1. Before you proceed further ensure again,  you are in the correct chapter:
    • Before you proceed further ensure again, you are in the correct chapter:

    • The longest and biggest sleeve is a textile sleeve. If so, you can proceed according to this chapter.

    • If the longest and biggest sleeve is a spiral wrap, please use this chapter instead: 5. E-axis assembly (spiral wrap)

    Add Comment

  2. Needle-nose pliers for zip tie trimming.
    • Needle-nose pliers for zip tie trimming.

    • 2.5mm Allen key for M3 screws

    • 2mm Allen key for nut alignment

    • 1.5mm Allen key for tightening the pulley

    Add Comment

    • For the following steps, please prepare:

    • Extruder-idler (1x)

    • Bondtech pulley WITHOUT the hole for the lock screw (1x)

    • Pulley bearing (2x)

    • M3nS nut (2x)

    • Pulley shaft (1x)

    • Note there are two types of the Bondtech pulley in the package (one with hole and without hole for the lock screw). Make sure you are using the correct one.

    inside the bag wiht the idler+bearing and shaft, there where also one tiny set-screw, where does that belong?

    Asbjorn Mikkelsen - Reply

    Hi Asbjorn, it’s the spare screw for bondtech gears.

    Official Prusa Support

    Filip Misiło -

    • Press the nuts to the slots on both sides of the idler.

    • Insert both bearings in the pulley. Be aware that bearings can slip out during assembly.

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

    I would suggest doing this part after the pulley so the nuts don't fall out while trying to get the pulls in place.

    Gary Minnick - Reply

    Hi Gary, last time i tried on 5 different pieces the nut traps were quite tight. Your were loose?

    Jakub Dolezal -

    Similar for me - until step 15 (where I’m now), I must have chased and reinserted these two nuts at least half a dozen times. I’d also recommend to leave them in the bag until step 16.

    But thanks for the spare nylon washers - when these drop of the workbench, they jump further than the screws :-)

    Markus Imhof - Reply

    It is true that these nuts tend to fall out, we do recommend to double check for their presence before starting the step 16.

    Martin L. - Customer Support -

    I put them in and they easily fell out, so I took two #10 bolts and screwed them in temporarily.

    Ybl84f1 - Reply

    • Ensure both bearings are inside the pulley!

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

    • Slide the shaft through the idler and pulley. Use reasonable force or you will BREAK the printed part.

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

    The shaft did not slide easily for me. I ended up putting it in a small vice to slowly and carefully squeeze the shaft into the idler. The shaft was flush with the inside idler support, but only through the first side (wasn't in the outside support at all). I used an M3x10 in the vice to push the shaft through until it was evenly inserted into both supports.

    Gabe Ferencz - Reply

    Gabe’s comment is extremely important as he had the foresight to make sure it was evenly into both supports. My printer died after 13.5 hours of printing because I did not realize the shaft had not entered the second support. The gear spun very easily even under decent force but when pushed on hard enough, the shaft/support bent and allowed the gear teeth to contact the plastic. This put load on the extruder motor which I believe lead to burning out the power supply. My printer can no longer warm up without the power supply cutting out.

    Derwyn Henderson -

    I don’t have a vise, but i was able to use a pair of adjustable pliers (vise grip) to do a similar type thing, using a M3x10 to push the rod evenly into both supports. Thanks for the tip.

    Michel Soudee -

    The hole was too tight to press fit for the 3 mm shaft, so I needed to carefully ream the hole with a #31/ 3 mm/ 0.120” drill bit.

    Dan Howe - Reply

    Yes, well done, I recommend being proactive and very carefully clearing/enlarging the holes with the 3 mm drill bit.

    Martin L. - Customer Support -

    The shaft seems very tight and a little short, doesn’t sit flush with outside edges of idler assembly

    Matthew Braggins - Reply

    Yes, that is correct, the shaft is not supposed to be flush on either side, it just has to sit firmly in both holes.

    Martin L. - Customer Support -

    Well… F, I finally broke a part. Didn’t have a drill, vise grips, or vice. Tried to align the shaft and slowly add more pressure and the first loop/hole snapped off. Does anyone have the .stl for this part?

    Adam Timmerberg - Reply

    Nevermind, I found the file on Prusa’s website.

    Adam Timmerberg -

    For anyone else, here are the STLs for all of our plastic parts: https://www.prusa3d.com/prusa-i3-printab...

    Martin L. - Customer Support -

    Another case where I got the part started - in fact, got it all the way in, and then used an aligning punch and a few light taps from a hammer. An aligning punch is like a center punch, except it has a blunt end, and is perfect for this application. Was able to get the axle in and perfectly centered in the holes.

    Matt Laudato - Reply

    I concur that the 3mm rod seemed too short and a slightly longer rod would go a long way to easy assembly with the tools provided. i was able to use a 3mm bolt with a pair of large adjustable pliers to adjust the pin to have good engagement on both sides. ALTERNATIVELY: I did not try this, but inserting the rod from the opposite side (top side, narrow side, side with the gear teeth) until flush would likely provide an acceptable engagement in both ends.

    Jared Ressler - Reply

    Longer shaft is being tested, also slight redesign of this part is in progress :)

    Jakub Dolezal -

    I reamed the holes with a 3mm drill bit and replaced the original 18mm long pin with a 24mm one. The new pin is almost flush with the outside of each mounting block. I liked this better than trying to center the short pin. You can find ground and polished pins on Amazon.

    Robert Van Hook - Reply

    Used the back of the screwdriver while resting the piece against a flat surface to get the shaft pushed down most of the way, then just pushed the pin a bit more with the other end of the screwdriver till it was even on both sides. Not pretty but got the job done.

    Brett Biery - Reply

    No way that shaft was going in, and I’m not a hammer as a first option kind of guy so I took a drill bit by hand and worked it in and out for a few minutes, then it went in snug.

    Ybl84f1 - Reply

    Manufactured with way too tight holes. Had 1 that broke, got two other tight ones. Gonna try with these now, probably have to drill it out with something first…

    Martin - Reply

    Like many other parts in this build the tolerances are far too tight for this piece, was pushing it in very slowly and it still broke. It is rather frustrating to have to order a replacement part an put my build on hold for days while it arrives. I do not have access to another 3d printer to print the part myself from the STL/gcode.

    Tendayi -

    The press fit of the pulley shaft into the Extruder-idler was very tight. I used a round diamond needle file to slightly ream out the idler holes and the shaft then inserted smoothly while remaining snug.

    Phil Morris - Reply

    • 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 (1x)

    • Filament sensor (1x)

    • The filament sensor is in the box labeled " SUP".

    • M3x10 screw (1x)

    • M3n nut (2x)

    Add Comment

    • 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.

    Hex nuts did not fit at all, had to use square nuts unlike in picture.

    Matthew Braggins - Reply

    They are hex holes, hex nuts fit in perfect. How did you get square nuts in a hex hole?

    Andrew Holloway -

    It’s very difficult to know if the nuts are “all the way in”. I thought I had them both in all the way, but when I put a screw in from the other side, I found that one was good but the other had a lot more depth left in the hole. May as well always pull them in with a screw.

    GregBelfor - Reply

    I used an M3x10 screw and threaded the M3n on the end about a quarter way through the nut. Then, I used the screw to manually place the nut into position, wiggle it down gently, and then backed off the screw out of the nut. This was better than tweezers or trying to fight the nut to go flat and into position.

    Phil Norris - Reply

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

    Add Comment

    • 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 (screw head touching the board) 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.

    I know the details were clear in saying “screw head touching the board” but that’s such an unnatural feeling for those of us that aren’t comfortable with small electronics. I would have preferred a photo to help me confirm that I indeed need to contact the board with the screw head. This is a photo of what my board and screw looked like when I had finished. https://i.imgur.com/YOL5ITV.png

    Phil Norris - Reply

    Thank you, I haven't gotten to this step yet and I'm just reading ahead but from reading the directions so far I believe that picture would / will be helpful to me when I get there

    Bill the Cat -

    Guys, thanks for the feedback, a photo will be added ;)

    Jakub Dolezal -

    • For the following steps, please prepare:

    • M3x30 screw (1x)

    • M3 translucent washer (2x)

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

    Add Comment

    • 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.

    • If the second washer keeps falling off. Use a M3n nut from the spare bag to fix it temporarily.

    Add Comment

    • For the following step, please prepare:

    • Extruder motor (1x)

    • Bondtech pulley WITH the hole for the lock screw (1x)

    • In case the lock screw is sent separately, screw it in the pulley slightly. Ensure the tip of the lock screw isn't reaching to the internal part of the pulley as it might block the shaft in the next step.

    • Ensure you are using the correct motor, there is a label on the bottom of the casing. The reason is, each motor has different cable length.

    • There is a second spare lock screw in the package.

    Add Comment

    • There is a flat part on the motor shaft, rotate it towards you.

    • Slide the pulley on, note the CORRECT orientation.

    • The screw must be facing directly against the pad (flat part) on the shaft. Slightly tighten the screw, the final adjustment will be done later.

    • Don't press the pulley against the motor. Leave it on the very top of the shaft, see the picture.

    • Before moving to the next step, rotate the pulley 90-degrees clockwise ( the lockscrew will be facing to the left).

    The grub screws for this pulley are trash. I only slightly tightened it on, but stripped the head of the screw. Couldn't get it back out ever again and had to buy a new bondtech drive gear pulley for $70 before I could finish my build. Did the same thing on the second set, stripped the screw head. Fortunately i could get the screw out this time, by using a larger than required imperial 1/16 hex wrench. Please make a big warning sign in the manual about this. I know it's not your fault, it's bond techs fault for providing crappy screws

    Gregory Dunbar - Reply

    Hello Gregory, thank you for this remark, we’ll discuss this and see if we can do something with this.

    Martin L. - Customer Support -

    The grub screw is first set on the flat part of the stepper motor shaft as noted in the instructions. When you do the final adjustment, make sure the grub screw stays on the flat part of the shaft, else it will protrude too far out of the bondtech drive gear pulley and this will prevent the shaft from turning. As a test: Once you have done the final adjustment, rotate the shaft using the end of a small allen key or some other method to rotate the stepper motor shaft. If the shaft does not rotate at this point because the grub screw catches onto the 3D printed part, resolve it now as it will cause filament feed failure when you do the first powered-up tests.

    Chas - Reply

    My screw stripped out on the pulley before it was on the motor shaft. I don’t think the bondteck pulley was fully tapped, the set screw wouldn’t even touch the motor shaft when it stripped.

    Chip Brown - Reply


    Have you tried using some other key or bit to tighten the screw? Perhaps torx bit will help.

    If it won’t, please contact our customer support via info@prusa3d.com or Livechat.

    Official Prusa Support

    Filip Misiło -

    • Find in the package two M3x30 screws and insert them into the holes.

    • Before mounting the motor, ensure the second translucent washer is still on the top M3x30 screw.

    • Mount the motor on the extruder body as shown in the picture, double check the proper orientation of the motor cables.

    • Tighten both screws firmly.

    • Tighten the screw, but only slightly, keep in mind the idler must rotate freely.

    When putting in the motor, before you start tightening the screws, check that the pulley on the motor shaft is approximately in the position shown in step 15. On my first attempt, the plastic parts inside the extruder pushed the pulley against the motor and then blocked it there - no movement of any kind possible. I had to unscrew the motor again, pull out the pulley and then tighten the motor screws again.

    Markus Imhof - Reply

    I tightened the motor on and then noticed the translucent washer had fallen off. Loosened all screws just enough so that I could sneak the washer back in place, and then tightened everything up. Keep an eye out for that washer - it’s important and falls off easily if you don’t pay attention.

    Matt Laudato - Reply

    • Open idler fully to have direct access to the pulley.

    • Use a piece of 1.75 mm filament (from the spool) to align the pulley with the openings for the filament (see the picture). Arrows only indicate the direction. Don't use the 3mm nylon filament!

    • Adjust the pulley and tighten it with 1.5mm Allen key. Use reasonable force as you might damage the thread.

    • Once the pulley is perfectly aligned, please remove the filament.

    Huh? do you mean “finished”. “When ready with the alignment, please remove the filament.”

    Doug Kline - Reply

    Yes, that is exactly what Jakub meant, Thank you for your remark, we will correct the sentence.

    Martin L. - Customer Support -

    In my set grab screw in the pulley is very shallow which makes impossible to tight it :-(

    Can you replace it?

    Vlad Rohoza - Reply

    There should be a spare grub screw in the bag nr. 9.

    Martin L. - Customer Support -

    Not sure what the alignment center is. The red arrows cover the image. What is perfect alignment? What is the filament centered on? Over the set screw or center on the small groves to the left of the set screw?

    Tom - Reply

    On the small groves, it’s the teeth that grab the filament and feed it into the hotend.

    Martin L. - Customer Support -

    Perfect alignment is when the filament is moving through the knurled channels smoothly - that’s how the filament feed works. Keep the screws just tight enough to move the filament back and forth, but loose enough to shift the pulley to get alignment. Tighten. Then push the filament back and forth - it will require some effort, but you should be able to see it moving centered in both knurled channels.

    Matt Laudato - Reply

    • For the following step, please prepare:

    • M3x40 screw (2x)

    • Extruder spring (2x)

    • Assemble springs on both screws, see the second picture.

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

    • Place both screws into the Extruder body (see the picture) and tighten them. The screw's head should be almost aligned with the printed surface.

    The screw closest to the motor does not secure on the other side. The hole is too large and does not fasten to it. I may need to stop installation until I get this resolved. The parts are B7.

    Trent Allen - Reply

    Just reached this step. If I may make a suggestion:

    - check you have the right screws. The M3x40 are the longest screws in the pack

    - check you haven’t lost one (or both) of the square nuts you inserted into the slots back up in step 4. The screw should grab the nuts, not the plastic.

    If you have the right screw length and aren’t missing a nut, I’d suggest you check if the threads on both the screw and the nut are ok, and otherwise replace them from the spare bag.

    Markus Imhof -

    Hi Trent, yes, Markus is absolutely correct, usually it is the square nuts that fall away from the Extruder Idler (the door-like part). See the step 4 in this guide.

    Martin L. - Customer Support -

    Make sure you screw these in from the side that doesn’t have the door (or the gear visible through the hole)!

    It’s very easy to get this flipped and get the screws stuck before you realize it’s incorrect. Then you may have to destroy the idler door to get them out again. I did this and had to have a friend re-print the part, and I just ran into someone else with the same mistake.

    Brian Bishop - Reply

    Hoe tighten is tighten? I mean because of the spring(s) the screw Will stick out! Is This ok ok or not?

    Peter - Reply


    Idler screw heads are supposed to stick out slightly. Please see the first point in our video below on how to adjust them properly.


    Official Prusa Support

    Marcin Mączewski -

    Why what Brian said isn't a large warning is beyond me. Very easy mistake to make that bricks the whole part. Now I gotta order a spare part.

    shibe - Reply

    Make sure the the 2 gears mesh together before tightening.

    Dewi Eirig Jones - Reply

    • For the following steps, please prepare:

    • Extruder-cover (1x)

    • M3nS nut (3x)

    • M3x25 screw (2x)

    • E3D V6 hotend (1x)

    Has the hotend already been properly tightened from the factory by heating it up and tightening it, or do I need to heat it up and tighten it before installation.

    Brian - Reply

    • In the kit you can find two versions of the hotend:

    • E3D V6 hotend with regular PTFE tube (sent until 11/2018, no marking)

    • E3D V6 hotend with MMU2 PTFE tube (sent from 11/2018 and marked with a green dot)

    • Both versions are perfectly fine for a single material MK3. The newer version is optimized for customers planning to upgrade to the MMU2 (with the previous "regular" version, you have to change the PTFE yourself).

    • DON'T REMOVE the PTFE tube, it has to be in the hotend.

    I just received and built my MK3 kit (11/23/18) and it didn’t have the green dot V6 hot end. I have also ordered a MMU2. So I was disappointed to not have the green dot version. I thought I’d just have to rebuild the extruder when I received the MMU2. I just realized now that I could have modified the PTFE tube myself and avoided the eventual rebuild of the extruder. Here’s the link to the modification: How to trim PTFE tube - Original Prusa i3 printers

    Andy McNelly - Reply

    • Take the E3D hotend and place it inclined into the Extruder body. Make sure the white PTFE tube fits in properly.

    • Insert the hotend into the Extruder body, see the picture.

    • Make sure the hotend is fully seated and the upper part aligned (almost in contact) with the surface of the printed part.

    • Note the CORRECT orientation of the hotend.

    • Be VERY CAREFUL with the hotend wires from now on, you can damage them.

    Is the hotend, heatblock, and nozzle already tightened up while hot from the factory. Or do I need to heat it up and tighten everything before installation?

    Brian - Reply

    Hi, this is a good question, but no worries, the hotend assembly is already tightened. If it would be needed to heat it up and tighten, it would be mentioned in the manual.

    Martin L. - Customer Support -

    Right here may be a good time to put a note about the fact that you need to change the PTFE tube if you are also installing the MMU 2.0. i’m not sure about other people but i bought them both together so it would have just been a nice note so i wouldn’t have to come back later and undo some of the work i had already done

    Ryan Sutherland - Reply

    Hi Ryan, good point, but I didn't want to confuse the majority of the assemblers, who will be using the MK3 without MMU2. So we found out a better way and very soon (might be this week) all the hotends leaving the factory will have the more precise PTFE tube already installed regardless if it is for MK3 or MMU2 :)

    Jakub Dolezal -

    Really important that the hot end go in here…it will actually assemble ok (and look okay) if it isn’t pushed in, but at the end of the build journey it will not calibrate and not print. I thought I was careful but goofed here and had to take the extruded apart to fix this.

    Ybl84f1 - Reply

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

    Add Comment

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

    • Check proper alignment with the 1.5mm Allen key.

    Add Comment

    • Rotate the extruder as shown in the first picture.

    • Take the extruder-cover and place it on the extruder body. Both printed parts must be in direct contact.

    • Using M3x25 screws tighten both parts together. If you can't reach the nuts, use temporarily a longer screw from the spare bag (e.g. M3x30).

    • Ensure again the hotend is properly assembled. The surface of the heatsink (part of the hotend with cooling ribs) must be aligned with the surface of the printed parts. See the last picture.

    Regarding the third picture, the right M3x25 screw does not reach any nut for me... I guess this means it simply taps a thread into the plastic, and that’s it, right?

    Francesco - Reply

    NVM, I just had to use a M30 screw to reach for the hex nut that I put there in step 6 and pull it all the way into the hole, it simply was not seated properly.

    Francesco -

    Hi Francesco, good approach with the longer screw. Just don't forget to replace it back to the M3x25.

    Jakub Dolezal -

    No Jacub, M3x25 are too short. Screws should be longer.

    Damian Brincat - Reply

    Make sure your nut is seated way down in the pocket.

    Bob Hayssen - Reply

    Zooming the 3rd picture results in the second picture being zoomed.

    Ybl84f1 - Reply

    • For the following steps, please prepare:

    • M3x18 screw (4x)

    • Left hotend fan (1x)

    • Front print fan (1x)

    • The left hotend fan has two sides, but the side with sticker must be always facing the hotend (not visible when the fan is mounted). Otherwise, the cooling won't work properly.

    • The left hotend fan (Noctua) can be also in a black colour without the rubber corners, other hardware parameters are the same.

    in my mk3 kit i had no idea the stock hotend fan was a noctua, so i purchased a 40mm 5v noctua separately

    until i got to this part in the instructions, hah.

    joe kitchin - Reply

    • Place the Extruder on the side and guide the wires from the motor in the slot.

    • Place the Left hotend fan on the Extruder. The cable must be placed in the top left corner, see the picture.

    • Note the correct orientation of the fan. The sticker has to face towards the hotend!

    • Insert M3x18 screws and tighten them slightly.

    • Now, tighten ALL screws, alternating diagonals. After tightening, check that the fan can still rotate freely.

    • DON'T tighten the screws too hard, all parts are made of plastic and you can break them.

    Remove the zip tie that is closest to the heater block.

    Otherwise, it will impinge against the frame and cause an x-axis length error during first self-test.

    Guy Kuo - Reply

    Hello Guy, actually it is not necessary to remove that zip tie, just make sure it doesn’t slide to a position where it would impede the x-axis movement.

    Martin L. - Customer Support -

    • 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.

    Add Comment

    • 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.

    • WARNING: there are pins of the filament sensor on the other side of the extruder. Be careful as you might bend them during the following steps!!!

    • 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.

    • Place the nozzle-fan on the extruder and secure it using M3x10 screw.

    Already in there from a previous step? There is no way to push it in from the side.

    Matthew Braggins - Reply

    Hi, Matthew, can you be more specific? Which part were you pushing from the side?

    Martin L. - Customer Support -

    I broke this part trying to get the nut in. Was able to epoxy it in place for now. Printed out a spare and broke it too. I’ll figure it out eventually. One thing, the screw could be replaced with a 12 mm instead of the 10 mm. There’s barely enough threads available on the screw to catch, even when you get the nut pushed in all the way. Since this part isn’t bearing any significant load, and since the extra 2mm wouldn’t get in the way, I’d recommend the change.

    Matt Laudato - Reply

    Maybe it should be mentioned that the extruder cover (B7) contains a design fault?!

    On the backside where the M3x10 screw for the fan duct goes is a recess for an embeded M3n nut.

    Under no circumstances insert a nut here! It will spin.

    In my case i had a bad nut witch made the screw stuck. There was no other way to get them out than chopping parts away from the cover.

    Christian Range - Reply

    I will just state that the nozzle-fan screw simply screws into the plastic. I thought I forgot a nut at first because of the comments and the pocket in the back, but the screw certainly goes in tight enough to hold the nozzle-fan without a nut (indeed it took some force just to thread it into the plastic).

    Jared Ressler - Reply

    Echoing Christian and Jared, there is indeed a hexagonal receiver space on the B7 build, implying a nut to hold the M3x10 screw that secures the nozzle fan. I looked through the printed documentation several times to see if I had missed inserting the nut as a step and *thankfully* checked here first. Not sure if the space is an artifact from a deprecated design but it should probably be a) omitted from the print or b) highlighted in the instructions that a nut should *not* be inserted in this space.

    Scott Boyer - Reply

    The nut support in the nozzle-fan-45deg-support is either undersized or had a fault in printing. Out of fear of breaking the part, as others have reported, I put a M3x40 screw through the hole, screwed the nut on the end, heated it with a lighter, and pulled in in about halfway, melting the plastic around the nut. Then I unscrewed the M3x40 after the plastic re-solidified. It still wasn’t in far enough for the M3x18mm screw in the next step, so I used an M3x25mm from the spare parts bag to attach the fan.

    Ben Renneberg - Reply

    DItto on this part breaking while drawing in the nut. I was performing the usual drawing in with a bolt process when the part snapped. Welded back together with soldering iron and melted the nut into position.

    Guy Kuo - Reply

    M3x10 is far too short for the nozzle fan 45deg support, M3x15 would’ve been better. I had to drill out the plastic for the M3x10 to catch the nut.

    Dewi Eirig Jones - Reply

    There is plenty of room to make the arm that the nut is attached to beefier, then you could put a slot in it and insert one of the M3nS nuts from the side. This would avoid trying to use a screw to pull the hex nut into the opening and cracking the part.

    Johnny Rodriguez - Reply

    Hey Johny,

    We’re confident that the arm is strong enough - if for some reason it fails, it’s mostly due to using too much force.

    Official Prusa Support

    Filip Misiło -

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

    • Secure the fan using a M3x18 screw.

    My nozzle-fan-45deg-support snapped during this step :(

    If the bottle was 20mm it probably wouldn’t of happened, I was struggling to get it to connect with the nut. Hopefully it’s something I can print later…

    Ben Vincent - Reply

    Hi Ben, here are the printable parts. Look for the MK3 bundle https://www.prusa3d.com/prusa-i3-printab... or contact our support to get a new one.

    Jakub Dolezal -

    Using the 18mm screw at first it doesn’t seem long enough. So I temporarily used a 25mm screw to pull the nut up through the support. Then I went back to the correct 18mm and all was well.


    Ian Teixeira - Reply

    Hi Ian, well done, this is exactly how this should be solved. If the longer screw is taken from the Spares bag, you can even leave it in.

    Martin L. - Customer Support -

    The screw head started to go through the hole on the fan, before I noticed it cracked. Maybe small washer to prevent the screw from going inside the fan housing?

    Mike St. Vincent - Reply

    Hello Mike, thanks for this suggestion, we will discuss this.

    Martin L. - Customer Support -

    I had the same problem as Ian Teixeira - October 9 . Solved problem same way. My 45 Deg arm seems to be a little to thick.


    William Wilson - Reply

    How far down into the orange pocket does the fan opening sit?

    My fan barely sits atop the pocket.

    Bob Hayssen - Reply

    I cracked the fan hole too - as Mike St. Vincent above.

    Going to fix it with 2-component super glue :D

    Martin Bech - Reply

    • For the following steps, please prepare:

    • P.I.N.D.A. sensor (1x)

    • M3x10 screw (1x)

    • M3nS nut (1x)

    • The probe is a sensitive device, please handle it with care during the assembly!

    • The P.I.N.D.A. cable can be either black or grey, both probes are the same.

    • Make sure there are FOUR wires in the connector, if not, please stop the assembly and contact our support asap.

    Add Comment

    • Start with the front print fan wire and place it under the cable clip.

    • Gently push the P.I.N.D.A. sensor through the holder. If the hole for the sensor is too tight, you can open it slightly, but be very careful as you might break it!

    • Create a loop on the probe wire, then place the wire under the cable clip.

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

    • The exact position of the P.I.N.D.A. probe will be adjusted later (in Chapter 9, Preflight check), so there is no need to adjust the probe or tighten the screw fully at this point.

    Fan wires = German flag colors. Nice!

    Adam Timmerberg - Reply

    Please note that the size of that PINDA wire loop is crucial: if it’s too big, you won’t find out until the very end of the assembly (near the end of section 8) when you go to plug the PINDA connector onto the board and it won’t quite reach! Then, like me, you’ll have to tear apart a bunch of work to adjust that loop. Blargh.

    John Lawler - Reply

    When zooming the 3rd picture it shows the second picture zoomed.

    Ybl84f1 - Reply

    • Place the Extruder on the Y-carriage as in the first picture. Ensure the correct orientation of the printer, shorter extrusions must be facing towards you.

    • If needed, lower the X-axis so you can see the entire X-carriage. It is needed for the next step.

    • Take the cables from P.I.N.D.A. probe and front print fan, slide it between the lower smooth rod and belt.

    • Take the cables from Extruder motor and left hotend fan, slide it between the lower smooth rod and belt.

    • IT IS VERY IMPORTANT to place the cables as shown in the pictures. Please double check your steps.

    • Cables from hotend will be placed under the lowest smooth rod. We will arrange them later.

    When zooming the 3rd picture it shows the second picture zoomed.

    Ybl84f1 - Reply

    • For the following step, please prepare:

    • M3x40 screw (1x)

    • M3x30 screw (1x)

    • M3x18 screw (1x)

    • Place the Extruder near the X-carriage and check no wire is pinched. There is a slot in the X-carriage for the motor wires, see the picture. Bend the motor cable in it and leave the fan wires straight.

    • Mount the Extruder on the X-carriage using the screws above. Tighten all screws, but not fully. We need to arrange the cables again, this time in the back.

    • Guide the cables through slots (channels) on both sides of the Extruder. On the left side, it is Front Print fan and P.I.N.D.A. probe, on the right side Extruder motor and Left Hotend fan.

    • Ensure again the cables are pushed to the channels (not sticking out) and not pinched between printed parts. Now, tighten all screws, equally to prevent issues.

    Consider adding a note to ensure that the pinda and print fan cables are still in the cable clip, as mine easily fell out during step 29, and there are no pictures from that angle. I realized after completing this section of the guide that the cables were laying on the outside. They were fairly tight and weren't touching any components, so I don't think it would have mattered much, but I still removed the zip ties and unscrewed the x-carriage to fix it.

    shibe - Reply

    • Locate the cable for filament sensor in the package.

    • There are two types of the connectors on the cable:

    • The 4-pin connector for the sensor (used now)

    • The 5-pin connector for the EINSY board (used later)

    Add Comment

    • Use the cable from the previous step and connect it carefully to the filament sensor.

    • Note the connector has two different sides. The side with safety pin must be on the left (white wire is facing up and red down).

    • Gently rotate the cable (clockwise) to create a small loop, see the second picture.

    • Push the cable through the opening on the X-carriage.

    i actually goofed but thinking the previous step was referencing a different cable somewhere else in the kit, but it meant there’s a 5 pin and 4 pin SIDE of the SAME cable. i put the 5 pin in thinking the 5th empty bit was just a consequence of a standardized pin layout or something.

    didn’t realize my mistake until step 47 when the cover didn’t fit.

    to fix it i’m using a small pick (a safety pin would work too) to push the pins out of the connectors and swap them

    joe kitchin - Reply

    Thanks for your comment, we are actually already working on a safety-pin solution.

    Martin L. - Customer Support -

    The braid of the filament sensor cable is twisted opposite to the braid that I see in the image. Because of this, I assume the clockwise loop should be changed to a counterclockwise loop, in my case. May want to update the instructions to allow for a loop to be made that follows the same braid direction that the sensor cable is in. If I do a clockwise loop, it unbraids the cable and I don’t think that’s what’s supposed to happen.

    Phil Norris - Reply

    Thank you @philamander, my wires were also twisted the opposite direction.

    Jen Johnson - Reply

    • Starting mid of February 2018, there will be only one 50cm NYLON filament included.

    • There are two NYLON filaments included in the kit with lengths 50 and 30 cm. Both have Ø 3 mm. For this step please use the longer one and DON'T TRIM any of them!

    • Using the pliers cut one end of the filament to create a tip.

    • Check the tip is similar to the third picture.

    Add Comment

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

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

    • BE EXTREMELY CAREFUL as the pliers tend to slide and you can easily damage the wires!!!

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

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

    I found that the hole wasn’t big enough for the nylon filament and even tapping it with an m3 screw didn’t help. Finally I got a 3mm drill out and very carefully cleared out the hole. After that the filament went in with no issues.

    Bill McRobb - Reply

    Same problem here. It won’t fit. How far did you drill?

    Maurice -

    Make sure you create a pointed tip on the end of the filament. Then as you push the filament in the hole will grab the 3mm filament. If you drill to 3mm it may not hold sufficiently.

    Neil Watts - Reply

    Stupid question. What is the point of having this filament here? Strengthen the cable bundle?

    Rick Sheppard - Reply

    Hi Rick, mainly to prevent to the entire bundle to sag down due its own weight and possibly hit the printed object. Also the nylon as the most stiff element takes majority of the load induced in the bundle.

    Jakub Dolezal -

    I am not being able to insert the filament. How much should be inserted, like 1cm or it should go through all the extruder? How much should I twist it, like 90 degrees or should I give it a few turns?

    Mario Ramírez - Reply

    Make sure to cut the nylon to make it pointy, as shown in the previous step. Roughly 5 mm should do. Twist it with pliers, 45° back and forth, until it doesn’t fall off.

    Martin L. - Customer Support -

    Well, mine went in eventually, I hope it stays put. Tough to get this to catch. Probably has to do with the exact shape of the tip. I did clean out the hole a bit with an allen wrench.

    Matt Laudato - Reply

    I found this step a bit confusing. My part we are inserting into here is the newer version, and I’m seeing that the hole that fits the filament is not below the belt passthrough as seen in the pictures here, even with where the belt ends terminate into this piece. There is a larger hole down where the picture shows on my version but that is far to big to hold the filament. A bit confusing due to the upgraded part I think.

    Daniel Bernard - Reply

    I got my kit a couple of weeks ago and the hole is in the same place as shown in the photo.

    Andrew Holloway -

    There has to be a better way. I finally got mine in. All most had to get some one to hold the head while pushed the wire in.


    William Wilson - Reply

    I drilled mine out as well. 1/8” bit (because I’m in the US…) still made for a very snug fit for the 3.5mm filament. Might nominally be 3.0mm, but I measured it at 3.5, and the hole at 3.1mm… which simply did not fit.

    Scott Tripp - Reply

    I ended up using a 1/8 bit as well. I tried to force the filament in with bigger pliers. It simply would not go. It would fall out under it's own weight. After opening the hole with a 1/8 bit, the filament fits perfectly.

    Brad -

    Good tip (Scott and Brad) about the 1/8” drill bit. I just stuck the drill bit in by hand and got only a few small shavings of material out, which allowed me to put the nylon filament in deep enough to stick.

    Ben Renneberg - Reply

    Ok, I'm tired of jerking around with a file and 1/8” drill, by hand, and cutting to make new points.

    What is it inside that grabs the filament? Is there harm in just more filing? Can I sand down the od of the filament.

    Bob Hayssen - Reply

    I got it. The point cut has to be oriented a certain way in the hole. If first try doesn't work, rotate 180 degrees.

    Bob Hayssen - Reply

    No, won't stay.

    Can I just be sure to contain it in the textile wrap? (Future steps)

    What will hold it at the other end?

    Can it sort of float free inside the wrap?

    Bob Hayssen - Reply

    I can not push this through no matter what… Please help

    Truc Tran - Reply

    This is so un do able, isn’t there an other way to get This fixed? Tought i had it done but plating the back part in its place the filament got loose. And the struggle starten all over again

    Peter - Reply

    Might sound like a silly question but which whole Neede to be used to put filament thru?

    i mean when using the one in the middle the back ends up to low, using the whole whre all the cbles go thru the back ends up to high.

    no way This Will fit propperly.what am i doing wrong here.

    Peter - Reply

    Wetting the sharp cut end of the nylon with rubbing alcohol reduces insertion force.

    Once the alcohol dries in a few minutes, friction fit grabs firm.

    Guy Kuo - Reply

    I have no idea how this mechanism works, or how to get something stuck in it. A picture of the operating principle is important if you want people to be able to complete this step — what are we even trying to do!?

    That said, eventually (after I chewed up the nylon severely, adjusted the tip three times, and switched to a larger, more secure set of pliers) something happened and the filament ended up stuck in the hole. (I’m just terrified it will decide to pop out again later on.)

    It’s possible it got threaded through some kind of cammed surfaces in the hole… It’s possible it got grabbed by some kind of spring-loaded barbs like an inside-out harpoon… It’s possible the tip got cold-forged into a mushroom-head rivet. It’s possible (though highly unlikely) my frenzied digging friction-welded it to the inside of the hole. I really don’t know.

    I still have no more idea what happened or how to make it happen after accomplishing it than I did when I started. That said, whatever it is, it’s a neat trick, when it works.

    Matias Rocha - Reply

    • For the following steps, please prepare:

    • X-carriage-back (1x)

    • Cable-holder (1x)

    • M3n nut (1x)

    • M3x10 screw (1x)

    • The M3x10 screw will be used temporarily, use one from the spare bag.

    • M3x40 screw (1x)

    Add Comment

    • Insert the M3x10 screw in the X-carriage-back. Tighten it completely.

    • Rotate the printed part and insert the M3n nut.

    • Tighten the M3x10 screw until the nut slides in the printed part. Note the shape of the cutout for the nut, you might need to adjust (rotate) the nut.

    • Remove the M3x10 screw and place it back in the spare bag.

    Just a thought; considering how often this procedure of drawing the nut into the printed part using a screw is used, but this is the first time in the manual it is explicitly shown, it may be helpful to place the procedure as one of the first orientations in the manual.

    Matthew Sekulic - Reply

    Right?! Here I am, probably 4 hours into the build, and this is the first time I’m seeing this procedure? I did it in all the other cases, but this is just odd to see it all the way on this step and not in the very beginning. I wouldn’t even bother telling people to do it any other way. Just do it this way every single time and save some headache.

    Phil Norris -

    Double check the x-belt tension NOW before attaching the X-carriage back. Once this back is in place, you cannot shift the x-belt to a different tooth position without undoing a lot of wire securing work . The x-motor tensioning adjustment mechanism has a very limited range of motion (about one belt tooth position). So, get your x-belt teeth in position with good tension now..

    There is a an alternative X-carriage back design on Thingiverse that splits the X-carriage into a top & bottom section. That allow s access to the x-belt without undoing the entire extruder wire securing system. Of course, that alternative design cover doesn’t do any good until you have assembled the printer.

    Guy Kuo - Reply

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

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

    • Note there is a recess (slot) for the screw's head on one side of the printed part.

    Add Comment

    • Place the X-carriage-back as in the picture. You must see the MK3 sign.

    • Tighten the X-carriage-back and the cable-holder together.

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

    Latest parts version does not have the Mk3 embossed logo (machine bought at TCT Show 2018 in Birmingham)

    Neil Watts - Reply

    Hi Neil, the logo should be there, I will discuss this with my colleagues.

    Jakub Dolezal -

    It’s there on mine.

    Ybl84f1 -

    Mine has the logo, but it's barely visible. It looks like the part was printed on the textured bed, which might be why the logo is so hard to see.

    Gabe Ferencz - Reply

    Same thought here. Logo looks to be lost in the texture.

    1Eye -

    As long as the part looks exactly like the one on the photo, it’s not a problem that the logo is not there /not clearly visible.

    Martin L. - Customer Support - Reply

    Terminology from the letterpress printing industry - Embossed is a raised image while debossed is a sunken image.

    Tom Parker - Reply

    • Push the cables from the Extruder THROUGH the X-carriage-back. Start with Extruder motor and the Left hotend fan.

    • In the next step add the Front print fan and P.I.N.D.A. probe cables.

    • Cables from hotend and filament sensor are NOT GOING through the X-carriage-back!

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

    My filament pops out.

    Back to jerking around in a previous step.

    Bob Hayssen - Reply

    • Before pressing the X-carriage-back against the X-axis, place the filament sensor cable through the slot. See both pictures.

    • Check the cables are not pinched between the X-carriage-back and the X-axis!!!

    Add Comment

    • Using five M3x10 screws tighten the parts together in following order:

    • Start in the middle and ensure proper alignment.

    • Continue in the corners, tighten all screws equally.

    • After the tightening is done, push the filament sensor cable in the slot along X-carriage-back, join the remaining cables.

    Make sure not to over tighten the screws at this point. Mine snapped without being too tight and are not covered under warranty :( A side on picture would be helpful to show proper alignment of the two pieces with each other and the bearings.

    Dave Black - Reply

    You will find out many steps from now that it’s important for the wires to be tucked completely into the slot and not protruding. If the wires protrude at all they can catch the filament holder when the print head is all the way up. The clearance between the back of this print head where the wires are, and the frame (which the filament holder mounts to) is only a couple of mm. Make sure the wires are neatly and completely tucked into the slot.

    Ybl84f1 - Reply

    • For the following steps, please prepare:

    • Zip tie (5x)

    • Textile sleeve 13 x 490 mm (1x)

    • There are three textile sleeves in the package, use the largest one (both diameter and length).

    Add Comment

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

    • Leave the cables from the Hotend out for now.

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

    • Gently twist the sleeve to make it smaller and tighter around the cables and slide the sleeve towards the extruder.

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

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

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

    Make sure you didn’t make the PINDA loop too big. The cable will be too short to hook to the circuit board. I had to go back, but in doing so I got a much better result with the textile sleeve.

    Bill Hines - Reply

    Hello Bill,

    In addition to this, it is worth noting that if any of the extruder cables (including PINDA) is sticking too far out to the side, it may obstruct X carriage movement, which can later cause issues during XYZ calibration.

    Official Prusa Support

    Marcin Mączewski -

    • 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 (provided in the kit and assembled later on). If you intend to use any other frame mounted type holder, make sure the zip ties won't crash into it, which might result in a print failure.

    FYI - I am at roughly 3.5 hours up to and including this step - pretty close now, maybe another 30 minutes based on what I see coming up.

    I did have maybe 15 minutes of rework based on my own mistakes.

    Hope this helps!

    Dave P - Reply

    Get the heads of your zip ties exactly in the positions illustrated. Also remove the zip ties that came already on the hot end cables. Otherwise, the zip tie heads impinge against the frame and cause an x-axis length error.

    Guy Kuo - Reply

    Check the hot end temperature sensor lead to prevent a thermal sensor wire failure that may occur after a few weeks of printer usage if the shrink wrap is in the wrong position.

    The plug end of that wire has a yellow/green shrink wrap. Ensure there is at least 5 mm of free wire between the plug body and the shrink wrap’s end. If the yellow/green shrink wrap ends too close to the plug, it acts as a rigid lever gradually pulling the wires out of their crimps once the EINSY door is closed. The wire crimps can fail a few weeks if under tension.

    Use sharp tipped scissors to carefully trim the shrink wrap back leaving adequate free wire to flex between the shrink wrap and the plug. Don’t cut the actual wires, though!

    Guy Kuo - Reply

    • For the following steps, please prepare:

    • Idler-plug (1x)

    • Filament-sensor-cover (1x)

    • PTFE tube 4x2x13 mm (1x)

    • M3x10 screw (2x)

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

    I have two pieces, they look virtually identical but not completely. Is one a spare?

    Ybl84f1 - Reply

    • Insert the short PTFE in the printed part from below. Orientation of the tube doesn't matter, both ends are the same.

    • Locate the largest circular opening for the PTFE tube on the top of the Extruder.

    I have no PTFE tube in my kit I have looked everywhere it’s the latest revision with new textile sleeve etc is the PTFE no longer used because of the filament sensor? How long should the tube be

    David Burgess - Reply

    Hi David, the PTFE tube should be there, it is a mistake on our side. I'm sorry about it. Proper size should be 4x13 mm, see the drawing here: How to trim PTFE tube - Original Prusa i3 printers

    Jakub Dolezal -

    • Carefully slide the filament cover on the extruder.

    • Using two M3x10 screws mount the cover.

    the connector on the filament sensor wire, have 4 wires, but is inserted into an plug for 5, so there are one free on the top, and that one extends a bit, so the filament cover does not fit.

    Asbjorn Mikkelsen - Reply

    ok, that was me putting the sensor wire wrong way around..

    Asbjorn Mikkelsen -

    • Locate the part, where the idler is cut out (M3 screw is visible).

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

    not sure what purpose this step serves.

    Trent Dye - Reply

    Hi Trent! If you look at the extruder from the right side, there is a hole in the Extruder Body that leads to the filament sensor. The idler plug is there to seal this hole, to prevent light from reaching the filament sensor.

    Martin L. - Customer Support -

    “Assemble the …”, you mean, just drop it in place? What is the hold it in place?

    Bob Hayssen - Reply

    • Are we there yet? Almost! You've just finished the hardest part of the assembly. Awesome job!

    • Check the final look, compare it to the picture. Note with B7/R3 parts the extruder looks different.

    • Checked everything? Let's move to: 6. LCD assembly

    I think a lot of parts, not just here but everywhere, the infill is not appropriate. For example, my pinda sensor holder isn’t very sturdy and flexes easily. I was doing some maintenance, and noticed the screws from step 15 were very loose. I may have overtightned slightly as I head some slightly unpleasant grinding and backed off. It’s counterintuitive for screws to be so lose on install, but I believe these screws loosen more over time as you print, even after only a week. My screws were sticking out and totally lose after 7 days of printing.

    Y axis motor mount is horrible. It cracked along a seam on install, luckily I was able to print a higher infill reinforced replacement before it lost more tolerance.

    Misiu Kowalski - Reply

    My Rambo board cover lower pin also snapped. My suggestion is raise infill % overall for all parts, and maybe make step 15 less heavy maintaince involved since screws loosen over a very short period of time and just “tightening everything” is pretty dangerous, especially for step 15 screws. Maybe you could redesign how these parts fit to make it more intuitive/less prone to any risks of damage. A maintenance guide for common loose screws etc might be useful, could include some info regarding rail, leadscrew, and bearing oil/grease also since after reading there isn’t any official stance regarding lubricants.

    Maybe also improve the PSU’s, since mine failed after 7 days. Maybe newer ones already better, my replacement seems to get less hot and slightly quieter. Hoping for the best with it!


    Misiu Kowalski - Reply

    Hi Misiu, thanks for the feedback. All the parts are updated based on our internal tests as well as your comments. We've just released a set of upgraded plastics (version B7). Regarding the PSU and other electronics, most of them are our own design and each unit is tested before being shipped to you, but sometimes it may break down anyway. Please always contact our support to get this sorted out ;)

    Jakub Dolezal -

    The little angle bracket that holds the tilted fan broke while I was inserting the nut using a screw from the other side.

    It only cracked one side, so I just went on, but might eventually reprint it or at least superglue the crack.

    I didn’t have serious trouble with any of the other nut insertions, and wasn’t being rough with it as far as I can tell.

    What kind of plastic are these parts?

    David Gustavson - Reply

    All of our parts are PETG, except the fan shroud (fan nozzle), which is ABS. If you don’t have PETG, this particular part will do just fine even if you print it from PLA.

    Martin L. - Customer Support -

    Suggestion: Add more Haribo breaks in this section.

    Adam Timmerberg - Reply

    Involved sequence of steps to be sure, but at this point, the hard part is mostly over!

    Matt Laudato - Reply

    How about a photo from the opposite side also.

    Bob Hayssen - Reply

Finish Line

151 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

112,986 Reputation

161 Guides authored


How long should the PTFE tube be as mine is missing. Should it go down past the laser sensor to the extruded gears?

David Burgess - Reply

Hi David, the PTFE tube should be there, it is a mistake on our side. I'm sorry about it. Proper size should be 4x13 mm, see the drawing here: How to trim PTFE tube - MK2/S, MK2.5 and MK3

Jakub Dolezal -

I recommend adding a note/alert/warning at the top of both this page and the spiral wrap page to check the contents of your pack and make sure you’re on the right page for the contents of your kit! It’s not until you’re on step 40+ that you actually figure out whether you’re on the right page or not.

Devon Bleak - Reply

Hi Devon, added. Thanks for the suggestion ;)

Jakub Dolezal -

FYI: 3 hours to complete.

Hate the textile wraps.

Keith Spitz - Reply

Hi Keith, the textile wrap requires a little bit more work, but it is worth the result :)

Jakub Dolezal -

Also took me 3 hours.

stonefred@gmx.at -

your photo does show where you put idler-plug (1x) . please help


william murillo - Reply

Hi William! See the step 48 for the Idler plug assembly. We always recommend to read all of the manuals until the end! :)

Martin L. - Customer Support -

took me 2:38, lost some minutes because i put the filament sensor wire on backwards

joe kitchin - Reply


Step 5 “Slide the shaft through the idler and pulley” was such a difficult thing to complete without breaking the Extruder-idler. The tolerances of the shaft hole loops are not that strong in the the orientation that the Extruder-idler is printed. Broke the part, and had to have someone print me the part out of black PTEG to continue the steps. They printed me two replacement parts in-case I broke one again. Well, yes I broke the first one (shaft hole snapped again). With the second replacement part, I took a drill and made the hole a little bigger. Both the part which came with the set, and the parts that were re-printed had the same hole diameters of 2.67mm, while the shaft is 3mm. In order to not break the last replacement part, I took a drill and a 3mm bit and made the holes bigger before inserting the shaft and finally got step 5 assembled.

Also, according to Bondtech’s website, they recommend adding a little white grease to the gear before assembling. Your site Reference https://bit.ly/2PTWOF1

Adam Timmerberg - Reply

What is the idler plug used for? It’s just sitting there on the screw, and I’m sure it’s going to fly away at some point.

Barak Ori - Reply

It is there to prevent too much light from reaching the filament sensor. You have to be careful about it when opening the idler door.

Martin L. - Customer Support -

3hours to complete this.

Paul Waldman - Reply

About 3 hours to complete. It would be handy at the end of the web page to have a link to the next set of steps.

Bill Hines - Reply

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