1. 13/17mm spanners
    • 13/17mm spanners

    • 3.6mm flathead screwdriver

    • Needle-nose pliers

    • 2.5 and 1.5mm Allen key

    Save your fingers and a lot of frustration and have some other tools on hand if at all possible. Although the ball end allen key is very useful for getting in at awkward angles a 2.5 hexagonal driver is so nice for this build. Digital calipers/Small Engineers square/Wire cutters for cable ties/Small steel rule/Pair of tweezers for picking up small parts like washers etc. Torch for seeing into holes to line up components and clean out foreign objects/small hammer to seat difficult nuts/small round files/sandpaper. Possibly a 3mm tap to clean out holes on frame but I found I did not need it in the end/Socket for the bed nuts, I scratched the y bed holder putting the bearings in with the pliers. Have fun, its a great kit.

    Jonathan Wise - Reply

    Hi Jonathan, thank you for the list of additional tools. We are trying to include only the necessary tools for you to build the printer. However, you can for sure use other tools to help you with the assembly.

    Jakub Dolezal -

  2. Y-corners
    • Y-corners

    • Y-belt-holder

    • Y-motor

    • Y-idler

    • PSU-Y-part

    • Y-motor-distance

    • 3D printed parts can slightly differ from pictures. It won't affect the printer's assembly.

    Before anything else, it is advisable to complete steps 17 & 18

    Ilya - Reply

    Hi Ilya, thanks for the feedback. We tried both ways several times and decided to first place Y-idler on threaded rods. It is, for example, easier for tightening.

    Jakub Dolezal -

    Maybe I''m nitpicking but the 2nd and 3rd items on this list are listed on the parts bag in the opposite order (motor before belt), also on the bag it appears as "Y-Motor", not "Y-motor-holder" as here.

    Udi Finkelstein - Reply

    Hi Udi, thanks for noticing. I will correct the manual.

    Jakub Dolezal -

    Now might be a good place to introduce the M10 treaded rods, because you introduce the tools and the 3D parts - but in Step 3, you suddenly have rods out of nowhere.

    Barnaby - Reply

    Hi Barnaby, thanks for the feedback. Noted for future improvements :)

    Jakub Dolezal -

    Hopefully you will make a sturdier y-motor mount part with increased thickness where the part mounts on the rods and an additional third hole at bottom for attaching the y-motor, as this thin part has many forces acting on it (screws, tension from belt, and four bolts and washers and need to be aligned to span two rods). Mine broke due to all these forces. Looking up this issue online, many others have had this part fail, and there are modified versions available, but improving the one that comes with the official Prusa printer would be best. Thanks.

    Eri - Reply

    Hi Eri, all printed parts on the printer are getting constant updates. I'm sure our developers will have a look on it.

    Jakub Dolezal -

    • Use M10n nuts (14 pcs) , M10w washers (12 pcs) and M10 threaded rods (2 pcs).

    • Screw the nuts on and place washers, Y-corners and PSU-Y-part on the threaded rod as shown in the picture.

    • Ensure initial 100mm (3.937inches) distance between a washer after counter-nut and the Y-axis corner. Use the photo as a reference.

    • The 2 nuts have to be tightened against each other (counter-nut).

    • Note that there is no gap between parts, they have to fit together.

    • For the initial position of Y-corners, you can temporarily mount the rods (see step 10, 11).

    This comment is from the previous version i wrote, but it applies also to the MK2s. That is normally the comment for Part 7 Step19 but i think it is good to know now.

    !!! The 100 mm are a good start. But i spend lot of time to get the 100mm between the printed parts and the Z-frame, and still got 'severely skewed'...Final solution was to use a 90° square/corner tool on the 155 line (any line) on one side of the heated bed and gently push the y-axis against the x-axis rods, and then without touching the y-axis place the 90° corner tool on the other side of the heated bed against the x-axis rods and eyeball/measure the difference/distance. In my case i had to adjust it to 101.80mm and 100.10mm to get the 'congratulations, you are a master MK2 kit builder' :-) i mean perpendicular.

    Conclusion: Try to get the 100mm distance BUT check the heated bed lines up in 90° angle with the x-axis, even if you get different distances (1-2cm not more, then something else can be wrong)

    Waldemar - Reply

    Hi Waldemar, thanks for the feedback. At this step it is important to ensure initial 100mm distance, the exact position will be achieved later in another chapter.

    Jakub Dolezal -

    I agree with other tips - I found it very helpful to temporarily install the appropriate 8mm rods to help locate the y corners during assembly.

    Keith Ottlinger - Reply

    Hi Keith, glad to hear the tips helped you ;)

    Jakub Dolezal -

    Go ahead an get the M3 nuts out of the PSU hardware bag and tap them into the nut traps of the PSU Y-part now. This will save you some trouble later on when you go to install the PSU. It keeps you from having to worry about messing up the frame you spent so much time getting perfect. You will see what I mean when you get to that section.

    Paul Betz - Reply

    Hi Paul, the nuts for PSU might fall out during the next steps. That is why the nut insertion is done, just before connecting the PSU to the printer.

    Jakub Dolezal -

    Thanks Paul. I read the comments on that step (Section 7 PSU - step 5 7. PSU & Heatbed assembly ) and thought I would try to fit the nuts in the holes prior to assemble it. The holes were too small, I had to trim them with a very small chisel. There is no way I would have managed to do this in section 7. The nuts fit so tightly now, there is no way they are going to fall off. I added the washer and the M3 screw just to be sure.

    Gael Lafond -

    To speed up threading the nuts in the middle I just put the rod in a cordless drill while I held the nuts, and it worked great! Good fun too.

    Barnaby - Reply

    Hi Barnaby, thanks for the tip. You can use other tools besides those included in the kit, just be careful ;)

    Jakub Dolezal -

    I used digital calipers to set the spacing to +/- 0.1mm to 100mm & ended up with a calibration error (could not fully read front calibration points). Changing the spacing closer to 101mm (a real challenge after the build is complete) resolved the calibration error.

    Stuart - Reply

    Hi Stuart, thanks for the feedback.

    Jakub Dolezal -

    M10 350mm threaded rod had 10mm of its threads dinged. Dressed up with file.

    Merrill Albury - Reply

    all videos prior to steps and then again as a post assemble check after steps completed. Caught so errors or things I missed the first time.

    Merrill Albury - Reply

    Had to dress up, with diamond file, "Y" motor part and "Y" Idler so rods could slip through holes.

    Merrill Albury - Reply

    Made a drawing of what measurements said final "Y" axis assembly should look like and then placed assembly on the drawing as I built. Helped ensuring only minor adjustments later.

    Merrill Albury - Reply

    Made a 100 mm cutout and used it to check spacing of M10 nuts and washers on 350 mm threaded rods as required.

    Merrill Albury - Reply

    1. It is not clear from the description what should be the position of the end screw and nuts against the rods ends. e.g. should they be located flash (aligned) with the end of the threaded rods?

    2. What are the tolerances for the 100mm?

    3. The 100 mm distance is relevant for both rods?

    Shachar Rotem - Reply

    Hi Shachar,

    1) Use smooth rods to set the proper distance (see step 10 & 11), then you can tighten the nuts.

    2) This is crucial part of the assembly, so please try to achieve 100mm distance with minimal tolerances (+/- 0.2 mm)

    3) Yes, the distance is given for both rods, ensure it is the same, or your printer will warp.

    Jakub Dolezal -

    If you don't have any yet, go ahead and get yourself a pair of digital calipers for this chapter's build. Six inch calipers will do for all but the measurement from the outside of one smooth rod to the other.

    I found myself constantly checking and rechecking my measurements. Calipers will help in a big way.

    Tony Williaims - Reply

    Do NOT tighten down the nuts at this stage. You will do that in steps 8-12. Everything should remain loose fitting for now.

    Brendon Mikula - Reply

    Do NOT tighten down the nuts at this point. You will do that in steps 8-12. Everything should remain loose fitting for now.

    Brendon Mikula - Reply

    The 100mm distance seems off later in the instructions when mounting the PSU (by about a quarter inch) because the PSU-Y-part has holes in the wrong place. It seems the PSU is 100mm wide including the printed plastic cover, which should be designed to line up with the inside edge of the Y-corner. Instead, the metal part of the PSU which is about a quarter inch smaller lines up with that measurement and so everything has to be readjusted after mounting the PSU. That is too bad because I was so careful to make the Y axis perfectly level and square as strongly warned to do but then adjusting it when adding the PSU as instructed there caused it to be completely out of kilter. Then it will have to be adjusted again on the other end to make it square. All this could be avoided by modifying one part and the instructions could remain the same but actually work. (This is the worst problem yet in the design or instructions - almost done but needed updated instructions for a mod that didn’t match the printed manual.)

    Dr. Ted - Reply

    • Use M8n nuts (8 pcs), M8w washers (8 pcs) and M8 threaded rods (2 pcs).

    • Screw the nuts and place washers and Y-motor part on threaded rod as shown in the picture.

    • Y-motor part should be somewhere in the middle of the threaded rod. The precise position doesn't matter at this time.

    • Ensure the correct orientation of the Y-motor part.

    • 3D printed parts can slightly differ from pictures. It won't affect the assembly.

    the photo is from the MK2 and not the MK2s, the printed part is a little bit different.

    Laurent DELPRAT - Reply

    Hi Laurent, thanks for noticing. Motor holder is a bit different, but it won't affect the assembly. I've added a note to this step.

    Jakub Dolezal -

    Motor mount will not end up being in the "center" of the threaded rod. My final position was 64.42mm between the motor side of the mount and the y corner.

    Keith Ottlinger - Reply

    Hi Keith, thanks for sharing your value, we will improve this manual with recommended distances.

    Jakub Dolezal -

    I don't think there is a "correct orientation" for this step - the rods, nuts, and bolts are symmetrical.

    Christopher Bonner - Reply

    Hi Christopher, yes you're right. Point is to show the correct position/orientation of this part of the Y-axis.

    Jakub Dolezal -

    It would be useful to add that the end nuts should be about 30mm onto the rod, much further than the picture suggests to save having to go back at the assembly stage.

    Matt Lemon - Reply

    Hi Matt, thanks for the feedback.

    Jakub Dolezal -

    Cracked the motor mount when working with the wrenches. Can't glue it. CA doesn't work. You may consider a warning. The wrech can easily hit the mount. Was lucky that it didn't break entirely, just cracked, so I reinforced it with two long M2 screws. Seems to work for now.

    Alexander Buschek - Reply

    It's important that the Y motor mount can move on the rods, so file a little bit if it can't. This is important when aligning later on.

    Doc Wilco - Reply

    Also, as per a comment later on, the v notch should probably be at roughly the center of the rod.

    Doc Wilco - Reply

    • Use M8n nuts (6 pcs), M8w washers (6 pcs) and M8 threaded rods (2 pcs).

    • Screw the nuts and place washers and Y-idler on threaded rod as shown in the picture.

    • The Y-idler should be somewhere in the middle of the threaded rod. The precise position doesn't matter at this time.

    It would be useful to add that the end nuts should be about 30mm onto the rod, much further than the picture suggests to save having to go back at the assembly stage.

    Matt Lemon - Reply

    Hi Matt, thanks for the feedback. I will try to update the manual later on.

    Jakub Dolezal -

    • Use M8n nuts (8 pcs) and M8w washers (8 pcs).

    • Y-axis stage front

    • Y-axis stage back

    • Insert Y-axis stage front and back into Y-axis side elements and lock it with washers and nuts like in the picture.

    • Ensure the correct placement. The Y-axis rear stage has to be closer to the double-nuts!

    • !!! Given dimensions are recommended, not absolute. Use them as a guidance for your assembly. Your final values can slightly differ.

    I think it would be good at this stage to suggest an actual dimension to locate the y-axis back and front. If you are not close, you will be removing the y axis motor in a later step to make the adjustments. I'll measure mine and post result.

    Keith Ottlinger - Reply

    Hi Keith, thank you for the feedback. We will measure several assembled printers and adjust this step.

    Jakub Dolezal -

    Still waiting for measurements Jakub...

    Wol Bar - Reply

    Hi Wol Bar, sorry for the delay. Picture updated with measured values.

    Jakub Dolezal -

    At this point I was unsure which if any nuts needed tightening. A good statement would be that everything needs to be finger-tight because the assembly will be aligned and tightened in later steps.

    Lane Hauck - Reply

    Hi, Lane,

    When the assembly of the stage is finished tighten the nuts. However, don't tighten them too firmly, as you might need to adjust them later to fit other parts of the printer.

    Jakub Dolezal -

    At this stage, you might want to peek at 7. PSU & Heatbed assembly

    At this stage many people have problems inserting the nut into the PSU holder (The L-shaped black piece).

    This can be done easily by screwing in an M3x18 or M3x25 with the nut in the other side unti the nut locks firmly deep inside this part, and then remove the screw. The nut will not fall off, and this will save you the troubles later.

    Udi Finkelstein - Reply

    Hi Udi, thanks for the suggestion. We are working on adjustments, in general, I suggest to stick with the manual.

    Jakub Dolezal -

    Just a note to add that you have access to another printer, this 3D printed helper tool helped enormously with this step. https://www.thingiverse.com/thing:184665.... The print bed on my Monoprice Mini was to small but someone remixed it so I could still use it: https://www.thingiverse.com/thing:199530...

    Super useful.

    Also thanks to Keith, Won, and Jakob for the dimensions. Great idea and also very useful.

    Gabe Dover - Reply

    Hi, Gabe, in case you have another calibrated printer, this might be useful ;)

    Jakub Dolezal -

    It would be useful to specify if the parts are being assembled "loosely" (to be fitted and tightened in a later step) or if this step requires "tightening" also (whether in this step or another). I tightened everything down in step 6 only to find step 9 has the tightening video. Now I'm finding I'm having to read ahead a few steps to see if I will get the change come back tighten from this step or if this step is final and everything can be appropriately tightened and I can move on.

    Paul Matthews - Reply

    Hi Paul, thanks for the feedback, I will add this information.

    Jakub Dolezal -

    While being approximate dimensions which you will later deviate slightly from, adhering to them for now will save you time adjusting the motor and idler mount later.

    Anton Eliasson - Reply

    Would be great if there was either a mention of step 43, or at least a more significant warning that the right side should be closer to the PSU holder. I used the “Given dimensions are recommended, not absolute. Use them as a guidance for your assembly. Your final values can slightly differ “ too literally and later had to disassemble a lot to move the Y-motor, because mine would only move by screwing the rod.

    Jakub Arnold - Reply

    • Prusa i3 frame

    • Y-axis stage

    Add Comment

    • Insert the Y-axis stage into the frame as close to Y-corners as possible.

    • Adjust and tighten the M8n nuts.

    • Rotate the Y-axis stage and repeat.

    • After adjusting, the Y-axis stage should cause minimum movement while inserted into the frame.

    • Tighten the M8n nuts gently or you'll risk damaging the 3D printed parts.

    • It is incredibly important that the axis is perfectly rectangular at this stage of construction, all rods need to be perfectly straight and level. If not, you'll have troubles calibrating later on!

    • The aluminium frame is used just to set the proper dimension, do not mount it to the Y-axis, we will do that later.

    Recommended M8n nut torque values?

    Corner-to-corner measurement of 'perfectly rectangular axis'?

    John Sloop - Reply

    Hi, John, for now, there are no recommended torque values nor distances, but I'm working on it ;)

    Jakub Dolezal -

    Which are the correct measurements to have?

    I have 152.0 mm on both inner short sides

    I have 292 mm on both inner long sides

    I have 376 mm on one diagonal and 374.5 mm on the other i.e. a rombus

    So I squeezed the long diagonal a bit by hand and got both to be approximately 375.2 mm

    Claus - Reply

    Hi, Claus, for now, there are no official measurements. I will let you guys know as soon as we have something.

    Jakub Dolezal -

    Shouldn't the note about being perfectly rectangular be in step 11, rather than here? I spent a good deal of time working to get the frame perfectly aligned, then had to rework the alignment in step 11.

    Ann Boes - Reply

    Hi Ann, as you are tightening the corners at this step, it is more convenient to check the rectangular shape now. Step 11 is all about setting proper distance for Z axis assembly.

    Jakub Dolezal -

    My M10 threaded rods are so thick so they cannot be inserted in the holes of the frame.

    Kang Sin Choi - Reply

    Hi, Kang, can you please send photos to info@prusa3d.com?

    Jakub Dolezal -

    Somebody needs to tell the guy in the video to tighten the M8n nuts "gently" ;-)

    Lane Hauck - Reply

    Hi, Lane, the "guy" on the video is our most experienced assembler. He knows ;)

    Jakub Dolezal -

    Thanks to others for tips on measuring both diagonals to ensure square. I found that the medium length smooth rods happen (at least in my case) to be exactly the right length to measure the two diagonals between the inner corners of the 3D printed parts. As noted in another comment, I'm using the square brace from Thingiverse which helped enormously. I seem to be square, fingers crossed. Onward!

    Gabe Dover - Reply

    Hi Gabe, looking forward to seeing your prints! :)

    Jakub Dolezal -

    This threw me off this at first so I thought it should be pointed out (probably obvious to everyone else, lol), but the Y-axis stage is not being mounted at this point. You are just using the Z frame to get the proper with measurement for both ends of the Y-axis stage, hence the reason it is revers between the 2 picutres.

    Jeremy Martin - Reply

    Hi Jeremy, good point, I will make a note in the manual. Thanks ;)

    Jakub Dolezal -

    I disagree that this is the time to tighten the nuts on the shorter sides. You can get an estimate of the width of the Y-axis stage by placing it in the aluminium frame, but the precise width does not matter at this point. Not until step 12 (not shown in step 11) do you know the correct width, which is measured between the smooth rods and not between the plastic corners. So I would argue that you should still only finger-tighten the nuts at this point. If I built a second printer I also wouldn't worry too much about the feet being level here. I think you should make them roughly level at step 12 and precisely level at step 41.

    Anton Eliasson - Reply

    In case you’re reading the comments before you do the step. There is a video of this in the next step. There are more videos in this chapter, but they are always after the step involved. So save yourself some time now and look for “video” in this chapter.

    Olafur Egilsson - Reply

    • Insert the Y-axis stage into the frame as close to Y-corners as possible. Adjust and tighten the M8n nuts. Rotate the Y-axis stage and repeat.

    • Make sure Y-corners are vertical. If not, insert the spanners between the M8 threaded rods. Use any fabric to protect them from scratching. Push the spanners to straighten the corners.

    • Video is available in an online (digital) version only.

    Somehow both in the video as well as the pictures there is some metal part showing in the y-idler. Not described until step 17. Had me confused for a while :-)

    Gert - Reply

    There are more videos in this chapter (3 at the time of writing), but they are always after the step, so save yourself some time now and look for the word “video” on this page so you can watch them before you do the step.

    Olafur Egilsson - Reply

    • In the following steps, use the mid-sized smooth rods (330 mm).

    • Don't throw away included plastic spiral wraps, you will need them later for cable management.

    I ran out of Haribo.

    Is this expected? Maybe I was eating them too fast?

    Barnaby - Reply

    That is too fast Barnaby, I will think about splitting an exact portion of Gummy Bears for each chapter :D

    Jakub Dolezal -

    My two medium length smooth rods are 2mm different in length. I’m hoping this won’t be a problem as long as the y axis remains a rectangle.

    David Perry - Reply

    • Insert the two medium length 8mm smooth rods into the Y-axis stage. Rods length is 330 mm.

    • Adjust and tighten the M10n nuts.

    • After tightening the nuts, there shouldn't be any gap between 8mm rods and Y-axis corners.

    • Retain 100mm distance between a washer after counter-nut and the Y-axis corner.

    • Remove the 8mm rods.

    In step 25, we're told to insert the 330 mm rods into the bearings on the Y axis carriage. I was give 2- 320 mm rods, 2 - 330 mm rods, and 2 -370 mm rods. Which length is supposed to be inserted here seeing as the 330 mm rods are supposed to be used later, but also qualify as the medium length rods?

    David Miller - Reply

    Hi, David, the length of the rod for this step is 330 mm as described at previous step 10.

    Jakub Dolezal -

    What will become clearer in later stage is why these 100mm are critical: after mounting the frame holding the X and Z axes, the PSU needs to be mounted next to it, and its two horizontal mounting holes should match the two holes in the PSU Y-part (The L-shaped piece on the upper left).

    It might be a good point after measuring and securing the bolts, to temporarily put the X/Z frame in its intended position, and hold the PSU next to it just to make sure that the PSU horizontal mounting holes match those on the PSU Y-part.

    I found out the hard way, when I needed to mount my PSU, that the holes were 1-2mm off, and so I had to separate my Y-axis from the X/Z frame, move the bolts holding the X/Z frame and recalibrate it again.

    Udi Finkelstein - Reply

    Hi Udi, thanks for the feedback. Following the manual is crucial for successful assembly.

    Jakub Dolezal -

    I initially misunderstood this text:

    Retain 100mm distance between a washer after counter-nut and the Y-axis corner.

    So I had measured measured 100mm from the Y-Axis corner to the end of the second counter nut, but that will not allow the PSU to connect, luckily I dry fitted it at this stage.

    You need 100mm from the Y-Axis corner to the end of the first washer after the two counter nuts, or in other words 100mm from the Y-Axis Corner to the X/Z Frame.

    Karsten Green - Reply

    Hi, Karsten, did you use the pictures? The first picture for this step includes a dimension for you to see between which objects is the distance measured.

    Jakub Dolezal -

    I would recommend 101mm. With 100mm exact the printer will most likely generate an error that it is not able to reach the front calibration spots even with the belt connector moved al the way to the front of the Y carriage.. Also the the power supply case could have some lengthier holes to allow for a bit of customisation and an easier fit that wont put any stress on the frame.

    ChrisPetit - Reply

    Chris is correct, I spent ages getting 100.0x. When the printer is built, this measurement actually only affects the power supply. In reality, it needs to be a little more than 101 because otherwise the probe can't reach over the front dots. The other important thing is pay careful attention to the part where you look down the X-axis rods to the lines in the bed to get it perpendicular, this then involves adjusting the left (from front) M12 near the RAMBO side because the power supply fixes the other side. I got compromised front left even though I thought that I had this perfect. I was also concerned that one side sat higher. In the end trying to solve the calibration and reading this Calibration Compromised, cannot reach front points.. I find myself completely changing this as I have described above. Better to get it built without perfecting this.

    John -

    I noticed my two 330mm rods are not the same length. They are about 1mm apart. I assume it is more important to have the assembly square than making sure one of the rods don't have extra space. So I ended up adjusting the width with respect to the longer rod. Anyone have experience with uneven rod lengths?

    Taroko - Reply

    Hi Taroko, yes it is crucial to have the frame square. I'm sorry for the issues with uneven length.

    Jakub Dolezal -

    Make sure the rods are not too tight otherwise you make break a Y-corner later on in Step 26.

    Kevin - Reply

    • Insert the two medium length 8mm smooth rods into the Y-axis stage. Adjust and tighten the M10n nuts. After tightening the nuts, there shouldn't be any gap between 8mm rods and Y-axis corners. Retain 100mm distance between a washer after counter-nut and the Y-axis corner. Remove the 8mm rods.

    • Video is available in an online (digital) version only.

    If the distance between the "washer after counter-nut and the Y axis corner" is not 100mm, will that cause problems at calibration time?

    john vanhoozer - Reply

    Hi John, it is strongly recommended to follow this guide step by step including provided values, namely to have exactly 100 mm, however, +/- 2 mm should be still ok, anything larger can cause issues during calibration.

    Jakub Dolezal -

    I would class this part as hard not moderate, it was difficult to get square and level. Its also quite easy to over tighten the nuts and crack the corner pieces if your not careful.

    Jonathan Wise - Reply

    Hi Jonathan, thank you for your input. We will think about it. You are right this chapter is slightly more difficult than the others in this manual.

    Jakub Dolezal -

    I found it easier to square the Y-axis stage post-assembly because the weight of the printer results in an 'auto alignment' once you loosen the large nuts. I used a flat glass plate to sit the printer on to ensure it was as level as possible.

    TCC - Reply

    Hi TCC, thanks, I will discuss your suggestion with our development team.

    Jakub Dolezal -

    Just a note as someone who read the whole assembly twice before buying "toys", then apparently didn't buy a big enough caliper...

    If you only have a 6" (~156mm) digital caliper and not a 8" one, you can't measure the rod to rod outside distance of 178mm...

    BUT if you slide 2 of the bearings on the 8mm shafts (they're 15mm) the bearing to bearing inside distance will be 155mm...

    That's something your calipers can handle (just)...

    178mmOD-(2x8mmOD/2)=170mm c.t.c (oc); 170mmOC-(2x15mmOD/2)=155mmID)

    Garrett Sloan - Reply

    Hi Garrett, thanks for the tip :)

    Jakub Dolezal -

    Great suggestion Garrett. Thank you. Unfortunately, my 6-inch Mitutoyo caliper maxes out at 153.59mm. When I'm ready to assemble I will have to borrow an 8-inch from work.

    Tyrone McCloud -

    If the caliper is even smaller (~154mm) one can measure between two printed parts which is 152mm for me.

    kazem -

    Being a machinist and perfectionist, I think rather than using all thread, these rods should be machined to exact length with shoulders on them, then threaded so that you can simply put everything together and just tighten the nuts down. There would be absolutely no guessing or squaring to get it perfect.

    Randy H - Reply

    Hi Randy, thank you for the feedback. We are constantly working on improvements and we will definitely try to improve this for future.

    Jakub Dolezal -

    Garrett, great suggestion, thanks. Saved me a trip to Harbor Freight.

    Lane Hauck - Reply

    Hi, Lane, thanks for the comment.

    Jakub Dolezal -

    There seem to be something wrong with the rod to rod outside distance of 178mm, in my printer (delivered last week) making y-axis like this results in 180.6mm as outside dimension between M10 threaded rods which makes them not fit into the printer frame which has 179.5mm as a max fittable outside dimension between M10 threaded rods . Am I missing something ?

    Rafal W - Reply

    Hi, Rafal, did you manage to assemble the printer? If not please contact our support at info@prusa3d.com.

    Jakub Dolezal -

    Upgrade TIP: way not to perforate two semi holes on the frame edge to use as a temporary measurement tool (178mm)

    julio - Reply

    Hi, Julio, thanks for sharing your tip. You shouldn't definitely perforate anything :)

    Jakub Dolezal -

    I mean from factory design

    julio - Reply

    Regarding the rod to rod outside distance of 178mm, as mentioned by Rafal, that width seems to hose up the setting in the previous step where you insert the y-axis stage in the frame and tighten accordingly. the 178mm is wider than the frame allows. please explain what I'm missing.

    Gary Bly - Reply

    Hi Gary, regarding dimensions please follow the manual. Set shorter sides of Y-axis as in step 6, for the longer sides use step 11.

    Jakub Dolezal -

    The second half of this video contains crucial information that is not covered in step 11. Following Garret's tip I slid the three bearings onto the smooth rods here and was able to measure the inside distance with my ~155 mm callipers. I used another trick to make sure that the bearings would fit the rods when they were mounted on the Y-carriage:

    Place the Y-carriage loosely on top of the bearings at this point. The bearings should lay flat in their slots on the Y-carriage. If there is a gap in any of the slots, the distance between the rods must be adjusted. Try both end positions. This will ensure that the Y-carriage rides smoothly on the rods when later mounted. In my testing, this requires a precision of around +/- 0,1 mm. An error of +/- 0,2 mm away from the correct 155 mm or 178 mm I think would be too far off.

    Only when this is done I think is the right time to tighten the nuts on the short sides of the Y-axis assembly.

    Anton Eliasson - Reply

    Measuring the distance with calipers actually makes sense. But then, the manual should mention them as a recommended tool. Bought one to complete this step as mine were too small.

    Tux Prints - Reply

    The video makes calipers seem very necessary. Probably should be included as part of the tools or at least a not included, but highly recommended bullet point included under the tool section.

    Seth H Ellsworth - Reply

    I didnt know where to put this but it may save someone several hours of figuring out what went wrong. I assembled the whole thing only to come back to this stage and do a little tweaking. if your screws which are required to fix the heat bed in place interfere with your z axis frame, make sure the the y-axis long threaded rails are in the middle of your 3d printed legs (i.e. the black threaded rail is concentric with the hole in the orange legs…THEN TIGHTEN). The holes in the legs evidently have some wiggle room and this can skew the height of the bed.

    sean n - Reply

    From what I've managed to approximate in my case, it looks like I have a distance of less than 178mm.

    I also have another problem, I can not get a calipers greater than 150mm. What can I do?

    Alexandru - Reply

    nobody has a 200 mm caliper and sounds expensive but most can come up with an accurate steel straight edge. My suggestion to add ‘index’ markers on the top of the of printed corner pieces - easy to add to your 3d design. Align the index marker with the center line of the 300 mm rod. Provide the appropriate distance to measure between index markers using a straight steel straight edge. You have to be confident the 300 mm rod centerline is on the index marker though.

    jgrieco - Reply

    sorry i meant 330 mm rod

    jgrieco - Reply

    • The marker (used in the next steps) is made as a countersunk hole, see the picture.

    Does "marker" refer to the countersunk hole, or the white dot?

    Mark Molus - Reply

    Hi Mark, thanks for the feedback. The marker is now made only as a countersunk hole.

    Jakub Dolezal -

    Why not write "TOP" on the top side. That way certain people (yes, I've seen the video) won't accidentally get it the wrong way around.

    Stephen Boyd - Reply

    Hi Stephen, thanks. I forwarded your idea to the developers. They will have a chat with carriage manufacturer to see, what are the options.

    Jakub Dolezal -

    Exactly what I was thinking!

    Randy H - Reply

    Hi Randy, thanks. We will try to improve this part.

    Jakub Dolezal -

    • When placing bearings onto the Y-carriage, make sure that they are oriented as shown in the picture. One of the tracks has to be in line with the cutout for the bearing!

    • This orientation has to be followed in all 3 bearings on the Y-carriage!

    • Marker on the Y-carriage must be facing the table (not visible)!

    As mentioned in the comments for Step 4 of the X axis consider rotating the two bearings at a 45 degree angle so the balls are offset and the rod will slide better. Refer to Step 4 on the X axis for a picture of what this rotation looks like.

    Steve Trefethen - Reply

    Hi Steve, I discussed this bearing arrangement with our leading engineer and it is recommended to align bearings as described at this step (do not rotate them mutually).

    Jakub Dolezal -

    One of the bearings in my kit has a small piece of what looks like the black rubber seal sticking up about .5 mm. Has anybody seen this before? Should I continue with the build or get a replacement bearing?

    Frank Thomas - Reply

    Hi Frank, some photos would be helpful. Please start a discussion at https://prusa3d.dozuki.com/Answers and upload them. In general, it depends, if the bearing works properly (smooth movement) or not.

    Jakub Dolezal -

    To help the orientation of the bearing, it can help making a line on the outer side in correspondence with the track

    Fabio Bonvento - Reply

    The following warning, would have been nice to see next to the picture of the countersunk dimple from the previous step.

    Marker on the Y-carriage must be facing the table (not visible)!

    I know it sounds silly, but it took me forever to finally slow down read the _warnings_ from the subsequent step (IMO, an unusual place to look to understand the significance of a previous “step” in the instructions). This simple distraction was enough to make me put down the assembly project for the day.

    Zachary J. Fields - Reply

    • Begin by locating the marker, at this step the marker should be facing the table (not visible) and only then you can add the bearings. If you place bearings to the same side as marker, you will have issues later!

    • Insert a 3x20x16 u-shaped bolt into the Y-carriage as shown on the picture.

    • Place the linear bearings in cutouts.

    • On side with two bearings slide bearings to the center, towards each other as close as possible.

    • DON'T tighten the u-shaped bolts!!! Wait for the next step.

    None of the pictures are using a Y-carriage with the position marker. See step 26 for a better picture with the maker in the correct position.

    Reece Dike - Reply

    Hi Reece, the marker must be facing the table at this stage (not visible), I've changed the description so it is more clear.

    Jakub Dolezal -

    Is because the MARK shows the upper side and these pictures showing the bottom side of the Y-carriage.

    Waldemar - Reply

    Hi Waldemar, thanks for reply. The marker must be facing the table at this stage.

    Jakub Dolezal -

    Watch that you do not over tighten these U bolts as I lost a few bearing balls by presumably doing this.

    Jonathan Wise - Reply

    Hi Jonathan, yes you have to be very careful not to deform the bearings. Following Step 16 will prevent it.

    Jakub Dolezal -

    Yeah I did the same thing I think, I overtightened the nuts and now I am unsure if my bearings are damaged, they don't run super smooth. I really wish there was a better warning in step 15, the warning doesn't come until step 16 where it is too late. Maybe 15 and 16 can be put together?

    Tobias Hansen -

    Hi Tobi (@monotovarisj), thanks for the feedback a note added to this step.

    Jakub Dolezal -

    "On side with two bearings slide bearings to the center, towards each other as close as possible." -> does this mean even if they end up "uncentered" within the U shape?

    Alex Tutusaus - Reply

    Hi, Alex, yes the bearing might be slightly off centered to the U shape bolt, but that is ok. Important is their mutual alignment, so the smooth rod slides in nicely.

    Jakub Dolezal -

    I had to open up the holes for the bearing brackets by .3 mil because they were undersized with powder coat within them. Is this normal?

    Doxie Lain - Reply

    Hi, Doxie, the openings are designed with powder coating in mind. There shouldn't be any adjusting needed. Thanks for the feedback, I will forward this.

    Jakub Dolezal -

    I am having to take use a hammer to get these u bolts in. is that expected?

    Kevin Hart - Reply

    Hi Kevin, definitely no hammering. There might be a thicker layer of paint in the opening. If you can't slide the bolts in, please carefully widen the opening with 3.1 mm drill bit. Ensure you are drilling perpendicularly! As a reference, you can use this chapter: 1. Y-carriage drilling

    Jakub Dolezal -

    Please add a warning to this step to not tighten the nuts until the next step. I had found the bearings, u-bolts and nuts, and assembled them here. Then I read step 16, including the "now too late" warning about not over tightening. My replacement bearings should arrive tomorrow...

    Bret McKee - Reply

    Hi Bret, I will add a warning, thank you for the feedback.

    Jakub Dolezal -

    • Use pliers to tighten the u-shaped bolts.

    • Step 1: place the nuts (M3nN) on the u-shaped bolt and insert a bearing.

    • Step 2: using pliers tighten the nuts until you reach the surface of the Y-carriage, then stop tightening!

    • Step 3: use pliers again and rotate with the nuts only 1/4 of circle to finish the tightening. Tighten all six nuts this way.

    • Don't tighten the nuts more than it is described above or you will deform the bearings!

    Better to use a wrench/spanner but this size is not included, so they use pliers.

    Waldemar - Reply

    Hi Waldemar, we are using only those tools, which are in the kit however, you can use your own tools, if it makes the assembly easier for you.

    Jakub Dolezal -

    On the image is wrong description. 1/4 of circle is 90* not 45*.

    Michal - Reply

    Hi Michal, thanks for noticing, it has been fixed already.

    Jakub Dolezal -

    A 1/4 circle would be 90° whereas the picture states 45°. Erring on the side of caution i used an 1/8 turn (so 45°), though this step should probably be corrected.

    Roland Grichnik - Reply

    Hi Roland, you're right, we've fixed the picture.

    Jakub Dolezal -

    yes use a box spanner if you have one. they are self locking nuts so wont come undone

    Neil Winstanley - Reply

    Hi Neil, you're right. Once tightened, the nuts won't loosen themselves.

    Jakub Dolezal -

    Clarification: Turn *both* nuts the additional 90°, or only *one* of them?

    Kenneth Quick - Reply

    I also need this clarification.

    John Wells -

    Also need clarification on this

    Morgan Jonasson -

    Turn both nuts. Ideally you'll want both nuts the same distance in to ensure the bearing is properly inside the U shape and not misaligned. Don't worry too much about breaking the bearings. You'd still have to apply quite some force. I turned all the nuts with my fingers till I couldn't anymore, then turned them 90° with the pliers and were done.

    Mario Liebisch -

    Hi Kenneth, John and Morgan, there are 3 u-shaped bolts and together 6 nuts, which must be tightened this way. In other words, yes turn both nuts on each u-shaped bolt.

    Jakub Dolezal -

    Any recommendations on lubricating the bearings?

    Keith Ottlinger - Reply

    They're prelubricated (you should be able to feel it once unpacking). Later on you can use pretty much any lubricant of your choice (I prefer liquid ones).

    Mario Liebisch -

    Hi Keith, for the assembly we send the bearings pre-lubricated and it is enough for start. For maintenance, I suggest following Josef's 3D printing handbook http://prusa3d.com/downloads/manual/prus...

    Jakub Dolezal -

    Please don't suggest using plyers (aka "butcher tools") to tighten nuts &\or bolts!

    John Sloop - Reply

    Hi, John, we are suggesting tools, which are included in the kit. There are of course better tools for nut tightening and if you have them at home use them instead of pliers.

    Jakub Dolezal -

    OMG, why do these bearings sound so bad? The rods feels rough when sliding it back and forth. No the nuts are not to tight!

    Randy H - Reply

    Hi, Randy, this is very strange. Brand new bearings and rods should be fluid. Try to put some machine oil on the rod and see (hear) if it helps.

    Jakub Dolezal -

    Hi Randy, Did you figure this out? I'm having the same thing - bearings are loud and scratchy sounding right out of the box. Thanks!

    Jordan Vallis -

    Yes, mine sound rough and feel lumpy too. They're very oily, so that's not the problem, and I've not over-tightened them.

    Anselm Eustace -

    Possible to get a video showing what the bearings should sound like as the carriage slides if it's all aligned correctly?

    Daniel Loughmiller - Reply

    Hi, Daniel, we will try to tape it. However, I'm not sure if it will help, the new bearings and rods are very quiet.

    Jakub Dolezal -

    Would it be a good idea to temporarily insert a rod through both bearings before tightening to insure alignment?

    Lane Hauck - Reply

    Hi Lane, the Y-carriage openings for the bearings are designed to align the bearings for you. However, if you are unsure about the proper alignment, you can temporarily insert the rod. Just be careful to slide it in and out without excessive force.

    Jakub Dolezal -

    I hate this step. What is too tight? A 90 degree turn, my finger tight might be tighter than your finger tight plus 90. How much bolt shows in the nuts? The way I have it, I could turn 90 or 180 more, before the bolts are even flush with the nut. The nuts are 5.5mm, by the way.

    I also don't like the way that you are suppose to slide the two bearings towards the center, because of the rounded holes, this could bring them up, throwing off alignment.

    Todd Christopherson - Reply

    Hi Todd, you should tighten the nuts until you can see the U-shaped bolt touches the bearing casing. Then turn with the nuts again for 90° and that's it. If you tighten more, you can easily deform the casing and the whole heatbed won't be sliding properly. The bearing shouldn't wiggle, it should be sitting tight in the Y-carriage.

    Jakub Dolezal -

    I have a similar question to Todd. How tight is too tight? Should there be any wiggle in the bearings at all or should the nuts be just tight enough to restrict any wiggle movement?

    Chris Cooke - Reply

    Hi Chris, please see my previous comment to Todd. Thanks

    Jakub Dolezal -

    I’m going to ask another way. How can we tell if we did not tighten enough? I assume snug is good. But mine have jest enough leeway that I ca. Twist the bearing with a bit of effort. Is this good or should I tighten more?

    Brian - Reply

    Hi Brian, the bearing should be sitting tight. You shouldn't be able to rotate with the bearing. Just be careful not to overtighten the screws and deform the bearing. You can check that by inserting the rod inside bearing at the beginning after the tightening the resistance should be the same.

    Jakub Dolezal -

    Ook hier het zelfde probleem de lagers maken hels lawaai zelfs zonder de beugels er op soepel schuiven is zeker het geval niet.

    Jos Uit Belgie

    Jos de deken - Reply

    Hi Jos, I'm sorry, but I can help you only in English. Can you describe your problem again? or write an email to info@prusa3d.com. Thanks

    Jakub Dolezal -

    Here, and other places where there's confusion about how much to tighten, it would be helpful to have torque values. I understand not everyone has a torque wrench, but my guess is that many people either do, or would be willing to buy one to alleviate their concerns. Even if they don't, 20 ft/lbs (or 20 kg/m) is a lot more informative than "snug" or "not too much pressure".

    Nick - Reply

    Hi Nick, thanks for the suggestion. I will try to tighten all parts using a torque wrench and see what numbers are coming up.

    Jakub Dolezal -

    volledig mee eens

    Jos de deken - Reply

    Hi Jos, did you manage to solve your issue?

    Jakub Dolezal -

    Here's what I did. Use a 6mm socket to tighten the nuts evenly and LITTLE BY LITTLE (when I say evenly, I mean watch how much of the bolt-ends stick out from the nut and keep it even as you go). Keep going BUT wiggle the u-bolt after tightening each nut a bit. STOP as soon as you can no longer wiggle the bolt. If it wiggles slightly, tighten it a TINY, TINY bit until it stops. Then stop.

    Jeremy Martin - Reply

    To revise my last comment. I ended up loosening the nuts on the U-bolts so that the U-bolts had a slight amount of wiggle when I pushed or tugged them firmly. I feel this loosed up the bearings a bit and gave me a smoother glide on the rods later on.

    Jeremy Martin - Reply

    Hi Jeremy, important is to achieve two things:

    1) Tighten the U-bolts enough to prevent movement of the bearings.

    2) Tighten the U-bolts in a way you won't deform the bearings and therefore the smooth movement of the rods is kept.

    Jakub Dolezal -

    Even though I aligned the balls correctly in the "Correct bearing orientation" step, by the time I secured all of the bolts 2 of them had rotated about 5 degrees. I did not notice this until much later when the bearings started scraping the rods.

    I would suggest changing the order of these steps. It's not really important to check the orientation of the bearing until right before you make the last turn on the nuts. This would actually serve to disambiguate the tightness confusion a lot of people seem to have. The nuts are "touching the surface" when the bearing does not move up and down, but can still rotate freely.

    Jared Deckard - Reply


    - Remove step 14 "Correct bearing orientation".

    - Replace "until you reach the surface of the Y-carriage" in 16.2 with "until the bearing can't move up and down, but can still rotate under the U-bolt".

    - After 16.2 add a step to align the bearing balls with the Y-carriage.

    Jared Deckard -

    Hi Jared, thanks for your insight. I will think about a solution, maybe add an extra warning to this step. Mutual rotation of the bearings, however, shouldn't cause scraping, are you sure there weren't any particles on the smooth rod, or inside the bearings?

    Jakub Dolezal -

    This is the first time the nuts are mentioned, as far as I can see. Please add an intro with the part number (M3nN) and quantity (6), and also for the bearings and U-bolts.

    ecc - Reply

    Hi Ecc, thanks for noticing. I will update the manual.

    Jakub Dolezal -

    It would be great to include a little 3d printed tool which could be used to tightened these, rather than requiring the use of the pliers. Just a small piece of plastic with the correctly sized hexagonal hole should work.

    Ben Gruver - Reply

    I followed the directions, yet the bearings are rough as the rods slide through. I thought the sliding of the rods should be as smooth as butter. Am I wrong or missing something?

    scott chavez - Reply

    Late august printer kit and the bearings are still junk (run rough on the rods). I have now finished building and the printer runs, but the Y-axis is very *loud*. I haven't decided yet whether I will request new bearings.

    Anton Eliasson - Reply

    Hi Scott and Anton (@usxr & @antoneliasson), bearings and rods on MK2S should be running smooth and producing almost no noise. Before contacting our support please try the bearing on a single smooth rod to ensure it is a really bad bearing or bad rod because very often is the noise caused by misaligned rods.

    Jakub Dolezal - Reply

    Same problem here, sadly. All three bearings are quite rough fresh out of the box, on all rods.

    Chris` -

    My bearings sound and move like there is grit in them. They are jerky. I was realy careful to not over tighten and I know the rod alignment is great... This can’t be right. How do I go about requesting a new set or should I look for better quality bearings?

    Ian Edwards - Reply

    Hello! Both options are available. You can start by sending us a photo/video of how much jerky the bearings are to info@prusa3d.com, along with your order number. Check your smooth rods as well for any scratches.

    Martin L. - Customer Support -

    • M3x25 screw (1 pc)

    • M3w washer (2 pcs)

    • 623h bearing housing (1 pc)

    • M3nN nylock nut (1 pc)

    This should be done before placing the Y-idler on the rod.

    Ilya - Reply

    Hi Ilya, thank you for comment. The answer is the same as at Step 2. We tried both ways several times and decided to first place Y-idler on threaded rods. It is, for example, easier for tightening.

    Jakub Dolezal -

    Doing it before is slightly better because you can manipulate the allen wrench around the part better, but otherwise it doesn't matter too much.

    Neal Smith -

    Does the direction of 623h bearing housing matter? I cannot tell the direction based on the available pictures.

    Bret Lederle - Reply

    Hi, Bret the 623h bearing housing is symmetrical, therefore you can place it both ways.

    Jakub Dolezal -

    The hole in the printed Y-idler is just barely large enough for the M3x25 screw. I had to use the allen wrench to gently screw it in. It went easily without having to force it, but it was a bit stressful fearing that I’d break something…

    Bill Robitske, Jr. - Reply

    • To tighten the Y-idler, use the pliers and 2.5mm Allen key.

    • Tighten the screw gently, just half a turn max after the washers touch the 3D printed part.

    it would be much easier to do this before it is placed on the frame as one of the first steps.

    John Wells - Reply

    Hi John, I discussed this with guys, who assembling printers and we decided to keep the step as it is. Anyway, thank you for your feedback ;)

    Jakub Dolezal -

    Is there any wiggle room inside after installing the nut and screw?

    Simon Grigorian - Reply

    Hi Simon, yes there is a room (gap) for the idler to rotate freely.

    Jakub Dolezal -

    One more question. I feel like I tightened the screw going in from the left side a little too much. the little gap (if there is suppose to be a gap) seems a little more squeezed than natural. Should I loosen up the the screw so the gap Is nice and even / free?

    Simon Grigorian - Reply

    Hi, Simon, don't overtighten the idler. It has to rotate freely and you can also damage the printed part.

    Jakub Dolezal -

    It's an idler pulley Simon, there isn't any need to tighten that much. Leaving a gap between the pulley and the printed carrier won't hurt, in fact it's advisable to have some play.

    Scott Miles - Reply

    Hi, Scott, thanks for your comment.

    Jakub Dolezal -

    for when putting in the bearing housing do I put ashes between the nuts

    Maxim Bethurem - Reply

    never mind, I found out the answer.

    Maxim Bethurem - Reply

    I'm glad to hear you've found the answer. Would you mind sharing? Thanks

    Jakub Dolezal -

    Is the M3x25 screw supposed to thread into the plastic part, or should the screw slide through? I suspect the holes might be too tight on my idler housing and the screw is warping the sides inward as it is tightened.

    Jordan Valadas - Reply

    I was able to answer my own question. The screw threads should not engage the plastic. When removing the screw, the hole was noticeably more loose, so I used the threads of the screw as a file and cleaned up the hole. After this, the screw slid through cleanly.

    Jordan Valadas -

    Hi Jordan, important is to have the idler rotating freely.

    Jakub Dolezal -

    • Step 1: Place the motor temporarily in the frame next to the Y-motor part. See the first picture.

    • Step 2: Take the Y-motor-distance and place it at the very end of the motor casing. The two half-circle cuts on Y-motor- distance printed part must be facing the threaded rods. See the second picture.

    • Step 3: Take the motor away and press the Y-motor-distance printed part towards the threaded rods all the way in. See the third picture.

    • Note the correct orientation of the cutout for motor wires, it's very important!

    • It is recommended to use motor labeled "Y axis" as you will need it for the next step.

    from step 4

    Y-motor-mount should be somewhere in the middle of the threaded rod. The precise position doesn't matter at this time.

    i did not see any precise positioning of the motor mount yet. It is kind of late to position it now. Or did i missed it?

    Francois Bujold - Reply

    Hi Francois, we will adjust this chapter, so the precise Y-motor-mount is known. However placing the mount in the middle should be ok and precise position is adjusted at Step 39.

    Jakub Dolezal -

    1. Position of the motor: Same question of Francois. I center the motor but I did not see any mention of precision position.

    2. The images is also a little confusion has the motor is inverse from the step after with wiring going opposite for the cutout.

    E Phenix - Reply

    Hi E Phenix, for question number one, please see my answer to Francois above. Regarding question number two, you are placing the motor temporarily (as described) just to set the correct position for Y-motor distance. The correct position of the motor is shown at step 20.

    Jakub Dolezal -

    For anyone else unsure of the position, it looks like the small v-notch on the endstop mount should be roughly centered as a starting point.

    Jens Ehrich - Reply

    Hi Jens, thank you for the comment ;)

    Jakub Dolezal -

    This step (and the next) are simply misleading. Just follow them, no matter where your motor is right now (as long as you've got enough space). Just skip the endstop and the distance piece for now. Place the distance piece once the motor is aligned (see below; just unscrew it one last time) and add the endstop once you're done with the motor alignment (getting the cable through is a bit tricky but not impossible).

    Mario Liebisch - Reply

    Hi Mario, I'm sorry you find the steps seems misleading to you. The purpose of this step is to set correct position of the Y-motor- distance. Unscrewing and rescrewing any component several times is not recommended. We will try to improve these steps, so they are more clear.

    Jakub Dolezal -

    major issue with this step that will bite you in the ass on step 39, also you can check for end stop engagement at step 26, problem is, once that y motor distance piece is installed, and you need to scoot the motor over to make room for the belt holder to hit the endstop, if you have to move the mount over towards the PSU part (which if you put it in the middle of the rods, like the instructions recommends your gonna have to move it a good ways). the motor moves, that distance assembly doesn't, you are making a shear that WILL cut the motor wires off if you adjust it too much outboard, and keep cranking without paying attention, i would HIGHLY recommend merging this step with 32

    Andrew B - Reply

    Hi Andrew, thank you for the feedback. We will adjust the manual, so the precise position of Y-motor-holder is known and therefore future issues are avoided.

    Jakub Dolezal -

    I agree. I made an earlier comment back in step 6 - a fixed dimension should be given in step 6 to get close enough to avoid having to remove the motor and limit switch at this point and readjust.

    Keith Ottlinger - Reply

    Hi Keith, yes we will do this adjustment to the manual. Thank you.

    Jakub Dolezal -

    Motor holder has a small notch. In my case, the distance to steel rod on a motor side, after calibrating, was 88mm.

    Radoslaw Wisniewski - Reply

    Hi Radoslaw, thank you for sharing your value.

    Jakub Dolezal -

    This is just plain stupid! Give us a fixed dimension from the corner bracket!

    Randy H - Reply

    Hi Randy, we will work on this, to give your more precise values.

    Jakub Dolezal -

    After assembling the rest of the Y carriage and stop to locate everything I came back to the this step to figure out exactly where it needs to go. I have 26mm between the inside of the corner piece and this distance spacer. Why not just tell people this up front! (and no editing after 5 minutes? Who came up with this?

    Randy H - Reply

    Hi Randy, thank you for your feedback. We are working on a better solution for this part of the assembly.

    Jakub Dolezal -

    Jacub, I'm sure you folks are doing your best, but you really need someone fluent in the English language to author/edit these instructions.

    Scott Miles - Reply

    Hi, Scott, thanks for the feedback. Which sentences do you have in mind?

    Jakub Dolezal -

    I didn't realize the motors were differently marked until I discovered, assembling my X-Axis, that I had installed my X Motor here. Instructions are clear for the X-Axis, could be made clear here, too.

    Gordon McDonough - Reply

    Hi, Gordon, they are, have a look at step 20 ;)

    Jakub Dolezal -

    Might I suggest that Y-Motor distance be renamed Y-Motor-Spacer. I mistook the instruction to be poor English rather than the name of the part. Distance is a measurement, a number, not an object. Spacer is a very common term for an object that ensures proper spacing.

    Lance Pearson - Reply

    Hi Lance, renaming of any part is a great deal because its name is in many internal systems. However, you are right with the "distance" and I will forward this to our developers.

    Jakub Dolezal -

    Not to be too picky here, but I agree a line telling you to choose the motor with the Y on the wires belongs in this step which is where you choose the motor

    Lance Pearson - Reply

    Hi Lance, it is better to use Y-axis motor. However, you are setting a distance and all motors are the same size.

    Jakub Dolezal -

    The orientation of the Y-axis motor is not clear, nor is it mentioned later. If you look at the motor with the words “up” so you can read them, the wires are coming out of the “bottom” (of the motor).

    In step 26, it appears as though the y-axis motor is “laying on its side” (relative to the threaded rods), and the wires are coming out of the “bottom” of the motor are are oriented such that the wires are coming out of the side (of the motor) adjacent to the threaded rods. There is a square notch that lines up with the area where the wires come out of the motor, so I’m assuming this square notch is there to allow the wires to escape the motor and not interfere with the Y-motor distance.

    I believe what I’ve written now makes sense in my brain, the clarification would be helpful. Thanks.

    Roger Allen - Reply

    Hi Roger, this step is not about the motor, it is about proper placement of the printed part, which is supporting the motor. Correct placement of the motor will be solved in the next step.

    Jakub Dolezal -

    SERIOUSLY, what is the purpose of this step if we don't know how far to place the motor mount and tighten in down???

    Jeremy Martin - Reply

    Hi Jeremy, the point is to set proper distance for the printed part. It is written to place the motor "temporarily" and you are not asked to tighten anything. Mounting of the motor will come in the next step ;)

    Jakub Dolezal -

    I discovered a MASSIVE flaw in the Y-motor mount, or at least I have not seen it mentioned here. The Y-motor mount cannot SLIDE on the threaded rods. Upon reaching this step, I remembered that I had to "thread" the rods into the mount. Nobody here has mentioned this, so not sure if mine is faulty.

    Well, at first, this seemed like a fatal error because how am I supposed to adjust the mount up and down the rods later on? Well, I realized you can use the nuts that secure the mount to force the mount one way or the other. Simply thread the nuts on one side to force the mount in the direction you need it to go. I have not seen this mentioned yet.

    Jeremy Martin - Reply

    Hi Jeremy, I think there is no "massive flaw". You are given recommended position of the Y-motor part in step 6. You might need to adjust the position slightly later on and this can be achieved by threading the nuts, which is shown in step 38.

    Jakub Dolezal -

    The "Y-motor-distance" is a Czech-ism. The proper English term would be the "Y-motor-spacer". As it stands, the use of the word "distance" is misleading.

    Kuba Ober - Reply

    Hi Kuba, I will pass your feedback to the designers.

    Jakub Dolezal -

    I agree, Y-motor- distance it confusing. Go with Y-motor-spacer instead and the problem is fixed (quickly).

    Cristian Leon - Reply

    Hi Cristian, thanks for the suggestion, "spacer" seems more adequate. Just for your information, renaming any printed part has a lot of consequences through the entire company.

    Jakub Dolezal -

    You really don’t have to rename it… just do this in the instructions.. Y-motor distance (spacer) and put the word spacer over the orange arrow in the picture

    Dave Collea - Reply

    In my kit (delivered April 2nd 2018) I didn’t get a motor spacer/distance part - but instead, I have two motor mounts. The instructions say that the parts might have changed - which makes it unclear whether I have a mistaken part or something changed in the instructions.

    Stephen Baker - Reply

    • Y-axis motor (the one labeled with Y axis)

    • M3x10 screw (2 pcs)

    • Motor cables must be facing threaded rods!

    • Don't tighten the motor yet, in the next step you need to add another cable from an endstop.

    Make sure you use the right length of screw here. If you use your M3x12mm screws, they'll hold the motor in place, but M3x10mm screws are too short for step 24

    Matty D - Reply

    Hi Matty D, you are right. Screws must be used according to the manual. Using different length will end up in issues later.

    Jakub Dolezal -

    You can leave the bottom screw off the motor until step 35 because you have to remove it at step 30 anyways. You can also temporally install the pinion now and adjust it at step 31.

    Paul Betz - Reply

    Hi, Paul, I suggest following the manual. Otherwise, the motor is hanging just on one screw.

    Jakub Dolezal -

    Careful not to use the M3x12 screws from the packet by mistake. Use the shorter M3x10

    Jeremy Martin - Reply

    Hi Jeremy, it is always good to double check and you can use the printed label to measure the distance.

    Jakub Dolezal -

    I'm confused about the orientation of the motor. I currently have the multi-color connector at the bottom but the image appears to have it at the side facing the rods. However, having the motor oriented with the multicolor cable coming out from the side does not work iwith the y-motor distance part. Is having the cable come out from the bottom instead of the side nearest the rods going to work?

    scott chavez - Reply

    Hi Scott, the correct orientation for Y-axis motor is when cables are facing the rods. In the Y-motor-distance-part is designed opening through which you must lead the cables. Rotating the motor 90° shouldn't be a problem. However, I recommend following the manual to avoid issues.

    Jakub Dolezal -

    I have 3 motors, none of which have any markings whatsoever where the green arrow is pointing (or on any part of the casing, for that matter). Can I use any one for the Y-motor?

    Stacy Boatman - Reply

    I have 3 motors, none of which have a "Y” imprinted where the green arrow shows (or any kind of imprinting anywhere, for that matter). Do I just use any of the 3 motors?

    Stacy Boatman - Reply

    My motors are labeled on the back (not the side, where the green arrow in the photo points), and also have a small yellow collar around the wires with a Y on it.

    Tobias Boyd -

    Do you recommend use of thread locker for metal to meal threads? I use this in other projects. Removal blue thread lock.

    jgrieco - Reply

    spelling ‘removable’ not removal

    jgrieco - Reply

    The 10 and 12mm m3s are easy to mix up, why not have 4x12mm?

    Doc Wilco - Reply

    • Insert the Y-axis endstop connector between the motor and threaded rods.

    • Gently pull the connector of the cable in the direction away from the frame (see the picture).

    • Using the 2.5mm Allen key, secure the motor to the 3D printed part.

    • Tighten the motor gently to avoid damage to the 3D printed part.

    • Endstops are part of the box

    To make it easier later with the electronics assembly i marked the white cable of the y-endstop on both ends with a pen so i can distinguish which endstop is the y. Both endstops have the the same cable color code and length.

    Waldemar - Reply

    Hi Waldemar, thanks for the feedback. I've forwarded this idea to our development team ;)

    Jakub Dolezal -

    Hi! The 2 endstops i got came with no "lever", is this a new version or a deffective version??

    Alex Tutusaus - Reply

    Hi Alex, you mean there is no "button" on both endstops? Can you send picture to info@prusa3d.com? Thanks

    Jakub Dolezal -

    The picture is a bit deceptive: what you see is the plug/connector at the end of the endstop cable, not the endstop switch. The endstop is *not* installed in this step!

    Kuba Ober -

    Well i have the Problem to finde the Y-axis endstop connector

    Where is it?

    Ramón Fürst - Reply

    I couldn't find mine for the longest time. Found it in a short flat box marked "2. 3. 4. 5. SUP". the box that contained the nozzle, a couple fans, some felt pads and a couple other bits.

    Chris Bauer -

    Would be nice with the info box in the beginning of the step ;-)

    Tobias Hansen -

    Hi Tobias (@monotovarisj), I've added a note to this step, see the last row :)

    Jakub Dolezal -

    Its easier to insert the Y-Axis entstop connector when you change step 20 and 21.

    Marko Röschmann - Reply

    Ok..there is a hint at step 20 not to tighten the Motor. But on the pictures the screws are already added. Its better to put first the cabel and add then the Motor .

    Marko Röschmann -

    The M3x10 screws seem to only barely stick out of the 3D printed part when pushed through and not far enough to secure the motor. Any suggestion as to where I'm going wrong here?

    Kyle Watson - Reply

    Fixed! For anyone with the same issue tightening the screw with the Allen key allows it to move further into the 3D printed part.

    Kyle Watson -

    There are two endstop connector cables in the box and they aren’t labelled X and Y. Are they identical, and if not, how do I distinguish the X from the Y?

    Van Albert - Reply

    They seem to be identically. That’s why they are marked with “2x Endstop”, and are not displayed as different items.

    Wolfsblvt -

    Check the next step for cable orientation

    Doc Wilco - Reply

    • M2x12 screw (2 pcs)

    • Y-axis endstop

    • Ensure the correct placement using marker on the printed part. See third picture with pink arrows.

    • Secure the endstop by two M2x12 screws and push it forward in the direction of the arrow.

    • To tighten the Y-axis endstop use 1.5mm Allen key. Use gentle force to avoid damage to the printed part.

    I will move the endstop information line to the step before

    E Phenix - Reply

    Hi E Phenix, you're right. I will move the info line to the previous step. Thanks ;)

    Jakub Dolezal -

    Are one of those pink arrows suppose to correspond with a pink bullet point? vs a caution symbol?

    Fewze - Reply

    Hi, Fewze, yes with the sentence "Ensure the correct placement using marker on the printed part." However, I can't create pink caution symbol, but this step is very important, so I used caution symbol in red. I will change the description, so it is more obvious.

    Jakub Dolezal -

    I dont get it. In the previous step you clearly put the connector between the motor and the rods, and then "Pull gently the connector with the cable in the direction away from the frame (see the picture)" as per blue arrow, the endstop is now away from the rods from the TOP of the motor, hence positioning the Endstop in the endstop carrier (orange part) makes no sense like it's pictured :???

    Alex Tutusaus - Reply

    Hi Alex, let me rephrase the description above. You need to take the connector of the endstop and drag it between the motor and threaded rods. This way you can drag about 3/4 of the endstop cable length. In the next step, you can't place the endstop directly on its position, because you need to first tighten the motor. This screw is not reachable when endstop is in its final position. On the pictures, we therefore, placed both parts of the endstop cable to the left, but after tightening we placed it on the motor holder. Please let me know if it is more understandable now. Thanks

    Jakub Dolezal -

    Yes I just took the pic in the last post wrong, I thought your endstops featured a metal "lever" and that the lever was the "greyish" part I was seeing in previous picture. Nevermind, all sorted ;)

    Alex Tutusaus - Reply

    Hi Alex, glad to hear everything is ok now ;)

    Jakub Dolezal -

    Because the screws are self-tapping, I found it much easier to start them (through the endstop microswitch holes) by first screwing them into the plastic a short distance (about 3-4 turns), removing them, then attaching the endstop.

    Lane Hauck - Reply

    Hi, Lane, you should be able to screw them in together with endstop. I wouldn't suggest screwing in the plastic part multiple times as you will most probably start each time a new thread.

    Jakub Dolezal -

    Could you clarify that there is no 'Y' endstop? I spent forever trying to figure out which of the two endstops was the 'Y' one.

    Spencer O - Reply

    Hi, Spencer, there is no endstop dedicated just to the Y axis. Both endstops from the package can be used since they are absolutely identical.

    Jakub Dolezal -

    Make sure the button on the endstop should not be facing towards the motor as in the picture. Otherwise, in a later step the y- carriage will not trigger the end stop.

    Jorren - Reply

    I switched the position but still when the plate doesnt hit the y endstop. it seems the hieght is too low , any advice on that?

    slav b - Reply

    Hi Slav, the endstop is triggered by the orange printed part called Y-belt-holder, not by the heatbed. Your printer is fine.

    Jakub Dolezal -

    • Guide the wires from the Y-axis endstop to go side by side with motor cables as shown in the picture.

    Add Comment

    • Place the Y-belt holder on the Y-carriage as shown in the picture.

    • M3x12 screw (2 pcs)

    • Be aware of the orientation of the Y-belt holder (belt entry should face towards single bearing).

    • There's no thread in the Y-carriage, just push the screws all the way in.

    • Assemble the M3 nuts on the screws from the opposite side of the Y-carriage as shown in the picture. Use nuts from 9.SPARE bag.

    • The nuts will be removed in Chapter 7.

    The m3x12 screws are too short for me.. they do not reach the other side of the Y-carriage

    Travel Me - Reply

    Hi, I tried several Y-belt-holders and the screws always reached the other side of the Y-carriage. Please check for possible obstacles in the opening and then try to push them all the way in. Anyway thanks for the feedback we will adjust the printed part.

    Jakub Dolezal -

    Happened to me too, then I found out I accidentally used the M3x12 for the motor assembly, leaving me with the M3x10's.

    Joost -

    Hi Joost, please use the lengths described in the manual.

    Jakub Dolezal -

    In my case the screw reach the Y-carriage if I push the screw all the way in, so that the head is inside the holder (hope that's normal)

    Kevin Lam - Reply

    Hi Kevin, yes the screws should be all the way in. Otherwise they won´t reach the other side of the Y-carriage.

    Jakub Dolezal -

    I used 2 bolts from spare to hold the piece (as shown in step 26). m3x12 screws were just long enough.

    Lyrandel - Reply

    Hi Lyrandel, M3x12 should be enough if you press them all the way in. However, we will adjust the printed part of easier assembly. Thank you for your feedback.

    Jakub Dolezal -

    Step 28 should be merged here. Use the nuts from the spare bag to keep the holder in place temporarily.

    Francisco Ramos - Reply

    +1 in fact the whole y carriage should be at the same time so we don't need so much space on a desk.

    John Wells -

    Hi Francisco and John, thank you for the feedback. We'll merge the steps as suggested.

    Jakub Dolezal -

    with belt holder oriented as shown the Y-end stop is not triggered. The switch bump falls right into the screw recess.reverse switch and problem solved

    Francois Bujold - Reply

    Hi Francois, you shouldn't have issues if you followed the manual steps completely. I don't recommend doing adjustments, which are in the contradiction with the manual.

    Jakub Dolezal -

    It's possible that the M3x12 where switched with the M3x10 of the Y motor. The extra 2mm is enough to go through the plate.

    Jasmin Lévesque - Reply

    Hi Jasmin, in this step you have to use M3x12.

    Jakub Dolezal -

    i had to use the 2 nuts from step 28 at this point, because the holes were too lose, if you were to tun it upside down everything would fall out/off

    Andrew B - Reply

    Hi Andrew, I adjusted the steps and you can place the nuts right away. Thank you for the feedback.

    Jakub Dolezal -

    I would add a remark that it's OK for the Y-belt holder to move, as it will be secured to the bed in chapter 7

    Nicolas Hunt - Reply

    Hi Nicolas, to prevent the movement you should add temporary nuts from the other side of the Y-carriage.

    Jakub Dolezal -

    People are likely having problems because they used the #12 screws to mount the Y axis motor instead of the #10 ones. Either will work for the motors and the difference is so small that it is an easy mistake to make.

    John Mangan - Reply

    Hi, John, the incorrect length can be the problem. That is why we include the stickers on the bags in scale 1:1 so you can check the proper length before using the screw.

    Jakub Dolezal -

    • Use the mid-sized smooth rods (330 mm)

    • Insert the 8mm smooth rods into the linear bearings on the Y-carriage.

    • Be very careful! Insert the rod straight into the bearings, do not apply too much force and do not tilt the rod!

    • Try to move slightly with the smooth rod after being placed through the bearings. If there is an increased friction, check the bearings are placed straight and not tilted.

    Should I put a drop of machine grease into the bearings as a lubrication or are these bearings completely dry running? Would some grease help to prolong the lifetime?

    Tobias Werner - Reply

    Hi Tobias, for the assembly the bearings pre-lubricated and it is enough for start. For maintenance, I suggest following Josef's 3D printing handbook http://prusa3d.com/downloads/manual/prus...

    Jakub Dolezal -

    The linear bearings already have grease on them. The y carriage rods don't slide as smoothly as i would have thought. Nuts were not overtightened.

    MichaelNewham - Reply

    Hi Michael, if the Y-carriage isn't moving smoothly, check the position of the bearings. They might be slightly tilted causing bigger friction with the smooth rods.

    Jakub Dolezal -

    Mine were not nearly as smooth as I expected either, however the ones in the next chapter seem much better. Not sure if that's a problem or not. Could someone please comment on how easily the y-carriage should slide and how I can determine if mine is okay?

    Jens Ehrich - Reply

    Hi Jens, if the Y-carriage isn't moving smoothly, check the position of the bearings. They might be slightly tilted causing bigger friction with the smooth rods.

    Jakub Dolezal -

    Same here regarding lack of smoothness (and yes, I've checked the bearing alignment!!). The rods sound scratch moving through the bearings. I've uploaded a video of how it sounds here: https://youtu.be/kO1vgG_H2UM

    Mike Carter -

    Mine were perfectly smooth either. I slightly loosened the upper pair of nuts and re tightened them. Now everything is very smooth.

    Rick MIller - Reply

    Hi Rick, thanks for the tip. I added a note to this step to check the position of bearings by sliding the smooth rod

    Jakub Dolezal -

    Thanks for this! I thought mine were smooth, but decided to try your loosen-tighten trick on the side with two bearings. Now they are like silk - the rod will fall right out with gravity.

    Bill Robitske, Jr. -

    When I pushed the rod through some bearings fell out is this ok what should I do

    Rudy Aiello - Reply

    Have the bearings that fell out of your housings caused you issues? Have you completed your build since?

    Eric Grubisich -

    Hi Rudy, there should be nothing falling out. Please attach here a photo of what happened. Thanks

    Jakub Dolezal -

    I also did not push hard on the rods and the bearings were definitely not overtightened, but a few bearings fell out of each of the housings while the rod slid through. It is not terribly rough but still not as smooth of movement as I expected with the plate assembled. It slides, but I wonder if the 3-4 little bearings that fell out of each of the two housings will be a problem now.

    Eric Grubisich - Reply

    Hi Eric, I discussed your issue with the guys from development and you can assemble the printer with bearings missing few bearings in the housing. HOWEVER, it is not recommended to leave this in the long term as it might cause issues during prints. Contact our support at info@prusa3d.com and order replacement.

    Jakub Dolezal -

    I was given 2- 320 mm rods, 2-330 mm rods, and 2-370 mm rods. I used the 330 mm rods in step 10 since it said to use the medium length rods. Will I have issues if I use the 320's here?

    David Miller - Reply

    Step 11 clearly states to remove the 330mm rods, to be used here.

    Udi Finkelstein -

    Hi, David, as Udi correctly said the length is 330 mm.

    Jakub Dolezal -

    what to do if the bearing were alligned perefectly and when the rod slipped 3 balls dropped from 1 bearing (all the balls from the same)

    p.s did it with the bearing not tightned flat

    slav b - Reply

    Hi Slav, try to move with the Y-carriage. Is the movement smooth? If not please get a new bearing or contact our support at info@prusa3d.com

    Jakub Dolezal -

    The rod on the two linear bearings slides freely but resists rotation. Is this a problem?

    Jules - Reply

    Hi, Jules, the rod won't be rotating during printing, so as long the sliding is smooth, you should be fine.

    Jakub Dolezal -

    These three bearings were scratchy and rough. Aligned, did not tighten too much and kept moving the rod hoping it would become looser. It does not. It sticks and sounds awful. Just like Mike's video: https://youtu.be/kO1vgG_H2UM

    Larry R Dockery - Reply

    Four of my other bearings for the X-axis assembly are also bad. Nearly half of the bearings that came with this printer are nearly seized. One X-axis part won't even move without excessive force. If your Y-Axis is not moving smoothly or sounds like loud scraping, stop assembly and buy new bearings. The ones you have are likely bad. I had to stop at X-axis assembly as only half of the bearings are good.

    Larry R Dockery -

    I had similar issue. See my post later

    gaazolee -

    +1 for scratchy bearings like Mikes video on a kit that arrived last week. Please can let us know if this is an issue and whether it is worth continuing the build as they are?

    Dom Bramley - Reply

    There is friction on a single side, about 1.5 inches from the end without the motor... Can't seem to find the source...

    Jean-Luc Caron - Reply

    Like David Miller, I was having trouble at Step 25 with confusion about the 330mm rods. Although the last point in Step 11 says to remove the rods, but I think many people will miss this step, and wonder why they have no 330mm rods for step 25.

    Maybe, in the instructions for step 25, add a comment that you are (re)using the 330mm rods that you **removed** as the past action in step 11.

    RPG - Reply

    Another +1 on scratchy bearings. This has nothing to do with alignment, as the bearings are scratchy even with using only one at a time. I'm not sure wherther to keep going, or to wait until I have ordered a complete new set of bearings.

    RPG - Reply

    I had scratchy bearing issue too. Sound pretty similar what is on the video created by Larry. So I investigated further. I found that less or more rod is in the charge not the bearing itself.

    1. I fount there tiny pits and irregularities on the rod. Those pits are randomly located.

    2. When I measured distances between rods I found out that rods are not 100 straight. In the worst case distance difference between ends and the the middle was 0.6mm. (Might be it is within required tolerance.)

    I did following:

    1. Rotating rods around until distance difference was minimal. In my case under 0.05mm (All the length is 178 and distance between two bearing housing is 155mm.

    2. Tried to minimize pitted area which is being touched by balls itself. Bearing has 4 row of balls positioned regularly around . I rotated road to the position where pits goes via bearing between ball rows.

    I found a position where scratching is gone and movement is smooth.

    3. A little loosening of bearing holder eased movement even more.

    gaazolee - Reply

    BTW highlight desired tolerance would be great. In some cases doesn't make sense to play with assembly and achieve sub tents of mm precision and +- 1-2 mm accuracy is enough sometime it does.

    gaazolee - Reply

    Guys, regarding the "scratchy" bearings. The sound in Larry's video is very often caused by the geometry of the frame, which isn't as it should be. Release slightly the U-bolts and realign the bearings. In the case of a Y-axis you need to release slightly the nuts on the Y-corners and move with the Y-carriage, which will align the position of the smooth rods for you, then you can tighten the nuts again.

    Jakub Dolezal - Reply

    Would it be possible to post a video of what is normal for the y carriage, both the sound with movement and how well it "glides"?

    Brad Barber - Reply

    Hi Brad, this might be tricky, but I will ask our video guy if he can capture the sound.

    Jakub Dolezal -

    Hi Jakub, this would be good - even some indication of how smoothly the carriage is meant to glide along the rails, e.g. does it keep sliding after you push it a bit, etc.

    RPG -

    Jakub, as I mentioned, I get what I perceive as a scratchy sound even when pushing a rod through a single bearing, so I don't think it's related to misaligned bearings or frame.

    Has anyone here tried the Drylin bearings? I don't want to go any further with my build until this is sorted out.

    RPG - Reply

    Hi RPG, you're right, if you take just one bearing and smooth rod, it shouldn't produce any scratchy sound. Try to contact our support and ask for replacement (info@prusa3d.com).

    Jakub Dolezal -

    I was having the same rough grinding issue. I noticed that if I loosened the u-bolts holding the bearings it was a lot smoother. That told me (in my case) that it's an alignment problem.

    To fix it, I started moving the stage back and forth feeling where it was roughest. I would take that corner and back the 13mm bolts off one side then tighten them on the other. I'd check the stage again to see if it improved. If it got worse, I'd move it the other way. Once it was smooth all the way across, I tightened up the u-bolts and repeated the process again.

    I'm not feeling any grinding or roughness now. It's not silent but it's smooth. I don't have a set of calipers so this method might work for others who also don't have that tool.

    Joe Goldthwaite - Reply

    What’s the consensus on these bearings needing replacement?

    Same issues as the video above. Definitely not alignment problem, happens when sliding free bearing on free rod also.

    Spent several hours tuning the frame as square as possible, so I know thats not the problem.

    Also not overtightened, getting the same behavior from the bearings that are in the “x axis” bag too.

    There’s only one bearing (out of all, including x axis bag) that moves like I would expect (minor sliding noise, low friction) the rest of the ones in the kit make the scraping sound and seem pretty “sticky”. Tried on multiple rods to rule that out.

    Just curious because its not really clear what’s intended here. The carraige moves without binding, but with much much higher friction than I would expect. It requires much more effort to move it than seems appropriate. The one smooth bearing has me second guessing the rest of them. Is the video above considered "normal?"

    Thanks for your help

    Scott - Reply

    Hi Scott, it is very hard to explain the "smooth" movement by words. I'm working with my colleague on a video, but it will take some time.

    Jakub Dolezal -

    Hi Jakub, any news on the video? My unit is gathering dust at step 25 until I can figure out what’s going on. I don’t to do anything past this step if my bearings and/or rods are bad in some way. It’s a bit frustrating; I probably should have paid a bit extra for a pre-built unit :-)

    RPG - Reply


    Can someone recommend a reputable retailer selling good quality LM8UU linear ball bearings?

    I have to say the quality of the ones I got were sub-optimal, to put it lightly. Judging other peoples comments on this, I’m far from being alone. Thankfully I read those comments and tested them before I put them in, so they’re not suffering from “over tightening”.

    If I order another 3 from Prusa, I’m afraid I’ll just the the same again.

    The Rods:

    They are smooth, but nowhere as smooth as I’d expect. Has anyone tried polishing them, and if so, what did you use?

    They also differ in length by 1mm.

    Olafur Egilsson - Reply

    Just received my kit and now I’m at this step, and also wondering if the bearings I received are “good enough”, or need to be replaced. When I put the 8mm rods in the bearings by themselves, they will slide all the way out pretty easily if I tilt it towards a vertical position. Same once I put them in the bearings after they’re attached to the y-carriage. I’ve carefully aligned the frame, and have 178mm distance between rods. The y-carriage slides fairly easily, but the side with the single bearing is pretty noisy compared to the side with two bearings. I’ve tried adjusting the u-bolts for the bearings, but I haven’t noticed a big difference.

    Prusa: What do you suggest? Should I keep going, or request new bearings? Changing these out later would be a hassle.

    Mike Baker - Reply

    UPDATE: I removed the single bearing that was noisy, and compared it to all of the other bearings that I hadn’t opened yet, and this one definitely seems bad. All of the other ones glide very easily, without a lot of noise, so I used one of those to replace the noisy/scratchy one. When I was getting ready to put the y-carriage on again, I noticed I had to slightly flex the rod with the single bearing to get it aligned with the y-corners. As a result, I moved the 2 y-corners on that side in about 1mm, put the y-carriage back on, and now it is moving very smoothly without a lot of noise. So, while the video says 178mm, mine is much smoother at 177mm. Your results may vary.

    At any rate, I need to contact Prusa for a replacement bearing.

    Mike Baker -

    Hello, I juste received my kit and have the same scratchy noisy issue. One rod seems ok but noisy; the one bearing. The second one less: any misalignment or rod bend is payed twice. Once mounted is like it has more difficulty on the end of the courses…. I feel that’s come from the step 11: streching the assembly with the rods may bend them.

    Jean-Baptiste Bussard - Reply

    If anyone wants my kit (which is stuck at this stage without much in the way of replies from the team) and is prepared to pay some much-less-than-original price for it (plus shipping from Asia), please email me at rrrppp999999 at gmail dot com.

    RPG - Reply

    When inserting rod into bearing, about 3 or 4 small ball bearings fell out. I completed the assembly and have sent a request for a new bearing.

    Joe O. - Reply

    • Insert the assembled Y-carriage into the Y-axis stage.

    • Ensure the correct orientation of parts (the Y-motor mount is on the right and the single bearing is on the bottom).

    • Note the location of the Y-carriage orientation marker - it's important the Y-carriage is oriented as in the picture !

    • Insert zip ties into the holes in Y-corners.

    • Ensure the correct orientation of zip ties (head of the zip tie should be facing out from the Y-axis stage).

    • Press smooth rods (330 mm) all the way in the Y-corners holders. Don't use excessive force.

    Step 28 should be before Step 26

    Petri Nurminen - Reply

    Hi Petri, yes you're right. I moved the step 28 in step 24.

    Jakub Dolezal -

    Agree with above comment and it make no sense to not include the in the bag of section 2.

    E Phenix - Reply

    Hi E Phenix, I made adjustments regarding the steps order. Regarding the nuts, we will keep them in bag 9.SPARE.

    Jakub Dolezal -

    At this point, I have it all assembled correctly. However, I've noticed a squeak and increased resistance when pushing the stage the last 2 cm before hitting the end stop. The squeak comes from the single bearing (motor side of assembly) and the increased resistance is fairly significant. I've swapped the rods and it still happens so it's not like one rod is bent. I've swapped bearings and it still persists.

    The assembly glides fairly well all throughout it's range EXCEPT for the last 2 cm of the single bearing rod close to the motor. Any ideas?

    Marcus Pienaar - Reply

    Edit: Found it. The y-belt holder was rubbing against the motor enough to make a noise and add significant friction.

    Marcus Pienaar -

    Hi Marcus, did you solve the problem and can you attach a photo? The belt holder shouldn't be touching the motor at all.

    Jakub Dolezal -

    Need to add steps to verify the parallelism of the smooth rods with a caliper. Confirm that the external distance from rod to rod is 178mm at the beginning , center and end. Lack of parallelism will cause excessive bearing noise due to misalignment. "Misalignment that can lead to increased co-efficient of friction, premature wear, and possibly binding that results in catastrophic failure." - (source: PBC Linear, Pacific Bearing). This is included in the video, but without explanation of the impact. Recommend to add warning note with posible impact.

    Waldo - Reply

    Hi Waldo, thank you for the comment. We are constantly asking through the whole chapter, the user to ensure correct positioning of the bearings (their mutual position), rectangular shape of the Y axis and check the smoothness of the movement.

    Jakub Dolezal -


    It should be assumed that all parts are perfect (bearing and rods). However free motion of an 'over defined' sliding stage (as in the case of the MK2S stage) is impossible to be achieved per the assembly instruction up to know (position tolerances of perfect alignment of the rods and bearings must be in the range of no more than 0.01 mm).

    Remember: Free, frictionless, motion of the stage is critical and must be assured!!!

    Shachar Rotem - Reply

    If free motion was not present, do the following:

    1. Move the stage back and forth all the way and check for free motion on both sides of the stage.

    2. If motion is not COMPLETELY free on both sides, continue to my step 3.

    3. If motion is free on the left side continue to my step 8, else: Move the stage all the way to the right (per picture 1). Loose both nuts of the top upper threaded rod of Y-AXIS FRONT (upper left corner in picture 1).

    4. Recheck free motion per my step 1.

    5. Re-tighten the nuts in order to reduce or increases the distance between the 2 bearing rods (smooth rods) until free motion is achieved on the left side of the stage.

    6. Note: if all previous assembly steps were preformed correctly, reposition of the nuts should be in the range of no more than 3/4 rotation.

    7. If free motion cannot be achieved, go back to Prusa assembly Step 9.

    Shachar Rotem - Reply

    8. If free motion in now achieved on both sides of the stage you're done, else: move the stage all the way to the left and loos both nuts on the top upper right corner of the stage, of Y-AXIS REAR (see my step 3)

    9. Repeat my step 4 to 8, this time for the right side of the stage

    Note: if the initial position of the different stage parts was highly misaligned, it may be necessary to repeat this sequence more than once.

    Shachar Rotem - Reply

    We should use a jig for this critical step!

    If the bottom of the Y corners had 2 holes each (small enough for M3 to thread into) and they lined up with holes in the Prusa i3 frame you would have a jig that ensured everything was square and parallel. Follow the steps to get things close to right place, screw down the corners to the frame, and then check that the Y-carriage moves freely and the rods have no slack. Tighten incrementally and carefully and you should be aces, right?

    This kit is brilliant, but this is the slowest and most difficult step I found. It seems easy to continue on with a less than optimal Y-axis condition. Without adding an parts, but a few extra holes in the frame and corners, it could be foolproof. My 2cents.

    Guy - Reply

    I’m at this step, and motion is free for the length of the rods. But the bearings are kind of noisy - is that normal? Even before inserting the rods into the stage (with the rods just in the bearings), there was still the same noise.

    Ira Schonfeld - Reply

    Hello everyone…how freely is the y-carriage supposed to move? like ABSOLUTELY NO friction? because I have to inflict a little force to move it…does it have to be like butter? I am not very confident with how I built this so far especially because of this friction…it moves at around 80-90% ‘freedom’…thanks

    Martin Sipos - Reply

    This is where one of the Y-corners cracked. They have redesigned the parts to be a little larger than is shown here but the part still broke.

    Kevin - Reply

    Also, to get the 8mm rods aligned, I measured the inside distance on each end with a digital caliper (you will need to place a block or something inside to able to measure with a 6” or 150 mm caliper.). I loosened only the M8 nuts on one Y-corner at a time. Using small turns (about 1/4 turn) I was able to get two ends of the within about 0.05 mm. Next, I loosened all the M3 nuts holding the bearing U-bolts.. Then, I moved the Y-carriage back and for while slowly and evenly tightening the M3 nuts with a socket. This got the carriage fairly smooth but still the bearings are noisy

    Kevin - Reply

    I’d recommend a “gravity test” here - the y-axis stage should freely slide by gravity alone when you lift one end of the assembly or the other. Mine didn’t, and I found the rods were not fully parallel. A caliper check and slight adjustment later, it now slides perfectly.

    Bill Robitske, Jr. - Reply

    • Using pliers, tighten the zipties as shown in the picture.

    • Ensure the correct orientation of zipties connection.

    • Trim the zip ties after tightening.

    Feel free to skip these zip ties until you're done building and sure your printer's frame is perpendicular and perfect. The printer works even without them, they're just some additional security to keep the rods in place.

    Also make sure the ziptie heads are on the side and not on top of the rods. Otherwise they'll stop the printbed from moving correctly. (The warning above sounds a bit misleading as it might only cover the side where the head is going to be.)

    Mario Liebisch - Reply

    Hi Mario, I recommend sticking to the manual. We include extra zip ties in case you discover, you have done something wrong later, so you can cut them, correct the issue and replace them with new.

    Jakub Dolezal -

    May we trim the zip ties at this point? (I don't see tails in the subsequent photos.)

    Gordon McDonough - Reply

    Hi, Gordon, yes trim the zip ties after tightening. Thanks for the feedback ;)

    Jakub Dolezal -

    Needs updating in printed manual.

    Merrill Albury - Reply

    Hi Merrill, printed manual is updated from the online version frequently. However, there will be always slight delay as we are improving the online version on a daily basis.

    Jakub Dolezal -

    Hi, at this point, I tried sliding the Y-carriage gently back and forth to test how it goes. I can feel a bit of resistance (not very smooth sliding) and after some time, I noticed some lateral scratch starts to appear on the rod. It looks to me to be caused by the bearing as the scratches terminate at the extremes of the reach of the bearing along the rod. Am I doing anything wrong here? Does it make sense to continue proceeding with the succeeding steps? Please note that the carriage still slide easily by just gravity, it is just it's not very smooth. This is my first time assembling a Prusa as well, so I am not really sure how smooth the Y-axis should be.

    Ruchie Custan - Reply

    Hi Ruchie, the movement should be smooth. You might have one side of the Y-axis smaller (too tight) compared to the other. This is causing inclination of the smooth rods and leading to increased resistance.

    Jakub Dolezal -

    I feel I have the same issue as you…there is some resistance…smoothness is like 80-90%..so how do we make it right? any tips please?

    Martin Sipos -

    • DON'T TRIM THE BELT unless you are asked in the instructions!!!

    • Insert the Y-GT2 belt (shorter one) in the Y-belt holder as shown in the picture.

    • First insert the flat part of the belt in the holder.

    • A reference video is included at step 36 covering steps 29-35.

    Although it is obscured by the pliers in the first picture, the belt is flipped in the second picture.

    Robert Klein - Reply

    Hi, Robert, you are right the belt in the pliers is flipped, I will correct it.

    Jakub Dolezal -

    Instructions say "Insert the Y-GT2 belt (shorter one) ", but there is only one belt included in bag 2. Am I supposed to have 2 belts?

    Spencer O - Reply

    Hi Spencer, there are two belts in the kit. One is for Y-axis (shorter) and second for X-axis (longer). We are mentioning the relative length to ensure nobody swaps the belts.

    Jakub Dolezal -

    I agree, the "shorter one" comment threw me off as well as there is only one in the #2 bag. Adding a few more words to clarify would help...like "do not use the longer belt from bag #3"

    Chad S Richardson -

    I agree with Chad. A simple update to the instructions will help reduce confusion.

    Justin -

    I also wasted a couple minutes searching for the second belt in the step 2 bag.

    Doc Wilco -

    FYI, the reference video is on Step 36 not Step 37.

    Steve Trefethen - Reply

    Hi Steve, thank you for noticing. Steps were corrected.

    Jakub Dolezal -

    I tried to count the teeth in the picture to figure out how much overlap to use.

    I counted 32 teeth, and that’s how far in I matched the end of the belt to before engaging the two pieces. I used the same 32 tooth spacing in step 33.

    My tension was just fine using this method.

    Paul Isaacs - Reply

    • Guide the belt around the pin as shown in the picture.

    • Push the belt all the way into the belt holder.

    It might help to provide a measurement as to the amount of overlap on the belt. I had too much on this step and had to redo this when I got to step 33.

    Cory McWilliams - Reply

    Hi Cory, thanks for the suggestion. I will try to measure few printers and see if I can get reasonable numbers to share.

    Jakub Dolezal -

    As Cory mentioned, a measurement for the "right amount" of overlap would be helpful for tensioning.

    However, more importantly IMO would be to have a measurement for the maximum amount of overlap so that the overlap doesn't interfere on either side.

    During my build, I placed the belt such that the overlap was even on both sides (as recommended in step 34) and got interference, when I moved it a tooth to the other side, I got interference on the opposite side. I was forced to cut a tooth from the belt. Perhaps environmental differences (temperature, humidity, etc.) are causing some of the belt issues raised here (though there's no way to know if people are simply bad at following directions). In any case, knowing the maximum amount of overlap before it would interfere with either pulley would be helpful.

    Nick - Reply

    Hi Nick, we are on it. I will update the manual as soon as I have values to share.

    Jakub Dolezal -

    I suggest including the length of the belt with tolerance (i.e. 650mm +-2mm) as well as the amount of expected overlap would help. My belt measures ~665mm, I get considerable overlap. Online support still told me I should not cut the belt, but told me the length of the belt should be 65cm.

    For now, I will leave the overlap, complete the build and trim if necessary.

    Frederick Steinmann - Reply

    • Undo the M3x10 screw.

    • Rotate the motor until it hits the surface (table) as shown in the picture.

    Add Comment

    • Place a GT2-16 pulley on the Y-motor shaft as shown in the picture.

    • One of the screws must be facing directly against the pad (flat part) on the shaft. Note you don't have to remove the motor from the frame.

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

    • Don't tighten it yet, we'll get to that later.

    The pulley should be towards the end of the shaft, away from the body of the motor.

    Tony Hansen - Reply

    Hi Tony, thanks for the comment. Just yesterday I added a picture showing gap between the pulley and the motor.

    Jakub Dolezal -

    Use a ziptie as a space between te pulley and the motor housing. As this has a thickness of 1 mm, this allows for a correct offset while mounting the pulley.

    Mathieu Robroek - Reply

    Hi Mathieu, good point. Zip ties are around 1.1 mm thick. Thanks for the suggestion.

    Jakub Dolezal -

    Tony’s comment that the pulley should be towards the end of the shaft is misleading — that can only happen if the pulley is on the wrong way around. If you find that the motor runs into the Y carriage mount unless you put the pulley out towards the end of the shaft (i.e. a distance of more than 3mm between the pulley and the motor body), then check the orientation of the pulley on the shaft. You might, like me, at first put the pulley on backwards. When I flipped the pulley back around the right way, everything lined up with the recommended 1mm distance.

    Van Albert - Reply

    • Run the Y-axis belt through the Y-motor pulley and the Y-idler part.

    Add Comment

    • Using the pliers, insert the flat sides of the belt into the Y-belt holder as shown in the picture.

    • Then guide the belt around the bottom pit as shown in the second picture.

    How much should I be concerned about excess belt sticking out on the motor side? It currently winds onto the pulley a little bit just before the limit switch clicks. Not sure if this could be a positive or a negative, as it would provide some damping before hitting the switch with too much force.

    Andrew Ahlfield - Reply

    Hi, Andrew, the belt sticking out shouldn't wind onto the pulley. Is the belt evenly distributed?

    Jakub Dolezal -

    I am having the same issue. And no, it is not evenly distributed. I did the first side leaving the same amount sticking out as in the picture (1/8"), then the other side (motor side) is ending up with about 1.25" hanging out....getting caught in the pulley.

    Not sure how consistent the belt lengths are, but if so, it might be better to show a more realistic picture of the extra hanging out on the first picture to help you have a better chance of getting the distribution even in the first try.

    Also this (being a bit more specific on excess belt lengths on each side) would help in gauging if the belt tension is within a good range. I.e. if you have 1.5" or more of excess belt, you may have it too tight...or vise versa.

    Chad S Richardson -

    • Using the pliers insert the belt all the way into the belt holder.

    • Do not cut any excess of the belt, it should be evenly distributed on both sides as shown in the picture.

    • The belt shouldn't be tight at the moment.

    This did not work for me. After following these instructions I was getting ovals rather than circles for my printing. I went back and took the one screw off the motor and loosened it again, then tightened this belt as tight as I could by fingers/hand, it is not good to use pliers and there is no need for pliers! Then I rotated the motor back. The belt could "twang" like a guitar string and my ovals are now circles.

    You will see that the 'twang' also applies for the x-axis belt.

    Wol Bar - Reply

    Hi Wol Bar, you can use any tool that fits you. However, I wouldn't recommend completely abandon pliers, because the belt overhang is too short for you to tighten it properly by fingers. Also with fingers, you might not place the belt all the way in.

    Jakub Dolezal -

    The twang like a guitar string metaphor is perfect. Makes me feel confident that I've got the tension that I'm looking for, but not too much.

    Andrew Ahlfield -

    Belt loop on the left should not protrude more than two tooth. If more, it will interfere with the motor pulley not allowing for a smooth trigger of the limit switch. You can verify this by manually pulling the table to trigger the limit switch, if an extra pull is needed it will be due to the belt loop. This verification is in step 43, but the note should be on steps 33 and 34.

    Waldo - Reply

    Hi Waldo, if you place the belt evenly on both sides of the holder, you shouldn't have any issues. The length of the belt is designed so it doesn't interfere with any other part of Y-axis.

    Jakub Dolezal -

    Thank you for this insight Waldo! I re-spaced my belt and now I'm not getting interference on either side. Jakub, would it make sense to include a detail picture noting the equal spacing on both sides of the belt? A caution about interference with the pulley could be good as well.

    Andrew Ahlfield -

    Hi Andrew, noted and photo will be added. Thank you for the feedback :)

    Jakub Dolezal -

    I evenly distributed my belt but I had several belt teeth exposed on both sides, and it was interfering with the endstop switch. I had to trim 5 teeth off the belt to allow it to work properly

    Nik W - Reply

    I had many teeth poking out and decided to cut it. Turns out I used the shorter linear rods. Don't make the same mistake I did.

    Bob Strait - Reply

    My belt is evenly distributed as well, and I verified the linear rod sizes, but I still have protruding bits of the belt interfering with the endstop. I'll postpone cutting off the excess until the very end of the build, but from the photos it looks like the 3D printed Y-idler part might be slightly longer on my machine, resulting in the belt being too long.

    Denis Kobozev - Reply

    my belt is far too short to make a loop around the motor and pulley and back to the y belt holder. I've verified I'm using the 330mm rods which should be the middle size of the 3 rods, I believe. the belt, laid flat measures about 490mm. is that correct? I've a sinking feeling I got shorted. I'm very excited to get this together and afraid I'll have to wait to have one sent. Can someone confirm the measurements I've stated are correct? thanks

    Skip McBride - Reply

    What is the correct belt length? Mine is ~670mm and I can't get the belt tight at all without 1-1.5cm overlap. If I use 2 teeth overlap like on the pictures the belt is completely loose.

    Kamil - Reply

    I agree on belt length. It is a little longer and maybe someone from prude can tell us what the length should be. Just make sure you leave enough say a couple of teeth. That's what I have done.

    les - Reply

    My belt was too long as well. I went to online chat support and asked what the length of the belt should be and was told that it should be 65cm, mine was ~66.5cm. I ended up cutting the belt, but not until after I had completed the assembly, I wanted to make sure that I had everything else correct.

    Frederick Steinmann - Reply

    Guys current correct length of the belt for Y-axis is 650 mm, please cut the belt ONLY if you are exceeding this dimension. Also, this value might change in future, so please always check the manual or ask our support before any trimming.

    Jakub Dolezal - Reply

    I had to cut 8 teeth too. Guys, save your time and measure belt length before installing it. 650mm is exact length needed.

    TOMAS - Reply

    Please promote the following comment into the instructions…

    I had to cut 8 teeth too. Guys, save your time and measure belt length before installing it. 650mm is exact length needed.

    Zachary J. Fields - Reply

    • Rotate the motor back.

    • Screw in the removed M3x10 screw.

    • If you have to apply too much force and experiencing troubles, rotate the motor back, repeat previous step while making the belt more loose.

    • The belt should be quite tight, check it by pressing together both sides in the middle of the frame with little force.

    This is the only part I had to go back to after finishing the printer and even getting it perpendicular at first try: Make sure the belt is very tight. Tension changes a bit once you put the whole printer upside down, so make sure its tight. Don't worry about stressing the belt. If you can still screw in the screw, you should be fine. If you're getting slightly unclean vertical edges in one direction in your prints, this is the culprit.

    Mario Liebisch - Reply

    Hi Mario, you should definitely tighten the belt, but not too much. You can then experience layer shifts during print. You are right that screwing/unscrewing the motor can be used as a check.

    Jakub Dolezal -

    How do you know if you have tightened the belt too much? Mine is very tight. So much so that it makes the y axis harder to move than before. Is this normal?

    Hayden P Mcgarity-Bashiri - Reply

    Hi, Hayden, the belt should be tight, however, it shouldn't prevent the movement of the Y-carriage. If you move the Y-carriage with your hand the movement should be fluid and smooth, you shouldn't fight with the carriage to move.

    Jakub Dolezal -

    It might be good to add a caution note here and step 21 to make sure that the motor wires are in the notch in the Y-motor distance part and not getting pinched between it and the motor. Perhaps the notch could be made a little wider / flared at the bottom to help prevent this.

    Mike Behnke - Reply

    Hi Mike, thanks for the suggestion, I will discuss the possibility to make the adjustment.

    Jakub Dolezal -

    Am struggling with getting belt tension right. I've actually loosed it as it seemed to be making carriage movement more noisy ... and hence probably adding to bearing wear. Will this bring problems down the line?

    Mark Enderby - Reply

    Hi Mark, the tension of the belt shouldn't be too big to prevent you from moving the carriage by hand, but it shouldn't be too loose. The belt should be working like a "string".

    Jakub Dolezal -

    Hi Prusa and fellow builders, why such a very unspecific instruction on this point? The guitar string analogy is excellent. Anyone with a guitar or a piano or a mobile phone can check the frequency by ear or by some guitar tuning app. Mine appears to have a low note at about 61 Hz (which my phone could measure directly) + a faint twang at approximately 375 Hz (between the F4# and the G4 right below the tuning fork 440 Hz A4). Perhaps Prusa could specify the ideal frequencies and tolerances?

    I did not measure my Y-axis belt before assembly, and have 5-6 teeth free on both sides - clearly interfering with the roller and the motor pulley. Will not trim until the build is finished, and I have verified everything else is correct.

    Terje Krognes - Reply

    Hi Terje, thank you for the suggestion. We are trying to find a way for everyone to setup their belt properly. However, so far no solution was good enough. Your idea with string analogy is very interesting and might be working. I need to check, whether the belt is always the same in terms of frequency properties and also the difference in measurement between several phones. I’m afraid each phone (even from the same manufacturer) will have different sensitivity and range.

    Jakub Dolezal -

    Watch you don’t pinch the motor wires when rotating the motor back into position.

    David H. Brown - Reply

    Might have pinched the green wire. Guess I have to wait to finish before I know. How difficult is it to fix the wire?

    Dory Sheldan - Reply

    Im having quite a bit of trouble getting the belt to be tight enough while also making sure the excess doesn’t interfere with the pulley or motor. I’ve tried it 3 times and each time i’ve either gotten the belt tight enough but not been able to hear the click of the endstop, or ive been able to hear the click but the belt is way too loose. Any suggestions?

    Scott Smith - Reply

    • Insert the Y-GT2 belt (shorter one) in the Y-belt holder. Run the Y-axis belt through Y-idler part and the Y-motor pulley. insert the belt all the way into the belt holder.

    • The belt should be quite tight, check it by pressing together both sides in the middle of the frame by gentle force.

    @Pursa: Thanks for the video! But i think this should be updated because the belt is not evenly distributed as mentioned in Step 25. Left side has around 7 teeth sticking out and the right none. This will prevent the Y-carriage move freely to the front because the 3-4 of 7 teeth will get in the Y-idler and cause issues within calibration and so on.

    Waldemar - Reply

    Hi Waldemar, thank you for feedback. There is a new video with the correct belt distribution.

    Jakub Dolezal -

    The holder is rotated 180 degrees with respect to what is earlier pictures. This is confusing.

    Michal - Reply

    Hi Michal, sorry for confusion. Video is now corrected.

    Jakub Dolezal -

    In step 25, the belt tentioner is shown to have its back towards the two bearings, and in the video it is shown reversed - with its back towards the single bearing. Perhaps this is of little importance, but which one is correct?

    Saulius - Reply

    Hi Salius, the correct position is Y-belt-holder facing the single bearing, like in step 25. The video is now in comply with the photos.

    Jakub Dolezal -

    I don't think it's possible to install the Y belt holder the way the video shows. The holder has a longer side and a shorter side. When flipped the way the video shows, the short side would have to contact the end stop but probably won't clear the pulley. I install the way the instructions said but measured and it looks to me like the short side would hit the pulley with about 2mm before it hits the end stop. That's just rough measurements, but if I lose 2-3 mm of travel at my end stop by playing it safe then I'm ok with that.

    Mythandar - Reply

    Hi Mythandar, you are right. I'm sorry for confusion. The video was corrected.

    Jakub Dolezal -

    Yes as mentioned video doesn't match instructions exactly but is useful to aid the assembly. This was the trickiest step to complete and I had to snip the excessive off the belt to stop if fouling the end stop switch

    Neil Winstanley - Reply

    Hi Neil, the video was corrected. Anyway, the belt length for Y axis should be just right, therefore no need for snipping.

    Jakub Dolezal -

    Hi, I agree, the belt is a bit too long for me too. I need no more than 2 teeth out from the Y belt holder, otherwise the holder can't touch correctly the endstop (the end of the belt touches the motor pulley and stops the Y holder before the latter touches the endstop button). But the problem now it that I have 5 teeth out from the Y holder on the other side, and the belt touches now the pulley of the Y-Idler. I should cut at least 3 teeth to solve the problem. But I do not know if it's important or not that the belt touches the Y-Idler pulley? If not I do not have to cut it.

    Note that below this ratio of 2 teeth/5teeth on each side of the Y belt holder, the belt is not tight enough - according to your video.

    Thanks for your answer.

    P.S. you should perhaps precise how many teeth have to come out from both sides of the Y belt holder.

    Cedric Bellissent - Reply

    • Move the Y-carriage as close as possible to the Y-idler.

    • Adjust the Y-idler as shown in the picture (623h bearing housing should be in alignment with the belt).

    • Before tightening the nuts, ensure the Y-idler is in horizontal position.

    • Tighten the M8n nuts gently to avoid damaging the 3D printed part.

    (also here like in the v1.05 assembly manual) At this end of the y idler no endstop is present. I think the "make sure that you heard click sound" belongs to the next Step 39

    Daniel Neudert - Reply

    Daniel, thanks for the feedback. I moved this part to the step 39.

    Jakub Dolezal -

    This says "Move the Y-carriage as close as possible to the Y-end-motor." But the photo shows it close to the idler (which is where you want it.)

    Glenn H Shelton III - Reply

    Hi Glenn, you're right. I will correct the description. Thanks.

    Jakub Dolezal -

    I'm pretty well lined up, but the belt is to one side of the 623h bearing housing and not centered. Thought I'd adjust it over just a bit, but can't. My guess is that there's too much friction between the Y-idler material and the threads on the threaded rod - given the tension on the belt. Should I be concerned?

    Mike Ogilvie - Reply

    • Adjust the Y-motor-mount as shown in the picture (the belt must remain straight and the motor should not collide with the Y-belt holder part).

    • Make sure that you heard "click" sound and the Y-endstop is triggered.

    • The belt part of the pulley has to be in axis with the belt itself.

    • Tighten the M8n nuts gently to avoid damaging the 3D printed part.

    I had to move my motor mount remember to undo both M8 nuts or you can distort the printed motor mount

    Neil Winstanley - Reply

    Hi Neil, thank you for your suggestion. When moving the motor, you must release all nuts, move the holder freely and then tighten them again.

    Jakub Dolezal -

    My motor mount didn't really slide on the threaded rod, the hole was to tight, so I had to slide it over by moving the nuts on one side to where I wanted it, roughly, then slowly tightening the other side back and forth trying to keep the motor mount moving evenly.

    One thing I found is while I do get the end stop click, right before the plate is all the way at the end there's more resistance in sliding, the last cm or so takes more effort to push to engage the end stop. Guessing the guide rails may be off on that end? I get even measurements corner to corner but I guess I need to check for square more closely.

    Daniel Loughmiller - Reply

    Hi Daniel, thanks for the feedback. We increased the holes a bit to improve the movement ;)

    Jakub Dolezal -

    The holes on my Y Motor Mount were also too tight. Was a bit of a hassle, but I made it work.

    Eitan Cher -

    I'm seeing a similar issue to Daniel except pushing the carriage all of the way towards the motor doesn't reach the limit switch because the Y-belt holder part is hitting the pulley before it reaches the limit switch. At first, on my assembly, the tail of the timing belt was sticking out from the Y-belt holder and hitting the pulley before the pulley hit the Y-belt holder. Also, when I was installing the Y-belt holder part I noticed that the hole for the bolt away from the motor had a different depth than the hole for the bolt near the motor. This prevented the bolt from being long enough to reach through the Y carriage. Another issue that I noticed about the Y-belt holder part is that it doesn't provide very good axial alignment of the belt with the pulley and the idler. I think the Y-belt holder design needs some refinement.

    Murray Foster - Reply

    Hi Murray, thanks for the comment. I will forward your findings to the developers.

    Jakub Dolezal -

    I had an overlap of four teeth coming out of the belt holder on the motor side and this is enough for the motor pulley to hit the overlap before the end stop engages. I think something should be mentioned about this in the belt step

    Jules - Reply

    Hi Jules, is your belt distributed evenly on both sides? It is mentioned in step 34.

    Jakub Dolezal -

    I am also finding that the Y-belt holder contacts the Y-motor pinion before it engages the limit switch.

    Brandon Gleeson - Reply

    Hi Brandon, can you please send photos to info@prusa3d.com including my name? I've checked several printers in our assembly room and they are all fine. I need to see, what is happening with your printer. Thanks

    Jakub Dolezal -

    The Y-GY2 belt appears too long as others have found. I have refitted and pretensioned it about 10 times and still have too many teeth overhanging which prevents the stops switch & idler interference. I have checked I'm using the correct 330mm rods and slack only just taken up on the ends in the Y-corners.

    The Motor side has 9 teeth overhang and the Idler side has 5 teeth overhang. Equally distributing the overhangs won't take up the excess.

    I have measured the belt .. it is 67 cm long (being the shorter of the two belts in the kit). I am reluctant to cut the belt at this time without guidance.

    Brian Knight - Reply

    Hi Brian, current correct length is 650 mm for Y-axis. If your belt is longer, please trim it, but measure it twice ;)

    Jakub Dolezal -

    Same situation as Brian, belt far too long - have to choose whether to obstruct switch or pulley. If I distribute it evenly without obstructing either side, it has so much slop that I wouldn't trust it. Have it tuned to slight twang - have 2 teeth sticking out on motor side and 7 on pulley side. Hesitant to cut it though, especially the ~7mm I'd need to lose to clear the pulley. Rest of frame is very precise, used correct 330mm rods, etc etc. FYI Brian I'm getting about 66cm on my belt. Any official word on how long its supposed to be?

    Scott - Reply

    Hi Scott. No response back from Prusa yet, but it seems we're not alone with this issue.

    I found an article with same problem on the site by Ed Lingo .. Y-GT2 Belt length

    I think the cutters are coming out shortly despite the party-line from Prusa when responding to other User's comments.

    Brian Knight -

    Hi Scott, current correct length is 650 mm for Y-axis.

    Jakub Dolezal -

    Hi Scott and Brian. Same problem here, Y-GT2 is way too long. Waiting for official guidance on how much to cut before doing anything !

    MichelS - Reply

    Hi MichelS, current correct length is 650 mm for Y-axis.

    Jakub Dolezal -

    Thanks Jakub ! Mine was 9mm too long. I trimmed it and the tenion looks much better now.

    MichelS -

    I had an email response when I got a bit impatient waiting ... Tech Support said "For the assembly. It is better to have longer belt than needed. Otherwise it would be pretty hard to put it around the Y-belt holder, motor and pulley. Btw. are you sure that you used the proper belt? there are two. One for Y and 2nd for X axis."

    By this time I had already cut off the spare teeth leaving 2 showing on each side of the Y-Belt-Holder.

    I have finished the build, tested and calibrated and printed first demo print successfully so don't think I did wrong !

    Brian Knight - Reply

    Hi Brian. Thanks for the information ! My belt is the right one, I just checked again. I will then cut it shorter too.

    MichelS - Reply

    My belt holder is at least 2mm short of reaching the limit switch when it hits the pulley. I have opted for black parts - don't know if this makes a difference. I will have to glue a packer piece to the belt holder. Not very happy with that.

    Graham Legg - Reply

    Hi Graham, there is no difference between black and orange printed parts, they should be the same size. Would you be so kind and take some photos of your situation? Please send them to info@prusa3d.com, we will sort this out and also it is valuable feedback. Thanks

    Jakub Dolezal -

    Hi - What does it mean: Make sure that you heard a “click” sound and the Y-endstop is triggered. I can’t figure out what that means? Thanks

    Kimberly Hobson - Reply

    What does “Make sure that you heard "click" sound and the Y-endstop is triggered” mean?? When/how would I have heard a click?

    Kimberly Hobson - Reply

    I’ve noticed that I have to push quite hard to get the limiter switch to click against the motor holder. Is this normal or did I not assemble the base straight?

    Joe P - Reply

    • Tighten the screws in the pulley.

    • One of the screws has to be tightened directly against the pad (flat part) on the shaft.

    • Keep a small gap between the motor and the pulley.

    Not sure what size these screws are but neither supplied allen key fits them. One too large, one too small.

    Matt Lemon - Reply

    Hi Matt, in the package should be Allen key size 1.5 mm, 2.0 mm and 2.5 mm, to tighten pulley please use the 2.0 mm size.

    Jakub Dolezal -

    My kit also does not appear to have a 2.0 mm Allen key included needed to tighten these screws. I received the kit around the same time as Matt Lemon's comment. I have 2 2.5 mm Allen keys (different lengths) and 3 1.5 mm Allen keys. Maybe kits packaged around mid August are packaged with the wrong key? I was able to tighten the screw with one of my own 2.0 mm Allen keys.

    James Varvaro - Reply

    Hi James, thanks for the feedback. I will report it to the production team.

    Jakub Dolezal -

    What is the size of the screw that goes in the pulley?

    Kim Vojensky - Reply

    • Ziptie the cables to the threaded rods as shown in the picture.

    • Cut and discard excess ziptie.

    • Tighten the zipties carefully to avoid damaging the wires.

    • Be careful while cutting the zipties to avoid cutting the wires.

    The double nuts shown here look like they are far out of spec from the 100mm that was specified earlier. Is this correct?

    John Mangan - Reply

    Hi John, keep the 100 mm distance.

    Jakub Dolezal -

    They might be a little shy- mine looked like the picture and I found that they were only 90mm. I went back and moved them up to 100mm. I don't have mine tightened in yet, as there has been nothing to mate against yet that will provide the proper constraint, so they may have moved around a bit. I'm waiting to tighten the ziptie closest to them until I find out their exact destination.

    Andrew Ahlfield - Reply

    Hi Andrew, yes please keep the 100 mm distance until you assemble the Z axis aluminium frame.

    Jakub Dolezal -

    • Place the assembled Y-axis on a flat surface.

    • Check if every corner is touching the ground.

    • If some corner is in the air, try twisting the axis slightly.

    • You can also check it by tapping each corner and listen if it's making any noise.

    • This is your last chance to ensure the Y-axis is perfectly angled and level. It'll save you a lot of hassle later!

    • You can use aluminium frame for check, but be careful for possible scratches.

    Watch the video on y axis levelling. It's good.

    Wol Bar - Reply

    Hi, Wol Bar, thank you ;)

    Jakub Dolezal -

    Where is this video you speak of?

    Andrew Ahlfield -

    See the video for Step 9.

    John McNelly -

    The suggestion to use the aluminum frame as a flat reference is a good one. It would be even more helpful if you move the suggestion to the initial leveling step 9. I couldn't find a perfectly flat table in my home until I remembered the granite slab in the bathroom.

    Lane Hauck - Reply

    I found that if I set the aluminum frame on a surface that was not level, it would deform slightly. This gave me an overall false sense of level. When I picked up the frame with the y-axis assembly on top of it, my "out-of-level" issues went away. Would love to hear other's thoughts on this.

    Andrew Ahlfield -

    Hi Lane, thanks for the suggestion, we will consider it. However, it is crucial to check the possible distortions also at the very end.

    Jakub Dolezal -

    Hi Andrew, alumininum frame should provide you with flat surface, however the frame isn't rigid enough to be placed on very uneven surface. Please ensure your table or any surface is flat with significant height differences.

    Jakub Dolezal -

    I used my coffee table up until this step (moving around the table to make sure it was flat in all areas) then double checked at this point using a mirror.

    Gabe Dover - Reply

    Hi, Gabe, we are always sticking to the tools you have in your kit, but a mirror is also possible to use. Thanks for sharing your approach.

    Jakub Dolezal -

    Make sure the bottom of your 3d printed "feet" are not deformed or curled. Mine had significant deformities that had to be shaved off with a knife (a file or coarse sandpaper would be better).

    Larry R Dockery - Reply

    Hi Larry, thanks for the feedback. Each part is checked before shipping, I'm sorry your Y-corners slipped through with some deformities.

    Jakub Dolezal -

    It's not exactly clear *how* to level if you're having a corner wobble - you need to slightly loosen the surrounding nuts just until the corner stops wobbling, then alternate gently tightening each sets of nuts, testing for wobble between each tighten - if you get wobbling again after tightening, loosen and try again.

    Rose - Reply

    The step 12 video on how to 'twist'the frame if one corner was lifting up was quite useful to me. So check it out if you have a bouncy frame.

    Marauderz - Reply

    Hi folks, this one can be really tricky! But - there’s hope. First, in steps 6-9, I used the specified distance of 152 mm, and checked this with calipers at top and bottom for each side, to a tolerance of +- 0.05 mm for all the four M8 bolts, while gradually tightening all the nuts. Also made the corners as vertical as I could check without additional tools (could easily 3D-print two 15 cm long indicator arms to fit snugly over the bolts).

    Now, in step 41, with all the 8 10mm nuts (nearly) completely tightened, I held three corners down towards the aluminum frame, and the fourth corner was in the air by some fraction of a millimeter (tapping test is excellent). This meant for me that I should work on the high corner, and on the opposite corner along the diagonal of the frame. I needed to gradually tighten the inner nut (extend the distance along the 10mm bolt) in one or both of these corners, until all corners have come down and all nuts are tightened. If you expand too much, the opposite corners will come up.

    Terje Krognes - Reply

    • Stick the felt pad on each Y-corner.

    • Felt pad is in the box

    I'd recommend skipping the felt pads for now (noise reduction only). If you notice misalignment later, fixing it will be impossible with the pads attached, so I'd add them once calibration is done.

    Mario Liebisch - Reply

    Hi Mario, sticking pads in this step shouldn't prevent you from fixing any misalignment. What problems had you with yours?

    Jakub Dolezal -

    Just a neat pick. Pads is actually bigger than the corner "leg" so I trimmed it with a scissor to the exact size which nicely fits without any overhang.

    gaazolee - Reply

    Hi, Gaazolee, yes the pads are a bit bigger, but it is ok to leave them as they are :)

    Jakub Dolezal -

    • Move the Y-carriage as close as possible to the Y-end-motor.

    • Make sure that you heard the "click" sound and the Y-endstop is triggered as shown in the picture.

    • The colors on the picture are a bit over-saturated to highlight the endstop button.

    @Prusa: Please add a picture that actually has the belt mounted to the Y-belt holder, so we can see the the belt is not touching the pulley while triggering the endstop.

    @Everyone: It is important that the loop of the belt coming back out of the Y-belt holder is not getting in the pulley AND the Y-idler. The Y-carriage has to be able to move back and trigger the endstop and move to the front without bouncing back. So if you push the y-carriage to the each end and it bounces back, then you have to readjust the belt in the y-belt holder. I had to do that 3-4 times and even Prusa will not like it i had to cut 1-2 teeth of the belt.

    Waldemar - Reply

    Hi Waldemar, thank you for your feedback. We updated the picture to show the endstop check from a better angle.

    Jakub Dolezal -

    Thanks for the tip. I thought it was odd that the Y-carriage bounced back. When I read your comment I checked the belt and it was as you said. I also had to cut a cuple of teeth.

    TDWL -

    Thanks for updating the picture!

    Waldemar - Reply

    You are welcome ;)

    Jakub Dolezal -

    My y-belt holder’s lip bumps up against the endstop instead of going over/under it, and stops it from clicking. Anyone else?

    Chris` - Reply

    Hi Chris, can you take a picture of your Y-belt holder and send it to us? Use info@prusa3d.com or Answers section here. Thanks

    Jakub Dolezal -

    Mine ia not clicking. It is 1mm apart and i cant make it touch.

    Eric Kindi - Reply

    I noticed that when you orient the assembly as shown in the picture, the top of my belt(with teeth facing toward the table) makes very small contact with the top y-belt holder(on the flat surface). Is this a problem. It’s very small contact, but the teeth do touch the surface.

    Zach Margulies - Reply

    • This is a crucial part of the assembly. Please check again you can see the marked part of the Y-carriage (as shown in the picture), otherwise your heatbed won't fit properly!

    Add Comment

    • Congratulations, you have assembled the Y-axis!

    • You can continue by assembling the X-axis in the next chapter - 3. X-axis assembly

    Longest part of build for me: 6 Hrs 25 Min

    Merrill Albury - Reply

    I build it in aprox 6h too (my first 3D printer).

    Cristian Leon - Reply

    I always have loose pulley in motor Y when trying to pass selftest.....tighten the belt, untighten it, tight the pulley, diassemble motor and assemble it again....nothing thta I do works...

    Sergio Fernandez - Reply

    I’m another one of the slow ones, I guess, but it’s the results that matter. :D

    Bill Robitske, Jr. - Reply

    First time doing this, and this part took me 5 hours :(

    I wish I read ahead, so much time wasted re-aligning everything after realizing that “rectangle” means “rectangle as &&^&^$^ accurate as humanly possible” :D And also the part in step 43 would be nice if it was highlighted at step 6

    Jakub Arnold - Reply

    It only took me 218 hours! My kit had a faulty u-bolt and it took awhile to get here… but 9 days and two hours later I finished the Y axis! :)

    Kale Macormic - Reply

    As an added assurance of the alignment - it would be worth suggesting that people measure the length of the diagonals and ensure that they are the same. None of the tests in the instructions can distinguish a parallelogram from a rectangle!

    Stephen Baker - Reply

    Glad everyone posted 6+ hours. 6 hours on the dot!

    Kim Vojensky - Reply

Finish Line

604 other people completed this guide.

Josef Prusa

Member since: 01/05/2015

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141 Guides authored


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141 Guides authored


First go out of the box took me 2 hrs to complete this step and this isn't my first 3d printer build. The M8 rods where tight in the printed parts so adjustment had to be done by rotating the rods as opposed to forcing it using the nuts. I did however ditch the supplied linear bearings in favour of the igus drylin linear bearings. It would be nice to have the bearings with a support that is less sensitive to crushing them as you tighten though. Overall I am really happy and really like that so much thought has gone into the detail and each part feels like it is real quality.

James Hawkes - Reply

Hi James, thanks for your feedback, I will check the printed parts for rods.

Jakub Dolezal -

I thought the same, I broke one bearing due to that u shaped screw, I'm sure it could be changed for a 3d printed part with more surface.

David Sastre -

2:30h completed time ~

printHead - Reply

Hi printhead, thanks for sharing your build time.

Jakub Dolezal -

I took my time over this and was initially concerned about the linear bearings as I thought they were 'coarse' in operation and went through all the bearings in kit before I decided that they are fine and wouldn't change them for a drylin bearing as you can feel the ball bearings doing their job if there is any side loading for example. I would recommend leaving the bearing ever so slightly loose until you clip the smooth rods into their printed holders. I would also recommend measuring the distance between the 2 rods accurately either make up a template or check with a Vernier gauge or some callipers

Neil Winstanley - Reply

Hi Neil, with new smooth rods and bearings for MK2S the movement should be even smoother than on MK2. I strongly recommend tightening the bearings before you place the whole Y-carriage in the Y-axis-corners (follow the manual steps).

Jakub Dolezal -

I suspect the linear bearings are shipped with a transport oil and should be packed with some synthetic grease before assembly but don't know for certain

Neil Winstanley - Reply

Hi Neil, there is no need to add extra oil in the beginning. Assemble the printer and you are ready to go. For maintenance please follow Josef's 3D printing handbook: http://prusa3d.com/downloads/manual/prus...

Jakub Dolezal -

Having a proper caliper really is crucial to building this thing. I was originally going to start building without but gave in and bought one.

Jared T - Reply

Hi Jared, for what parts did you use calliper?

Jakub Dolezal -

I 1000% Completely Agree!!!

Especially for getting the distance between the rails EXACTLY the same from one end to the other! Mine came out to 7.007" from outside to outside of the rods which is what the rods were when the bearings were attached to the plate but before the rest of the frame. There was less than .005" difference no matter where I measured, and it was so much smoother than before I adjusted it. To me this is one of the most important thing you should do along with squaring up the frame.

Any digital calipers 8" or better would be advised!

3hrs total only because I was overly cautious and paid to much attention to the guide. You will be better off just using the pictures as a reference and using common sense, especially when it comes to the order of things. I could do it again with confidence and precision in under 2hrs.

Randy H -

You will also need gage blocks or setup blocks to properly measure as most of the affordable 6” / 150 mm calipers won’t be big enough to make measurements

Kevin -

about 1 hour to complete

Robert S. - Reply

Hi Robert, thanks for sharing your time.

Jakub Dolezal -

I don't see how you could ever do this in an hour and it be perfect.

Randy H -

My caliper was only for 15 cm so hopefully the assembly is within tolerances done with roll measurement

Petri Nurminen - Reply

You can measure distance between bearing housing barrel. It is 15 mm and rod diameter 8. So required 178 - 7.5 * 2 - 4 * 2 = 155 and you 150 cm caliper will work ;-)

gaazolee -

Read and look at doc actually takes more than the work itself ;-) I am enjoining it and trying to understand reasons behind the design ;-). It is not about speed it is about passion.

gaazolee -

I took careful notes and went back after to see how I would improve if doing again. When I completed assembly my printer passed self check and XYZ calibration first try and now printing great. Hope these tips help others. I recommend writing these extra notes on the steps in your assembly manual.


Y assembly is one of the most important steps to ensure quality construction. Take your time and do not rush!!


2_3: On end where you want 100mm space, set the end nut with one thread sticking out. Then measure 100mm with digital caliper and lock opposing nuts. Now you won't have to repeat this in step 11 and only adjust other end when setting rods.


2_4 and 2_5: end nuts should be more like 1 inch from end to fit easier in step 6


2_8: before tightening nuts, use a square to make sure feet are vertical. this avoids part of step 9 which can add unnecessary stress in frame.


Jon - Reply

2_15: use a sharpie to mark outside of bearing aligned with one of the internal tracks. place this down in the carriage notch. When tightening u-bolts can easily make sure bearing mark is aligned


2_21: make sure motor screw next to end stop is snug (not too tight) before adding end stop because it blocks access to screw. make sure wires are gathered to fit into notch and not pinched


2_24: immediately do step 28 right after this. this is mistake in manual


2_26: make sure Y carriage slides smoothly across whole range before proceeding!


2_34: Important! if too much belt tail stick out on side with end stop it will prevent hitting end stop well. Example: I first ended up with 2 belt teeth on one side and 4 teeth on end stop side. I had to rebalance so only 2 teeth on end stop side to click easily


2_39: before tightening pulley, double check Y carriage slides smoothly and belt is centered on pulley. once pulley is tightened, motor will add resistance possibly masking another issue.

Jon - Reply

I have 4 teeth on each side of mine. I do see what you mean with it sticking out and getting into the motor pulley. Thanks for pointing that out! I guess I will just cut 2 teeth off on that side. It seems fine on the idler side.

Randy H -

3:25 was my build time for this step. It went pretty smoothly, but this is my first printer build and I double-checked everything.

Jake Block - Reply

3.5hours with breaks. Checked and rechecked everything. Works smoothly.

Tonu Jaansoo - Reply

All Haribo consumed by the 13th step. Cannot continue. There really should be enough consumables included to see you through the entire build rather than just enough to be a tease ;)

Graham Clifton - Reply

Exactly! LOL... But I do have to admit, it was a nice surprise!

Randy H -

3.5 hours total with a long break in the middle.

James Miller - Reply

Noticed one 'ball' fall out of a bearing, I didn't think I was being rough. The bearing seems to work fine and I rotated it so the track missing one isn't where the y carriage rests, should that be fine or should I look into replacing the bearing?

Daniel Loughmiller - Reply

Has the missing ball(s) caused any issue with your printing? Have you completed assembly and printed yet?

Eric Grubisich -

Hi Daniel, one missing ball from bearing shouldn't affect the movement at all. In a case of more balls fall out, I suggest to check the smoothness of the movement and if you feel increased friction, replace the bearing.

Jakub Dolezal -

once i finally finished assembling mine, the movement of the y axis without rhe belt on seemed much....rougher and did not glide more than a few mm's when pushed and let go to keep going by itself. This is in stark contrast to my Anet A6 assembly. that print bed Glides effortlessly while still having virtually no play when attempting to turn the bed left to right. can someone please let me know why this may be? I have already fully assembled my MK2S and it passed all calibration checks. But i am still worried about just how tough it was to move the bed frame on the Y axis. Any suggestions? Any reason why its like this? ( the rods were tough to move through the bearings which i took GREAT CARE in not crushing. in so much that i put in an old bearing and test fitted it + felt the tension before placing in the new ones. Are these bearings supposed to be super tight around the rods like this? is there a reference video i can watch to see how it should move when free from the belt?

Courtney Bennett - Reply

I didn't have calipers long enough, so took two combination squares and mounted both frames on one ruler. Instant calipers. Even better, I could tighten down the frames on the ruler and check if the rods were the proper distance apart.

Tony Hansen - Reply

Excellent idea. When I go back and readjust my bed I shall try that.

Jonathan Wise -

It took me a little over two hours to finish this.

Harald Schmid - Reply

This chapter took me about 45 minutes.

Harald Schmid - Reply

2.75 hour build time. first printer, double and triple checked almost every step. took a couple bathroom/stretch breaks

Antonio Calderon - Reply

It took me 3,5 hours with breaks. This is my first 3D printer, heck the first electronics build and probably the closest thing I did was Lego as a kid. I really appreciate the manual from the positioning of parts to prepare, to the photos in different angles. Some feedback:

- You have placed video after steps; personally, I would want them before to see what will happen and then dive into each step in more detail.

- What would also help me is to start with an overview of the whole printer and what I am working on because as a newbie I don't even know where this all will go, but that makes it all the more exciting.

- I was unsure about how 'smooth' the bearings should operate. Took great care in positioning and placing rods, so I do not think I broke anything, but I expected them to go smoother. I guess I will find out whether it all works.

Jelly delight is a great bonus!

Codrin Kruijne - Reply

I had five zip-ties and two M8 nuts left at the end of the assembly, hoping it was a miscount in Prague and not at my house in Brooklyn! :)

Gabe Dover - Reply

First ever 3D printer and I believe I have made the best choice!! I am still in the middle of building the first stage - Fantastic, easy to follow instructions... The main thing I was concerned about was getting the spacing correct and everything square.. One of the things i did to help me was to create a foot print drawing in AutoCAD showing the locations of the feet (y-corners) and the other important locations (100mm distance and dimensions shown in step 6). I printed it out and laid everything on top of the printout.. It's only a suggestion, but i think it would help enormously and would speed the build process up if you were to supply a printed footprint out of the important locations.. It would not have to be detailed, but just show the y-corner locations and other important dimensions.. Can't wait to complete it and start printing... Carl

carl phillips - Reply

I performed this build section with my 14 year old grandson who did most of the building. Working together is easier with an extra set of hands and eyes. It is definitely helpful to use a vernier caliper. We took extra time in the beginning to be sure idler and motor mount placements were exactly right. This made a big difference at the end when installing the belt as we did not need to make any adjustments to be sure the belt was aligned. We put the rods in the bearings when snugging up the linear bearing mount nuts to be sure we did not distort the bearing housing. We spent about 5 hours on this step. I recommend reading most of the comments. However, I did find some of the comments misleading. Generally I think the online instructions and videos are very well done.

Dave DeWitt - Reply

Hi Dave, I hope you both enjoyed the assembly. We are constantly improving the manual, so thank you for your feedback.

Jakub Dolezal -

about 4 hours to complete.

Dustin B - Reply

This is my first time building a 3d printer and it took me about 3.5 hours. Only mistake I made was on the divet that needed to be on the top left, but quickly realized and fixed before I did any ziptie-ing. Thank God! I'm on to next section, but so far so good and everything is aligning well and all my measurements look good!

Aron Elston - Reply

Around 3h 30m for my first build of my first printer ever. My 12 yr old helped tremendously with this so it was even better!

S Javeed - Reply

About 3.5 hours across a few days for this part. All seems good.. couple minor missteps (M3-10's vs.12's), meine Schuld.. Sprayed a little white grease on the rods and bed seems to be moving well.. ready for the next step.. Nice job on the tutorial, definitely good to read ahead and all the comments.. Digital calipers or similar really required for measuring and 80132/94123 Cross Wrench Maintenance tool good to have as well

Gary Sinkowitz - Reply

Confused why I had 2 extra M8 nuts - Triple checked the instructions but only are 22. - The I saw on the package the print 22(+2)x M8n - Are these supposed to be extras (not going into the spare bag) ?

Michael Berneis - Reply

6h and many double and triple checks (my first 3D printer)

Cristian Leon - Reply

4.5 hours to complete in various stages. The comments of the people were very helpfull, specially with the sound of the rods (I think I'll change them pretty soon) and the length of the belt, I have not cut it, but I guess I'll have to do it once the printer is working.

Juan Sotres - Reply

3h and also loosing one ball from a bearing

Carsten Seibert - Reply


First printer, so far this is looking great. Great manual, I like that you can read others' opinions and tips on the step and I appreciate the attention to detail with everything. My y carriage seems to be moving smoothly, without too much resistance because of the belt. All in all, very excited to continue!

I had a few problems, but they were very minor:

*I didn't get any m3 nuts in my y-axis bag, but there were extras in the spare bag so all was well.

*I had a similar problem as others with slightly scratchy bearings at first, but after a bit of loosening and readjustment it seems good. Would be nice to have an audio recording of what the bearings should sound like, as others have said.

*Another problem I had was, like many people, my belt was a tad bit too long and so would catch in the pulley/idler, even after properly tensioned and with equal extra belt on both sides. In the end I followed someone's tip and just zip-tied the ends in place.

Nicholas Vellenga - Reply

Hi Nicholas,

I'm sorry for the missing nuts, I will forward this further. Regarding the belt, adjustments were made to prevent it in the future.

Jakub Dolezal -


I'd like to mention that I never used a pair of calipers. I saw everyone recommending them (and Jakub denying they were needed), but they can get very expensive and I couldn't wait to get started building. I grabbed a metric ruler and did all my measuring, including the 100mm counternut, by just lining the 0 mark up with one plastic part and going from there. I did the 152mm measurement for the sides in the same way, and since the bearings run smoothly I guess it's fine (?). Just pointing out that what they say is true, you don't need to go out and buy 3 more expensive tools just for a few steps of the build! :)

Nicholas Vellenga - Reply

Hi Nicholas,

thank you very much for your feedback! The whole kit is designed to be built with the provided tools only and while making the manuals, we aren't using anything else. Using calipers or any other tool might speed up the build or make things a bit easier, but is definitely not necessary to purchase them.

Jakub Dolezal -

I had two extra 22xm8n nuts after this. I triple checked and everything is installed with the correct number of nuts so they must be extra from a miscount when packaged.

Josh - Reply

Hi Josh, just ensure you've used proper amount during the assembly. It can happen there will be some nuts or screws extra.

Jakub Dolezal -

I seem to hold the current record at just over 7 hours. :)

I was probably too thorough measuring making sure everything was lined up and rectangular in the early steps, only to have to re-do all that work later. My printer did however pass calibration successfully with only minor frame tweaking. I've left comments on the steps in this part that I think could be improved.

Anton Eliasson - Reply

To make the y stage run really smooth I did the final adjustments to distance between the corners just prior to pressing the smooth rods into the corners (step 26). If you place the assembled Y stage loosely on top of the printed corners it is easy to adjust to exact distance by adjusting the 8mm nuts. When the distance is exactly right pushing the wagon back and forth it is very easy.

Kristian Glejbøl - Reply

you need to put the warnings and tips at the start of the section in which they are needed.

Bradley Dorner - Reply

Hi Bradley, tips and tricks for general purpose are given in the beginning, but the others are given at the particular step. Can you give me an example, what would you place at the start? Thanks

Jakub Dolezal -

Jakub, Step 16 is a good example. The warning to not crush the bearing is at the end of that step. Of course, one should read the entire step before beginning it, but I agree with Bradley that such important things should come first.

Steven Gardner -

Hello. When i was assembling this section of the printer, a section of the y-belt holder broke off (i am currently glueing that back together). On top of this, the y-belt holder seems to be out of alignment with the stepper motor, as the closer the y-belt holder gets to the motor, the more force is required to move it, eventually causing the y-belt holder to come within millimetres from the button. Would you be able to help me with this problem?

Thank you

Mortbros - Reply

I think that using threadlocker would help greatly to maintain a solid frame of reference after all the adjustments were made.

Mihai Voiculescu - Reply

Thank you for putting together this detailed guide. The pictures really helped.

Sarah - Reply

About three hours of building time so far, I really take my time :)

This is my second printer and therefore I want to go as precise as possible. The previous one being a Chinese beginner model that I slightly bodged.

It was a bit tough to get the belt to go in, give it the right tension (I’m afraid it is a little bit much currently) and straighten the motor and idler.

Be sure to keep a minimal piece of belt at the side of the motor, otherwise the belt will hit the motor before the Y-endstop clicks.

Merijn Vogel - Reply

Being an old-hand with two hand-built laser cutters (I have two “Lasersaurs” - those babies take about 2 weeks to build!) - I’m acutely aware of how care and attention to alignment (and especially belt tension) can result in a good machine or a poor one at the end of the day.

I refuse to measure how long it took me - it’s not a race. On the laser cutters, belt tension is absolutely critical - because the belts are much longer and the laser alignment is critical to not setting fire to things! Too much tension and the stepper motors may lose an occasional step - too little tension and the positional hysteresis gets bad. I *really* wish someone could figure out a way to measure belt tension cheaply and effectively. All of the build instructions (including these) use fuzzy language that really doesn’t give you confidence that you have it right.

Anyway - these are beautiful instructions - and if you pay close attention and check your build against the photos at every chance - you should get it done right.

Stephen Baker - Reply

In Step 11 of the 2. Y-Axis Assembly, when tightening the 10mm nuts to ensure there was no gap with the 8mm rods in the Y-corners, one of the Y-corners broke. I can’t print a replacement (yet) so how can I get a replacement part? I have the black printed parts.

Bruce Parshall - Reply

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