Material Station if another spool of the same material type is not available.
Note: The flow sensor is always disabled for the first two layers of a print job. This is because the pressure from the build plate on the nozzle would otherwise trigger too many false positives. If no material is extruding (due to a blockage or insufficient material) at the start of a print, it is normal that the warning will only appear on layer 3.
Troubleshooting
If the flow sensor is triggered because the material spool is empty, simply unload the material and replace it with a new spool.
If the material is not empty, but it is tangled on the spool, you can also unload it via the menu, untangle it, and reload the material to continue your print.
If there are no visible problems with the material spool, you can try to continue the print progress. The material error will only pause the print, not abort it. If the warning was caused by a false positive, the print can likely continue and finish successfully. However, if the message persistently reappears, check the tips below.
During the print
Without aborting the print process, the troubleshooting options are fairly limited, but you can check the following:
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Check the feeder lever
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Make sure that the lever of the indicated feeder is fully down. If the feeder lever is left (partially) up, it will not give sufficient pressure on the filament while feeding.
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Check the feeder tension
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For UltiMaker materials, the feeder tension should be at the middle mark. If the tension is too high, the feeder may flatten the filament, but if the tension is too low, the material can slip inside the feeder. Use a 2 mm hex key or screwdriver to turn the bolt at the top of the feeder housing to adjust the feeder tension.
Tip: Learn more about the recommended feeder tension and how to adjust it on this page.
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Check the nozzle cover
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Printing without a nozzle cover, or with a worn / damaged one, can negatively affect the extrusion. One of the functions of the nozzle cover is to shield the print cores from the cold airflow of the fans during printing. Printing with a missing or damaged cover can cause temperature fluctuations in the print cores, possibly leading to under-extrusion and the material error message.
If the nozzle cover is missing or damaged, install a new one. This can be done during the paused state, although it is better to check this before starting a print.
Tip: Regularly check the nozzle cover according to the maintenance schedule to prevent problems during printing.
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Adjust print settings
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During a print, it is possible to slightly tweak the print settings. Printing too fast and/or at too low temperatures can cause extrusion problems. Try adjusting the settings via the display of the printer before continuing the print job.
Note: This is just a quick fix; remember to update the print settings in UltiMaker Cura for the next print job with this material.
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After the print
If the print has finished, or it had to be aborted due to extrusion issues, you can do further checks and perform maintenance actions:
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Check for grinding
| Unload the material and check for signs of grinding on the filament. Remove the damaged part. It is highly recommended to also clean the feeders and the Bowden tubes to remove filament debris if grinding is observed. |
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Clean the print cores
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Under-extrusion and grinding are often caused by degraded or carbonized material in the nozzle. Clear any blockages by cleaning the print core(s) with the hot and cold pull method.
Tip: It is recommended to preventively clean most print cores after a certain number of printing hours. For the AA(+) cores, it can help to clean the core when switching to a material with a very different printing temperature to prevent issues.
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Check the front fan
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The front fan cools the print cores during printing. If this fan does not spin, the heat can creep too far upwards in the print cores, causing the material to swell up. This will lead to extrusion problems. The front fan should spin when either of the print cores is hot. Especially on the UltiMaker S3 and S5, the fan could get blocked by thin strands of filament. Check and clean the front print head fan regularly.
Tip: On later production models of the S3 and S5, as well as on all later S series printer models (S6, S7, and S8), the front fan is reversed to prevent blockages.
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Filament quality
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Ensure the material you are using is of good quality. Only use filaments from reliable manufacturers to prevent seeing deviations in the filament diameter. Material that has absorbed moisture can also cause extrusion problems. Try drying the material.
Note: For certain UltiMaker materials, including PVA, PET CF, and Nylon CF Slide, it is recommended to dry the material before use for the best results.
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Disable flow sensors
If the error is persistent while there is no end of filament or extrusion problem, this can be a false positive. It is recommended to contact support for further assistance. Please include your log files and information about the print job, including material types.
In the meantime, you can bypass this error by temporarily disabling the flow sensors in the menu. This will allow you to continue printing while waiting for additional support. To disable the flow sensors, click on the gear icon, then select Settings. Toggle the switch for the flow sensors to turn them off.
Note: If you are seeing print quality problems such as under-extrusion in your print with the flow sensors disabled, the encountered errors were valid and not false positives.
