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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

    Note there are two types of the 2.5mm Allen keys. Use the longer one for screws, which are difficult to reach as this Allen key has a ball end.

    Thomas Gelsdorf - Reply

    I did not find a digital caliper in my bag of tools. I was so dissapointed by this fact that I had to go to the store, buy a new pack of gummy bears and stuff them down my throat… :-)

    Seriously, what would life be without humor?

    tomas.repisky@seznam.cz - Reply

    Can’t agree more! :)

    Martin L. - Official Prusa CS -

  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 ;)

    Duh, are you serious ;-)

    Chris Boer - Reply

    It would be helpful for debugging problems if the pulley body had another filament hole for when the selector is in the right most position to check the clearance for the selector input

    eman - Reply

  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.

    The top nut of the 3 from the purple insertions was loose enough in the slot that it was likely to fall out. I used a temporary M310 to hold it in place until the actual longer piece went in near the end. Having the temporary bolt sticking up didn’t affect any of the in-between steps.

    Eric Lindow - Reply

    I suggest to keep the two nuts in step three out and only insert them during the next phase as they will not be used during this phase and have a tendency to fall out.

    Uli Braun - Reply

    Yes, one nut fallout without I noticed. I had to unmount the pulley motor and insert the lost nut to be able to mount correctly the frame holders on the next chapter (6. Electronics and MMU2S unit assembly).

    Ron - Reply

  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.

    Hey Prusa Team!

    Thanks so much for your help and the great assembly guides. May I suggest putting one or two of the small black set screws (I think you called them “grub screws” in the MK3S guide) in the spare parts bag? One of my pulleys in this step was missing the black set screw, but I was able to use a spare one that was included in the MK3S kit.

    Thanks again!

    Zach Underwood - Reply

    Hi Zach, thank you for the feedback - we’ll consider it.

    Filip M - Official Prusa CS -

  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

    Watch out - I followed the wrong manual from this point for quite some time…

    Skip to Step 9 points to an osolete manual (2. Pulley body assembly).

    It should be 5. Pulley body assembly instead.

    Suggestion: Besides correcting the link, include some version information (or “obsolete” banner) in the page header.

    Boris - Reply

    Hi Boris, thanks for the suggestion. Most of the assembly manuals have a warning at the very beginning and obsolete versions are in a separate category.

    Jakub Dolezal -

    Please correct the link! Adds a lot of confusion following along with the MMU2 guide instead of MMU2S…

    Daniel B - Reply

    Hi Daniel, technical error, fixed. Sorry for the confusion ;)

    Jakub Dolezal -

  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.

    Gap between the motor and the shaft coupler should be 9mm. Otherwise the shaft coupler could collide with the mmu2-pulley-body

    Thomas Gelsdorf - Reply

    Hi Thomas, 10 mm is a value confirmed by our devs. I will recheck on it.

    Jakub Dolezal -

  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.

    Make sure you have the pulleys oriented correctly. The lock screws should be away from the motor as shown in the 3rd picture. If you get them backwards, the lock screws will wind up binding against the pulley body, which will prevent correct operation. The MMU won’t be able to load filament.

    Ray Benjamin - Reply

    The grub screws on the pulleys are actually T6, (torx) if you use a hex key be careful. If you’ve got a T6 it’s a lot easier.

    Kevin G Osborn - Reply

    One of my pulleys didn't come with the little black screw.  and I don't see any spare pulleys anywhere in the kit.  Is there anything I can do?

    Karl Reimer - Reply

    Hi Karl, check all the bags - perhaps it just got loose. If you can’t find it, then please contact our customer support.

    Filip M - Official Prusa CS -

    Thank you for the reply.  I checked every bag but there was no tiny little screw.  I contacted support and they are sending a new pully.   Karl

    Karl Reimer - Reply

  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.

    Use the Allen key with ball end for easier access to the lower screw heads.

    Thomas Gelsdorf - Reply

    This isn’t the Idler. this is the pulley assembly.

    Nature Kitty - Reply

    Be careful when inserting the ball bearing. Mine didn’t fit, so I tried to force it in a bit with an Allen key… and ended up damaging the thin metal housing which covers the bearings.

    Guido Hoss - Reply

    use a tiny drop of dishwashing soap on the end of the shaft to insert smoothly in the bearing

    Rudolph Sand - Reply

    I used a screwdriver and a hammer. I put the whole assembly on a flat surface with the bearing on the bottom and then I positioned the screwdriver on the back of the motor shaft. Tapped it VERY GENTLY with the hammer and the motor shaft was all the way inside the bearing.

    tomas.repisky@seznam.cz -

    Check if the bearing fits on the shaft before installing. Mine was very tight and needed to be sanded slightly for a press fit.

    Nick Jobbitt - Reply

    A chopstick is handy for seating the ball bearing.

    Carroll Campbell - Reply

    I ended up using the handle from a small pair of pliers to push the bearing in. The handle was small enough to fit in the space but big enough to not damage the bearing. (It did take a fair amount of force to seat the bearing properly.)

    Richard Murray - Reply

  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.

    I have used blue … I am sure that will make a difference ;-)

    Chris Boer - Reply

    I reiterate that the grub screws are torx T6. Much easier to not strip if you have the proper tool

    Kevin G Osborn - Reply

    I used a 2mm hex key inserted from the side with 2 green arrows and worked quite well

    Mark Stubblefield - Reply

    Genius, this was a great way to double check the alignment. Thanks @Mark.

    Eric C -

    Is the Pulley Motor and Extruder motor mixed up? These are extruder gears - not pully? The Pulley motor runs backwards - ie unloads filament when it should load it !

    greg.greene74@gmail.com - Reply

    Hi Greg,

    The 5 gears on the shaft are also called pulleys, the motor that spins these is the Pulley Motor. They are not mixed up.

    Marcin M. - Official Prusa CS -

    Ok… so… its true that a Torx T6 seems to grab the screw better but i’ve been using the hex and it has been working fine, I can get a good grip and it doesnt strip.

    Just make sure you are not gorilla tightening those screws xD

    Leonardo Delgado Graça - Reply

    Torx T6 is too small for my screws. I have a perfect fit with the allen key on these. I guess both variants exists.

    Anders -

  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.

    I was missing 3 of the 5 PTFE tubes for this step. It would be nice to note which, if any, of the other long PTFE tubes could be safely cut (in terms of length,) to provide spares. Thanks.

    Tim Deagan - Reply

    Hi Tim, please contact our support if there’s anything missing from your upgrade kit. Other than that, theoretically you could cut the missing tubes from the longest tubing available.

    Filip M - Official Prusa CS -

    I was missing 3 of the PTFE tubes as well. I would cut them but the instructions are clear that they should have a chamfered end.

    Sean M -

    PLease note that I received white PTFE tubings - some changes were made in the process.

    Piotr Fedorowicz - Reply

    Correct, but no worries , the color does not matter.

    Martin L. - Official Prusa CS -

    I’m missing 3 of the tubes as well -.-

    Really messed up my plans for the week.

    Alex McKenize - Reply

    Hi Alex, please contact our support - we’ll send you the missing tubes.

    Filip M - Official Prusa CS -

    Hi, I have all 5 of them but one is missing chamfering. Would it be safe to try to add chamfering myself to the missing one?

    mathias broxvall - Reply

    Hello Mathias,

    Sure thing, you can see our guide for chamfering here: How to trim PTFE tube - Multi Material

    Marcin M. - Official Prusa CS -

    I also am missing 3 of the tubes. Quality Control failed in this location.

    Caleb Solomon - Reply

    Hello Caleb, we will check this with the Quality department, in the meantime please contact us by email, we’ll send you the missing tubes.

    Martin L. - Official Prusa CS -

    I didn’t receive any of the 5 tubes. They are clearly marked on the bag, but are not in the bag. I’ve checked the other bags as well.

    Penjim - Reply

    Hello, the tubes can be white, are you sure you don’t have any white tubes of this length either?

    Martin L. - Official Prusa CS -

    I am quite sure- I have checked all the bags, and all around my workspace. There are none of these 5 tubes his length in any color.

    Penjim - Reply

    I am also missing 3 of the 5 tubes. I triple and quadruple checked. I do have some longer tubes from previous upgrades which I could trim, but those have a smaller diameter (1.85 instead of 2mm) - can I use those?

    Emil Rydza - Reply

    Hello Emil,

    No, it’s best to contact us in this case, we’ll help you.

    Martin L. - Official Prusa CS -

    I ended up cutting some of the longer tubing that came with the MMU2S (internal diameter of 2mm) to fashion these little tubes, and hand chamfered them with an exacto knife. I finished the assembly with these and the printer works fine.

    Support offered to either send the tubes directly or to give me a discount to add them to my next order.

    Emil Rydza -

    I am also missing 3 of the tubes.

    Andrew Torgerson - Reply

    Hello @andrewtorgerson , @ekr and @penjim,

    Please make a photo of all the parts you have received in your package, send it to info@prusa3d.com and mention that you are missing 3 of these 4x2x19 tubes.

    Martin L. - Official Prusa CS - Reply

    Seems like a quality control issue here - I’m missing three of the tubes too. I’ll talk to support.

    Russ Pitcher - Reply

    I sent an email to info and they actually suggested I purchase some. Really???…

    Andrew Torgerson - Reply

    Hello Andrew, please check your inbox, I took care of your case personally.

    Martin L. - Official Prusa CS -

  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!

    Since the filament comes from the pulley body, should not the chamfered end of the tubes be facing towards it, instead of the opposite, to ease the filament insertion?

    Why it has to be facing towards the selector?

    emanuele@fondani.it - Reply

    Hey Emanuele, it should be facing the selector as the filament will be moving through this part much more often.

    Filip M - Official Prusa CS -

    Hello,

    I agree with Emanuele, the tubes should be facing the “arrival” points of filaments to ease the insertion.

    After lots of unsuccessful loads, I finally turn the tubes and it then starts to work perfectly !

    The chamfered should “guide” the filament through the pulley.

    Franck Olivier - Reply

    I would agree with Emanuele and Franck.

    When the filament is pulled back. it does not need the chamfered edge to guide it. but when it is pushed to the printer it needs the chamfered edge for better alignment.

    Mikkel Posselt Bruun Rasmussen - Reply

    Hi Mikkel,

    We have tested it thoroughly - it’s better to install the tubes according to the manual.

    Filip M - Official Prusa CS -

    Hello Filip M

    Thanks for the response. I will keep it as it is and try to test with my printer.

    Mikkel Posselt Bruun Rasmussen - Reply

    I'm experiencing a much better filament load, when I put the chamfered edges inside (opposite then described) in the manual. Why not chamfering both sides from the ptfe?

    Martin - Reply

    Hi Martin,

    The load from spool holder to MMU body only happens once, while filament changes can happen hundreds of times.

    That’s why the chamfered end must be facing the selector.

    Filip M - Official Prusa CS -

    True, but the filament doesn’t need guidance when exiting from or retracting into the tube. It very much does need guidance when entering the tube! I’ve tried printing a 2-color Benchy three times and ran into load failures 3/3 times. I found that the filament caught on some edge when trying to push it into the selector. I then turned around the PTFE tubes as suggested here (not according to the manual) and succeeded with the 2-color Benchy on the very next try.

    So, so far, the stats are: “normal” orientation: 0/3, “reversed”: 1/1

    Balz - Reply

    I decided to play it safe and camfer the other side. I cannot lose that way.

    Michael Barnhart - Reply

    I like your solution. Probably worth a few minutes with an exact-o knife.

    Rocky Marcus -

    I did the same, not really sure what the issue could be with chamfering both ends. I used a noga chamfering tool, took 2s per tube

    Mark Stubblefield -

    With the chamfered edges as described the filament has a much greater chance of “curving” away from the entry hole of the selector hole. It makes no sense what you are describing of why it must face that way. Please take it back to the designers.

    Chris tenDen - Reply

    After reversing the tubes I was finally able to load all 5 filaments without problem.

    Chris tenDen -

    Hi Chris,

    the chamfered edges have their purpose. Each provides extra space for the unloaded filament, because the tip might be slightly bigger. If you turn them the other way around, it might cause issues. I suggest following the manual.

    Jakub Dolezal -

    I flared the ptfe tubes behind the selector on all 2 parts and now it's much better. I don't understand why you insist on saying that they are flared only on the outside

    riccardo zaccarelli - Reply

    Hi Ricardo, it’s important for the tubes to be chamfered on the selector end.

    The other end doesn’t matter, but you can chamfer it if you want to.

    Filip M - Official Prusa CS -

  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.

    For the square nut in the third picture, the one that is shown cocked, I found it easier to put it in if I turned the part upside down. That way gravity could aid me in keeping it in the top slot (if you hold it according to the picture) as I slid it back into proper place.

    Michael Barnhart - Reply

    use an M3x10 screw to gently finish pulling the m3n nut all the way in. just enough to seat it, make sure you don’t deface the part surface.

    david avery - Reply

    Very helpful!

    Elijah Jackson -

  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!

    The screwdriver fits easily all the way inside the tube and the flat part on the plastic handle pushes evenly around the tube.

    Gabe Ferencz - Reply

    Thanks for that tip! Very useful!

    Lenno Alanis -

    Agreed, this helped me a lot.

    RednaxNewo -

    Prusa should send you a bag of Haribo’s for that tip, it really makes it easy.

    Michael Barnhart -

    awesone idea!

    Jan Albiez -

    Very useful tip, Gabe. Thanks for sharing!

    Sean Dowling -

    Well pushing tube on wood block. Broke the part. Printing replacement and will try screwdriver trick'

    Garth Olivier - Reply

    yep that worked

    Garth Olivier -

  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.

    I had a lot of difficulty using an M3x10 screw for the screw on the left in the picture — it would push the M3n nut out of the slot before engaging. Used a longer screw that I had laying around instead.

    Matt Welsh - Reply

    I agree with Matt – I fumbled around for an eternity until the screw caught with the nut. A longer screw should be supplied for convenience (e.g. M3x20), especially since there’s plenty of depth on the back side.

    Guido Hoss - Reply

    Hello, if need be, there should be some longer screws in the Spares bag.

    Martin L. - Official Prusa CS -

    I also used a longer screw from my I3S upgrade remaining screws

    Chris Boer - Reply

    I found that the length of the screw stops being a problem if the nut is pulled further into the hole using the standard method (screw into the nut tightly before adding the lead screw nut)

    Damien - Reply

    exactly what I did… Assembling my Mk3s was so fresh in my mind, that this was quasi automatic.

    Jan Albiez -

    Also found the M3x10 to be too short.

    TJ Harris - Reply

    see my note in step 15: i used a m3x10 screw to gently pull the m3n nut all the way in before mounting the shaft nut

    david avery - Reply

    Step 18 Nut Assembly. I don’t have any nut that looks like the black collar in the 2nd and 3rd image. Further, in my Pulley Body package, there is no listing of a nut either. What’s the situation??

    John Sullivan - Reply

    Ahh, found it. Change your directions. Indicate that the Nut is threaded onto the selector motor!

    John Sullivan - Reply

    John, see Step 17, last sentence. Also, see the photos of step 17.

    Martin L. - Official Prusa CS -

    M3x10 screws can be used but only if first the nut is pulled all the way in with a M3x14 screw from the spare bag. After this replace the m3x14 by the intended M3x10 screw.

    Charles Buddendorf - Reply

    For the M3n nut , use the long M3x40 screw (Step 15) and leave it attached with 1 turn (attached but not threaded in far). Use the 40mm bolt to hold the nut in place while tightening the M3x10 screw or M3x18 screw

    Jason Welch - Reply

    We used the M3-10 without the lead screw nut in place, just to draw the hex nut into position. Then, removed the M3-10, placed the lead screw nut, and then used the same M3-10 to attach. This worked fine because the hex nut had been drawn into proper position.

    David - Reply

    I agree with David. I had a hard time, used an M3-20 to pull the nut tight, then replaced it with the 10mm. It reached, no problem.

    Mike McGlumphy - Reply

    This step took me about 25 seconds whilst chewing on a gummy bear. Why does everyone have such a problem with this step? :-)

    tomas.repisky@seznam.cz - Reply

  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!

    Wow. not much of a blade seat.

    Suggestion: when placing the blade, put a drop of liquid soap where the blade seats. It will help keep it in place while attaching the blade holder.

    Robert Flickinger - Reply

    Indeed not much of a blade seat! Also I had mine, after a few successful prints, flies through the room after the mmu2s tries to switch filaments! What is the reason for the blade. Cutting the filament (where is the waste going then?)

    Martin - Reply

    Martin,

    the blade is there to cut the filament strings if there are any. The waste is just falling off and is to be cleaned off once a while.

    Martin L. - Official Prusa CS -

    Blade seat was non-existent! Reprinted ‘selector-finda body’ at 0.15mm to get a decent result.

    David - Reply

    Hello David,

    It is less of a “blade seat”, and more of a contour to help you put the blade in a correct position. If it was any deeper, users could have issues with the blade staying correctly in place, even after tightening the blade holder part.

    Marcin M. - Official Prusa CS -

    Thanks Marcin…there was no outline on the original print and the re-print gave a better location outline for the blade

    David -

    I dumped the cover because it was warped. I have instead clamped the blade directly using washers under the capscrews. This clamps the blade far more effectively than the cover.

    Ian Bunce - Reply

    I a little filed the blade’s place out with a detailing triangle file. It worked out great. No soap or other clue was needed.

    gaazolee - Reply

    I could just about see the blade seat marking on the printed part. you need to look closely

    Alan J Roberts - Reply

    I used a drop of superglue to prevent the blade from moving around while attaching the blade-holder.

    Guido Hoss - Reply

    I love that you repurposed SD card holders!

    Michael Barnhart - Reply

    There was also a very light cut out area (maybe 0.1mm tall) to set the blade onto. I tilted the blade holder assembly downward on the screw side so that gravity would help keep the blade in place. Not much is needed, just a little to overcome the bit of blade that sticks out past the support.

    Michael Barnhart - Reply

    Hello Michael,

    As Robert suggested earlier, helping yourself with a dab of dish soap is a good solution to keep the blade in place during assembly.

    Marcin M. - Official Prusa CS -

    My seat also wasn’t very effective. My blade has rotated out of position and now I get to disassemble and try to fix it in the proper position again.

    Bret Wortman - Reply

    a better method of printing the cut-out would be to have a recess entirely enclosing the blade, then the blade holder can have a blade shaped protrusion to hold the blade into the cut-out

    Damien - Reply

    I like the thinking…

    Not this:

    ————————

    ——______———

    but this:

    ———_____———

    ———_____———

    with the recess then being a bit deeper for the blade

    However I actually think the stress on the blade during a filament cut could actually split the layers if that were the design approach.

    (need to have an ASCII art option in the comments :-)

    gstroot@gmail.com -

    Hi,

    thanks for the suggestion, we have some ideas about the new design, we will consider yours as well.

    Jakub Dolezal -

    After several failed prints, I discovered that the blade cover had two mounded regions around each screw hole on the blade side that probably restricted the amount of pressure that could be applied to the blade. I don’t know if that was by design or if they were printing artifacts. That is probably why my blade kept being dislodged during prints. The solution appears to be to sand the back side of the blade holder flat, being careful not to destroy the shallow imprint for the blade.

    Don Carpenter - Reply

    Sticky tape wil hold the blade while mounting!

    Hessel Moleman - Reply

    @Prusa: this step needs to be improved, thanks.

    Aaron Melocik - Reply

    Hi Arron, can you please be more specific? Do want to improve the step description or the design of the printed part? Thanks :)

    Jakub Dolezal -

    I think the design Jakub. I’d be reluctant to include superglue in the assembly :-)

    gstroot@gmail.com -

    Prusa has always impressed me with its quality and great design. This component seems out of character.

    After some jams during assembly I also had to use superglue. I’m contemplating a remix of this component. Maybe a rounded blade (scalpel - since it seemed to get caught on the return trip) or a thicker blade with some locating holes (pencil sharpener blade).

    Thoughts?

    gstroot@gmail.com - Reply

    Hi,

    each printed part is being checked before the shipping, but it might be my colleagues missed something. Take a picture of this part and send it to the info@prusa3d.com. In general, the blade should hold in just fine.

    Jakub Dolezal -

    This step is a safety hazard even if you follow the instructions perfectly. My husband was an electronics technician in the military so he knows what he is doing. The blade is aligned exactly as the picture indicates.

    He was in the middle of calibrating the filament length for the tube (which is a whole other issue, the settings on the calibration are not saving). The blade flew off and is now somewhere in our apartment.

    There needs to be a more secure way to fix the blade to this part so it remains in place during calibration.

    Kate Martin - Reply

    Hi Kate, the tube calibration is no longed needed with MMU2S.

    The blade should not fly away if it’s properly inserted and the cover is tightened - if it keeps happening, then perhaps there’s something wrong with the printed part. In this case it’s best to contact our customer support or simply re-print the selector & blade cover.

    Filip M - Official Prusa CS -

    It really seems like the blade is mounted backwards. This part is intended to cut a filament that is currently going through a hole that the blade is not angled towards for cutting, it is physically impossible to move the cutter into position to cut the filament without first withdrawing the filament or moving through it blunt side first, defeating the whole purpose of having a cutter. I had the blade come out of the part a bunch of times as it attempts to cut the filament with a flat edge of the blade. I eventually printed a new blade holder that uses metal pins to hold the blade in position, after a blade went flying somewhere. I haven’t even found that loose blade yet, I hope it doesn’t find me first.

    Eric Martin - Reply

    I think it would be helpful to add a zoomed in photo of the finished product to see how much of the blade should be visible once the holder is secure.

    Gabe Garcia - Reply

    Hi Gabe, all the pictures can be zoomed in after you click on them (or on the magnifying glass) :)

    Filip M - Official Prusa CS -

  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.

    After the rods are in, make sure the selector can move back and forth without the blade catching.

    (Added after my blade got stuck causing the selector to be jammed in position. I’m removing the blade after discussing with support)

    Matt P - Reply

    Yes, the blade is critical. Some Dec of mm.. and the blade will block the movement

    Roberto Coli - Reply

    I removed the blade cover after inserting the shafts, reinstalled the blade and tightened the cover. Now it slides freely.

    Kevin G Osborn - Reply

    Excellent tip. Thanks.

    Rick -

    How freely should the selector move on the rods ? Eg, if I tilt the assembly, should gravity allow it to move freely back and forth ? How many Newtons of manual force should be adequate to move the selector ?

    Harvey Kennett - Reply

    Hi Harvey, the selector should be movable by hand without much trouble.

    Later it will be moved by the stepper motor with integrated lead screw.

    Filip M - Official Prusa CS -

    The upper shaft is not a press fit and slides out of the bore.

    Is this supposed to be a press fit?

    Dave Okun - Reply

    Hello Dave, no worries, it is OK if the upper rod moves right to left a little.

    Martin L. - Official Prusa CS -

    When the selector is all the way on the left, is it meant to be aligned with the first filament hole?

    eman - Reply

    Hi, there might be a small gap when the selector is aligned with the first extruder.

    Filip M - Official Prusa CS -

  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.

    What made it a little easier for me was to turn the whole motor, rather than just the lead screw. Have to be a little mindful of the wires, but I found it easier than turning the shaft directly.

    Don Johnson - Reply

    Rotate motor shaft is pretty easy and fast. It took about 10 sec to get it on place right ;-)

    gaazolee - Reply

    This is probably a good point to test that filament loads from the back and goes through the selector without obstruction

    eman - Reply

    theese 3 screws are not counter in the beginning of the chapter. 10 screws are needed not 7.

    Michele Bordoni - Reply

    check if the nut from step out fell out … this is the time to look for it from now on its fixed by the motor

    Markus Weiler - Reply

  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.

    Hi. Am I missing something? I drop the ball (not push as the opening is larger than the diameter of the ball), then I add the F.I.N.D.A sensor to the hole. It says screw the F.I.N.D.A sensor in. Screw it into what? There are no threads in the cylindrical hole. I went back to see if I missed adding something but I can’t find anything. What did I do wrong?

    Peggy Helms - Reply

    Hi Peggy, you can just insert it the FINDA, but sometimes it’s needed to twist it or even screw it. But if you can just insert it, that’s fine. :)

    Martin L. - Official Prusa CS -

    I didn’t mention above that the diameter of the F.I.N.D.A. sensor is smaller than the diameter of the hole.

    Peggy Helms -

    Thanks. Apparently, we were commenting at the same time. :)

    Peggy Helms - Reply

    is it possible i got a pinda instead of a finda in my mmu2 kit?

    mine has a grey tip in stead of black and the thread extends all the way to the top an it doesnt say finda

    ron meiboom

    ron meiboom - Reply

    Hi Ron,

    If the probe you have received has 3 wires, then you got the correct one. You can always double check if it works by going to the Sensor Info in Support menu and check FINDA state value (0/1). If it gets triggered properly when putting a metal under the probe, it will work fine :)

    Marcin M. - Official Prusa CS -

    I exchanged the M3x10 screws in the selector-front-plate for M3x8. The M3x10 where too long and they can be seen interfering with the hole for the FINDA senzor.

    tomas.repisky@seznam.cz - Reply

  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.

    Should probably add a mention here not to over-tighten as well as what to do if you can’t tighten the FINDA probe. Looks like I’ll to re-print this part :/ Also, on that note, instructions mention setting up the extruder later but, uhh, I’m gonna have to do that now since I need to print this part again as the square nut has stripped the plastic so I can’t back the screw itself out now (and the FINDA probe still falls right out, poop). Having a functioning printer is probably worth doing after rebuilding the extruder before MMU?

    Tim S - Reply

    I built the MMU first. Then took extruder apart. So I was safe in case of any necessary reprints.

    gaazolee -

    I used different technique. I kept loosen the screw to be able to rotate FINDA then turned the MMU2 upside down and looking to the filament hole against a light source. Screwed in FINDA until the ball was visible in the hole. Then released it until ball just disappeared and secured it on place tighten the screw. With this step I minimized the friction, because the hole can be befully clear for the filament and assured that ball getting as close to the FINDA as possible when filament is inserted.

    gaazolee - Reply

    Very good technique! I did it as you told, got a very smooth filament feed.

    Felix -

    Super easy technique, consider adding it to the manual.

    Werner Marais -

    Hi there,

    Actually I was testing this technique myself and I found it quite too complicated, in comparison to the one described in the step.

    Martin L. - Official Prusa CS -

    This is much easier and more accurate than the process from the manual.

    Elijah Jackson -

    This! This is a MUCH better way of doing this… thank you very much for that Gaazolee!

    Kyle Pendleton -

    How are you supposed to know when the FINDA is touching the filament? It’s hard to feel changes in friction just moving the filament — should it be much harder to move you have it tight enough? (Just before you untighten it half a step)

    Chris - Reply

    Hi Chris, you should be able to feel the moment when the probe touches the metal ball. You can always adjust it later if it’s not done properly right now. You can also remove the filament and re-insert it - if it’s not going through, then you have pushed the probe too far.

    Filip M - Official Prusa CS -

    Wouldn’t it be easier to know how much of the probe should ideally stick out in mm or inch?

    Werner Marais - Reply

    Hi Werner,

    Not really, because at the end, you would still have to test it with an actual piece of filament to see if it works in practice.

    Martin L. - Official Prusa CS -

    I also found that if the probe is too far out the ball rattles when you shake the assembly. Once it is touching there is no rattle.

    Damien - Reply

    I miss here is to know what the goal is.

    Should the filament move freely? When is it too tight? When too lose?

    Also i can’t really screw the sensor..

    Markus Weiler - Reply

    Hi Markus,

    Yes, do not screw the sensor, just push/pull it down/up. The filament and the steel ball have to move absolutely freely.

    Martin L. - Official Prusa CS -

  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.

    Be careful you can easily crack the bearing housing due to the print orientation of the part. I had to widen both bearing housings a little bit with a slow Dremel drill, fits perfect now.

    Werner Marais - Reply

    I measured the bearing and the bearing hole in the printed part with a digital caliper .

    The bearing is 15.98 mm

    The hole form the bearing in the supplied printed part is 15.68 mm

    The bearings does not fit you have to widen the holes.

    I cracked one side tapping the bearing in with the handle of the screwdriver.

    Sean Eliseev - Reply

    Hello Sean, thank you for the feedback, we will check the tolerances.

    Martin L. - Official Prusa CS -

  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.

    I used a bar/screw clamp to move the bearings into pulley-body.

    Thomas Gelsdorf - Reply

    I layed them flat on a glass table and gently pushed them in, otherwise there is the change that they go in sidewise and they will not glide anymore

    Chris Boer - Reply

    the gap for the bearing was too small and the plastic part cracked.

    Thomas - Reply

    Hi Thomas, it’s possible the bearing was inserted at an angle, or something made its way inside the hole.

    Filip M - Official Prusa CS -

    These steps should definitely be performed before Step 2… The Pulley motor prevents from any clean alignment of a tool - such as a 11mm pipe key that would allow to insert the bearing w/o risking touching the inner part.

    Emmanuel Blot - Reply

    I agree with Emmanuel on the above comment. DEFINITELY would be much better to press the bearing in place before installing the Pulley motor!!!

    Michael Kebre - Reply

    I used the nylon hammer from my firearms repair kit. - ‘merica

    David - Reply

    This might be a “Thomas-Thing” but when pressing them in, not in an angle, the plastic part around cracked, two printed sheets separated to a crack :’(

    Thomas Rose - Reply

  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.

    There are missing instructions at this point. No where can I find the directions for assembly of the idler-body, placement of the bearings and shafts that hold them in place, etc. The alignment of the motor - that what rotation should be so that the wiring heads in the correct direction. I printed out the following: 5. Pulley body assembly, Written By: Jakub Dolezal. I think there are some pages missing after page 24. (excellent guide to this point) Page 25 shows the idler-body fully loaded with the bearings, and the two parts assembled together and the electric motor on the end (and I presume everything is snug and ready for installation). So how do I get from page 24 to page 25 (without the assembly instructions for the idler-body) to continue on with the assembly process??? In another guide I noticed the same issue exists between Step29 to Step30 - that guide is also missing the important assembly instructions for the idler-body. Help please.

    William Eaton - Reply

    There are missing instructions at this point. No where can I find the directions for assembly of the idler-body, placement of the bearings and shafts that hold them in place, etc. The alignment of the motor - that what rotation should be so that the wiring heads in the correct direction. I printed out the following: 5. Pulley body assembly, Written By: Jakub Dolezal. I think there are some pages missing after page 24. (excellent guide to this point) Page 25 shows the idler-body fully loaded with the bearings, and the two parts assembled together and the electric motor on the end (and I presume everything is snug and ready for installation). So how do I get from page 24 to page 25 (without the assembly instructions for the idler-body) to continue on with the assembly process??? In another guide I noticed the same issue exists between Step29 to Step30 - that guide is also missing the important assembly instructions for the idler-body. Help please.

    William Eaton - Reply

    OK, further research and I located a specific set of instructions for the idler-body construction. Maybe a note to seek the idler-body assembly instructions inserted into the document at this point, would be nice for those of us that are newbies to this process. That is between step 29 and step 30 in one document, and on Page 24 of 29 for the other document. Thank you.

    William Eaton - Reply

  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.

    I initially inserted the first shaft to far. I used one of the Allen wrenches to push it back out using the small hole at the end of the long grove on the opposite side of the bearing.

    skysport@wvi.com - Reply

  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.

    In my opinion, the screw does not prevent the shaft from falling out, because it is positioned too far away. It is better to mount a washer.

    hans-juergen.sasse@t-online.de - Reply

    Hello Hans, a washer from the spare bag will sure help, but the screw alone should just do the trick, according to our testing.

    Martin L. - Official Prusa CS -

    I had the same feeling so I tested it out and it works without washer. It just blocks it enough. Well done ;-) You can try it out. There is a hole on inner side you can use to push shafts out.

    gaazolee -

    I fitted a washer :-)

    Alan J Roberts - Reply

    I looked using a magnifier glass and it does cover the shaft hole slightly, which is all it needs to do since the shaft fits in the hole perfectly.

    Michael Barnhart - Reply

    I used an allen key from the other side to test it and the rod slid out without resistance… heading to the spare bag for washers.

    Tracy Miller - Reply

    The problem only happened on the side with 2 motors. Although I couldn’t find a spare washer I found a square nut worked well.

    Tracy Miller -

    I used a washer on both sides — screw head did not cover either shaft end at all. Would recommend adding two washers to this step to be safe.

    Mark - Reply

  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.

    For some reason I had a large amount of stringing in these two screw holes. Some of it kept the spring from seating all the way down, so that the spring compression and hence the tension was much higher on one side. Cleaned everything out with a small flat-bladed screwdriver and everything fit much better.

    Jason Tibbitts - Reply

  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.

    I already ran out of gummies

    Chris Boer - Reply

    I think they need a “Deluxe” version of all their products, with multiple large haribo bags, for an extra few $$.

    I mean they must get a good price when they buy them by the thousand!

    would help with the bear shortage I’m experiencing….

    Jonathan Tall - Reply

    Hehe, that almost sounds like you bought the printer only to get the gummy bears :)

    Martin L. - Official Prusa CS -

    Was not able to eat the gummies. Please add a note to not do the assembly right after going to a buffet restaurant. Marked step as complete, but will have to wait until later to finish haribo consumption.

    Jonathan Hoback - Reply

  36. Make sure all parts are tightened.
Finish Line

405 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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364 Guides authored

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 -

My kit came with a couple of rare earth bar magnets included (As well as a couple of spares). But they don’t seem to be mentioned anywhere int he instructions. Where do they belong?

Phil Desrosiers - Reply

The magnets are used in the MK3S without MMU. You can keep them aside or (pro tip: ) you can use them to prevent the idler screws from step 34 from falling out when you open the MMU. : )

Martin L. - Official Prusa CS -

Step 28 part 1 can crack the pull body while putting in the bearings.

Stephen Daire - Reply

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