Clogged nozzle

Updated 3 months ago ​by Tomáš Chvalina

Clogs are one of the most common 3D printing troubles you may encounter with your printer. If you want to fix a clogged nozzle or even prevent it from happening altogether, follow the steps below.

There are two kinds of clogs:

  • Mid-print clogs: A clog that happens ONLY while printing. That means you are still able to unload the filament. 
  • Full clogs: A clog that makes it impossible to unload filaments and is PERMANENT (but can be removed through extra steps). 

Mid-print clogs

  1. Clogs are often caused by a malfunctioning fan or incorrect temperatures in general. First, check your extruder fans visually, if they spin during the printing process. To be 100% sure that both fans are ok, you can go through the Selftest and let it check your printer thoroughly. Selftest can be found in LCD Menu - Calibration - Selftest. Original Prusa i3 MK2/S requires you to manually go through the testing, while the MK3 runs a fully automated procedure.
  2. Make sure that the hotend fan is attached to the extruder properly. While spinning, it must push air inside, not outside. 
  3. Make sure that you selected the correct temperatures for the filament you want to use for printing. 
  4. A good way how to locate the source of the problem is to use a different filament/spool for printing. This way, you can check whether the clog is caused by the filament.
  5. Try to play around with your printing temperatures a little. Shift the temperature by + / - 5°C, since materials from other suppliers might need a little different temperature setting.
If none of the above solved your problem, follow the instructions for a Fully clogged nozzle.

Fully clogged nozzle

    Depending on the situation, try our suggestions below:

    The filament is pouring out a little
    Be careful not to touch the nozzle during this procedure. 
    1. Heat up the nozzle to the temperature recommended for the loaded filament 
    2. Push the bundled acupunctural needle (0,3mm to 0,35mm diameter) into the nozzle from below.
    3. Do this multiple times, until the material stuck inside weakens. Then try to load a new filament. When the filament is extruded correctly, it means the nozzle is clear.
    The filament is not pouring out of the nozzle
    1. Heat the nozzle to 250°C for PLA and 270°C for ABS in the LCD Menu - Settings - Temperatures - Nozzle
    2. Keep it at the selected temperature for about 5 minutes, then try to load a new filament. When the filament is extruded properly, it means the nozzle is clear.

    If it did not clear the clog, then there is one last trick you can try: 

    For this procedure, you will need a 1.5mm thick metal wire. Be very careful while pushing the wire through the extruder.
    1. Unload the filament.
    2. Loosen the tension bolts on the extruder idler. The process slightly differs depending on your printer model:
      1. Original Prusa i3 MK2/S: check STEP 16 in the MK2 Extruder assembly guide. Fully open the extruder idler and dis-assemble the filament sensor cover.
      2. Original Prusa i3 MK3: check STEP 15 & STEP 43 in the MK3 E-axis assembly guide.  Fully open the extruder idler and dis-assemble the filament sensor cover.
    3. Heat up the nozzle to 250°C for PLA and 270°C for ABS in the LCD Menu - Settings - Temperatures - Nozzle.
    4. Push a 1.5mm thick wire through the extruder. It should push the accumulated debris out of the nozzle. 
    5. Once this procedure is done, reassemble all parts and try to load a new filament. If the filament is extruded correctly, it means the nozzle is clear.

    How to prevent clogs from happening?

    1. Make sure that when loading/unloading a filament, the nozzle is heated up to the right temperature required by the filament. When you swap one type of material with another, it's often needed to change the temperature in the process. To unload ABS, preheat the nozzle to 255°C. However, to load PLA correctly, you need to decrease the temperature to 215°C.
    2. Be careful with G-codes, because they also store information about materials (and temperatures), not just extruder movement. For example, printing ABS with PLA temperatures will clog the nozzle almost instantly.
    3. Use high-quality filaments. Going for the cheapest option usually means getting low-quality filaments, which tend to create clogs more often.
    4. Try to store your filaments in a dry area.

    If you were unable to clear the clog, contact our support at info@prusa3d.com, and we will help you out! :) 


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