3.6. Swapping nozzles on the Prusa i3 Mk3

Note

These notes are based on my experiences with the Prusa i3 Mk3 and Artillery/Evnovo Sidewinder X1 printers. If you are using a different printer, please verify the hardware details are similar.

Changing the nozzle on your Mk3 is a straightforward procedure, and only takes a few minutes. These notes highlight a few tips and tricks to avoid common mistakes during this procedure.

3.6.1. Recommended tools

You could just use a pair of gnarly old pliers or an adjustable wrench for changing nozzles. However, I recommend using the appropriate tools:

A 16mm open wrench or spanner to brace the heater block. A crescent wrench will work, but is larger and more difficult to work with. Throughout this procedure:
- Keep a firm grasp on the heater block so it cannot rotate to avoid twisting and snapping the narrow heatbreak.
- Avoid damaging the thermistor and heater cartridge wires located on the left of the heater block as viewed from the front.
A 7mm socket wrench. An open wrench will work, but beware dropping a small hot nozzle as you work. I was using an open wrench and had a hot nozzle drop and disappear into my printer innards. I later found it stuck to a magnet underneath the bed. Black hardened steel nozzles are hard to spot under there!

User Aeronautical produced a neat design for an E3D heater block holder design foe download on Thingiverse. It is no longer available for download, but you can buy the whole thing ready to use on Amazon. I haven’t assembled mine yet, but it should provide a more secure grip on the heater block without any twisting.

3.6.2. Preparing for the nozzle swap

It’s a good idea to prepare things for doing the nozzle swap to avoid repeating steps.

Do a cold pull to clear the currently-mounted nozzle before removing. This will keep the stored nozzle clean and ready to print, and will avoid potential problems with higher-temp material accumulating in the nozzle interfering with later prints at lower temps.
Raise Z to max. Press and hold the front knob until it chirps, then rotate it to lift the Z axis. Push the knob again when done.
Heat hotend to a high temp (e.g. 280C) well above normal print temps. The goal is to heat the hotend and nozzle for maximum expansion so things will fit tightly as they cool.
As you wait for things to heat up, clean the hotend using a soft brass brush. Give the hotend and nozzle a light scrubbing, being careful to avoid the thermistor and heater cartridge wires that protrude from the left side as viewed from the front of the printer. You want to remove any built-up filament and other gunk that has built up before it starts dropping into your prints.
Give the nozzle a cleaning as well. If you are using a coated nozzle, replace the brass brush with a small width of cardboard to avoid removing the coating. Be sure to clear any build-up obscuring the nozzle size markings.

3.6.3. Old nozzle removal

Caution

As you remove the mounted nozzle, be sure to brace the heater block to avoid twisting the heat break.

Use a 16mm spanner or block holder to brace the heater block.
Use a 7mm socket wrench to loosen the mounted nozzle. Rotate from right to left as viewed from the front (counter-clockwise if viewed from below). Loosen until the nozzle comes loose in the socket.
Set aside the hot nozzle. Use pliers to remove it and set it on a surface to cool. The nozzle is extremely hot, so be sure to place it in a safe space.

Note

Steel nozzles are magnetic and can pop up into odd places on the printer underside. If you drop one, be sure to check the magnets under the print bed.

3.6.4. New nozzle prep

Spend a minute preparing the new nozzle to avoid headaches later on.

Check to make sure the nozzle is the appropriate size and type. Nozzle markings are small and easily obscured. Last chance!
Buff the nozzle tip on a leather strop or jeans. This helps by providing a shiny surface that is less prone to attracting and snagging filament during the print.

3.6.5. New nozzle installation

Caution

As you mount the new nozzle, be sure to brace the heater block avoid twisting the heat break.

Use a 16mm spanner to brace the heater block.
Insert the new nozzle into the 7mm socket with the threads protruding.
Insert the new nozzle into the heater block. Rotate from left to right as viewed from the front. Tighten until the nozzle fits snugly. Do not over-tighten! Two fingers should be sufficient to tighten the nozzle. Make sure it is snug so filament can’t ooze out over the top.

This is a good time to store the old nozzle before it wanders off.

3.6.6. Live-Z recalibration

You should re-do Live-Z calibration after every nozzle swap.

At this point, you should be able to resume printing. Remember that you need to re-slice any models to use different nozzle sizes.