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  1. 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

    I don’t see anywhere in this step that zip ties are used. Why are the needle nose pliers mentioned as being needed?

    Stephen Cooper - Reply

    Stephen, you can need them during the manupulation with the bearings, as well as for insterting nuts into their traps.

    Martin L. - Official Prusa CS -

  2. For the following steps, please prepare: X-end-motor (1x)
    • For the following steps, please prepare:

    • X-end-motor (1x)

    • X-end-idler (1x)

    • Linear bearing (4x)

    • M3x18 screw (2x)

    • M3nN nyloc nut (1x)

    • M3nS nut (1x)

    • 623h bearing with housing (1x)

    The itme with blue arrow is not the motor.

    Catherine Wykes - Reply

    Hi Catherine, “X-end-motor” is the name of the plastic part.

    Filip M - Official Prusa CS -

  3. Insert LM8UU linear bearings into the printed parts (X-end-motor and X-end-idler) as shown in the picture. Make sure the first bearing in each printed part is pushed all the way down. DON'T TRY TO PUSH the bearings from the other side. There is a rim (smaller diameter of the hole). First pair of bearings should be in line with the top surface on both X-ends.
    • Insert LM8UU linear bearings into the printed parts (X-end-motor and X-end-idler) as shown in the picture. Make sure the first bearing in each printed part is pushed all the way down.

    • DON'T TRY TO PUSH the bearings from the other side. There is a rim (smaller diameter of the hole).

    • First pair of bearings should be in line with the top surface on both X-ends.

    • Second pair of bearings should be seated on the rim (close to the lower surface) on both X-ends.

    • You can press the bearings against the flat surface for easier insertion.

    • Place two bearings in a way that the inner balls of the second bearing are rotated 45° compared to the first. This way you will achieve greater contact with the smooth rod. See the third picture for more details.

    To adjust the position or rotation of the linear bearings push the 2mm allen key inside the bending split, so it grow a bit wider, now you can turn or position the bearing with much less force.

    Patrick Kirsch - Reply

    That’s right. Please just be careful, everybody, not to break the part.

    Martin L. - Official Prusa CS -

    Instead of risking breaking the part. Use a 10mm socket to push the bearings back out again to re-align them

    Dakota - Reply

    The size of socket will vary by set. My 11mm socket was the right size. The key is to push on the metal outer part with the socket, NOT the rubber seal.

    Mark Jurisch -

    wish this step made more sense about the 45 degrees, the picture does not help at all

    Eric Jordan - Reply

    Hey Eric, do you have any suggestions on how to make it clearer?

    Martin L. - Official Prusa CS -

    Perhaps, in addition to the graphic showing the desired 45-degree rotation offset, it might help to also show (with red “X”) what it looks like to have both bearings’ ball lines in-line instead of offset. (“What NOT to do”)

    Todd Kanning -

    Imagine the letter “X” and a “+” sign, both of them the size of the inside of the bearing. Then the X and the +, when laid on top of each other, make an evenly-spaced 8-point arrangement. Align the four tiny rows of balls in the first bearing to the endpoints of the X, the four tiny rows of balls in the second bearing to the +, and the two bearings will then be at 45 degrees to each other. It also helps to use a small flashlight to look “down the barrel” of each bearing, in order to see the four rows of tiny balls that are the active parts of the bearing.

    John Drabik -

    I used the handle of the pliers to gently move the bearing down the tube.  Being soft surfaced but firm, it made an easy job of this.

    Roy Steiner - Reply

    There should be a note that when inserting the first bearing of each pair, ensure it is slid to its end-position before inserting the second of the pair.

    I used the second to push the first down, then realized I had no “gap” between the them to allow me to continue pushing the first the remaining few mm.

    Scott Mutton - Reply

    I agree with Scott . . . I did exactly the same thing.

    - insert first bearing

    - push it all the way to the stop

    - insert second bearing rotated axially 45degrees.

    - press it in flush to the face

    Greg Sanders - Reply

    Great points, Greg (and Scott)! Agreed! (Had to read these instructions a few times as well as comments before beginning with confidence.)

    Perhaps your fourth step could be fortified as follows, “- press second bearing in flush to the face, leaving a small gap between the two bearings”?

    Todd Kanning -

    I agree with greg and scott.

    Pascal Robert - Reply

    Good points. I’d stress: a reminder about reading all steps here first before inserting the bearings, and recommendation as per Scott on how to properly insert these.

    Per Farny - Reply

    I did the same mistake as Scott and Greg. I solved it by inserting the smallest allen key into the plastic crack and made contact with the bearing on it’s line dent to push the first one to the proper position.

    mhm - Reply

    So just to clarify - it seems that when pushing the bearings in, the side that you enter the bearing is a full circle but splits from the pressure. It also appears that this is completely normal. The picture shows a cut that doesn’t exist in the real part. It might help folks to mention that the part will split at this point and not to worry.

    Michael Pennachio - Reply

    General suggestion1: Perhaps orient the orange X-end pieces the same in the first two pictures just for clear/consistent reference.

    General suggestion2: At this stage I’m afraid it’s not yet clear (at least to me) which is the “top surface” and which is the “lower surface” as referenced in the instructions. Perhaps it would be helpful to only reference sides/ends within the scope of these two X-end pieces themselves; such as “rim-end” and “non-rim end”?

    Todd Kanning - Reply

    General suggestion3: Regarding the green dot note, “First pair of bearings should be in line with the top surface on both X-ends.” Isn’t it true that the second pair of bearings (the bearings we must insert second) should be in line with the top surface at both X-ends? Out of necessity, the first pair of bearings must be against the rim-end since they must be inserted first, correct? I may be misreading, but it seems that the references to “first pair” and “second pair” in these notes are reversed (assuming you are referring to the order in which the bearings are inserted).

    Minor semantic suggestion regarding, “You can press the bearings against the flat surface for easier insertion.”… If I understand correctly, I think you’re suggesting using “a” flat surface (e.g., benchtop) to press the bearing into place. The words, “against the flat surface” made me wonder at first if you were referring to a specific portion/surface of the X-end itself.

    Todd Kanning - Reply

    Hey Todd, thank you for all the feedback. We’ll try to update this step.

    Filip M - Official Prusa CS -

    The first bearing I inserted was really tough to get in, all the way to the rim. Therefore, even though I used my workbench to put it in, the second bearing I inserted went in with full force and got right next to the first, when they should be separated.

    Not wanting to destroy the bearing’s rubber seal nor the part with the allen keys, I scratched my head. My solution was to take the GT2-16 which has a slightly smaller diameter than the linear bearings and use the rubber end of the pliers to push on the GT2-16 which in turn pushed on both bearings from the “rim” side until one fell out. Then pushed the first one in again against the rim (and the GT2-16 out) and then more gently this time inserted the second bearing.

    Miguel Barroso - Reply

    Hi Miguel,

    Thanks for your feedback.

    Martini H. - Official Prusa CS -

    I think that what they are trying to convey is that each bearing should be closest to it’s perspective end of the printed part (nearly flush). This will leave a gap between the bearings . This confusion might be mitigated with a spacer to prevent having the bearings too close together. But I might be mistaken.

    Robert Shimel - Reply

    Hello Robert,

    each bearing should be closest to it’s respective end of the printed part. :) Otherwise you’re absolutely correct.

    Martin L. - Official Prusa CS -

    I completely ruined a bearing on this step. Can we please get better instructions on how to perform this task.

    John Dupras - Reply

    Hey John,

    Please let us know which part was unclear - we’ll do our best to adjust the manual.

    Filip M - Official Prusa CS -

    My complete method using Miguel Barroso’s excellent suggestion:

    1. Insert the first bearing into an orange piece so that it is wholly just inside the entry opening

    2. Insert the GT2-16 Pulley piece from the X-axis hardware bag (has not yet been used)

    3. Orient the orange piece on the table so that you are pushing the bearing and GT2-16 downward. Use the soft, rubber handle of the pliers to push the two pieces into the shaft until the bearing meets the surface of the workbench. Turn the orange piece over so that the GT2-16 falls out.

    4. Insert the next bearing partway (sticking out) with the lines of balls inside at a 45-degree angle difference to the previous bearing

    5. Turn the piece over again, so that the second bearing is on the workbench. Apply pressure downward on the orange piece until the second bearing is flush with the opening.

    If you accidentally press either piece too far in, you can use the GT2-16 and the plier handles to push the bearings back out without damaging them and try again.

    Spacer please :(

    Wesley Boynton - Reply

    I fell trap to the lack of instruction that says insert first bearing to bottom before proceeding to second. If you too find out it's wrong, use your smallest Allen key and stick it into the slot and push slightly against the bottom bearing (there is a groove that you can use to push). Then, once it's freed, use the Allen key and contact the top (as if the key was laying on top) and pull down til the bearing hits the rim.

    Jeffrey Foley - Reply

    We could really use a spacer here.

    Ben M - Reply

    Hi Ben, a spacer is not necessary in this step - the bearings will be properly secured within the plastic part.

    Filip M - Official Prusa CS -

    This step is poorly explained. Does the first bearing have to have its row of balls facing down, or does it not matter as long as the second one is 45 degrees in relation to the first one. I spent fifteen minutes just trying to get the bearing into the tube, the tube being a full mm too tight, and the slot was held closed by a small bridge of material. I was trying to get the bearings into the end without the rim. Ended up using a stanley knife to cut the bridging material free, which allowed the part to flex enough that the bearing could be forced in. Then had to do several removals and reinsertions because the bearings rotated as they were being pushed down the tube.

    Based on my own experiences and the comments so far, it seems like there is little or no effort put into quality control with these printers.

    Lessian - Reply

    Perhaps include a 3D printed pusher rod to press the first bearings in place? That process would be easy to show & clarify how they should be inserted, making it go much easier for folks.

    Jim M - Reply

    Hi Jim, it should be possible to do this with fingers only - tools aren’t necessary at this point.

    Filip M - Official Prusa CS -

    while we set up this printer, if instructions themselves not enough and if we have to read all comments also, it clearly shows that these manuals and parts prepared poorly… i have no idea why they imagined all customers have mechanic backgrounds to deal with even the angles of bearings… i share the same doubts about quality control of these printers

    kivanc aladag - Reply

    Hello Kivanc,

    What wasn’t clear in the steps in this manual? Please let us know, so that we can improve it and make it easier to understand for other users. Also, if you are struggling with any steps, you can always reach out to us via our 24/7 livechat and ask for help :)

    Marcin M. - Official Prusa CS -

    The lower bearing bottoms out on the lip but what’s keeping the top bearing from slowly creeping down the steel rod, over time?

    David Vo - Reply

    Hello, no worries, that never happens thanks to the tightness of the plastic part.

    Martin L. - Official Prusa CS -

    On the bottom bearing, if you line up a row with the cut, as you slide it down, you can then put the top bearing row 45 degrees from the cut and you’ll have the effect that you need.

    Daniel - Reply

    A 3/8” or 9mm socket with extension is perfect for setting the first bearings all the way into the piece.

    Bob Baltz - Reply

    Another helpful suggestion (given in part 1) is to read ALL of the instructions first. I tell my students this all the time, yet just like I tend to do, they skip this first step [of reading everything first, especially on an unfamiliar task].

    Laurie S - Reply

    Shouldn’t the green arrows be purple while the purple arrows be green? Alternatively, in the instructions, shouldn’t the green dot be purple and the purple dot be green?

    pcprusa - Reply

  4. Insert nut all the way in (deeper than in the picture) and then add the screw. For now, we need the screw just to hold in place. Tighten the screw, until its head almost reaches the surface of the printed part. We will adjust the final position later.
    • Insert nut all the way in (deeper than in the picture) and then add the screw. For now, we need the screw just to hold in place. Tighten the screw, until its head almost reaches the surface of the printed part. We will adjust the final position later.

    • Make sure the M3x18 screw is not visible in the marked hole as it will block other screw in future step. If you can see the screw in the hole now, please release it slightly.

    Perhaps mention that the nut must go much deeper into the part than the graphic above suggests. If the edge of the nut is left flush with the part-surface (as shown), it will neither line up with the screw hole nor even block it (which would make it obvious that it wasn’t fully inserted).

    Scott Mutton - Reply

    Hey Scott,

    Thanks for the feedback, we’ll add a note about it.

    Filip M - Official Prusa CS -

    Indeed – just got bitten by this. The image above is precisely what it looks like when the square nut is sitting on top of the screw. If you turned the part upside down after taking the above picture the nut will fall out.

    Mark Wheadon - Reply

    My preassembled printer came up with this screw loose, as on the picture above. So perhaps some of the Prusa employees also get confused by this instruction.

    George Yohng - Reply

    Hey George, it’s not necessary to use the tensioner.

    Filip M - Official Prusa CS -

    If its not necessary to tighten this screw, why is it there? And if it is supposed to be tightened at some point, this response from customer service is completely lacking in actual help.

    Lessian -

    Hi Lessian, the screw is there in case you need to use it. Good tension can be achieved without it, too - but then in some cases it might be needed.

    Filip M - Official Prusa CS -

    Prusa CS FTW

    Alan Ostroff - Reply

    The nut falls easily into the opening at first, but is easily pushed all the way down into the hole by the smallest allen wrench, which can also be used to center the screw hole through the screw opening. The nut should not be flush with the top of the piece as in the picture, as noted by Scott Mutton.

    Prusa — Please modify picture so that the nut is still hanging partway out of the hole with the downward arrow. This will make it visually clearer that the instruction image is portraying an insertion, rather than the desired placement of the piece (since pushing the nut all the way in the picture would just cause it not to be visible, lol)

    Wesley Boynton - Reply

    Hi Wesley, make sure to read the description - it explains what should happen to the nut from the picture.

    Filip M - Official Prusa CS -

    It is worth mentioning that if you have any M3x16 bolts, use one here! It is very common to accidentally overtension the X axis later because the 18mm screw won’t bottom out when it gets in all the way, fooling you into thinking you have more room. I did it, and I’ve seen many others on Reddit do it too.

    Ken Robertson - Reply

  5. ATTENTION: be very careful during the tightening, check the nut orientation and DO NOT use excessive force, you can break this part. Insert the M3nN nyloc nut in the X-end-idler. In case you can't press the nut in, don't use excessive force. Leave the nut for now and proceed with the other components for this step.
    • ATTENTION: be very careful during the tightening, check the nut orientation and DO NOT use excessive force, you can break this part.

    • Insert the M3nN nyloc nut in the X-end-idler.

    • In case you can't press the nut in, don't use excessive force. Leave the nut for now and proceed with the other components for this step.

    • Insert the 623h bearing into the X-end idler.

    • Secure it in place using an M3x18 screw.

    • Now, if needed, use the M3 screw to pull the nut in.

    • Place your finger on the bearing and ensure it can rotate freely. If needed adjust the screw.

    Screwing the M3x18 screw onto the nut allows you to adjust the angle of the nut as you press it into the X-end-idler. Then unscrew it once the nut is in place.

    Ken biles - Reply

    If you try and use the screw to pull the nut in, be very careful as the part can bow in or break. I noticed mine was bowing in so I had to figure out a different approach.

    Mark Jurisch - Reply

    if you pull in the locknut using a screw use the plastic washers from the spare bag on the screw head to avoid damage

    twostone - Reply

    If you put that screw to far in it will stick out and rub against the frame.

    Harvey Stein - Reply

    That is right, we don’t want that. Also the bearing would not turn freely in that case.

    Martin L. - Official Prusa CS -

    I think its important to mentions that the locknut will stick out some from the X-end-idler. Maybe add another image with more of an angle or some kind of note.

    Steve Pilon - Reply

    I agree with steve. I wasnt sure how deep the nut should be in the hole.

    Tony Mastrangeli -

    I agree, mine was sticking out significantly but it held firmly. Image confirmation would be appreciated.

    Brandon Sutton -

    The orange plastic part in this picture is a bit differently shaped from the model that I received in my Mk3S kit. The width of the B7 part shown in the rightmost picture, the arch exactly positioned under the thumb there, is looking considerably narrower than the width of the piece I received (13,5mm). There are also no diagonal supports on the arch of the piece I received. Do I have an older or newer model part B7 or did something else change since this manual was printed?

    Wilko van den Bergh - Reply

    Hi Wilko, the design of your parts might be slightly different when compared to those from the manual.

    Filip M - Official Prusa CS -

    After a chat with support: these photo’s seem to be from the MK2 version. The plastic on the X-end-idler on the MK3s has some bulging around the recess where the nyloc nut goes (reinforcement?) This bulging is per design for the MK3s and so it is normal.

    lvwouwe - Reply

    Quick Tip, insert the bearing before seating the nylock nut using the pull method to keep the part from bowing/breaking.

    Matthew Hall - Reply


    Insert the 623h bearing into the X-end idler.


    It does not matter which direction the 623h bearing is inserted into the X-end idler.

    Ron - Reply

    My part cracked a little but seems ok. A statement is needed that this nut, unlike the others, rests on the surface.

    Darrell - Reply

    On the first MK3 I built I managed to crack this part trying to pull in the nylock nut. On this MK3S build I tried a different method. There’s a 3mm x 40mm bolt and plain hex nut in the spares bag. I inserted the bolt halfway through the x-end-idler, threaded on the plain hex nut, and slipped in a 5.5mm box end wrench. Then I passed the bolt out the other side and threaded on the nylock nut:

    After pushing the nylock nut down tight against the x-end-idler and lining up the flats on the nut with the nut pocket, I was able to hold the bolt with a hex key while turning the plain nut with the box end wrench to draw in the nylock nut. This kept me from squeezing the two walls together and risking cracking the printed part.

    Stephen - Reply

    For the M3X18 screw and M3nN nyloc nut, how deep should they go in to the orange part respectively? Do I have to use force to push the M3nN nyloc nut completely into the orange part?

    pcprusa - Reply

    I had the same questions about the nyloc nut sticking out of the top. Step 12 has a good view of the piece finished, and the nut sticks out a bit. Mine looks like this so I think I'm good.

    Tom Brooks - Reply

  6. Take remaining smooth rods and compare their length. For X-axis you need longest rods (370 mm). Linear bearing (3x) NOW, PLEASE BE VERY CAREFUL! Gently insert the rod straight into the bearings, do not apply too much force and do not tilt the rod!
    • Take remaining smooth rods and compare their length. For X-axis you need longest rods (370 mm).

    • Linear bearing (3x)

    • NOW, PLEASE BE VERY CAREFUL! Gently insert the rod straight into the bearings, do not apply too much force and do not tilt the rod!

    • In case you manage to push out balls from the bearings, please count them. One or two balls are ok, if there are more of them, please consider ordering new bearings.

    For this step, one of my bearings does not move freely on the rod with gravity. The bearings will cruise from left to right when I tilt the rods, this bearing does not. I feel there is something faulty with it. Is this common?

    josh deaugustine - Reply

    Hi Josh,

    Please test the bearing by moving it with hand. If it moves smoothly, then it will be OK.

    Filip M - Official Prusa CS -

    Do we have to care about the orientation of the balls (45 degrees) like in step 3? I think this would make sense because of the fast and repetitive X-axis movements.

    Elio - Reply


    you can try, yes, but with all the manipulation necessary in the upcoming steps it is very difficult to keep track of the orientation.

    Martin L. - Official Prusa CS -

    There’s a way to accomplish this: before inserting the bearing. make a mark on the exterior using a sharpie marker indicating the transversal lines of bearings. To turn a bearing move it back and forth while applying twisting force.

    A 2 E -

  7. Insert the rods with bearings fully into the printed parts. Insert the rods very carefully. Do not tilt the rods too much.
    • Insert the rods with bearings fully into the printed parts.

    • Insert the rods very carefully. Do not tilt the rods too much.

    • Ensure the correct orientation of the parts and rods.

    • There is a special opening in the top/bottom of both X-ends. Check if you pressed the smooth rod all the way in.

    I’m a pretty big dude, pushing with all my strength I couldn’t get the rods pushed all the way in. I ended up taking one of the cardboard strips to cover the printed part and putting the other end against the carpet and tapped it on until I could see the rod through the hole.

    thehoof - Reply

    My mk3s kit did come with the special openings on top and bottom of both printed pieces for this step.

    Matthew Bell - Reply

    Mine does, too.

    John Merling -

    I placed both rods into one part, one rod at a time. I started the rod by hand, then placed the rod end on my work bench (so the rod is vertical, with the printed part on top) and pressed down on the printed part. I repeated this for the second rod. I then started both rods into the second printed part, then placed the first part onto the table, and pressed both rods home. Rod ends show through end openings on both top and bottom.

    Ken biles - Reply

    OK, so I had the same problem with inserting the rods. I want to share my experience to help the next guy. As a disclaimer I accidentally fractured the outside corner of b7 but that was a mistake that can be avoided.

    I started them by hand OK as much as I can but could not seat them all the way. So what I had to do was take a soft hammer, though any soft banging too should work fine, and gently tapped the end of the rods one at a time. Fully seating one side. It may be a good suggestion to use a permanent marker and mark near the printed part on the rod to observe how you are making progress since this was risky. you should only tap is as hard as you need to to move it a little at a time. Then I applied the other end and gently tapped on that after pushing it on as much as I can by hand.

    My mistake was I din’t seat any of the rods fully in any component before I took the hammer out. But if you tackle one side at a time you should be good. - Reply

    I ended up using a pipe clamp (made for wood working) to slowly move the rods fully into the 3d printed parts. Worked great!

    Keith - Reply

    OMG Thank you thank you thank you! I used a bar clamp, made it so easy!

    David Krauss -

    Agreed! Pipe clamp worked like a charm. You just have to be careful when applying pressure to the rod with two bearings since the force is a bit off-axis.

    Steve Gowin -

    Agreed, I used a bar clamp and it worked perfectly, thanks for the suggestion!

    Brandon Sutton -

    Bar clamp works fine. Rods advance by little jumps.

    Miles Odonnol -

    I placed a piece of cardboard, from the packing, on the floor … pleased the assembly vertically and pressed firmly straight down … and it snapped into place.

    Dennis H Mathes - Reply

    This worked for me as well, not too much forced was needed this way. Would like to say that I was a bit hesitant to do this, I preferred to clean the wholes with the allen key, but I could not get them out that easy.

    Morris -

    I find pushing the rods in solely by hand was easy in the MK3S.

    Ezekiel - Reply

    No banging with a hammer is necessary. It may twist the rod, and you most definitely doesn’t want that. If it doesn’t go in easily, then clean up the hole a little with an allen key, then slowly put in the rod until it goes all the way, if it doesn’t, then clean up a little more.

    Take the rod out and repeat the process with all 4 holes. Afterwards, it’s easy to assemble it all together.

    Knieza - Reply

    I have a MK3S and no amount of cleaning would make the rods easily enter the holes. I had to resort to a rubber mallet and gentle tapping.

    Jack McGwire - Reply

    I found that using a small round file in the holes made it much easier to install the rods, as they are a very tight fit. Also using a peice of cardboard on the table/floor and putting some weight on them made them go in, but make sure you get the bearing on the right way round as its never coming apart again ;) It feels like the printed parts are faily strong, as I put a fair amount of pressure on them and they didn’t snap in half, but be careful as they are still only plastic.

    Samuel Knowles - Reply

    I seated the rods initially but they didn’t go fully in, so I used a cloth to hold each X end (to protect the part and stop it slipping) and then by applying steady pressure and a small amount of twisting the rods clicked in all the way.

    John Megarry - Reply

    Hello John,

    Perhaps there was some excess material extruded in the printed parts, which prevented the rods from going in - in case of all printed parts included in our kits, we always recommend to always inspect every part and clean it with a hobby knife if necessary.

    Marcin M. - Official Prusa CS -

    Nope nope nope.. The holes in the parts were clear and yet no amount of twisting and pushing would budge the rods any more after the 1st cm or so. After that I had no choice but to use a hammer, and make very small and gentle taps on each rod in turn until everything was fully seated. Added another 10 minutes or so to the build, but took it nice and slow and careful to avoid breaking anything.

    I think the main source of the issue is that the rod ends are very square, with virtually no bevel whatsoever, so the rod ends dig into the sides of the very tight holes whereas a slight chamfer on the ends of the rods would allow them to go in a lot easier.

    Ian Morgan - Reply

    What worked for me: pushed in all 4 as best as I could taking care not to bend rods. Then used rubber mallet on printed parts to gently tap them in while the other printed part was on workbench. A few taps and they were in.

    Per Farny - Reply

    I used my 3kg rubber-covered dumbell ( it was all I had available ) to gently tap it in , wow that was nerve wrecking but it worked

    Joandri Meyer - Reply

    Thank you Prusa for letting us put comments on here.

    I had the same problem. No way these rods would go in all the way without a lot of force. I did not want to do that so I first used a marker to mark in the rods how far they should go down. Then I used a round file to file out the holes till the rods would snugly fit.

    Michael Minden - Reply

    I was able to get the rods into the idler (flat side) with a lot of muscle, but I could not, for the life of me, get the rods into the X-end-motor (hook shaped) end. I got it about an inch in and it stopped like it hit a brick wall. I tried a light hammering, and it would not budge (used marker to track progress). I stopped for a couple days to think about it.

    I was able to remove the rods from the idler piece to start over. This time I started with the X-end motor (hook shaped) side first. I used a piece of neoprene 1/16” rubber that I had from another project as a grip. I wrapped it around the rod and was able to insert the rods with a twisting motion, one at a time. Then I was able to cap the other side with the idler part. I celebrated with a gummy bear, then realized I forgot to put the bearings on the rods.

    Hope that helps others!

    Andrew VanHeuklon - Reply

    Use tiny hammer or small dead blow mallet. Start with the piece with the L off of it. Hammer the ends of the rods into the part slowly. Hammer both rods all the way in. Then put the other end on, and hammer each side of it slowly alternating each blow of the hammer. Do this with the other end on the table with the L hanging off the edge of the table so the force does not affect that piece of the part.

    Doug - Reply

    I am having this problem too. I checked the inside of the holes, and poked with an Allen wrench, and they seem very clean. . The tolerance is just too tight. I now have one rod stuck in the hook-shaped piece and am trying to figure out how to proceed.

    Sounds like, if I can get it out again, the best way is to get a round file and file down the holes.

    If I cannot remove the rod, which is less risky to its integrity: 1) place the printed end on the floor (with padding) and push down on the rod? or 2) rubber hammer?

    Laurel W - Reply

    Update: I used electric plastic safe lubricant to remove the stuck rod. Then I used a round file on the holes. It seemed to work very well to use the end of the file to push down the inside of the holes. Using a cell phone flashlight to look inside the holes (not easy to see inside black parts….), I did not see any obvious strings or artifacts though the inside of the hole is a little rough. I noticed there is a slight artifact of 3D printing the holes, with a little flatness on 2 opposite sides. I don’t know if that caused the difficulty or whether the holes are just slightly too small. But after a little cleaning out the rods slid in perfectly. I had expected to have to tweak/adjust the filing a lot and it was much easier than that.

    Laurel W - Reply

    I used a small Dremel bit to clean it out, very careful to just clean and not take too much material out. Much better fit!

    Paul alvarez - Reply

    (MK3S) Just don’t use hammers or whatever. The key is cleaning the hole (suggest adding that to the guide). I use one brush of my “gun cleaning tools” which is kinda like a narrower tooth brush for cleaning (use it for airsoft) which did the trick easily. From “this thing is so stuck how am i gonna do this” to “ah how did this suddenly get so easy” where i could just push the rods in by hand and little force.

    Bryan O'Neil - Reply

    Instead of banging them in use a DRY rubber glove to get better grip on the rod and twist it it place.

    James - Reply

    Prusa - absolutely no way would the rods go into the holes without risk of damaging something; also I couldn’t see any extraneous plastic blocking the holes. The rods are 8mm diameter so I looked for an 8mm drill … could only fine an 8mm flat-bladed wood drill and so used that; turned the drill bit by hand and slowly worked my way down each hole removing quite a bit of plastic. Only after reaming the holes in this manner would the rods finally fit … and still quite a tight fit at that! - Reply

    OK, got the X-end-idler in all the way then tried the x-end-motor but couldn’t get them in far at all. I came straight here to ensure I wasn’t doing anything wrong and after reading the other comments thought I’d better try rechecking the holes for any debris. Problem is I can’t get the rods out of the x-end-motor piece now! They just won’t budge. Tried using dry rubber gloves (thanks James) but not even a slight movement. So, do I try to tap the rods further into the x-end-motor piece with a rubber mallet or???

    Matt - Reply

    Update - Managed to twist them in using a plumbers wrench around a rubber glove… worked a dream with no damage… administered a gummie bear early to replenish energy :)

    Matt - Reply

    Hit it with your purse!

    Matthew Hall - Reply

    Let me share how I did it:

    Many have said, “use a hammer” but that risks bending the rods.

    Instead, I first inspected the holes. Then I put the X-idler on a rug on the floor and gently pushed one rod in from above using my body weight and at intervalls making sure that I didn’t over do it. Then, I took the second rod (with bearings of course) and did the same again.

    The x-tensioner has a hook and therefore can not lie on the floor like the x-idler can. So here, I inserted both rods into the x-tensioner and pushed on it with the x-idler still on the floor, using my weight. It worked well, I think. Just be careful and you’ll be fine.

    Miguel Barroso - Reply

    i found an easy way to get the rods all the way in , first slide the bearing all the way to the end a few times and the rod will get greased a little from the oil coming out for the bearing which should help the rod go in.

    Houssam Abi-issa - Reply

    I could not get mine seated without resorting to a rubber mallet. I couldn’t seat one side even with muscle alone. Unfortunately even with very small taps, both sides cracked.

    I re-printed them on another 3D printer and managed to get them in with the rubber mallet.

    vpkirk - Reply

    Whoa! Getting the rods in!.. After quite a struggle I took a 5/16” drill bit (which is 7.94mm) and discovered that the holes were even a snug fit for the undersized bit. I manually pushed the drill bit in and out of the holes several times (not using a drill) until the hole felt slightly less snug to the bit. I applied lithium lube spray onto the rods and used my air compressor to clean out any possible plastic debris in the hole and the rods were still a very snug fit but they made it to the end of the plastic parts without damaging anything.

    Ken.Lotts - Reply

    Yet one more way to get the rods in, without any impacts. I wrapped a light rope around the whole assembly a few times, end to end, then used a stick (any tool with a straight handle) to twist the rope. As I increased tension, the rods went in little by little

    Bruce Fleischer - Reply

    My ends were stuck on and neither side had bottomed out yet. In fact, I couldn't even see the rod through the view holes. I used my body weight and pushed down on them with one end resting on a hard surface. This method got one end bottomed out. The other end wouldn't budge at all, until I found out that I could rock it slightly from rod to rod. I rocked the part from side to side while putting heavy downward force and got the last piece to go in all the way! I was worried for a bit.

    Joel - Reply

    It definitely helps to open up the holes in the printed parts with a fine round file or similar. The printing process leaves small flats in the circular holes - remove those gently with the file so the hole looks circular, and my rods slid in without excessive force or any hammering.

    Tim Bergel - Reply

    I used a tiny rubber (less than 1in diameter) mallet for small machine work to tap the pieces in. two light taps in and the corner shattered. these parts have very little to no infill. I would recommend Prusa updates the instructions to not use a hammer, or to increase the infill percentage on these parts. Gotta order a new part now since I don’t have an operating 3d printer.

    Travis Marshall - Reply

    Can’t get the smooth rods in without using a hammer because i am worried of bending the rods. Please fix this design flaw. I tried getting my in by hand after filling the inside for a bit, but while trying to get it in afterwards, the rod got stuck and could no longer get it out nor further in.

    Troy Leishman - Reply

    Hey Troy, you can try using a rubber mallet if you’re unable to fully push rods in.

    Filip M - Official Prusa CS -

    My experience with this was similar to others who posted here. I approached it by putting both ends on to both rods simultaneously. I pushed to the point where neither side would budge. I didn’t want to try and force the parts further or take them off for fear of breaking them. They were stuck. What I did then was to get a rubber mallet (which others here have done) but I did one other thing that made a huge difference. I got a hairdryer and heated the plastic to make it more forgiving. I want to be very clear. I heated the plastic VERY GENTLY. That is why I used a hairdryer. I could easily control the amount of heat applied. You don’t want to warp (or worse, melt) the parts obviously. I barely had to warm them. Then I placed the assembly vertically on a hard, level surface (with cardboard on top for protection of the bottom part) and tapped extremely gently so there was no chance of breaking the plastic or bending the rods. This technique worked perfectly. The rods went in with ease.

    Frank Belme - Reply

    I came here after getting first rod stuck firmly about 1” into one of the pieces. I scanned everything here and came up with the following revised procedure. Credits to previous posters for sharing the ideas here:

    (1) Remove the stuck rod. I was able to clamp the rod in the wooden jaws of a woodworking vice and spin the block off easily. Plan B was going to be gripping the rod with pliers, close to the block so that any marring would end up being pressed inside the block.

    (2) Ream the holes with a 5/16” drill bit. Just undersized, as previously posted. Spin the bit by hand while rotating against the inside walls. Just enough to polish the walls a bit, the edges of the bit won’t really cut.

    (3) Chamfer the ends of the rods with a fine file, just enough so they would not dig in.

    (4) Lube the holes (not the bars). I used silicon grease b/c it’s not as messy as lithium grease.

    After this, the rods pressed in easily and seated firmly.

    Reed K - Reply

    Start rods on both parts, get them in as far as you can by hand. Keep one hand on each side, put between your legs (knee area) and squeeze progressively harder until the rods go home. As soon as I start to squeeze my legs, the rods went right to the ends. Your legs are much stronger at squeezing this way than your arms are.

    Erick Taschereau - Reply

    The motor-side printed part cracked in two places on inserting the rods, despite doing so very gently and with force of hand only (no tools, no pushing against the table etc).

    When the instructions say to be careful here, they are not kidding around.

    In my case the cracks are of a size and placement that they should not cause problems - and will hopefully last long enough to print a replacement - but that’s yet to be seen :)

    Paul Bransford - Reply

    A combination of comments by James and Houssam helped me manage this step without much fuss.

    1. Run the bearings all the way up and down their respective shafts, so that the shafts get a little grease on them from the bearings to help with insertion.

    2. Use a dry rubber glove to twist the rod (do this relatively closely to the orange piece to avoid bending/warping

    My orange piece was a tight fit, but certainly not so tight that I had to dremel any plastic out to re-fit the part. Still, Prusa would do well to adjust the blueprint for these parts so that the hole comes out slightly larger.

    Wesley Boynton - Reply

    For the second part of this step (X-end motor piece), twisting the rod is not so easily an option since it’s already in another piece at the other end of the rod, and the rod would not budge more than halfway in. To deal with this, I employed another strategy:

    1. Place the piece on top of the motor assembly cardboard box, with only the x-end IDLER hanging off the edge (the rod-accepting face of the idler should be flush with the box side, just beneath the rods)

    2. Scoot the box so that the X-end IDLER is against a wall

    3. Use a rubber mallet to gently tap the X-end MOTOR piece onto the rods, using the cardboard box to help ensure the rods do not bend or warp and using the wall as a backstop to help the mallet apply force

    (P.S. Prusa, it’s silly that we can’t edit our comments after five minutes. Make the timeframe 24 hours or something, so one can revise comments within an assembly day)

    Wesley Boynton - Reply

    I really struggled with this step and setting the rods in place completely. I found that after inserting the rods part of the way and then pressing one of the X-Axis ends into my shoulder and then pressing the other end with my palms worked quite well. Press it into your shoulder like you would a rifle/shotgun and press in with hands without twisting.

    Robert Bost - Reply

    Hello Robert,

    We always recommend checking all the holes in the printed parts for any flashes/extra printed material, sometimes they need a bit of cleaning before inserting screws/nuts, or rods for that matter here. In case of X-ends, the holes in these have lower tolerance, to ensure that rods will not get loose with extended use. As some users have suggested above, lightly tapping either X-end while laid flat on a table with a wooden/rubber mallet should work fine.

    Marcin M. - Official Prusa CS -

    Caused a hairline crack in the x-ender idler. Will this cause a problem in the future?

    Michael McKenzie - Reply

    Hello Michael,

    It depends how big of a crack it is and where. You can glue it together for now and see if you are able to pass the selftest and XYZ calibration after having finished your build. Then you can print a new part yourself.

    Marcin M. - Official Prusa CS -

    I found an easy way to put the rods in just install them first in the part without the motor housing, they do not have to be fully in. Add the top part where the motor will be placed. Now place with the first part on an flat surface an push on the part both rods will snap in to place …

    Lander Benoit - Reply

    Turned a 5/16 drill bit in by hand to clean out holes. Get yourself a tube of Super Lube (multi-purpose synthetic grease).

    Lube the end of rods and they snap right in without much force.

    Ken M. - Reply

    Guys, try to use work gloves with some rubber, like these - helped me to put the rods in place by hand, without hummers and drills.

    Alex - Reply

    Holey smokes! I deserve more than 10% of those Haribo’s for what I just went through!

    Bryan Price - Reply

    I found that adding a tiny bit of silicone spray lubricant (let it dry!) to the plastic parts before inserting the rods made it much easier to get the rods in. After the silicone, I could get them to push in with just my hands — no hammer or anything else that risks breaking the plastic or bending the rods.

    Adam Roach - Reply

    I smoothed the inner surface with a small round file, just removed the rough a little. After that the rods slipped in with very few force and fit precisely.

    Olaf - Reply

    This step almost determined that I would not be able to complete the assembly process. I am a small female, with damaged shoulders and minimal upper body strength. I do not have access to the various tools that other users have used to make the process work. The holes were too small to stick a stanley knife blade into, even if there were any noticeable printing artifacts. I had to get a friend to brace the parts against a piece of furniture and put his weight into it. If the part had broken as has happened with some users due to defective printing settings, I do not have the option to simply download and reprint a replacement. Would I have been expected to purchase a new part, or would Prusa have sent me a replacement as a courtesy?

    Lessian - Reply

    Hi Lessian, not all printed parts are equal, but we’re doing our best to control the quality of them all and to ensure they are identical.

    If something like that happened, then we would do our best to help you.

    Filip M - Official Prusa CS -

    Suggestion: If you are going to make a part that has such a high rate of being damaged during assembly, include a spare one in the kit. This will save time and stress for the users, save time for customer service having to deal with replacing parts, and save the reputation of the company.

    Lessian - Reply

    that was stupidly difficult. I had to use my body weight to push the rods in! You should include spares for this part

    Jack - Reply

    Does anyone have any advice on removing the orange end pieces off the rods. In other words - reversing this step? I have two small cracks on my X-Idler so I am having a friend print replacement pieces. I suspect the rods will be really hard to get out. I read advice on the forums to chuck them into a drill so I’ll try that but I still need to get one side off first. Has anyone removed them without breaking?

    I completely agree on having spares included. I spent an hour submitting the x-idler part to 6 different services and they are charging $50-95 to print it.

    David Vo - Reply

    Hi David, you could try pulling one side while holding the other (you might want to ask someone for help).

    If nothing works, then you can resort to a hammer - just be careful and don’t scratch the rods.

    Filip M - Official Prusa CS -

    I found that gently using a round file in the holes plus lubricating with silicone spray made the job very easy. Only a light tap was needed

    David Edley - Reply

    Used an 8mm drill to manually ream out the holes in the printed parts .my parts are black not orange, not sure if that makes a difference. Had to run the drill in an out about 5 or 6 times. Then used latex gloves to get a better grip on the rods. Was ok after that, but I’m glad I stopped last night and had a break, to think about why they wouldn’t go in. Agree that the instructions need improving here and some spares maybe just in case.

    myPinballs Electronics - Reply

    This worked without issues:

    (1) Rods into the printed parts … as far you can go just by hand.

    (2) Using 2 jar openers I got for free (others are using a rubber glove), place X-end-idler on a flat surface. I just used my carpeted floor. If you have hardwood floors, careful! The plastic printed parts can slip right out from under you.

    (3) Hold both rods with the X-end idler flat and just use you weight to gently force them into place.

    (4) The x-end motor piece isn’t flat, but that’s okay. With the x-end still flat on the floor, wrap your hand around the x-end motor piece to ensure even pressure when you gently push down with your body weight. It will slide into place.


    2x Rubber jar openers


    Always apply even pressure

    Ron - Reply

    No problems getting the rods in . I first located rods in holes then put the flat end on the table and leaned on the top part , woooof down they went.

    Alex - Reply

    I used a 1x2 piece of hardwood and a deadblow hammer. Carefully went back and forth on one end, then the other. Could not do it with twisting, pushing, or bodyweight. Got it in the end without a problem, though, and it’s not going anywhere…

    Paul Meyer - Reply

  8. For the following steps, please prepare: X-axis motor (1x)
    • For the following steps, please prepare:

    • X-axis motor (1x)

    • GT2-16 pulley (1x)

    • 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.

    I got to this point and discovered I didn’t have an x-axis stepper motor but two y-axis motors instead. I have emailed CS (using the online form in the eshop) asking for an x-axis stepper motor.

    Roy Brown - Reply

    Hello Roy!

    We’re sorry for that, thanks for contacting us!

    Martin L. - Official Prusa CS -

    I’ve yet to receive a response though.

    Roy Brown - Reply

    Hi Roy, replies can be slower during the weekend. I also noticed your case was already solved :)

    Filip M - Official Prusa CS -

    Hi, Yes, I contacted CS via Live Chat yesterday evening and Marina kindly resolved the issue of the wrong stepper motor. The correct one is winging its way to me as I type.

    Thank you all for the excellent support although I didn’t realise they gave you guys the weekend off :))

    Roy Brown -

    This should be re-photographed showing the pulley with the setscrew end on the top (correct orientation relative to the motor). The warning in step 9 about checking the pulley orientation is good, but this picture is misleading. I somehow missed the warning and the second picture of step 9 and did not realize I had put in on backwards until Chapter 5, Step 49.

    Alexander McCaskill - Reply

  9. There is a flat part on the motor shaft, rotate it upwards. Slide the Pulley on, note the CORRECT orientation. Compare it with the second picture!
    • There is a flat part on the motor shaft, rotate it upwards.

    • Slide the Pulley on, note the CORRECT orientation. Compare it with the second picture!

    • One of the screws must be facing directly against the pad (flat part) on the shaft. Slightly tighten both screws.

    • Don't press the pulley against the motor. Leave a gap so the pulley can rotate freely.

    • Don't tighten the pulley firmly yet, we'll get to that later.

    One of the screws must be facing directly against the pad (flat part) on the shaft. Slightly tighten both screws…Don't tighten the pulley firmly yet, we'll get to that later.

    Here it says to only tighten slightly. It also says we will come back to this. Does the manual ever come back to this to fully tighten it? I completed the build (it works great now!) built my prints kept failing over and over. It passed all the calibrations. On first layer leveling, it kept printing the rectangle with shifted layers. The problem was the screw was not tight enough. Maybe I missed it later in the manual, but this screw should be tightened completely against the flat portion, or during faster speeds will slip and cause all kinds of issues. If anyone else has issues like this, its easy to fix even while fully assembled. Simple loosen the screws around the pad of the shaft. Hold the shaft with pliers and rotate it into position. Lock them up tight. This was my only issue with the whole build. It now prints perfect.

    Ian Hickey - Reply

    Update: Step 51 Aligning the X-axis belt of the E-axis chapter has you tighten these. I did miss it.

    Ian Hickey -

    Thanks for coming back to update this comment :)

    Wesley Boynton -

    it would also be helpful here to minimize confusion and state that the pulley has “grub” screws that may not be evident at first, at least to the uninitiated.

    Alan Ostroff - Reply

    Hello Alan,

    Check the photos closely, the orange arrows are pointing at it. :)

    Martin L. - Official Prusa CS -

  10. Prepare M3x18 screws (3x) Prepare the motor for X-axis with an assembled pulley.
    • Prepare M3x18 screws (3x)

    • Prepare the motor for X-axis with an assembled pulley.

    • Place the X-axis on the motor as shown in the picture.

    • Insert the M3x18 screws and tighten them.

    2 of my holes are wider and more elliptical than round … so it’s a bit free. What should I do?

    Itamar - Reply

    Simply tighten the screws. It doesn’t matter at this point if they are more to the left or right.

    Filip M - Official Prusa CS -

    In Step 4 and 5 it is written they require 1- M3x18 screw in each. Step 10 requires 3-M3x18 for a total of 5-M3x18 screws. My #3. X-Axis hardware bag only has 4-M3x18 and on the label is illustrated with having only 4. I have not seen anyone call out a typo error so I must be doing something wrong. Please help! Thanks.

    Daniel Bilotta - Reply

    Hey Daniel, remember about spares bag - you can always use it if certain screw is missing.

    Filip M - Official Prusa CS -

    I got to this step and took a moment to study how well everything looked. As I was inspecting, I noticed that one of the linear bearings wouldn’t slide back and forth as smooth as the others. It snagged very slightly as I slid it back and forth. I carefully pulled the assembly apart to inspect the bearing (which visually looked fine) and this video is to show you the overall roughness.. I know that these linear bearings were not designed to rotate on the rod but I found it interesting that the snaggy one would not rotate at all without great force. The other two linear bearings rotated freely.

    Ken.Lotts - Reply

    Hey Ken, it shouldn’t behave like that. Please contact our tech support, we’ll arrange new bearings for you.

    You can either send an email ( or use LiveChat ( Make sure to include that video.

    Filip M - Official Prusa CS -

    If assembling as shown (motor shaft facing upwards) it’s easy to get the motor aligned with the holes on the orange motor holder, but the other end of the metal rods would be floating freely. If turning the motor on its side to avoid gravity pulling on (and potentially warping) the rods and screws, however, it’s difficult to align the holes.

    I may be over-complicating it, but just to be safe, I pulled out the extruder motor and sat it beneath the other end of the metal rods, so that the whole axis assembly was level as I was screwing the X-axis motor on.

    Wesley Boynton - Reply

  11. This is an easy easy chapter, have a 10% dose of bears ;)
    • This is an easy easy chapter, have a 10% dose of bears ;)

    You didn't supply enough transparent bears so I substituted with an orange one. Will I be OK or is my blood sugar now an incompatible hue?

    Mark Wheadon - Reply

    You probably will need to head to your nearest gummy bear dealer to get some more.

    Spencer Brown -

    X-D Soooooo Gooooood!!!! Soooooo Fun!!!!!

    Justin Valois - Reply

    I think I cheated…

    Ed Sinigur - Reply

    I'm glad there were extras in the bag. Inserting those x acid rods were more than 10%.

    Daniel Friesen - Reply

    My niece was watching and I had to give her candy

    Esdras Alvarez - Reply

  12. X-axis is done!
    • X-axis is done!

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

    • Checked everything? It's time for: 4. Z-axis assembly

Finish Line

816 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

217 Guides authored


Prusa Research Member of Prusa Research


3 Members

359 Guides authored


thanks guys!

Richard Perkins - Reply

Inserting the rods in the printed parts was a pain. I had to use a ratchet to push them all the way in.

Razvan Simionescu - Reply

Had similar issues with the rods….. managed to get them in cocking the axis like a shotgun (index on the longer part and palm on the flat part)

Be fairly strong, but gentle!

Ismael Abufon -

I put the rods in the freezer for about 2 hours. Took them out and they slid in with minimal effort. A few light taps with a rubber hammer put them in place.

Bryan W - Reply

Genius! I just pushed, hard. It worked.

Shane B -

Got em started straight by hand, then bar clamp worked fine. Rods advance by little jumps.

Miles Odonnol - Reply

use a plastic mallet and gently tap with the faces carefully flat on another flat surface, very easy.

tonygray - Reply

It would be pretty helpful if you linked to the next chapter of the manual at the end of the previous one!

Mila Santana - Reply

See the last bullet point of step 12 ;) To move back, you can use the “back” button of your browser.

Martin L. - Official Prusa CS -

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