UltiMaker S: print core not recognised, incompatible or clogged, or the feeder grinds the filament
Guide based on the manufacturer's official documentation; usi3d has not yet verified it on a machine.
Technology: FDM · Brand: UltiMaker · Symptoms: The printer shows an error code or message, Clogged nozzle or hotend, The extruder grinds or snaps the filament, Too little filament (under-extrusion) · Updated on 9 October 2026
Symptom
The UltiMaker S reports that it does not recognise a print core or that it is not compatible with the loaded material; or material does not flow consistently (gaps, thin layers or a rough surface) and on the S8 the flow sensor pauses the print although the spool is not empty; or the feeder grinds the filament, especially PVA.
Likely causes, from most to least likely
- Dirty contact points on the PCB at the back of the print core: the most common reason it is not recognised.
- An unsupported print core and material combination; on the S8, for example, PLA is blocked in the CC+ print core because it causes severe under-extrusion.
- The print core is fully or partly clogged with degraded material.
- Wrong feeder tension (too low: the filament slips; too high: it grinds) or filament particles on its wheel or in the Bowden tube.
- Damp or low-quality material, or friction in the filament path.
- Badly stored PVA: with moisture, the feeder grinds it.
Checks to tell which one it is
- Read the message on the display (not recognised, incompatible or paused by the flow sensor) and note the ER code if there is one.
- Take out the print core and look at its rear contacts: dirt or residue.
- Check that the loaded material is supported by that type of print core.
- Open the feeder and look for filament dust on the knurled wheel; check where the tension is set.
Before you start
Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.
Step-by-step fix
Clean the print core contacts
From the configuration menu, choose the print core and Change: the printer heats it, unloads the material and cools it. Open the door and the print head fan bracket and slide it out by squeezing the levers, keeping it vertical. Clean the rear contacts with a cotton swab and isopropyl alcohol, without touching them with your fingers, and slide it back in until it clicks.
Check: The printer recognises the print core.
If that does not fix it: If it still does not, contact UltiMaker support with the serial number (it starts with BPP-), the logs and the message on the display.
Use a compatible combination
If an incompatibility warning appears, change the print core or the material to a supported combination. On the S8: AA+ and CC+ for high speed, BB for PVA and Breakaway, DD for Ultrafuse Support Layer, and never PLA in the CC+.
Check: The warning disappears and the print starts.
If that does not fix it: If the warning remains with a supported combination, contact UltiMaker support.
Clean a clogged print core
Start the assisted procedure in Preferences → Maintenance → Print head → Print core cleaning (Options on the S8) and follow the screen: it uses hot and cold pulls with UltiMaker cleaning filament or PLA. Mind the hot parts of the print head.
Check: Material flows consistently again and the flow sensor stops pausing the print.
If that does not fix it: If nothing changes, check the feeder (next step).
Clean and adjust the feeder
Unload the materials, open the feeder and clean its inside with a small brush. Set the tension: for UltiMaker materials, in the middle position.
Check: The filament feeds without slipping or being chewed.
If that does not fix it: Check the material and the Bowden tubes (next step).
Material, PVA and Bowden tubes
Dry the material if it has absorbed moisture. For PVA, UltiMaker advises storing it below 50 % humidity, printing below 55 % and below 28 °C ambient, and cleaning and thoroughly drying a coated Bowden tube. Keep feeders, Bowden tubes and print cores clean, and replace the Bowden tubes after a year of use.
Check: Extrusion is consistent and the feeder no longer grinds the filament.
If that does not fix it: Go back to a standard UltiMaker Cura profile and, if it persists, contact support with the serial number, the logs and the ER code.
Prevention
- Never touch the print core contacts with your fingers, and always insert and remove it vertically.
- Clean the BB print core preventively every 400 printing hours with Print core cleaning.
- Store materials, especially PVA, dry and sealed.
- Clean the feeders according to the maintenance schedule.
Still not fixed?
Tell usi3d's AI about your case: choose your printer, describe what you see and add photos if you like. It proposes checks step by step, with their sources.
Printers it applies to
The UltiMaker S family: S3, S5, S6, S7 and S8.
Official sources
This guide summarises the official documentation linked here:
This guide is general information: usi3d has summarised it from the official documentation linked here, and it may not match your model, its version or its firmware. If in doubt, follow the manual and the support of your printer's manufacturer. You decide what you do with your machine, and working on it may affect its warranty.