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Changing or replacing the nozzle (MK2.5S/MK3S/MK3S+/MK3.5)

Last updated 4 months ago
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The Original Prusa i3 printers use the E3D V6 Hotend. Any nozzle that is compatible with the E3D V6 Hotend can be installed on it. The stock nozzle that accompanies the printer is an E3D V6 0.4 mm brass nozzle, but other types and diameters can be used as well. The following procedure applies to all nozzles, except the Olsson Ruby.

To replace the Olsson Ruby nozzle, follow the instructions on the official 3DVERKSTAN website. Otherwise, you could damage it!

Why change the nozzle?

There might be two main reasons for replacing the nozzle:

  • The nozzle is worn out and needs a replacement.
  • You want to print using a different nozzle type, and/or diameter.
Unless you print abrasive materials with a brass nozzle, the stock brass nozzle will last you many hundreds of printing hours. Changing a relatively new nozzle to resolve a clog is not the solution!
The stock 0.4mm Nozzle installed on the Original Prusa i3 printers can be found in the eshop. We also offer an alternative 0.4mm nozzle compatible with i3 and MINI/+ printers.

Tools necessary

  • 2.5 mm Allen key (Included with assembled printers and kits)
  • 7 mm spanner/socket or pliers (7 mm spanner/socket not included with assembled printers and kits)
  • 17 mm spanner (not included with assembled printers and kits)
  • Small plate or aluminium foil (not included with assembled printers and kits)


The following procedure assumes that a firmware version from 3.12.0 or above is installed. In case your printer has a previous firmware version, we recommend upgrading to the latest version. If you did not flash a newer firmware version, follow the procedure, except for "Step 3 alternative" instead of step 3.

Follow this procedure exactly! Omitting steps can cause leaking and extrusion issues outlined at the end of this article.
  1. Unload the filament, if it is loaded, from LCD Menu - Unload Filament. Optionally, perform a Cold pull (MK3S/MK2.5S).
  2. Navigate to LCD Menu - Settings - HW Setup - Nozzle Change.
    1. The printer will display a message with a link to this guide.
    2. Click the LCD encoder: the printer will auto-home, and subsequently move the Z axis to the topmost position, and the X axis to the center. In the meantime, the printer will automatically heat the nozzle to 280 °C. Heating the nozzle is essential for this process.
    3. Once the nozzle is at 280 °C, the printer screen will display the following message: "Hotend at 280C! Nozzle changed and tightened to specs?". Do not click on the LCD encoder for now. 
  3. Unscrew the two screws on the print fan and the single screw securing the fan shroud. Remove both parts (picture below).

Step 2 alternative: if you could not follow step 3 due to firmware version up to 3.11.0 being installed, gain better access to the nozzle by moving the extruder (Z-axis) as high as possible: go to LCD Menu - Settings - Move Axis - Move Z. Spin the Knob to adjust the height. Once this is done, preheat the nozzle to 280 °C from LCD Menu - Settings - Temperature - Nozzle. Heating the nozzle is essential for this process.

CAUTION: Heated parts can cause severe burns!
  1. Hold the heater block with a 17 mm spanner (M10) or adjustable wrench.
Be extra careful around the fragile hotend heater and thermistor wires. You can break them off or short-circuit the heater with your spanner!
  1. Unscrew the nozzle using the supplied pliers. If you are using the E3D nozzles from our online store, use a 7mm spanner (M4) or 7 mm socket. Be careful, the nozzle is still hot! Place it out of the way on your non-flammable surface.
  2. Make sure that the printer is still on the screen described in step 3c, and that the set temperature (280 °C) didn't change. Holding the heater block with your spanner, carefully screw the new nozzle in and tighten it gently, but firmly. Do not use excessive force!
Our service and assembly teams use a torque wrench rated for 1 - 5 N m and tighten the nozzle with a force of 2.5 N m (Newton Meter).

Final inspection

There must always be a gap (~0.5 mm) between the nozzle and the heater block (left picture). The nozzle must be tightened/secured in the heater block, and locked against the heat break while heated (right picture). Failing to do so will cause leaks (center picture).

It is necessary to redo the First Layer Calibration (i3) after replacing the nozzle. If you installed a nozzle with a diameter other than 0.4 mm (0.25, 0.6, 0.8 mm), please see Different nozzle types.
You can find this procedure as a video on our YouTube channel. Be aware that some steps may differ slightly from the procedure outlined here, and printed parts of the extruder may look a little different than yours.
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