⬢Extruder-body (1x)

⬢M3x10 screw (1x)

⬢M3nS nut (2x)

⬢M3n nut (2x)

⬢Adapter-printer-mmu2s

MMU2S specific printed parts for the extruder are included in the MMU2S Extruder Bag.

⬢Extruder motor (1x)

⬢Extruder-motor-plate (1x)

⬢M3x10 screw (2x)

⬢Take the Extruder-motor-plate and secure it using two M3x10 screws. Use the cable as a guide to properly orient the part.

⬢Resist the temptation to place a screw in the third hole! Leave it for later ;)

⬢Rotate the shaft as in the picture. Flat part must in the direction of the arrow.

⬢Slide the gear on the shaft, the lock screw must be facing against the flat part of the shaft. Tighten the screw slightly.

⬢There is a "channel" for the filament inside the printed part. Align approximately the teeth on the gear with it.

⬢Don't tighten the screw just yet. We will align it properly first. See the next step.

⬢Take a piece of the 1.75mm filament. You can use the bundled one on a spool, don't use the black nylon, which is too thick. Straighten the filament as much as possible.

⬢Place the filament along the path and align the gear properly.

⬢The filament will be always slightly bent. Use it anyway for the initial alignment.

⬢For a final check replace the filament with an Allen key. Bear in mind, the key has slightly different size than the filament.

⬢Tighten the screw slightly to temporarily fix it, we will make the final check and tightening later on. Be careful, you can strip the thread.

Don't use any glue to fix the screw in place, you won't be able to release it, in such case you might have to replace the entire motor.

⬢Extruder-cover (1x)

⬢M3nS nut (1x)

⬢Slide the nut all the way in.

Ensure correct alignment using the Allen key.

⬢Leave the second slot empty, we will use it later.

⬢Hotend for MK3S/MK2.5S (1x)

⬢M3x40 screw (2x)

⬢M3x10 screw (2x)

We will use some screws later, so keep them around.

Your MK3 hotend might have a green dot or no dot at all, it is ok.

⬢Take the orange Adapter-printer-mmu2s (without hole for steel ball) and insert it in the Extruder-body. The surfaces of both parts should be almost aligned.

⬢Take two M3x10 screws and insert them in the holes. Doing this now makes the assembly slightly easier, but both holes are shallow and the screws might fall out. If this happens, you can continue without them and put them back later on (you will be notified). Also note, that in few upcoming pictures the screws might be missing.

Hotend assembly was completely reworked from MK3/MK2.5 to avoid bad placement. Also any future maintenance is much easier.

⬢Place the hotend next to the Extruder-body, see the grooves in the printed part, which are in the shape of the hotend.

⬢Correctly placed hotend. Cables should point in the direction behind the hand, we will align them in the next step.

⬢Place the Extruder-body with the hotend on the box and make sure the cables are pointing down.

⬢Place the extruder motor assembly on the Extruder-body.

⬢Make sure both parts are aligned.

⬢Place the Extruder-cover on the Extruder-body. Again, make sure parts are properly aligned.

⬢Insert two M3x40 screws, you've prepared earlier. Tighten them, but be careful, they are slightly longer, than the thickness of the entire assembly.

Place the extruder aside for few upcoming steps, we need to prepare other parts now. Leave it on the box to prevent damage to the cables.

⬢Prusa IR filament sensor (1x)

⬢M2x8 screw (1x)

⬢Take the smaller connector WITHOUT THE SENSOR! and carefully push it all the way through the IR-sensor-holder-mmu2s.

⬢Once the connector is through, connect the cable and the sensor together.

Pictures show MK3S IR-sensor cable, but use the same procedure for the MK2.5S cable. This is valid for the entire manual.

⬢Take the IR filament sensor and place it in the holder, make sure the orientation is the same as in the picture.

⬢Take cover and place it on the top. The cover is asymmetrical, see the picture. The smaller gap in the cover should be on the left.

⬢Secure the IR filament sensor and the cover using an M2x8 screw.

⬢Carefully insert the cable in the channel, make sure it is all the way in.

⬢Take the FS-cover-mmu2s and push in the M3n nut.

⬢Slide the holder on the cover, again make sure it is all the way in, otherwise, the holes won't align properly.

⬢Secure both parts using an M3x10 screw, see the picture for the correct hole.

This entire IR filament sensor assembly is also called "chimney" in the Handbook.

Tip: If you can't reach the nut, try pulling it up using a longer full-threaded screw from the spare bag.

⬢X-carriage (1x)

⬢M3n nut (2x)

⬢M3nS nut (4x)

⬢M3x40 screw (1x)

⬢Take both M3n nuts and using pliers (or screw) push them in the X-carriage, then using a screw from the other side, pull them all the way in.

⬢Don't forget to remove the screw.

⬢Take all four M3nS nuts and insert them in. Ensure correct alignment using the Allen key.

From now on, keep in mind the nuts are inside, avoid rotating the X-carriage "downwards", or the nuts might fall out.

In case the nuts keep falling out, use short screws from the spare bag to fix them temporarily.

⬢Place cable in the X-carriage, use the small printed overhangs to keep the cable inside.

⬢Gently place the FS-cover assembly on the rear side. The length of the cable isn't important for now, we will adjust it later.

⬢Guide the cable through the slot, remember this path, we will use it for other cables as well.

⬢Grab the X-carriage and place it from the back of the extruder.

⬢Make sure the motor cable follows the channel both in Extruder-body and X-carriage. In the X-carriage the motor cable will follow the path of the IR-sensor cable.

⬢ENSURE NO WIRE IS PINCHED! Then use the M3x10 screw and Allen key with ball end to connect both parts together. If you are inserting the screw at this moment, it will be slightly inclined in the beginning, but it will "straighten up" after few turns. Don't tighten the screw completely, we need to adjust the IR-sensor cable.

⬢Turn the extruder to the other side and if needed insert the second M3x10 screw. Don't tighten the screw, we need to adjust the IR-sensor cable.

Good job! Grab one extra gummy bear ;)

⬢Flip the FS-cover assembly on top of the Extruder.

⬢Align the left edge with the extruder body.

⬢Use a M3x18 screw to join both parts together.

⬢The IR-sensor cable can go straight in the extruder, no need for any additional loop. Carefully pull the cable, contrary if the cable is stretched, push it slightly in.

⬢Finish the sensor assembly by inserting an M3x40 screw.

⬢Make sure all the gaps are gone.

⬢Now you can tighten screws on both sides.

⬢Before you move to the next step, take an Allen key and GENTLY PUSH the motor cable to the channel to create space for the fan cable.

⬢First, create a loop on the cable. Make sure the black protective wrap is close to the edge of the fan. See the picture.

⬢Place the fan on the extruder and proceed in the following way:

⬢Extruder-idler-mmu2s (1x)

⬢Bondtech WITHOUT the hole for the lock screw (1x)

⬢Bearing (2x) might be stuck inside the gear

⬢Shaft (1x)

⬢M3n nut (1x)

⬢M3x40 screw (2x)

⬢Idler spring (1x) place the spring on the screw

⬢Take M3n nut and place it in the Extruder-idler-mmu2s.

Use the screw pulling technique.

⬢Insert the pulley in idler as shown in the picture.

⬢Slide the shaft through the idler and pulley. Use reasonable force or you will BREAK the printed part. In case of a self-printed part, please drill both holes for the shaft with a 3mm drill before inserting the shaft.

⬢Place your finger on the bearing and ensure it can rotate freely.

⬢Place the Extruder-idler-mmu2s in place and secure it using a M3x40 screw.

⬢Don't tighten the screw too firmly, it serves as a shaft for the idler. Check that the idler can rotate freely (though the range of the movement is small).

⬢Use the M3x40 screw with the spring to introduce tension to the Extruder-idler-mmu2s.

Hold the Extruder-idler-mmu2s on the other side, until the screw reaches the nut.

⬢Since there is only one screw, you need to introduce a large force. The head of the screw, should be aligned or slightly below the surface.

⬢Take the M3n nut and insert it all the way to the support. It is crucial!

Use the screw pulling technique.

⬢Place the support on the extruder and ensure the inclined part is facing "down" (towards the nozzle).

⬢Secure the support using an M3x10 screw.

⬢Insert M3nS nut in the Fan-shroud, all the way in.

Ensure correct alignment using the Allen key.

⬢Mount the Fan-shroud to the extruder, secure it using an M3x20 screw. Don't over tighten the screw, you can break the fan's plastic casing. Also make sure the fan can rotate freely.

⬢First, slide the fan in the Fan-shroud and make sure it is aligned properly.

⬢Second, fix the fan in place using one M3x20 screw. Tighten carefully, or you will damage the fan's casing.

⬢Turn the extruder around and insert the M3n nut. No need to pull it in, we will use the screw.

⬢Place the remaining M3x20 screw from the other side and tighten it, but carefully, or you will damage the fan's casing.

⬢Guide the cable according to the picture in the channel. Bend it slightly towards the extruder. DON'T stretch the cable!

⬢Insert the zip ties in the X-carriage like in the picture.

⬢Lower the X-axis at about 1/3 from the top.

⬢Turn the printer with X-axis motor and PSU facing towards you. LCD is on the other side. Align the bearings similarly to the picture. The exact position of the lower bearing doesn't matter for now.

⬢Place the extruder on the bearings, the top couple must fit perfectly. Make sure the X-carriage with the "belt inserts" is facing towards you.

⬢We will adjust the lower bearing later on.

⬢Tighten and cut the zip ties.

Check all the square M3nS nuts are still in the X-carriage.

⬢Place the cables on the P.I.N.D.A. probe side over the lower smooth rod and push them back in the channel.

⬢Place the cables on the hotend fan side over the lower smooth rod and push them back in the channel.

⬢Align the bearing, so it fits nicely in the X-carriage

⬢Guide the X-axis belt through the X-end-idler, around the 623h bearing with the housing and back.

⬢Continue with the belt through the X-carriage.

⬢Guide the X-axis belt through the X-end-motor, around the GT2-16 pulley and back.

Note that MK2.5 has a slightly different X-end design, namely the absence of the tensioning screw from the top.

⬢MK3 owners only: release the screw used later for fine tuning the belt tension. No need to remove the screw, just make sure it is loose.

⬢Please release two M3 screws on the X-end.

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

⬢Insert the flat part of the X-GT2 belt into the X-carriage as in the second picture.

Use a screwdriver or the smallest Allen key to push the belt in.

⬢Using right hand rotate the motor to its original position and hold it (tension is applied to the belt).

⬢Using two fingers on your left hand push the belt together. Very small force should be needed for bending the belt, BUT the belt shouldn't be bent by its own weight before being pressed with your fingers, it must be straight.

If you are struggling to rotate the motor back into position, the belt tension is too high.

⬢Depending on the belt being under or overstretched, adjust the amount of the belt in the X-carriage.

⬢When done, rotate the motor to its original position and tighten the M3 screws again.

Your belt might be already trimmed, simply skip the trimming instructions and insert it in the X-carriage.

For the following step we recommend getting a white marker, but you can also trim the belt without it.

⬢Measure the part, which must be trimmed and gently take the end of the belt away, from the X-carriage, but make sure at least 3-4 teeth are still in the X-carriage, as you don't want to lose the tension. If possible make a mark, where to cut the belt.

⬢Ensure again your mark is in the correct position and the belt is still stretched.

⬢Using pliers cut the belt and push it inside X-carriage. Use screwdriver or Allen key, if needed.

If you have MK2.5S, please skip this step.

In this step, we will finish tensioning the belt. Please read the instructions first, your belt might have proper tension already.

⬢First, slightly release all the screws holding the motor, otherwise, the upper "tensioner" won't work (the motor must be able to move).

⬢Using Allen key start tightening the M3x18 screw inside the X-end-motor, but after each turn or two check the tension in the belt.

⬢For the optimal performance, the belt must be a bit harder to press with your fingers. Move the extruder all the way to the X-end-idler and try the belt tension in the middle of the X-axis.

⬢When you achieve optimal tension, please tighten the screws again.

In case you experience X-axis failure during calibration or skipped layers in the X direction, you can adjust this screw accordingly. Tightening the screw stretches the belt. Releasing the screw has opposite effect. Each time don't forget to release the screws on the motor first.

⬢Locate the hole for the NYLON filament. Using the smallest Allen key ensure there are no obstacles inside.

⬢Using the pliers insert and twist the NYLON filament in the slot. Hold the extruder with your other hand.

⬢To check if the filament is seated properly, gently pull it with your hand. The X-axis should bend a little, but the filament must remain in the slot.

⬢If you have issues, try to adjust the tip on the filament.

⬢Prepare the M3x40 screw and cable-holder from the previous step.

⬢Tighten the screw all the way through the printed part.

⬢Take the M3n nut and place it in the printed part (all the way in).

Use the screw pulling technique.

⬢Rotate the X-carriage-back and tighten it together with the cable-holder.

⬢Check the "u-shaped" slot is aligned properly on both parts.

⬢Push the cables from the Extruder THROUGH the X-carriage-back. Start with IR-sensor cable, then the extruder motor and hotend fan.

⬢Next, add the print fan and P.I.N.D.A. sensor cables.

⬢Carefully insert the nylon filament and then slide the X-carriage-back towards the X-axis.

⬢M3x10 screw (4x)

⬢Use all four screws and tighten the X-carriage-back.

Tighten the screws with a reasonable force, make sure you won't deform/squeeze the bearings between the printed parts.

⬢Zip tie (5x)

⬢Textile sleeve 13 x 490 mm (1x)

The MMU2S includes a textile sleeve for the oldest MK3/MK2.5 designs, use it to replace the spiral wrap.

⬢Open one end of the textile sleeve and slide it on the cable bundle leading from the extruder. Don't forget to include the nylon!

⬢Leave the cables from the hotend out for now.

⬢Length of the first wrap should be slightly longer than the cable-holder part, about 5 cm is enough.

⬢Gently twist the sleeve to make it smaller and tighter around the cables, orient the sleeve's seam downwards, then slide the sleeve towards the extruder.

⬢Take 3 zip ties and insert them into the lower row of holes on the cable-holder.

⬢Twist the sleeve again (without twisting the cables inside) and tighten the zip ties.

⬢Use two zip ties and push them through the upper slots on the cable-holder.

⬢ATTENTION! Before tightening the zip ties add the cables from the hotend. Use the channel in the printed part to arrange them properly.

⬢Once the hotend cables are included, tighten the zip ties and cut remaining parts.

⬢Open the textile sleeve and insert the cables from the hotend.

⬢Compare the look of the cable management with the last picture.

⬢Check the final look, compare it to the picture.

⬢Don't worry about the cables, we will connect them later ;)

⬢Checked everything? Let's move to MMU2S unit assembly.