1. This guide will take you through the entire process of how to disassemble the MK3/MK2.5 extruder, replace the printed parts B6 for B7, PTFE tube and assemble the extruder back. Note that MMU2 requires different PTFE tube.
    • This guide will take you through the entire process of how to disassemble the MK3/MK2.5 extruder, replace the printed parts B6 for B7, PTFE tube and assemble the extruder back. Note that MMU2 requires different PTFE tube.

    • 3D printed extruder parts were improved in order to achieve better cooling. More information including direct comparison can be found on our Prusa Research forum.

    • This update is recommended to all MK3 and MK2.5 owners before assembling the MMU2 upgrade.

    • All necessary parts are provided by Prusa Research in the MMU2 upgrade kit.

    • Parts printed by Prusa Research for the upgraded extruder are labelled B7, same parts are available to download with label R3.

    • This kit includes spare nuts, which might be difficult to retrieve from the disassembled extruder.

    • WARNING: in case you have a custom hotend or you bought it directly from E3D, you need a special Prusa MMU heatbreak. You can purchase it on Prusa eshop or from E3D. This heatbreak is included with all MK3 and majority of MK2S printers.

    • Your printer might be already upgraded to B7/R3 parts (see the forum for parts comparison). In that case you can skip to the next chapter 1. Idler body assembly

    Is this update only recommended, or actually required?

    Elisabetta Bini - Reply

    The printer is 100% operational even without this upgrade, but it will work even better with it.

    Martin L. - Official Prusa CS -

    Thanks to add: In case you have B7 (R3) already installed, you can skip

    Rodolphe - Reply

    Hi Rodolphe, this is exactly what is written in red letters in the last point of this step. : )

    Martin L. - Official Prusa CS -

    It’d be nice to have a step that shows moving the z axis up

    Calvin - Reply

    Hi Prusa,

    I have upgraded Mk2 MM1 to Mk2s + Mk2.5 (shipped end june 2018) in order to upgrade MM1 to MM2. I’m about to install MM2, could you confirm me if i received the special MMU heatbreak with my Mk2.5 upgrade kit ?

    Jeremy - Reply

    Hey Jeremy,

    MK2.5 doesn’t contain any hotend upgrades.

    Make sure to use the hotend you received with MMU1, it had the newer heatbreak. Also remember to change the PTFE to a newer one, provided with MMU2 kit.

    Filip M - Official Prusa CS -

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

    • 2.5mm Allen key for M3 screws

    • 1.5 or 2mm Allen key for nut alignment

    • Needle-nose pliers for zip ties

    • Apart from the mentioned tools, it is recommended getting a bowl or small box for the screws and parts you will remove during the disassembly, you will need some of them later.

    The spool holder bases worked great as a bowls to hold my screws and parts during disassembly.

    Cooper - Reply

    How many gummy bears do I need for this module?

    Clayton Fitchett - Reply

  3. Ensure the filament is not loaded in the hotend. Remove it before proceeding further. Release the marked M3 screws.
    • Ensure the filament is not loaded in the hotend. Remove it before proceeding further.

    • Release the marked M3 screws.

    • Remove the nozzle-fan printed part completely.

    • Carefully insert the Front print fan in the X-axis belt.

    • The 3D printed part nozzle-fan will be replaced with a new one.

    This sounds as if the fan will be replaced: “nozzle-fan will be replaced with a new one”. The fan is not replaced, only the orange shroud. It is a poor choice of words. The print fan (retained) is a fan. What you call the ‘nozzle-fan’ is a piece of plastic with no moving parts, and is not a fan.

    Paul Meyer - Reply

    Hi Paul, thanks for the feedback, the printed part is called nozzle-fan. I did adjustment to the description to make it clear.

    Jakub Dolezal -

    I agree with Paul. In my opinion, it would be a lot clearer if the part is renamed “fan-nozzle”. Then, it is clearer that it is a nozzle belonging to a fan.

    John Svensk - Reply

    Hi John, this part was named during the launch of the MK3, it is a heritage, which can't be easily changed as it written on hundreds of places.

    Jakub Dolezal -

    How about just using the full phrase “The nozzle-fan printed part will be replaced with a new one.”

    Brian Watt - Reply

    Hi Brian, thanks for the suggestion. Added to the description ;)

    Jakub Dolezal -

    I agree with the previous comments. IMHO it is still not clear enough. I think that in this case clarity is more important then keeping the heritage term. nozzle-fan should refer to the fan for the nozzle. and “fan-nozzle” or “nozzle-fan-shroud” are the appropriate names for the orange piece. I would go with the last option (nozzle-fan-shroud) because it will be simpler to upgrade the terminology and IMHO is more descriptive.

    Eyal Peleg - Reply

    I don’t know if it will matter in later steps but of the 3 screws one is shorter then the other two. when I removed all three I became worried not knowing which is which.

    Eyal Peleg - Reply

    One short screw is for the plastic part (M3x10 screw).

    2 longer screws are for the print fan in this case.

    Martin L. - Official Prusa CS -

  4. Release and remove all four M3x18 screws on the Left hotend fan. Move the fan carefully away from the extruder body as far as the cable allows. Move the extruder motor cable from the channel.
    • Release and remove all four M3x18 screws on the Left hotend fan.

    • Move the fan carefully away from the extruder body as far as the cable allows.

    • Move the extruder motor cable from the channel.

    • Release and remove both M3x25 screws, then remove carefully the extruder-cover part.

    • Your extruder and fan arrangement should look like in the last picture.

    • The extruder-cover will be replaced with a new one.

    Remove the Extruder motor wires from the cable channel before removing the cover

    Austin Hampton - Reply

    Hi Austin, good point. Thx ;)

    Jakub Dolezal -

    I was a bit puzzled as to what am I supposed to do with the motor cable. maybe “Lightly pull the extruder motor cable out of the plastic channel” would be clearer. also I would point the purple arrows downwards and not diagonally.

    Eyal Peleg - Reply

    removing the extruder cover required the use of some force for me.

    Eyal Peleg - Reply

  5. Turn the printer around and cut all five zip ties on the extruder cable bundle. Be very careful while cutting!
    • Turn the printer around and cut all five zip ties on the extruder cable bundle. Be very careful while cutting!

    • Remove all five zip ties from the extruder.

    The title says “removal”, but the actual instruction only says “cut”. Consider rephrasing from “Turn the printer around and cut …” to “Turn the printer around. Cut and remove …”

    Brian Watt - Reply

    Hi Brian, I've changed the description. Thanks for the feedback.

    Jakub Dolezal -

    what, no cutter in the kit? now what did I do with the one from the mk3 kit, hmm…

    Eyal Peleg - Reply

    Hi Eyal, you can use the pliers, tools are included.

    Jakub Dolezal -

    Should move this to between steps 9 and 10, cuts down on the need to turn the printer to cut, then turn around for hotend PTFE, then turn around again.

    ted - Reply

    True, but you need to have the hotend cables loose before removing the it from the plastic part. You want to avoid damaging them during the hotend manipulation.

    Martin L. - Official Prusa CS -

  6. WARNING:  Removing hotend from the extruder needs a "special" technique, then the hotend slides out quite easily. Don't use excessive force, or you will damage some parts irreversibly!!! The hotend is removed by inclining and pulling at the same time. See the first picture showing the WRONG inclination. This hotend is inclined too much to the front and there is no gap between the hotend and the extruder body. Hotend is partly inside and you won't be able to remove it. The second picture is showing the CORRECT inclination. The hotend is tilted, but there is a gap between the hotend and the extruder body. You will be able to remove it.
    • WARNING: Removing hotend from the extruder needs a "special" technique, then the hotend slides out quite easily. Don't use excessive force, or you will damage some parts irreversibly!!!

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

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

    • Now, let's incline the hotend properly. Take pliers in the second hand, grab the hotend above heatsink's ribs, pull downwards and slightly towards you. The hotend should "jump" out. Make sure you don't stretch the cables too much or you might damage them.

    I found the bad and good pictures confusing, because they are front views. I think having side views would be much better to show the bad and good inclination angles. Also I specifically held onto the cables with my left hand, rather than beneath the extruder body, to remove stress on them (now that they are freed from the zip ties).

    Brian Watt - Reply

    Hi Brian, I was trying different angles and this one seemed to me the best, but I can combine front with a side view.

    Jakub Dolezal -

    I also found the bad and good pictures difficult. The tip to open the idler door was very helpful.

    I had to pull it straight down (ever so slightly, with a light touch) and then i could pull the top (where the teflon tube is) towards me. Then it came right out nice and slow with out any sudden pops etc.

    I can see why you would want to be very careful at this part!

    Andy Johnson -

    I intuitively knew there was a magic way to do this after doing it so many times in my three printers. This helped articulate and make it reproducible. Thanks.

    Adam Luter - Reply

    Hi Adam, I'm glad it helped. Our technicians are using it on a daily basis, so I decided to share it with you :)

    Jakub Dolezal -

    flipping open the idler door allows to view the stuck teflon tube and resistance you are encountering

    ryan - Reply

    Hi Ryan, thanks for the tip ;)

    Jakub Dolezal -

    Yep, that did give a view of the PTFE tube and helped a bit to understand what is going on.

    Eyal Peleg -

    After having removed it I think the most important point to look at is near the top of the hotend where the thick ring sits inside the still on the printer half of the black printed part of the extruder. This determined the angle you need to get for the hotend to be able to move down. and some downward pressure during the tilting is require to pull the PTFE tube out.

    Eyal Peleg -

    And image of how it looks when its out might come a long way helping to understand how and what to expect.

    Eyal Peleg - Reply

    Thank you for the feedback. What is expected here is to simply take the hotend out from the plastic part (Extruder body) so that you could access the PTFE tube.

    Martin L. - Official Prusa CS -

    While the hotend is out would be a good time to clean it. Mine is coated in PLA.

    Perhaps a suggestion here to clean the hotend if needed and how to do it.

    joegchurch@gmail.com - Reply

  7. New PTFE tube is needed for MMU2 upgrade. Before you remove the PTFE tube, check the heaterblock. In case there is a green dot, the PTFE tube is MMU2 compatible and there is no need to change it.
    • New PTFE tube is needed for MMU2 upgrade.

    • Before you remove the PTFE tube, check the heaterblock. In case there is a green dot, the PTFE tube is MMU2 compatible and there is no need to change it.

    • Press the black plastic collet.

    • Remove the PTFE tube from the hotend.

    • Throw this old tube immediately to the nearest trash bin to avoid installing it back by accident ;)

    What is the difference between the old and the new PTFE tubes?

    Miguel Mancilla - Reply

    Hi Miguel, new PTFE is narrow compared to the “standard” MK3 PTFE tube.

    Jakub Dolezal -

    Hi Jakub, can you put the difference into numbers? How much narrower is the new PTFE?

    Alan H -

    Hi Alan, the new MMU2 PTFE tube has a 1.85 mm diameter. Standard hotend tubes are around 2.00 mm.

    Jakub Dolezal -

    You REALLY REALLY should say that this tube is available in the Step 3 Electronics bag of the MMU2. I couldn’t find it in the fan update kit so I didn’t replace it. Now I need to remove the print head again during the MMU2 install. All the instructions says is that it is needed.

    Chuck Genco - Reply

    Hi Chuck, you are instructed about the location of the new PTFE tube in the next step. For now you were asked to remove the old one, please follow the steps ;)

    Jakub Dolezal -

    Hi. Could this new ptfe be the reason why I`m no more able to print anything on my prusa after mmu2.0 update? Filament is no more coming out from the extruder. Tried several times to unclog the extruder following your tutorial, but it always seems partially clogged also with new filament. The mmu 2.0 loads the filament in a correct way, and the filament pass through the pulley all the way to the nozzle, but while printing it seems that there is some friction that brakes the filament.. and the pulley starts making clack clack noise. I still have the old ptfe. Can I come back to it? Should I solve the problem?

    hahanfry81@yahoo.it - Reply

    maybe you installed it the wrong way? (see the image in step 9.

    Eyal Peleg -

    Eyal is right. Please double check your hotend assembly see if the heatbreak is tightened firmly in the heatsink AND heater block, if not, unscrew it, apply some thermal paste and tighten. Also the PTFE tube must NOT be able to move back and forth in the hotend. If none of this solves the problem, please document it and contact us on info@prusa3d.com.

    Do not use the old PTFE tube (2mm inner diameter) with the MMU2!

    Martin L. - Official Prusa CS -

    I would say that throwing the old tube should be a bullet and not a warning… I actually skipped this and only when I took the new one out of the bag I though to myself, hmm… I wander what should I do with the old one… and only then I saw the warning. just saying.

    Eyal Peleg - Reply

    Hi. The tube is correctly mounted. I notice that I can only print with very high temperature, for example 250 degrees for pla. Probably the new ptfe keeps the filament very cold and when the filament arrives to the nozzle it doesn`t have enoughtime to reach the correct temperature?

    hahanfry81@yahoo.it -

    I ordered a “MK3 E3D V6.1 Assembled Hotend” on September 7th, 2018, and am installing that in place of the original hot end. The V6.1 hotend came with a PTFE tube that appears to be an exact match for the one provided with the MMU 2. Could someone confirm that? I’ve swapped it anyways, but I am loathe to toss a viable spare.

    W. Craig Trader - Reply

    Please add a warning that using a non-Prusa specific E3D heatbreak will cause issues with the MMU2 tip sizes after ramming because of the different internal geometry. I was having a terrible time with the MMU2 until I found this in the forum and realized I’d broken and replaced mine in the past.

    Matt Fielder - Reply

    Hi Matt,

    Whenever changing parts on the Original Prusa i3 printers, always ensure the part is designed for it. E3D has special section for MK3 parts including this custom heatbreak: https://e3d-online.com/prusa-mk3-spares

    Filip M - Official Prusa CS -

    Can this PTFE tube be purchased separately? I found this one but am not sure I found the correct one.

    Mihai-Andrei Stanimir - Reply

    It is the correct tube.

    Filip M - Official Prusa CS -

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

    • PTFE tube 4x1.85x50 (1x)

    • New PTFE tube is in the bag nr. 3.

    • There is an extra spare PTFE tube.

    Please Note that there are 2 bages that are labeld “3. Electronics”. one with plastic printed parts and one with many other parts. the PTFE tube is in the second one.

    Eyal Peleg - Reply

    I would expect the space tube to be in the “Spare parts” bag…

    Eyal Peleg - Reply

    Good idea! You should definitely keep all the spare parts together.

    Martin L. - Official Prusa CS -

    IMPORTANT: Please make note that the standard E3D heat break is not compatible with the MMU2. You need the PRUSA specific heat break for the E3D hot end. I spent weeks troubleshooting bad tips and jams until I found this out. So for those of us that may have replaced our hot end or heat breaks in the past, you need to order this specific part from PRUSA or E3D.

    Joey Cerone - Reply

    Hi Joey,

    good point, whenever changing parts on the Original Prusa i3 printers, always ensure the part is designed for it. E3D has special section for MK3 parts including this custom heatbreak: https://e3d-online.com/prusa-mk3-spares

    Jakub Dolezal -

    I killed the collet getting the PTFE tube out. Is there a spare collet in the spare parts bag? If not where can I get a new one?

    Alan Rhees - Reply

    Hi Alan, please get in touch with our support to get a new one, or if you have an E3D dealer nearby contact them directly.

    Jakub Dolezal -

  9. Now it is time to insert the new PTFE tube. Note there are two different ends. One end of the tube has "rounded" outer edge. This end must be inside the hotend.
    • Now it is time to insert the new PTFE tube. Note there are two different ends.

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

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

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

    • Using second hand pull the collet out and only then release the tube!!! THIS IS CRUCIAL for the hotend to work properly.

    The instructions refer to inserting / pulling collet / releasing the tube as being CRUCIAL. I felt a bit unsure as to what the result should look like. Maybe the maximal length of the PTFE tube sticking out can be provided? This could be checked with calipers. Another option is to insert a “check/inspection” picture of what the PTFE end looks like when assembled through the inspection hatch after “step 32”. I posted mine in the chat, as I felt it was maybe sticking out too much. It was inspected and proved OK fortunately.

    Rüedli - Reply

    Hi Rüedli,

    it is crucial, because if don't “lock” the tube against movement using the collet, it might happen the tube will lift up creating a gap inside the hotend, which will lead to filament jams.

    Jakub Dolezal -

    o.k. so how do I pull this collet ?

    Eyal Peleg -

    From what I can see the black collet can move like 1mm in or out. If I just pull the PTFE tube it pulls on the collet and locks. only when pushing back on the collet as explained in step 7 will it let the tube go out. so i pushed the tube in and then pulled it back like 1mm and it locked and I hope this is it.

    Eyal Peleg -

    i pushed the tube in and then pulled it back like 1mm and it locked

    Yes, that is exactly it!

    Martin L. - Official Prusa CS -

    The way I read it you should NOT pull on the tube to lock it in place but you should keep pressing down on it (gently) and then use your other hand to pull out the black “collet”. Of course it being so small I couldn’t really use my fingers but I could get my nails under it and pull it up without any problem. I hope that was the correct way to do it ;-)

    Tako Schotanus -

    Yes, that sounds like the correct way. To sum it up, you just need to push the collet and the tube in an then pull the collet up (most likely with your fingernails).

    Martin L. - Official Prusa CS -

    this step caused my extuder to miss steps when extruding because of blockage. My solution was to use a collet clip as seen in this link

    https://e3d-online.dozuki.com/Guide/V6+A...

    luckily i have another printer to print one from thingiverse/

    https://www.thingiverse.com/thing:258597...

    printing beautifully again :)

    Tony Wood - Reply

    Practicing the collet movement before inserting the tube helped me understand what it should look like when I performed the operation.

    Neal Palmquist - Reply

  10. Carefully push the unlock locking tab (safety pin) and unplug the filament sensor cable connector. Release all five M3x10 screws, you can leave them in the printed part.
    • Carefully push the unlock locking tab (safety pin) and unplug the filament sensor cable connector.

    • Release all five M3x10 screws, you can leave them in the printed part.

    • Make sure there are no zip ties left! Remove them before proceeding.

    • Carefully rotate the x-carriage-back printed part to the left. Make sure you are not twisting the cables.

    Carefully the unlock safety pin and unplug the filament sensor cable connector.

    I believe a word is missing here, possibly “push”.

    Benjamin Richter - Reply

    Hi Benjamin, thanks for noticing. Instruction adjusted :)

    Jakub Dolezal -

    Alternatively change from “Carefully the unlock safety pin” to “Carefully unlock the safety pin”.

    Brian Watt - Reply

    Hi Brian, I intended to use the “push”, text adjusted.

    Jakub Dolezal -

    Turn the printer around again… (this entire step is done from the backside.

    Eyal Peleg - Reply

    Also I think your images should show things "before the action” so because that is the position to find the “safety pin” .

    Eyal Peleg - Reply

    and finally, I personally I would say “unplug the filament sensor cable connector by carefully pushing the unlock “safety pin” and pulling the plug out at the same time” as the goal is to unplug the cable and not to push the “safety pin”.

    Eyal Peleg - Reply

    I can’t release the bottom right screw, because its M3n nut turns freely with it. Any suggestions on what to do?

    Elisabetta Bini - Reply

    Just because I’m a geek I know safety pin is really called a black MTA connector locking tab. No offense. I think it is amazing that the manuals are written in so many languages. I have written tech docs before at work and that was in my native language. Not easy. When I read safety pin I was imagining something else entirely.

    Neal Palmquist - Reply

    Hello Neal, thank you for this remark and for your kind words, we’ll update the description with the correct term.

    Martin L. - Official Prusa CS -

    step 11 could be miss leading . The first point “using both hands lower slowly the x axis down” I can see people trying to actually push the x axis down.

    I believe it should read “ using both hands wind the lead screws down and try to keep the x axis even”. Further down you mentioned to do just that but in the opposite direction. The words you will re calibrate the axis’s at the end of the upgrade, might a good reminder for later on.

    Ian McLeod - Reply

  11. Using both hands lower slowly the X-axis down. Stop when the P.I.N.D.A. is around 2-3 cm above the surface. Proceed carefully as you might scratch the surface.
    • Using both hands lower slowly the X-axis down. Stop when the P.I.N.D.A. is around 2-3 cm above the surface.

    • Proceed carefully as you might scratch the surface.

    • In case you have a piece of fabric or bubble foil you can use it now, to protect the sheet against scratches.

    Well, and the official recommendation is also not to touch the surface, as it will leave fatty fingerprints. I removed the build plate and covered the heatbed with bubble plastic, this was nicer to work on, keeping everything in place without damaging/dirtying anything.

    Rüedli - Reply

    Hi Rüedli, dust and grease can be cleaned with IPA after you finish this reassembly, but you have a good point with adding a protective layer ;)

    Jakub Dolezal -

    I found that pushing down on the x axis both sides of the extruder with my left hand while slightly rotating the z axis with my right hand required much less force to move the extruder downwards.

    Eyal Peleg - Reply

  12. Release both M3x10 screws and remove them. Remove the filament-sensor-cover part together with the (short) PTFE tube.
    • Release both M3x10 screws and remove them.

    • Remove the filament-sensor-cover part together with the (short) PTFE tube.

    • Release and remove both M3x40 screws including the springs.

    • Release the M3x30 screw, but leave it in place, we will remove it later.

    • Release and remove the M3x40 screw.

    Minor: orange bullet says “both M3x30” whereas they are “both M3x40”.

    Brian Watt - Reply

    Its in the first photo. Its the screw that you remove to open the door to the extruder gears. I was also trying to find it when I notice orange arrows in the small picture window.

    Steven Cowger -

    Hi Brian, you are correct, description updated. Thanks.

    Jakub Dolezal -

  13. In this step, we will remove the idler part. Before doing so, make sure you catch two translucent washers, which are on both sides! Remove the M3x30 screw from the idler. Remove the plug and the idler. Make sure you catch the translucent washers!
    • In this step, we will remove the idler part. Before doing so, make sure you catch two translucent washers, which are on both sides!

    • Remove the M3x30 screw from the idler.

    • Remove the plug and the idler. Make sure you catch the translucent washers!

    • Release the M3x10 screw and carefully remove the filament sensor. Avoid touching the chips on the PCB!

    • Release the M3x10 screw and push from below the extruder to remove the P.I.N.D.A. sensor. Avoid pulling the sensor out using cable!

    • In case you can't push the P.I.N.D.A. sensor up, very gently spread the holder around the sensor. Be careful as you might break it.

    To “remove the P.I.N.D.A. sensor” you might need to carefully spread apart the P.I.N.D.A. sensor holder.

    Brian Watt - Reply

    Hi Brian, thanks for the suggestion. You should be able to push the sensor up without spreading the holder, but good point ;)

    Jakub Dolezal -

    It should probably be noted that the top of the PINDA probe can end up under the blower fan wire because of where it was placed in the X-axis belts. Be careful and move the fan wire around the PINDA probe before attempting to remove it.

    Dave S - Reply

    Why is there a warning about breaking off the holder? This place is being replaced, so it doesn’t really matter. I was having the hardest time removing the PINDA and breaking this piece off would have saved me a lot of time, TBH. I suppose some people might want to keep the old printed part but I certainly don’t.

    Ryan A McQueen - Reply

  14. In this step, the extruder body will fall apart, make sure you hold the motor in the front! Release and remove both M3 screws holding the extruder-body on the X-axis.
    • In this step, the extruder body will fall apart, make sure you hold the motor in the front!

    • Release and remove both M3 screws holding the extruder-body on the X-axis.

    • Have a look at the printer from the top, gently lay the extruder-body with the motor on the heatbed.

    • Release and remove the last couple of M3 screws holding the motor and extruder-body together.

    • Now, remove the extruder-body part.

    • The extruder-body will be replaced with a new one.

  15. The final check of  the surgery!
    • The final check of the surgery!

    • Majority of the extruder's printed parts should be removed. The only remaining parts are X-carriage and X-carriage-back.

    • Make sure all the cables aren't stretched! Lower the X-axis down if needed.

    • Try removing all the nuts and screws from the disassembled parts. You will need them for the reassembly. Some nuts might be a bit difficult to remove from the extruder-body or extruder-cover, you can use the ones sent in the bag with the plastic parts.

    I am not clear as to which parts I need to take out screws from. e.g. what about the idler door of filament cover… I took out all but one square nut from the two large pieces (extruder body and and extruder cover). for some of them using a screw is very helpful and some other ones needed a small bang on the table to get released…

    Eyal Peleg - Reply

  16. Let's check the filament sensor. See the picture to compare two states of the sensor:
    • Let's check the filament sensor. See the picture to compare two states of the sensor:

    • A clean sensor is without any dust particles or grease. It is necessary to keep the sensor clean for precise readings of the filament.

    • A dirty sensor is covered with dust and grease, which can significantly reduce its precision.

    • How to clean it: use a Microfiber cloth and gently wipe the sensor in one direction only. To remove the grease, spray a bit of IPA on the cloth, not directly on the sensor!

    I’m hoping IPA stands for “Isopropyl alcohol” and not an “Indian pale ale from my fridge”?

    Joshua Levesque - Reply

    Hi Joshua, save the Indian pale for you :D To clean the sensor use the other IPA (isopropyl alcohol).

    Jakub Dolezal -

    I cracked the surface of my filament sensor. Is this commercially available in the USA? If so, what is the part number?

    emailjonathanwhite@gmail.com - Reply

    It is not, unfortunately. You can purchase your new sensor here. Make sure to be logged in!

    Martin L. - Official Prusa CS -

    yep mines clean now. I flashed it under a bright led. Now i cant see anything but the bright light!

    Ian McLeod - Reply

  17. BE CAREFUL with the filament sensor, do not touch the black PCB nor the chips on it.
    • BE CAREFUL with the filament sensor, do not touch the black PCB nor the chips on it.

    • For the following steps, please prepare:

    • Extruder-body B7 (1x)

    • Filament sensor (1x)

    • M3x10 screw (1x)

    • M3n nut (2x)

    • M3nS nut (2x)

  18. Before we continue with the assembly, we need to insert nuts in the Extruder-body. Take the extra time and effort to place them in properly. You won't be able to reach them later. Rotate the front part towards you and insert the M3 nut in the slot, all the way in.
    • Before we continue with the assembly, we need to insert nuts in the Extruder-body. Take the extra time and effort to place them in properly. You won't be able to reach them later.

    • Rotate the front part towards you and insert the M3 nut in the slot, all the way in.

    • Rotate the rear part towards you and insert the M3 nut in the slot, all the way in.

    • If you can't push the nuts in, use a longer screw from the other side and tighten it until you "pull" the nut in.

    FYI, inserting 2nd M3 nut by using longer screw from the other side … after seating the nut, I was initially unable to unscrew the long screw because the nut spun in the slot. Jammed tweezers between the nut and the wall to stop from spinning.

    Steve - Reply

    Hi Steve, thanks for the feedback and solution. The slot should be tight enough to prevent the nut from spinning.

    Jakub Dolezal -

    The second (blue) nut failed for me too, but it was when I was un-assembling the extruder previously, the nut started rotating inside the assembly. As the nut was impossible to reach inside the assembled part, I was eventually forced to tear the whole thing apart by force. I suggest that the dev team takes a look at this part.

    Samuli Teerilahti -

    Hi, this is just to let you know that we are discussing the tolerances for those nut holes.

    Martin L. - Official Prusa CS -

    The nut on the rear part (cyan) never stayed in place, I think due to the space-ish design of its hole. I re-tried it (assembling and dissasembling) three times, see step 32

    Zeev - Reply

    I have a kit later than the above. The nuts would not have seated well just pushing them into the hole, but pulled in perfectly using a screw from the other side. Nice snug fit.

    michael_farady - Reply

  19. Carefully insert the filament sensor in the slot, do not use force or you might damage the PCB! Carefully insert the filament sensor in the slot, do not use force or you might damage the PCB!
    • Carefully insert the filament sensor in the slot, do not use force or you might damage the PCB!

    The two pictures show different geometry slots, and A9 Parts. I’m having an issue later attaching the filament sensor cable and this difference here is not helping. My b7 part looks more like the first a9 part, with the overhang.

    Paul Meyer - Reply

    Hi Paul, there shouldn't be significant difference in the filament sensor “slot”. B7 has slightly bigger slot, which should enable easier assembly. Can you send some pics to info@prusa3D.com? Thanks

    Jakub Dolezal -

  20. Turn the extruder-body like in the picture. The pins of the filament sensor must be facing up. Locate the opening for the M3 screw.
    • Turn the extruder-body like in the picture. The pins of the filament sensor must be facing up.

    • Locate the opening for the M3 screw.

    • Take the M3x10 screw and tighten the sensor in place. No nut is needed, the screw will self-tap into the plastic.

    • The sensor must be tightened completely to prevent its movement BUT BE CAREFUL during tightening to avoid damage to the sensor.

    • Layers might be visible in this printed part due to the geometry. The functionality and strength remain unaffected.

    on my initial screwing of the sensor, it puulled the sensor into the scree and it seemed in place but was diagonal to the slot it is in. I tried again and then it crewed into the plastic on the other side of the sensor and pushed the sensor’s backside to the plastic and not it looks o.k. I would suggest adding a picture from the top side (i.e. showing the sensor alignment inside its slot.

    Eyal Peleg - Reply

    Please se the previous step for that picture.

    Martin L. - Official Prusa CS -

    I used a longer screw to start the self tap a thread or two and that made it less fumbling in my hands when mounting down the sensor with the real screw.

    Neal Palmquist - Reply

  21. Take two M3nS nuts from the package and insert them in the slots, all the way in.
    • Take two M3nS nuts from the package and insert them in the slots, all the way in.

    • Check proper alignment with the 1.5mm Allen key.

    same allen key can be used to clear any blockage inside the nut slots.

    Eyal Peleg - Reply

  22. For the following step, please prepare:
    • For the following step, please prepare:

    • M3x30 screw (3x)

    • M3 translucent washer (2x)

    • Translucent washers are placed on the idler for better visibility. No need to place them as in the picture ;)

    It’d be nice to include a washer in the spare parts bag. They’re a pain in the butt to find if you drop one. Thanks !

    Dave Cook - Reply

  23. Turn the Extruder-body like in the picture. The pins must be facing to the right. Insert M3x30 screw in the hole.
    • Turn the Extruder-body like in the picture. The pins must be facing to the right.

    • Insert M3x30 screw in the hole.

    • Place a washer from the other side.

    • Assemble the idler on the M3x30 screw.

    • Finish the assembly with the second washer.

    The M3S nut holes on my idler are very lose, so at this point I did the step 39 in order to have them aligned. Leaving the screws very lose in order to validate the idler movement.

    Petri Nurminen - Reply

  24. Connect carefully the extruder-body with the extruder motor and place it on the heatbed. Motor cable should be pointing in the indicated direction. Make sure both parts are properly aligned, then slightly tighten the M3x30 screw.
    • Connect carefully the extruder-body with the extruder motor and place it on the heatbed.

    • Motor cable should be pointing in the indicated direction.

    • Make sure both parts are properly aligned, then slightly tighten the M3x30 screw.

    • Insert two M3x30 screws and tighten them firmly.

    • Return to the idler screw and check, whether you can move with the idler part easily, if not release the screw. In case the idler part is too loose, you can tighten the screw a bit.

    • Leave the fourth hole empty for now, we will use it later ;)

  25. For the following step, please prepare:
    • For the following step, please prepare:

    • M3x30 screw (1x)

    • M3x18 screw (1x)

  26. Place the shorter M3x18 screw in the left hole. Place the longer M3x30 screw in the right hole. Check from the other side of the X-carriage, both screws should be sticking few millimetres out. It will help you during the assembly.
    • Place the shorter M3x18 screw in the left hole.

    • Place the longer M3x30 screw in the right hole.

    • Check from the other side of the X-carriage, both screws should be sticking few millimetres out. It will help you during the assembly.

    • Before you move to the next step, arrange the P.I.N.D.A. sensor and Front print fan cables. Push gently both cables in the channel and lay them over the extruder-body. See the third picture for details. Pay attention to this part or you might pinch and break them!

    Change from “arrange the P.I.N.D.A. sensor and Front print fan cables as in the picture” to “arrange the P.I.N.D.A. sensor and Front print fan cables in channel as shown in the picture”

    Brian Watt - Reply

    Hi Brian, there is more to this part. I rephrased the entire text, but thanks for your help. I appreciate it ;)

    Jakub Dolezal -

    “are few millimetres out “ was a bit confusing as I thought for a moment that this was an indication for the length of the screws and not for their positioning. the “Place the * M3x“ statments should say “ … but only push it in so that it is just a few milimeters out”.

    Eyal Peleg - Reply

    I would also add to this: “… but only push it in so that it is just a few milimeters out the other side”

    Gene Dahilig -

    Hello, OK we will modify the sentence to be more clear. Thanks for your suggestions!

    Martin L. - Official Prusa CS -

    I couldn’t use the 18 mm bolt, it wouldn’t reach the nut, a 25 mm did and didn’t protrude. I tried re seating the nut to no avail, so either the hole isn’t deep enough or the bolt length is a miss print. One other possibility is, there is still some wayward filament preventing the nut to seat further down. I tried using the bolt to seat it further but the nut wouldn’t go down any further. the 25 mm doesn’t protrude so I figure it will be fine to use.

    Ian McLeod - Reply

  27. Mount the extruder-body on the X-carriage and tighten slightly both screws.
    • Mount the extruder-body on the X-carriage and tighten slightly both screws.

    • Make sure no wires are pinched between both plastic parts.

    • Make sure the pins of the filament sensor aren't bent or in contact with the printed parts.

    • Check the proper alignment using the edge of both parts.

    • Tighten both screws.

    Difficulties here because the holes in the front were obstructed. On the step 21, had I checked alignment with an m3 bolt instead of an Allen key, this step would have been smoother.

    Paul Meyer - Reply

    Hi Paul, a check with the Allen key should be enough (works for me every time), using the M3 screws is also an option.

    Jakub Dolezal -

    be careful not to push the M3 nut from its hole when pushing the M3x30 screw into its hole.

    Eyal Peleg - Reply

    Reinforcing this advice, be sure it is there…mine pushed out onto the bubble wrap.

    Clayton Fitchett -

    Remember to check that both the fan and PINDA cables are aligned to the left side (looking from front) side of the up-side-down hook cable guide as shown in 1st picture in Step 28 BEFORE tightening the screws

    Petri Nurminen - Reply

    Motor screw #4? The M3x40? Not used here?

    I can find it in step 45, but why so late?

    Heiko Schultz - Reply

  28. Create a loop on the P.I.N.D.A. sensor cable.
    • Create a loop on the P.I.N.D.A. sensor cable.

    • Slide the sensor in the holder on the extruder body.

    • Exact position will be set later.

    At least for me - I had a PINDA sensor with full threading along the entire body, so the “3-4 threads above” is a bit confusing and misleading. I think having a different standard would be more helpful.

    Ryan A McQueen - Reply

    Hello Ryan, yes, in that case, set the PINDA so that the holder would be somewhere in the center of the PINDA body.

    Martin L. - Official Prusa CS -

  29. To have a better access to the lower part of the extruder, move carefully the X-axis up. Stop slightly above the middle of the height of the printer's frame.
    • To have a better access to the lower part of the extruder, move carefully the X-axis up. Stop slightly above the middle of the height of the printer's frame.

    • Using your fingers rotate the lead screws to move the X-axis up. Pulling the X-axis isn't recommended.

    • Move both sides up simultaneously!

    Isn’t that the Z-axis? Am I using the wrong convention?

    Jason Secrest - Reply

    In this photo we are showing how to level your X-axis, which is crucial. Although in order to do so, we are moving in the direction of the Z-axis. Hope thats clear :)

    Tom

    Tomáš -

    do you do this by turning the z-axis screws or just by using force on the x-axis bars?

    Andy Johnson - Reply

    Hi Andy, good point. Will add this to the description, turning the lead screws is better.

    Jakub Dolezal -

    this is odd. in a previous step we where instructed to push down on the X axis (which did seem weird to me then. is there a difference between pushing an pulling on the x axis?

    Eyal Peleg -

    No pushing/pulling on the axis is recommended. Please rotate the rods simultaneously with your fingers.

    Martin L. - Official Prusa CS -

  30. Carefully slide the hotend back to the extruder-body. CHECK THE PROPER ALIGNMENT of the hotend in the extruder body. THIS IS CRUCIAL. Otherwise, you won't be able to calibrate the printer later! Where to check the alignment:
    • Carefully slide the hotend back to the extruder-body.

    • CHECK THE PROPER ALIGNMENT of the hotend in the extruder body. THIS IS CRUCIAL. Otherwise, you won't be able to calibrate the printer later!

    • Where to check the alignment:

    • There should be no gap between the extruder-body and the hotend.

    • The last rib on the hotend's heatsink should be aligned with the printed part. See the photo.

    • Make sure the hotend's cables are on the left side. Compare your assembly with the picture.

    Thank you for adding the “CHECK THE PROPER ALIGNMENT” point. When I first built my kit, this was my only problem with my build. Seriously people… pay attention to this if you didn’t buy the kit version and are upgrading.

    Joshua Levesque - Reply

    Hi Joshua, this is very common issue with the MK3 kit assembly. That is why I included it here as well, to make sure your builds will be successful :)

    Jakub Dolezal -

    I assume that because this part is new, and hasn’t been exposed to a hot end before, it’s rather loose in the extruder assembly. I also assume that it will be nice and tight once the cover is attached in later steps. It might be worthwhile for illustration purposes to show how close the top of the PTFE tube is to the gears up above.

    Duane Pinkerton - Reply

    There should be a distinct gap between the top of the PTFE tube and the Bondtech gear. Before inserting the hotend, it is worth checking if the PTFE tube does not move in it.

    Martin L. - Official Prusa CS -

    yep, an image into the idler would be nice.

    Eyal Peleg -

    in my case the PTFE tube was very slightly too long, so was making hard contact with the gears. I triple checked the tube was inserted into the hotend correctly. Only solution was to trim down the tube very slightly. So definitely worth checking if your tube has enough clearance from the gears.

    Headfull -

    I was giving a different hotend. then the one in the picture

    Lewis Owen - Reply

    Did you purchase the printer/the hotend on our e-shop? If not, you may have only a clone of our machine.

    Martin L. - Official Prusa CS -

    A tip - insert a piece of filament from the top through the printed part and then into the PTFE tubing when installing the hotend. It both helps guide the PTFE tubing into the right place in the printed part, reduces risk of PTFE tubing being pinched during installation (which would increase friction later when trying to print), and when the hot is fully inserted, moving the filament up/down rotates the extrusion gear, making it easy to check alignment and bring the grub screw into view if adjustment is needed.

    Mathias - Reply

  31. For the following steps, please prepare: Extruder-cover B7 (1x) M3nS nut (1x)
    • For the following steps, please prepare:

    • Extruder-cover B7 (1x)

    • M3nS nut (1x)

    • M3x25 screw (2x)

    • Insert the M3nS nut in the extruder-cover. Ensure proper alignment using the smallest Allen key.

    Where should the two M3x25 screws come from? Should they have been part of the disassembly, or included in the upgrade kit? I didn’t see them in either, but I still had some in spare parts bag from originally assembling my MK3.

    Steve - Reply

    Hi Steve, M3x25 screws were used in the extruder-cover you've disassembled at step 4.

    Jakub Dolezal -

    Huh. I can only find one M3x25 screw. I think I’ve been pretty careful about keeping track of all the hardware I’ve pulled out. I had to go back to the spares from the original mk3 assembly kit.

    Oh Bee -

    DRATS! I can’t seem to find any 25mm M3 screws anywhere!!! I was super careful about screws, but I must have lost them along the way.

    I have a few M3 30mm, can I use them? If not, how do I get some replacements?

    Gene Dahilig - Reply

    Hey Gene,

    If any screws are missing, then you can always check the spare bag.

    If anything is missing from the package from us, then do not hesitate to contact our customer support for replacement.

    Filip M - Official Prusa CS -

  32. Arrange the extruder motor cables in the channel all the way to the back. Insert both M3x25 screws in the extruder-cover and slide it in above the extruder motor cable. Check the parts alignment and tighten both parts together.
    • Arrange the extruder motor cables in the channel all the way to the back.

    • Insert both M3x25 screws in the extruder-cover and slide it in above the extruder motor cable.

    • Check the parts alignment and tighten both parts together.

    The nut on the left kept sliding back. I tried tilting the whole printer downward so the M3x25 screw would “bite.” Even that didn’t work. I eventually had to remove the extruder from the X carriage, holding the hot-end+extruder assembly in place, and use a different screw to hold the nut in place from the other side, while I screwed in the M3x25 screw. If possible, a new revision where a square nut is used instead and slid into place like the right one might be easier.

    Joey Gil - Reply

    Hi Joey, thanks for the suggestion. Slots for the M3nS (square) nuts are a bit challenging to be printed perfectly, that is why we use them only if needed, but I will discuss possible improvements with my colleagues.

    Jakub Dolezal -

    Thanks Joey, your comment saved me some time! I had the same problem — could not get the nut to engage the screw without removing the extruder, then pressing the nut into the hole from the other side. It was a bit awkward and I had to be very careful to protect the pins on the filament sensor.

    Tim Beaton - Reply

    Same for me, this was nuts

    Zeev - Reply

    Thanks Joel, I ran into the same problem and your solution worked for me.

    Steve - Reply

    Ok, this part definitely sucked. Thanks Joey for the tip.

    Tako Schotanus - Reply

    Same problem as Joey and the rest. I was able to screw an M3x40 in and get that to grab and then switch back to the M3x25.

    Twerd - Reply

    My first try, I had the same issue with the left screw. I removed the extruder cover only, threaded the left screw normally to engage the nut and have it bite in. Then it assembled with no issue.

    Clayton Fitchett - Reply

    I would recommend mentioning to make sure the PINDA probe wire is not trapped. I could see that wire being easily pinched between the printed parts.

    Davis Berger - Reply

    Hey Davis,

    Thank you for the suggestion. If the PINDA probe is mounted properly, with the correct kink, then chances for this are extremely low.

    Filip M - Official Prusa CS -

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

    • M3x18 screw (4x)

    • The screws might be already in the Noctua fan.

  34. Check again the arrangement of the extruder motor cables in the channel all the way to the back. Place back the  Left hotend fan (Noctua) and make sure no wire is pinched.
    • Check again the arrangement of the extruder motor cables in the channel all the way to the back.

    • Place back the Left hotend fan (Noctua) and make sure no wire is pinched.

    • Insert and tighten all four M3x18 screws. Be careful with the tightening as you might break the plastic frame of the fan.

    you will have to tap all 4 holes with screws on this one… its a HUGE pain.

    Andy Johnson - Reply

    Just in case your fan got turned around while hanging loose or you forgot how it goes, the label on the fan should face in toward the hot end heat sink, not out into the room.

    Dave S - Reply

    Don't forget to make sure the fan cable is tucked into it’s slot, otherwise you won’t be able to hit the X end-stop on the MK2.5

    Scott Waun - Reply

    The last time I had the extruder apart, I didn’t pay attention to tucking the fan cable in. Rather than disassemble the extruder to fix the routing, I made a notch in the x-axis end with a Dremel. This extra clearance would make a nice addition to the x-axis end.

    dale.dunn@gmail.com - Reply

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

    • nozzle-fan-45deg-support (1x)

    • nozzle-fan-45deg (1x)

    • M3x18 screw (1x)

    • M3x10 screw (2x)

    • M3n nut (1x)

    • In case you are missing one M3x10 screw please use the spare bag.

    looks like the dark blue and pink arrow are switched in the picture

    Ivo van Gastel - Reply

    Thanks Ivo, fixed.

    Jakub Dolezal -

  36. Press the M3n nut in the support, all the way in. It will be barely visible. If needed use a screw from the other side to pull the nut in, then remove the screw. Connect the support to the extruder using the M3x10 screw. Note the correct orientation in the picture.
    • Press the M3n nut in the support, all the way in. It will be barely visible. If needed use a screw from the other side to pull the nut in, then remove the screw.

    • Connect the support to the extruder using the M3x10 screw. Note the correct orientation in the picture.

    • The inclined part of the support must be facing to the extruder cover.

  37. Place the nozzle-fan on the extruder and secure it using M3x10 screw. Slide the Front print fan in the nozzle-fan. Secure the fan using an M3x18 screw.
    • Place the nozzle-fan on the extruder and secure it using M3x10 screw.

    • Slide the Front print fan in the nozzle-fan.

    • Secure the fan using an M3x18 screw.

    • Note for the B7/R3 design only one instead of two M3x18 screws is needed you will have one M3x18 left, which is OK ;)

    • It might happen the fan cable is too short and you can't incline the fan. First, try gently pulling the cable from the spiral wrap. If this doesn't help there are two options:

    • In case you will be changing the spiral wrap for the textile sleeve, you can move the entire cable later, without unhooking the cable from the fan. Secure the fan in the X-axis for now.

    • If you won't be changing the spiral wrap. Unhook the cable (see the picture), but be extremely careful as you might disconnect the wires from the fan!

    M3x18 screw securing the fan is too short to make connection with the nut. Any idea around this problem?

    Yan Liang - Reply

    In step 36 make sure to do this “If needed use a screw from the other side to pull the nut in, then remove the screw.”

    Taylor Finklea -

    Agree with Taylor, I thought I had the nut all the way in but got to this step and had trouble getting to the nut. I used a slightly longer screw and pulled it in at that point.

    Adam Luter -

    Hi Yan, please use a shorter screw with thread along its entire body length and pull the nut inside the printed part.

    Jakub Dolezal -

    Yep, I also had to use the short screw. a warning about this might be a good idea here…

    Eyal Peleg -

    As I wrote in an earlier comment, the part called “nozzle-fan” ought to be renamed “fan nozzle” for clarity.

    Compare with “Print fan“, “Spool holder“ or “Printer firmware“.

    John Svensk - Reply

    Edit: The bag labelled “Extruder upgrade“ actually calls this item “Fan nozzle“

    John Svensk -

    Hi John, the part is named nozzle-fan, any other name is wrong at this point, but I will talk to my colleagues and rename it properly.

    Jakub Dolezal -

    My fan cable was way too short for inclining the fan and I even doubted that removing the cable pull protection (referered to as unhooking) would be sufficient. Also I did not like to unhook it, for reasons mentioned in the step. Instead I waited until the spiral cover was entirely removed and then getting more fan cable length was a piece of cake.

    Rüedli - Reply

    Hi Rüedli, this will also work ;)

    Jakub Dolezal -

    I get what I expected: after this and MMU installtion the printer fan is no longer working , no warning message , no cable problem (I verified cables electrical continuity). I destroyed my time and printer with these “update” $@$**. Very dissapointed, I have no way to get support from Prusa so I am f…ked, i lost 1300 euros…

    n_costique - Reply

    Hi, nothing is lost. Check the fan is properly connected to the Einsy board and then contact our support. See the chapter 0. Introduction for more contact info.

    Jakub Dolezal -

    why is there a Q about whether I will will be changing the spiral wrap for the textile sleeve or not? was the textile sleeve not sent in order to replace the spiral wrap ? are there downsides to replacing it?

    Eyal Peleg - Reply

    There are no downsides for the textile sleeve. Some people just may still have the spiral wrap installed.

    Martin L. - Official Prusa CS -

    It would be logical to swap second and third image / step. First unhook fan cable and then install it.

    Marek Běl - Reply

    Hi Marek, yes it does seem logical, but from our experience, the cable should not be too stretched. So the idea is to follow the steps in the current order and loosen the fan+unhook the cable only if you see it actually is stretched.

    Martin L. - Official Prusa CS -

    Do not unhook the fan cable from the cable support. The solder joints are extremely weak and have a HIGH chance of breaking as mine did. If you cable is not long enough loosen the extruder backplate and pull additional cable from the spiral wrap

    Connor Whitson - Reply

    I would suggest a note about how you should tighten the M3-18 screw until secure, tightening too much may split the plastic of the fan shell.

    Davis Berger - Reply

    Hey Davis,

    This note is present throughout all parts of the assembly, as all the plastic parts can be cracked if overtightened.

    Filip M - Official Prusa CS -

    +1 tightening warning on plastic parts. I ended up cracking the fan shell slightly. The button head of the screw is too big for the hole and stretch the shell around the hole until it cracked. It still holds, but to prevent further stress on the cracked shell, I added a washer so that force is distributed around and outside the screw hole. I think a warning note here at this step would be appropriate.

    Gene Dahilig - Reply

    Hey Gene,

    As I’ve mentioned it above, such note is already present throughout the assembly, as all the plastic parts can be cracked if overtightened.

    Filip M - Official Prusa CS -

  38. For the following step, please prepare:
    • For the following step, please prepare:

    • M3x40 screw (2x)

    • Extruder spring (2x)

  39. Assemble springs on both screws. Close the idler on the extruder, so the screws can reach it.
    • Assemble springs on both screws.

    • Close the idler on the extruder, so the screws can reach it.

    • Place both screws into the extruder body and tighten them. The screw's head should be almost aligned with the printed surface.

    The square nuts in the idler will likely have come out as you were moving the parts around. Remember to put them back in before attempting to screw screws into thin air.

    Duane Pinkerton - Reply

    Thank you for commenting this.

    Tenzin Gyaltsen - Reply

    Tighten them? Aren’t they supposed to have a little “give” in them so the springs can do their work?

    Tako Schotanus - Reply

    That is correct, as the next sentence says, the screw's head should be *almost* (but not entirely) flush with the printed part. It can stick out by approximately 0.5 mm.

    Martin L. - Official Prusa CS -

  40. For the this step, please prepare: mmu2-filament-sensor-cover (1x)
    • For the this step, please prepare:

    • mmu2-filament-sensor-cover (1x)

    • Idler-plug (1x)

    • M3x10 screw (2x)

    • PTFE tube 4x13 (1x)

    • Use a new PTFE tube (short 13 mm), which is in the MMU2 upgrade kit.

    • The new PTFE tube and mmu2-filament-sensor-cover are in the bag nr. 3.

    mmu2-filament-sensor-cover is in part bag 3

    Austin Hampton - Reply

    Thanks Austin, description updated :)

    Jakub Dolezal -

    Identifying the bag for the new cover would help (thanks, Austin). Also, quality control feedback: my mmu2-filament-sensor-cover was in an unmarked bag with four orange parts (two triangular braces and two other parts).

    Paul Meyer - Reply

    Description updated ;)

    Jakub Dolezal -

    Mine too. Wish I read this sooner!

    Jim -

    Also, a picture of the short PTFE tube with the cover or bolts for scale would help, as there is a spare ‘long’ PTFE tube in that bag. The next step makes it clear, but a picture here would simplify things.

    Paul Meyer - Reply

    Hi Paul, I've added a dimension to the description to inform about the exact length.

    Jakub Dolezal -

    FYI - my MMU kit for the prusa mk 3 has 2 bags marked “3 Electronics,” one with printed parts, and one with assorted pieces. The short PTFE was in one of them, and the Filament sensor cover was in the other. (I am assuming this is not a part for the MMU.)

    Harlan Howe - Reply

    Hi Harlan, this filament sensor cover is a special version for the MMU2.

    Jakub Dolezal -

    How necessary is the Idler-plug? I don’t have one….

    William - Reply

    Without the idler plug, the filament sensor may not work properly. You can print one even from PLA for example :)

    Martin L. - Official Prusa CS -

    William: I found it loose in the box when I received my (assembled) MK3. I saved it just in case, but I had no idea what it was until now. I have printed for months without idler-plug and had no problems.

    Elisabetta Bini - Reply

    zomg. I had no idea what this was either, until I saw your comment about finding it later. I looked back in my “Build Box” where I keep the spare parts and lo and behold, it was there. :) I’ve also printed for a while without.

    mark young -

    I found my new short PTFE tube in bag 3 (Electronics). It is 13mm long like it’s supposed to be. But the picture on bag 3 has a drawing of the tube which is 18mm long — this is confusing because usually the bag labels are printed to be actual size of the parts, which is very useful for checking that I’m pulling out the right parts

    Oh Bee - Reply

    where do I find the ‘idler plug’?

    danlicata@gmail.com - Reply

    Hi,

    The plug is part of the MK2.5 / MK3 kit. The plug is not required for the first print, but if it is not installed, the filament sensor may not work properly. You can print one from the PLA for example.

    - Official Prusa Support

    Martini H. - Official Prusa CS -

    @Paul +1 for a picture showing the PTFE tube with the other parts. It would be much clearer and does give valuable size scale next to the other parts.

    Gene Dahilig - Reply

    Hi Gene,

    Based on Paul’s feedback we have included size in description - it’s enough to distinguish both tubes.

    Filip M - Official Prusa CS -

  41. Locate the largest circular opening for the PTFE tube on the top of the Extruder. Push the PTFE tube in. Most of the tube's length will stick out. Orientation doesn't matter, both ends are the same.
    • Locate the largest circular opening for the PTFE tube on the top of the Extruder.

    • Push the PTFE tube in. Most of the tube's length will stick out. Orientation doesn't matter, both ends are the same.

    • In case the PTFE does not hold properly in the hole, you can assemble it to the cover first, BUT MAKE SURE there is no obstacle in the hole as you can easily deform the tube while placing as a part of the cover.

    Looks like the PTFE-4x13 tubes are internally beveled on both ends (no wrong way to insert) unlike the other PTFE tube for the extruder

    Austin Hampton - Reply

    Thank you.. I was realllllly trying to figure out which side was wider using my calipers and did not see hardly any difference.

    Joshua Levesque -

    Yes, the orientation doesn't matter as both ends are the same. Description updated.

    Jakub Dolezal -

    Be sure to check your PTFE tubes for loose PTFE wont melt, but block and cause 100s of hours of problems … or so I’ve heard :-) I used a piece of PLA filament to gently file until the bits were all out.

    timcdoc - Reply

    Be careful with the insert. My extruder body had a slight misprint in the hole, which caused misalignment and broke both my sensor as well as causing jams from the MMU2 unit while loading. I had to cut the extra plastic out to fix the issue.

    Nat - Reply

    It should be noted the tube sits on top of the filament sensor. DON’T try to push it past as this will damage the sensor.

    Ian McLeod - Reply

  42. Install the filament sensor cover and tighten it with the M3x10 screws from the previous cover.
    • Install the filament sensor cover and tighten it with the M3x10 screws from the previous cover.

    • Assemble the idler-plug and ensure it fits properly. Otherwise, it might fall down during the print.

    Unlike the direction of the red arrow, the idler plug installs from the top down.

    Mark Stevens - Reply

  43. First, rotate back the X-carriage-back part. Ensure no cables are pinched between X-carriage and X-carriage-back.
    • First, rotate back the X-carriage-back part.

    • Ensure no cables are pinched between X-carriage and X-carriage-back.

    • Guide the filament sensor cable as in the picture.

    • Tighten all five M3x10 screws.

    I can not get the middle screw to catch at all. is there a nut I forgot somewhere?

    Kawa Shwaish - Reply

    Hi Kawa, yes there should be a square nut inserted just under the 2 top bearings.

    Martin L. - Official Prusa CS -

    This step broke my x-carriage :( The nylon rod in the wire support was too long, and ended up causing the lower right bolt to crack the square nut that had been in the x-carriage. Currently working to reprint a new x-carriage without the nylon support going through the carriage.

    Chris Brinker - Reply

    BE CAREFUL NOT TO OVER-TIGHTEN THESE SCREWS!

    If you get them hand tight with a driver, back them off at least one full turn. Too tight and they will tweak the bearings, causing a variety of calibration and printing problems that no one who hasn’t experienced the issue will seem to know about, even Prusa support. I’ve helped several people with this when nothing else worked.

    Either the part needs to be redesigned with slightly greater tolerance so that screws can be fully tight with no ill effect on the bearings, or a note needs to be added to the assembly guide not to tighten them all the way down hard.

    ggaub@ggaub.com - Reply

    Hello,

    Thank you for your input, we will look into including a warning for this step.

    Marcin M. - Official Prusa CS -

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

    • M3x40 screw (1x)

  45. Let's connect back the filament sensor, there are two important things: There are four pins on the sensor, make sure the connector fits properly on them. There is a safety pin on the connector, which must face to the left, when connected to the sensor.
    • Let's connect back the filament sensor, there are two important things:

    • There are four pins on the sensor, make sure the connector fits properly on them.

    • There is a safety pin on the connector, which must face to the left, when connected to the sensor.

    • Secure the extruder-body with the screw M3x40.

    A safety pin is mentioned, but it is not used as a safety pin, as the body does not hold the latch. I noticed that after opening the sensor cover and seeing the cable fully seated, without latching. Interestingly enough, the step 41 picture already shows the cable plugged in, but then it is unplugged again in the in between pictures. Maybe consider printing the body, so the safety pin is “held"? And for now mention that the cable is just plugged, but does not need securing with the connector safety pin?

    Rüedli - Reply

    Hi Rüedli, the latch is not used for this connector, however, I use it to explain the proper orientation.

    Jakub Dolezal -

  46. Carefully slide the spiral wrap away from the X-carriage-back. One or two centimetres are enough. Find the end of the wrap and start unwrapping  towards the EINSY-case.
    • Carefully slide the spiral wrap away from the X-carriage-back. One or two centimetres are enough.

    • Find the end of the wrap and start unwrapping towards the EINSY-case.

    Any information on the shortcomings of the plastic wrap over the fabric? Is this a necessary step?

    Michael Dayah - Reply

    Hi Michael, we've made tests on our farm and fabric/textile sleeve are less rigid, which is better for the cables in a long-term. We will be switching to textile on MK3 kits in the upcoming weeks.

    Jakub Dolezal -

    Yes, it is necessary! at about 25 days of printing the plastic started breaking the wire to the part fan, at 50 days moving the extruder to the left caused the fan to ‘fail’ to the right, it worked. The break was inside the fan’s plastic wire insulation, so not visible, and about 2cm? past the zip tie post off the hot end. I am not the only one to run into this. FYI if the fan starts to error you can test this by turning it on in menu and moving the extruder left and right. This will save you some trouble

    timcdoc - Reply

  47. Using an Allen key release the M3x40 holding the EINSY-door and open it. Using pliers cut the zip tie holding the wrap. Be very careful, avoid cutting any wire.
    • Using an Allen key release the M3x40 holding the EINSY-door and open it.

    • Using pliers cut the zip tie holding the wrap. Be very careful, avoid cutting any wire.

    • Take the spiral wrap out including the cables and remove the wrap completely.

    The picture also shows a textile wrap for the heatbed cable. How did that get there?

    Rüedli - Reply

    Hi Rüedli, the heatbed cable can be wrapped in a plastic spiral wrap or in a textile sleeve, it depends on how “old” is your MK3. We are shipping the textile sleeve for months already. Anyway, it doesn't matter for this extruder reassembly.

    Jakub Dolezal -

    MK2.5 no zip on top of EINSY door but a printed part locking the cables and wrap in place

    Petri Nurminen - Reply

    I’ve got the printed part too, but it works fine with the new textile sleeve.

    Dave Cook - Reply

  48. For the following steps, please prepare: Zip tie (6x)
    • For the following steps, please prepare:

    • Zip tie (6x)

    • Textile sleeve 13 x 490 mm (1x)

    • There are two textile sleeves in the package, use the larger one (diameter).

    • Before wrapping the cables, you can adjust the cable length for the inclined front print fan.

    Note: In the multi material kit, there are two textile sleeves of two different sizes. Pick the larger one for this!

    Valerie Linscott - Reply

    Hi Valerie, good point. Thanks ;)

    Jakub Dolezal -

    There should probably be an additional conditional step here, reminding people to reconnect the fan that was supposed to be connected on step 37 if they had cable length issues like i had.

    Eyal Peleg - Reply

  49. Open one end of the textile sleeve and slide it on the cable bundle from the extruder including 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.
    • Open one end of the textile sleeve and slide it on the cable bundle from the extruder including 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 and slide the sleeve towards the extruder.

    • Use 3 zip ties and insert them in the lower row of holes on the cable-holder.

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

    • IMPORTANT: Cut the remaining part of each zip tie using pliers as closest to the head as possible. Note the correct position of each zip ties's head (slightly off-centre to the left).

    What was the purpose of this change? Can I leave the existing wrap or do I really need to change it out?

    Joshua Levesque - Reply

    Hi Joshua, it is OK to use both, the textile sleeve is softer and the cables inside the wrap aren't as loaded as with the spiral wrap.

    Jakub Dolezal -

    typo on the green note? is it missing a “be” at “should [be] slightly longer” — also what does the green comment mean. it caused me confusion… its not clear to me.

    Andy Johnson - Reply

    Hi Andy, thanks the “be” is missing in the sentence. Regarding the meaning, you will be sliding the sleeve on to the cable-holder, therefore you want the sleeve to be wrapped properly along the whole length of the cable holder. The holder itself has about 4 cm, the sleeve should be wrapped about 5 cm.

    Jakub Dolezal -

    MK2.5 no holes in the cable holder

    Petri Nurminen - Reply

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

    • 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.

    • The zip tie arrangement was tested with the injection molded double spool holder. If you are using any other frame mounted type holder, make sure the zip ties won't crash into it, which might result in a print failure.

    I think you should mention that there is a nylon filament in the bundle which should still run along with the cables.

    Brian Watt - Reply

    Hi Brian, this information was added to the previous step as now, it would be too late. Anyway thanks for the comment ;)

    Jakub Dolezal -

    Are the “injection molded double spool holder” available? The PETG single spool holder in the earlier MK3 units seem to warp/bend over time if spools are left in them.

    Erik Nygren - Reply

    Hello Erik, I’m not sure why are you asking this question here, but here’S the link for the double headed spool holder: https://shop.prusa3d.com/en/mk3-plastic-...

    Martin L. - Official Prusa CS -

  51. Continue wrapping the cables in the textile sleeve all the way to the EINSY-case. Notice the line of the "seam" will be most probably straight. Let's fix it ;)
    • Continue wrapping the cables in the textile sleeve all the way to the EINSY-case.

    • Notice the line of the "seam" will be most probably straight. Let's fix it ;)

    • Start twisting the textile sleeve (not the cables) to achieve a spiral like look. Thanks to this motion the sleeve will wrap evenly around the cables and it also prevent any cables from falling out of the bundle.

  52. Take the end of the cable bundle, find the nylon filament and separate 2-3 cm from the bundle. There is a small circular hole in the EINSY-case for the nylon filament. Find it and slide the filament in. Gently push the cables one by one to the opening in the  EINSY-case.
    • Take the end of the cable bundle, find the nylon filament and separate 2-3 cm from the bundle.

    • There is a small circular hole in the EINSY-case for the nylon filament. Find it and slide the filament in.

    • Gently push the cables one by one to the opening in the EINSY-case.

    • Slide the textile sleeve down at least 1 cm below lower edge of the opening.

    • Secure the entire bundle using a zip tie.

    Not sure how am i supposed to push the textile sleeve down when the part with the hole for the nylon filament is in its way :(

    Eyal Peleg - Reply

    Use an adequate amount of force.

    Martin L. - Official Prusa CS -

    This was not easy, and forcing really doesn’t help much, the sleeve is very particular about where it goes. Trying to fit the wires, the nylon, and the sleeve in was challenging, and at the end I had to give it a little more of a ‘shove it in’ then I should have.

    Given that the case, the nylon, and the wrap are all black, it’s not that easy to see what’s going on in the photo, and I’m not sure if I might have had the wrap going in the opposite direction, making it more difficult/impossible to get a clean overlap.

    I don’t know if this is usually a problem; I could possibly have benefited from more photos clearly showing which way the wrap is supposed to wrap, or a cross-sectional diagram suggesting how the wires, nylon, and the two leaves of the wrap are supposed to feed through the hole.

    Kenneth Albanowski - Reply

    Actually, this is easier than it may look like, you just have to fit the nylon into the hole and then gently push the wires in. There is no particular way of arrangement of the wires, and the zip tie can also be inserted both ways.

    Martin L. - Official Prusa CS -

  53. Close the EINSY-door and make sure no wire is pinched.
    • Close the EINSY-door and make sure no wire is pinched.

    • Use an Allen key and tighten the M3x40 screw.

    I notice here there is already the textile sleeve on the heat bed cables. I have an early release MK3 with the spiral wrap on this section. There doesn’t appear to be a second textile sleeve in the kit, is this an important upgrade?

    Austin Hampton - Reply

    Hi Austin, we've decided to change the spiral wrap for the textile sleeve on the entire MK3 as it is more friendly to the cables inside. In case you can buy 6mm textile sleeve from a local reseller, then change it. Also don't forget to remove the nylon from the heatbed, follow this guide: 7. Heatbed & PSU assembly (textile sleeve)

    Jakub Dolezal -

    Don’t screw the door closed yet, you’ll need it open to connect the MMU2 unit .

    Dave Cook - Reply

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

    • M3x10 screw (1x)

    • M3nS nut (1x)

  55. Slide the M3nS nut in the slot and tighten the probe SLIGHTLY with the M3x10 screw.
    • Slide the M3nS nut in the slot and tighten the probe SLIGHTLY with the M3x10 screw.

    • No need to set precise position of the sensor now, we will do it later.

    Should we be setting the PINDA to a specific height here?

    Todd Gisby - Reply

    Hi Todd, good question. No need to set precise position for now, we will do it later ;)

    Jakub Dolezal -

  56. Carefully and quietly open the bag with the Haribo sweets.  High level of  noise might attract nearby predators!
    • Carefully and quietly open the bag with the Haribo sweets. High level of noise might attract nearby predators!

    • Sort the bears into six rows according to the following scheme (colours might differ):

    • Current chapter was very difficult, at least 25 % of total amount is needed.

    • Idler assembly is quite easy, 10 % is enough.

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

    • Electronics assembly is the last chapter with high level of difficulty, consume 25 %.

    • Spool holders are easy to make, research shows that 10 % is enough.

    • Preflight check is almost effortless. Experienced user will require no more than 10 %.

    I did not lay my gummies out in this order, but rather closer to spectrum order (red/orange/lightorange/yellow/white/green).

    My distribution was: 8/10/5/10/7/3 (43 total gummies). This has a p of 0.37 that it is a fair distribution, pretty good!

    The distribution pictured above has a p of 0.31 (also respectable!)

    Enjoy your gummies everyone.

    Adam Luter - Reply

    Hi Adam, even though the last chapter is easy, eating on 3 gummy bears isn't enough. I suggest you start over with another package :D

    Jakub Dolezal -

    being a vegetarian I will skip this step. I hope this won’t hurt the printers functionality later on…

    Eyal Peleg - Reply

    I ended up eating all of my gummies just previewing all 56 steps!

    Clayton Fitchett - Reply

    Has anyone designed dentures for these poor bears?

    Pete Guerra - Reply

  57. You've just finished the upgrade of the extruder. Amazing job!
    • You've just finished the upgrade of the extruder. Amazing job!

    • Let's start with MMU2 upgrade in the next chapter - 1. Idler body assembly

Finish Line

129 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

213 Guides authored

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21 Comments

Hi Jakob, could you describe the steps needed in case we have already updated the extruder?

I think we would just need to:

1. Swap the hot end PTFE

2. Update the filament sensor cover and change the PTFE

3. Change the spiral wrap for textile sleeve

Is that it?

Miguel Mancilla - Reply

Good point Miguel, I will make it more clear in the beginning.

Jakub Dolezal -

I just realized that these instructions are located after section 3 step 18. We might need a note about that.

Miguel Mancilla - Reply

Those are for the owners of MK3/MK2.5 who already upgraded to R3 parts before getting the MMU upgrade. Also we are shipping the B7 (aka R3) parts, in that case you only need to change the PTFE tube for “MMU2” type.

Jakub Dolezal -

Hi, is it possible to upgrade from original parts (B5/R1?) to B7/R3 - if so are there any instructions on that, if not what other parts are needed? I have a prebuilt MK3 ordered last September (didnt come with spare nuts/bolts/ zip ties etc as it wasnt kit build). I ordered the MMU back in January so hopefully that should arrive soon but even if it includes B7 parts I think I might need to get some others as well - or is there any downside to using MMU2 with the original MK3 parts (I dont use flexible filaments)?

Daniel Triggs - Reply

Hi Daniel,

the R3/B7 design improves overall cooling performance of the extruder, so it recommended to upgrade your MK3. You have following options:

1) Wait for your MMU2 upgrade which includes all the parts.

2) Print the parts and follow this guide Upgrading extruder B6/R2 to R3 on MK3 (self-printed parts)

You can use MMU2 with older parts, but I recommend upgrading to improve the performance and avoid possible issues.

Jakub Dolezal -

Awesome to see the upgrade to the extruder will come with the MMU2. Also love to see that a textile sleeve is being used for the extruder wires! Can’t wait for my MMU2 to arrive so I can do this :)

Trevor Tennison - Reply

Suggested time to complete: 130 minutes.

That is the time I took without much preparation.

Benjamin Richter - Reply

That seems about right. I also finished at about 2 hours

Juan Cruz -

I would propose 2:30; it took me 60 minutes to disassemble and 90 to reassemble.

Tom Fennell -

I have absolutely no willingness to do it, I will leave it how it is until is crashing. Is to re-do a lot of things with a lot of risks and possible damages. I really don’t like this !!! Looking at the costs/benefits…I say no!

n_costique - Reply

PS: Doesn’t matter what I though, this action as total is an upgrade of mechanical/software functions related to MMU 2.0 unit and because the PFTE tube need anyway to be changed...I will make all the works related to this. I recomend to others to do it also.

n_costique - Reply

I made it and I lost it. Printer fan is not working, cables seem OK. I will verify with a baterry if work but anyway, this is a good way to destroy a good working device. BETTER is always enemy of GOOD.

n_costique - Reply

Hi,

please contact our support using livechat, my colleagues will help you troubleshot the printer and send replacement if needed ;)

Jakub Dolezal -

This process went remarkably smoothly for me. Took me about 2 hours 10 minutes. I recommend an estimate of 3 hours in case steps prove to be problem for someone else.

Dave S - Reply

I found no spare transparent washers. Since they are nearly invisible when lost I suggest a few extras.

I really enjoyed this online with photos approach. Congratulations.

joegchurch@gmail.com - Reply

so I was given a different hot end then the one in the pictures . This one has a nut type thing at the end of it. Can someone help please

Lewis Owen - Reply

Hello, that would be strange because we do hot use any other hotends. Please send us a photo of your hotend to info@prusa3d.com.

Martin L. - Official Prusa CS -

Section 3 of the MMU2 upgrade involves taking apart the extruder and putting it together again to change the PTFE tubing. Wouldn’t it be more time and labor efficient to upgrade extruder B6 to B7 at that time? Rather than diassembling and re-assembling the extruder twice. Or am I missing something important?

Darryl DLima - Reply

Hi Darryl, it is written in the Section 3 that if you already performed this upgrade following this section, you can skip the steps: 3. Electronics and MMU2 unit assembly so no worries, we won’t ask you to do the same thing twice. All everybody needs to do is to read and follow the instructions, even though they may seem sometimes counter-intuitive at first. :)

Martin L. - Official Prusa CS -

I have a few suggestions for anyone doing the upgrade to MMU2. I assembled my printer six months ago and knew the procedure I went ahead and adjusted the PINDA when I installed it so I would not have to do it later. When I reached the end of the upgrade and before I tied up the wire bundle I plugged the printer in, turned it on, and let it go through the self test to ensure the fans were working since some have commented here that their fan did not operate after the upgrade. I then unplugged it and went to the next step finished installing the tie wraps on the bundle.

Ricky Burnett - Reply

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