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  1. Please prepare tools for this chapter:
    • Please prepare tools for this chapter:

    • 2.5mm Allen key for M3 screws

    • 1.5mm Allen key for nut alignment

    • Needle-nose pliers for blade assembly

    • Measurement tool (optional), best is a digital caliper

  2. For the following steps, please prepare:
    • For the following steps, please prepare:

    • mmu2-pulley-body (1x)

    • M3nS nut (10x)

    • Nuts are placed in the pulley-body because of the photography, no need to arrange them like this ;)

  3. Insert four nuts from the top of the pulley-body. Insert three nuts from the side of the pulley-body. Finally, insert two nuts from the other side of the pulley-body.
    • Insert four nuts from the top of the pulley-body.

    • Insert three nuts from the side of the pulley-body.

    • Finally, insert two nuts from the other side of the pulley-body.

    • Ensure proper alignment of all nuts using 1.5mm Allen key.

  4. Finally, insert the last (tenth) M3nS nut in the slot.
    • Finally, insert the last (tenth) M3nS nut in the slot.

    • Ensure proper alignment of nut using 1.5mm Allen key.

  5. For the following steps, please prepare: Pulley (5x) M3x10 screw (4x)
    • For the following steps, please prepare:

    • Pulley (5x)

    • M3x10 screw (4x)

    • 625 bearing (1x)

    • Pulley motor* (1x)

    • Filament with length 10-15 cm (1x)

    • The filament is not part of the upgrade kit, use any 1.75mm you have. Use a straight filament if possible.

    • * The pulley motor is not included in the MMU1 to MMU2S upgrade kit, see the next step.

  6. This step is valid only for those, who are upgrading from MMU1 to MMU2S. Skip to the Step 9
    • This step is valid only for those, who are upgrading from MMU1 to MMU2S. Skip to the Step 9

    • For the following steps, please prepare:

    • Shaft coupler (1x)

    • Shaft 5h9x90 (1x)

    • Extruder motor* (1x)

    • * Use the motor from the disassembled MMU1. This motor is not included in the MMU1-MMU2S upgrade package

  7. This step is valid only for those, who are upgrading from MMU1 to MMU2S. Rotate the flat part of the shaft in the direction of the cable. Insert bundled pliers to create a gap between the motor and the shaft coupler. If you want to be precise, the gap should be 10 mm.
    • This step is valid only for those, who are upgrading from MMU1 to MMU2S.

    • Rotate the flat part of the shaft in the direction of the cable.

    • Insert bundled pliers to create a gap between the motor and the shaft coupler. If you want to be precise, the gap should be 10 mm.

    • Place the shaft coupler on the top of pliers and rotate the lock screw against the flat part of the shaft. Tighten the lower screw.

    • Slightly press on the shaft coupler from the top to ensure the lower lock screw is engaged.

  8. This step is valid only for those, who are upgrading from MMU1 to MMU2S.
    • This step is valid only for those, who are upgrading from MMU1 to MMU2S.

    • Insert the shaft into the shaft coupler and rotate the flat part against the lock screw.

    • Tighten the lock screw.

    • Even though this motor is labelled "Extruder" consider it "Pulley motor" from now on.

  9. First, make sure the motor cable is facing to the left. Find the flat part of the shaft and rotate it up. Slide the first pulley on the shaft, ensure the lock screw is on the top (against the flat part of the shaft). Tighten the lock screw just slightly.
    • First, make sure the motor cable is facing to the left.

    • Find the flat part of the shaft and rotate it up.

    • Slide the first pulley on the shaft, ensure the lock screw is on the top (against the flat part of the shaft). Tighten the lock screw just slightly.

    • The first pulley should be around 30 mm (1.18 inch) from the black "ring" on the motor. Don't tighten the lock screw, you will need to adjust the position later.

    • Slide the other pulleys in the same orientation (lock screw facing up). Tighten the lock screw on each just slightly.

    • Exact position of each pulley will be adjusted later.

  10. Insert the 625 bearing in the pulley-body. At the end the bearing should "snap" to the opening in the printed part. Slide in the Pulley motor, the shaft must enter the bearing. Cable of the motor should be oriented to the left, see the second photo.
    • Insert the 625 bearing in the pulley-body. At the end the bearing should "snap" to the opening in the printed part.

    • Slide in the Pulley motor, the shaft must enter the bearing.

    • Cable of the motor should be oriented to the left, see the second photo.

    • Slide two screws M3x10 in the opening on idler-body and tighten them slightly.

    • Turn the entire assembly upside-down and insert second couple of the M3x10 screws, again tighten them slightly.

    • Make sure the motor is seated properly (in direct contact with the idler-body), then tighten all four screws. Tighten screws on a diagonal.

  11. WARNING: this step is crucial for proper functioning of the Multi Material. Please check your alignment multiple times!!! Push the filament through the pulley body as in the picture. In case your filament is bent, make sure it is bent down, so the part above the pulley is straight.
    • WARNING: this step is crucial for proper functioning of the Multi Material. Please check your alignment multiple times!!!

    • Push the filament through the pulley body as in the picture.

    • In case your filament is bent, make sure it is bent down, so the part above the pulley is straight.

    • Adjust the position of the pulley, the teeth must be directly below the filament.

    • Check again the proper position relative to the teeth on the pulley.

    • Make sure the lock screw is still perpendicular to the flat part of the shaft and tighten it. Use reasonable force as you might strip the screw.

    • Repeat these instructions on the 4 remaining pulleys.

  12. For the following steps, please prepare: mmu2-front-PTFE-holder (1x)
    • For the following steps, please prepare:

    • mmu2-front-PTFE-holder (1x)

    • M3x10 screw (4x)

    • PTFE 4x2x19 (5x)

    • Note the PTFE tube has one end chamfered, please pay attention to the instructions about proper orientation.

    • The PTFE tubes can be also in white color, other parameters are same as the orange version.

  13. Insert the PTFE tubes in the pulley-body all the way in. Approximately half of their length should stick out. The chamfered end of the tube must be facing out!!!! Slide on the front-PTFE-holder, note the upper circular openings are for the tubes. Secure the front-PTFE-holder using four M3x10 screws.
    • Insert the PTFE tubes in the pulley-body all the way in. Approximately half of their length should stick out. The chamfered end of the tube must be facing out!!!!

    • Slide on the front-PTFE-holder, note the upper circular openings are for the tubes.

    • Secure the front-PTFE-holder using four M3x10 screws.

    • The pictures in the following steps might include old version of the tubes, which aren't chamfered. DON'T adjust the tubes, leave them oriented according to this step!

  14. For the following steps, please prepare:
    • For the following steps, please prepare:

    • mmu2-selector (1x)

    • M3nS nut (6x)

    • M3n nut (1x)

    • Tube 5x6x25bt (2x)

  15. Insert three M3nS nuts in the selector-finda body, all the way in. Ensure alignment with the 1.5mm Allen key. Slide in the M3n nut. If possible use long screw from the "Spare" bag or from your MK3 kit. Press the nut in using hand, hammer shouldn't be necessary. Insert remaining three M3nS nuts in the selector-finda body, all the way in. Ensure alignment with the 1.5mm Allen key.
    • Insert three M3nS nuts in the selector-finda body, all the way in. Ensure alignment with the 1.5mm Allen key.

    • Slide in the M3n nut. If possible use long screw from the "Spare" bag or from your MK3 kit. Press the nut in using hand, hammer shouldn't be necessary.

    • Insert remaining three M3nS nuts in the selector-finda body, all the way in. Ensure alignment with the 1.5mm Allen key.

  16. Rotate the selector-finda as in the picture. Holes for the tubes are bigger from this side. Insert the tubes all the way in. Both should be aligned with the surface of the printed part.
    • Rotate the selector-finda as in the picture. Holes for the tubes are bigger from this side.

    • Insert the tubes all the way in. Both should be aligned with the surface of the printed part.

    • In case you can't push the tubes in, try first rotating the tube while pushing down. Then turn the printed part and a use flat surface to push the tubes in evenly. Avoid using hammer as you can damage the tube's rim!

  17. For the following steps, please prepare: mmu2-selector-front-plate (1x) M3x10 screw (7x)
    • For the following steps, please prepare:

    • mmu2-selector-front-plate (1x)

    • M3x10 screw (7x)

    • Smooth rod 5x120sh 120 mm (2x)

    • Selector motor (1x)

    • Lead screw nut (1x)

    • The nut is on the motor, take it off the lead screw.

  18. Rotate the selector-finda as in the picture. There is a cut out for the nut. Place the nut on the selector-finda part, it should fit in the cut out. Secure the nut with two M3x10 screws.
    • Rotate the selector-finda as in the picture. There is a cut out for the nut.

    • Place the nut on the selector-finda part, it should fit in the cut out.

    • Secure the nut with two M3x10 screws.

    • There are four holes in the nut, you can use any of them, they are the same.

    • Tip: if you can't reach the M3n nut, use a M3x18 screw from the spare bag and by tightening it, pull the nut closer.

  19. Rotate the selector-finda as in the picture. Place the selector-front-plate as in the picture. Note, there is a flat and angled edge on this printed part. The angled edge should point toward the centre of the selector-finda body.
    • Rotate the selector-finda as in the picture.

    • Place the selector-front-plate as in the picture. Note, there is a flat and angled edge on this printed part. The angled edge should point toward the centre of the selector-finda body.

    • Secure it with two M3x10 screws.

    • In the next step we will assemble the blade, but keep the parts you have prepared at step 17, we will use them soon.

  20. !!! WARNING: in this and following steps you will be assembling the blade. Make sure you don't cut yourself. Use pliers or gloves to protect your fingers !!!
    • !!! WARNING: in this and following steps you will be assembling the blade. Make sure you don't cut yourself. Use pliers or gloves to protect your fingers !!!

    • For the following steps, please prepare:

    • mmu2-blade-holder (1x)

    • M3x10 screw (2x)

    • blade (1x)

    • There are two blades in the kit, the other one is a spare.

  21. Prepare the selector-finda part as in the picture. Carefully place the blade in the prepared cutout and align it with the top left corner. Make sure the sharp part of the blade is pointing in the indicated direction.
    • Prepare the selector-finda part as in the picture.

    • Carefully place the blade in the prepared cutout and align it with the top left corner.

    • Make sure the sharp part of the blade is pointing in the indicated direction.

    • Place the blade-holder on the top of the blade and secure it with two M3x10 screws. Before you tighten the screws fully, ensure the blade is seated properly. Gently push it with the Allen key.

    • From now on pay attention while handling this part. The blade sticks out and you can cut yourself!

  22. Before assembling the motor we need to assemble the selector-finda part. Place the selector-finda part as in the picture. Important is correct orientation, exact position doesn't matter now. Insert both shafts through the pulley-body and the selector-finda part.
    • Before assembling the motor we need to assemble the selector-finda part.

    • Place the selector-finda part as in the picture. Important is correct orientation, exact position doesn't matter now.

    • Insert both shafts through the pulley-body and the selector-finda part.

    • Make sure both shaft reached the end of the pulley-body. There are two circular holes for them.

    • Ensure the shafts are aligned with the pulley-body and move the selector-finda all the way to the left.

    • FINAL CHECK: move the selector back and forth along the entire length of the smooth rods to ensure the blade isn't colliding with the other printed parts.

  23. Slide the Selector motor in, make sure the cable points up. Check the thread on the shaft and ensure there is no piece of plastic in it. Otherwise, you might have issues with the assembly. As soon as you reach the thread of the nut, hold the selector-finda and start rotating the shaft clock wise.
    • Slide the Selector motor in, make sure the cable points up.

    • Check the thread on the shaft and ensure there is no piece of plastic in it. Otherwise, you might have issues with the assembly.

    • As soon as you reach the thread of the nut, hold the selector-finda and start rotating the shaft clock wise.

    • Rotate with the shaft until the motor touches the pulley body. Make sure the selector-finda is all the way to the left.

    • Secure the Selector motor using three M3x10 screws.

  24. Though the design is similar, please note there is a P.I.N.D.A. used in the extruder on regular Original Prusa i3 printer and new F.I.N.D.A., which is used only in the MMU unit.
    • Though the design is similar, please note there is a P.I.N.D.A. used in the extruder on regular Original Prusa i3 printer and new F.I.N.D.A., which is used only in the MMU unit.

    • For the following steps, please prepare:

    • F.I.N.D.A. sensor (1x)

    • F.I.N.D.A. ball (1x)

    • M3x10 screw (1x)

    • Extra ball is in the spare package ;)

  25. Push the ball in the selector-finda circular opening. Carefully screw in the F.I.N.D.A. sensor. We recommend wrapping the cable as in the picture to avoid damaging it. Exact position of the F.I.N.D.A. sensor will be set in the next step. For now, let about 6-7 mm (0.24 - 0.28 inch) of the threaded part above the printed part.
    • Push the ball in the selector-finda circular opening.

    • Carefully screw in the F.I.N.D.A. sensor. We recommend wrapping the cable as in the picture to avoid damaging it.

    • Exact position of the F.I.N.D.A. sensor will be set in the next step. For now, let about 6-7 mm (0.24 - 0.28 inch) of the threaded part above the printed part.

    • Insert M3x10 screw as in the picture, tighten it very slightly.

  26. Insert any 1.75mm filament in the selector. Start tightening the sensor. During tightening try moving with the filament, as soon as the tip of the sensor presses the filament, stop tightening.
    • Insert any 1.75mm filament in the selector.

    • Start tightening the sensor. During tightening try moving with the filament, as soon as the tip of the sensor presses the filament, stop tightening.

    • Turn the sensor counter-clockwise 90° to lift it up slightly.

    • Tighten the M3x10 screw.

  27. For the following steps, please prepare:
    • For the following steps, please prepare:

    • Shaft 5x16sh (2x)

    • 625 bearing (2x)

    • M3x10 screw (2x)

    • The MMU2 unit is considered as the set of all the printed parts, motors, shafts, etc. assembled together.

  28. Turn the pulley-body side without motors towards you. Push the bearing in. Make sure it is aligned with the pulley-body.
    • Turn the pulley-body side without motors towards you.

    • Push the bearing in. Make sure it is aligned with the pulley-body.

  29. Turn the pulley-body side with motors towards you. Push the bearing in. Make sure it is aligned with the pulley-body.
    • Turn the pulley-body side with motors towards you.

    • Push the bearing in. Make sure it is aligned with the pulley-body.

  30. Let's assemble the MMU2 unit ;) Prepare the pulley-body and idler-body as in the picture. Note position of the motors.
    • Let's assemble the MMU2 unit ;)

    • Prepare the pulley-body and idler-body as in the picture. Note position of the motors.

    • "Rotate" the idler-body on the pulley body.

    • Proper alignment will be done in the next step.

  31. Turn the side with two motors towards you. Slide in the shaft 5x16sh, align it with the outer surface.
    • Turn the side with two motors towards you.

    • Slide in the shaft 5x16sh, align it with the outer surface.

    • Turn the side with one motor towards you.

    • Slide in the second shaft 5x16sh, align it with the outer surface.

  32. Turn the side with two motors towards you. Use M3x10 screw to secure the shaft against falling out. Tighten the screw to the surface of the printed part.
    • Turn the side with two motors towards you.

    • Use M3x10 screw to secure the shaft against falling out. Tighten the screw to the surface of the printed part.

    • Turn the side with one motor towards you.

    • Use second M3x10 screw to secure the shaft against falling out. Tighten the screw to the surface of the printed part.

  33. For the following steps, please prepare:
    • For the following steps, please prepare:

    • M3x30 screw (2x)

    • spring 5x15s (2x)

  34. Slide the springs on the screws. Insert screws with the springs in the holes on idler-body.
    • Slide the springs on the screws.

    • Insert screws with the springs in the holes on idler-body.

    • Tighten the screw heads slightly below the surface of the printed part.

  35. Quite challenging chapter, wasn't it?
    • Quite challenging chapter, wasn't it?

    • Pulley body assembly required your attention, eat no less than 20 % of all bears.

  36. Make sure all parts are tightened.
Finish Line

368 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

222 Guides authored

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Prusa Research Member of Prusa Research

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8 Comments

Step 13 - the tubes need to be turned the other way around. Chamfered side must be facing in, instead of out, like seen on step 22, the tubes are the other way. I just finished my MK3 to MK3S + MMU2S upgrade and got an issue with loading filaments to MMU2S and I now see where the problem is…

Milan Leposavic - Reply

Mr Leposavic,

This has been reviewed and tested many times, according to our testing, the information in the manual is correct.

Martin L. - Official Prusa CS -

I had a problem when the tubes were put like shown on Step 13. When I changed them like pictures show in Step 22, I don’t have a problem anymore…

Milan Leposavic - Reply

I think the fundamental issue is that step 13 and step 22 show the tubes placed in opposite directions. Obviously it was tried in both orientations and the pictures in step 22 were taken during that testing. Even though step 22 isn’t about the PTFE tubes, it would still be good if all of the pictures were consistent, even if only for those of us who are in the habit of checking that things are identical at each step.

Jason Tibbitts - Reply

Hi Jason,

You’re right. Just a small note: originally, these tubes weren’t cut at all, the photos around the step 22 and further are older than the photos in the step 13. But yes, we are working on an update of all the photos.

Martin L. - Official Prusa CS -

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