Filament not extruding/ clogged hot-end / air printing

The causes for extrusion failure are listed in below categories from most common to least common.

Filament transport before entering hot-end

Most cases are because of the filament is hindered to enter the print head properly.

  1. Filament guiding accessoires not used. Make sure to use the supplied filament holder and guide to ensure proper filament transport to the printer.
  2. Filament tangled on spool. Make sure the filament is not tangled on the spool and that it properly rolls from the spool.
  3. Extruder arm is not properly tensioned. Especially for flexible filaments this is important, the filament arm regulates the amount of traction the extruder motor has on the filament. If there is too much traction the filament gets squashed too much causing excessive friction when entering the hot-end. Adjust the tensioning bolt on top of the extruder arm to give proper force. Consult the user manual to adjust the proper amount of clamping range.
  4. Extruder drive gear worn out or full of dirt. Inspect if the teeth on the filament drive gear are still intact and not filled with debris. Also it is recommended to use the stainless steel drive gear version with curved contact groove instead of the straight type brass extruder wheels.
  5. Hot-end entrance blocked by small piece of filament. In some occasions when pulling out filament when hot, a small piece of filament could stay behind between the extruder drivewheel and the hot-end. This causes a blokkage. The best option is to take out the hot-end and remove this piece of filament.

Hot-end/Printhead internals blokked

  1. Hot-end exit is blocked from outside.

      • The nozzle is too close to the bed at the first printed layer. Make sure the bed is properly leveled, flat and also the z-height is correctly calibrated.
      • Over extrusion. When too much filament is extruded at some point you will have a buildup of filament on the printed object and the nozzle exit will get blocked by already extruded filament. Adjust slicing settings and lower the extrusion flow rate and 
  2. Clogged from the inside. (check this guide how-to guide. )
    • Dust collector not applied around the filament. Filament attracts a lot of dust, which can potentially all come into the hot-end. In some dusty environments this could cause a clogged hot-end within a few hours.
    • Big particle. Caused by wood filament or other particles
    • Fragment of previously printed material still in extruder. If you print a material with a high melting temperature and next a material with a low melting temperature, it may be that a residue of the high melting temperature plastic causes issues inside the extruder. Try extruding some (20 cm) PLA filament manually at high temperature (220 °C). Make sure to turn back the temperature to normal while slowly extruding some more material to prevent it to coal inside the extruder.

Best way to unclog the hot-end with the dip-and-pull method:
Insert PLA in the hot end. Heat the hot end to about 220°C. Try to extrude some material.Set the hot end temperature to 80°C. Disable stepper motors (can be done via the Quick settings menu on the printer itself). Wait for the extruder to reach the set temperature. Pull out the filament in one smooth and quick move. With some luck, the clogging material is attached to the solidified end of the filament.
If that fails, you can try hand-drilling the nozzle opening with a drill that matches your nozzle diameter. Make sure the nozzle is warm, otherwise the small drill will most likely break inside the tip. If this happens you can throw away a drill and hot-end nozzle. We sell some small diameter drills which have a high quality in our web shop

Bad filament quality

Bad filament quality is a major cause for clogged print-heads. It is strongly recommended to buy filament from a respected filament supplier. The extra costs will definately be worth its value in cost and lost time. This is especially true when you make longer prints.Most common issues with filament are:

  1. Filament diameter out of specifications. Make sure there are no knots or extremely thin parts. The filament diameter tolerance is 1.75 +/- 0.15mm.
  2. Filament kept in a moist environment, in which it could degrade very fast. Especially PVA has a short shelvelife. It is recommended to consume PVA within 1 to 2 weeks after opening if you leave it out in the open.
  3. Bad consistency of the filament itself, where the chemical properties very a lot on the same spool.

Wrong software settings used.

A common but mostly overlooked issue causing filament jams are bad slicing settings. Make sure to use the supplied slicing settings with the printer, or get latest version from our download section. The slicing parameters are finetuned to achieve best possible reliability. Most common errors after changing slicing settings:

  1. Retraction settings too high. When the printer prints several islands in the same layer, the printer performs a retraction when it moves from one island to the other. If there are a lot of these retractions following eachother, the hot-filament comes into the cold zone of the hot-end and could cause a clog, when this retraction is too high.
  2. Too high infill parameter. It is not recommended to exceed an infill of 80 percent. Going higher than this value requires perfect filament calibration. Normally with a lower infill, overextrusion would solve itself, since it always has somewhere to go. If the infill is too high, there is no margin for error anymore with respect to the filament diameter.
  3. Improper first layer settings., In most cases there is too much or too little extrusion on the first layer.

Bad calibration of machine

Bad calibration of a printer is also a cause for filament clogs.

  1. Make sure the z-homing height calibration is performed properly.
  2. Make sure the bed is properly leveled.
  3. Also make sure the bed is still flat within tolerances.

In case of dual head:

  1. Make sure the xy calibration is performed properly in case of printing in dual head mode.
  2. Make sure the z-height between both hot-end is the same.

Temperature issues.

Too high temperatures usually result in that the top part of the hot-end gets too warm. This causes the filament to melt too early and it sticks to the sidewall inside the hot-end. Most common causes of overheating.

  1. Printing selected filament at wrong temperature. Check filament type and corresponding temperature. Make sure to not print the filament too hot. For instance PLA printing at 210 degC gives a high risk on filament jams. The filament melts too early causing increased friction inside the hot-end.
  2. Fan cap not closed (FELIX PRO). The front fan cap should be flipped closed all the time when the extruder heaters are active. Failure to do so can cause the cooled part of the extruder to become hot, and the filament will soften or melt too early, causing jamming.
  3. A bad or wrongly mounted thermistor. Make sure the thermistor is working properly. It should rise at least 3 deg per second. If this is less, the thermistor of the extruder is probably broken. Another check for dual head printer is to check if the temperature rises at the same speed for both hot-ends. When going from 25 to 180 degC, there should be no more than 10degC difference during heatup.
  4. Make sure the fan in front of the hot-end is properly working. Also check if it does not incidently turns off over the whole stroke along the x-axis. This might indicate a wire breakage.
  5. (Dual head DIY kit:) Wires cross-connected.extruder temperature sensor connected to the wrong thermistor input terminal or the extruder heater is connected to the wrong output terminal. The software then thinks one hot-end is hot, but in reality the other hot-end is hot. Please re-check the wiring.

Improperly assembled hot-end

When a hot-end is not properly assembled, there can exist cavities or sharp edges in the hot-end. This can result in a buildup of filament locally, causing increased friction.

In case of the FELIX 3. The PEEK part internal diameter can be visibly smaller than the top aluminum hot-end part. You can see or feel an edge internal the 2 mm pipe. Screw both PEEK and top part of the hot-end off together and drill from the peek side with a 2mm drill carefully to remove any visible edges

Electronics failure

In some rare cases it can be that the control board itself has a fabrication error, which can cause a temperature offset. causing overheating.



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