2C. MK3/MK2.5 extruder disassembly

Relevant for:

MMU2S

Last updated 3 years ago

Difficulty

Moderate

Steps

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Step 1 Preparing the printer

Before you start, make sure that:

⬢the filament is unloaded from the hotend

⬢the printer is properly cooled down

⬢the printer is unplugged

⬢you removed the steel sheet

This chapter is dedicated only to the MK3/MK2.5 owners. If you have new MK3S/MK2.5S, please follow: 2B. MK3S/MK2.5S extruder disassembly

The MK3 and MK2.5 have several design iterations and yours might differ from the one used as an example in this disassembly. As a result, some instructions might be not applicable to your printer (you can skip them).

Step 2 Releasing the cable bundle

⬢Using an Allen key release the M3x40 screw and open the door.

⬢Release two M3x10 screws and remove the extruder-cable-clip. On older printers cut the zip tie.

⬢In case there are zip ties inside the Einsy-case, carefully remove them.

⬢Remove the zip ties on the cable holder.

⬢Remove the textile sleeve (spiral wrap) all the way to the Einsy-case.

Step 3 Unplugging the extruder cables

⬢Open the Einsy-case and follow all the cables from the extruder. Unplug them one by one.

WARNING: some cables have a safety latch, don't pull them!

⬢Leave the other cables connected.

⬢MK2.5 requires similar disassembly, follow all cables from the extruder bundle and disconnect them.

Step 4 Removing the filament sensor cable

⬢Release all five screws and remove the X-carriage-back. Be careful with the wires. Disassemble the cable-holder printed part and keep it for the rebuild.

⬢Unplug the connector and remove the filament sensor cable. This cable is no longer needed and will be replaced with a new one.

⬢Carefully separate the cables and push them to sides.

Step 5 Releasing tension in the X-axis belt

⬢Depending on the version of your printer, you might have a tensioner on the top. Release the screw (until you can remove it by hand), but keep it in the X-end part.

⬢Release two M3 screws on the X-end.

⬢Rotate the X-axis motor as indicated towards the frame.

New version of X-end with tensioner provides easier fine-tuning of the tension in the belt, but you can assemble the printer without it. Printed parts are available at: prusa3d.com/prusa-i3-printable-parts/

Step 6 Removing the extruder

⬢Release and remove both M3 screws.

⬢Before releasing and removing the last screw, hold the extruder as it will fall down.

⬢Carefully lay the extruder on the heatbed and push the cables through the X-axis.

⬢Return to the X-carriage:

⬢Remove the black nylon and keep it for later.

⬢Remove the belt and keep it for later.

⬢Cut the zip ties and remove the carriage completely. For the MK3S/MK2.5S you will need a different one.

Step 7 Fans and motor removal

⬢Before removing the print fan, make sure the nozzle-fan (fan-shroud) is removed first.

⬢Release all screws on both fans and carefully remove them.

⬢Release both screws holding the idler.

⬢Remove the fan support.

WARNING: release and remove all three screws, but keep in mind the MOTOR WILL FALL OFF!

After you remove the motor, there will be two translucent washers on the idler, no need to keep them.

Step 8 P.I.N.D.A. probe removal

⬢Release and remove the M3x10 screw.

⬢Remove the probe by pushing it up. If necessary, open the printed bracket a little to increase the space for the probe to be pushed up.

Be careful with the wire! Don't pull the probe by the wire!

Keep the P.I.N.D.A probe for the reassembly.

Step 9 Hotend removal

⬢Release both M3 screws and remove the Extruder-cover so you can reach the hotend.

WARNING: Removing hotend from the extruder needs a "special" technique, then the hotend slides out quite easily. Don't use excessive force, or you will damage some parts irreversibly!!!

⬢The hotend is removed by inclining and pulling at the same time. See the picture showing the WRONG inclination. This hotend is inclined too much to the front and there is no gap between the hotend and the extruder body. Hotend is partly inside and you won't be able to remove it.

⬢The second picture is showing the CORRECT inclination. The hotend is tilted, but there is a gap between the hotend and the extruder body. You will be able to remove it.

Step 10 Removing the PTFE tube

THIS STEP IS OBLIGATORY! The MK3S/MK2.5S is using shorter PTFE tube compared to the MK3/MK2.5, let's replace it now!

⬢Press the black plastic collet down (towards the hotend) and hold it.

⬢Remove the old PTFE tube from the hotend.

⬢Release the collet.

See the next step on where to find and how to replace the new one.

Step 11 Inserting the new PTFE tube

⬢Open the upgrade package and look for a bag with the PTFE tubes.

⬢Check the new PTFE tube. Make sure both ends are clean.

⬢Now it is time to insert the new PTFE tube. Note there are two different ends.

⬢One end of the tube has "rounded" outer edge. This end must be inside the hotend.

⬢Look at the other end, where the tube is drilled inside, shape of the edge is "conical". This is the side, where filament enters the tube. This part must be outside the hotend.

⬢Push the black collet in. Slide the tube all the way in and hold it!

⬢Using second hand pull the collet out and only then release the tube!!! THIS IS CRUCIAL for the hotend to work properly. The tube must not be able to move in or out!

Step 12 Removing the Bondtech gear

EXTRA WARNING!!! Be extremely cautious during this step!!! You can easily strip the lock screw and irreversibly damage it.

⬢First, make sure the Bondtech isn't glued to the shaft. This is valid in case of the pre-assembled printer. If there is a glue, heat the shaft first (heatgun, lighter). Be careful, you can burn yourself.

⬢Second, carefully release the lock screw. If the resistance is too high, use a grease (e.g. WD-40) and wait for a while.

⬢Remove the Bondtech gear from the shaft and keep it for later.

Step 13 Idler disassembly

⬢Push and pull out the shaft. Keep it for later.

⬢Take out the Bondtech gear, BUT BE CAREFUL, there are two bearings inside. Don't lose them!!!

Step 14 Removing the filament sensor (optional)

This step is optional, there is no need to disassemble this part and you can skip this step. You will use a different sensor in the new extruder. Proceed only in case you want to use the sensor for other projects.

⬢Release two screws holding filament-sensor-cover.

⬢Release the M3x10 screw holding the filament sensor.

⬢Remove the sensor, avoid touching the PCB and the chips on it.