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

    • 3mm Allen key for M5 screws

    • 2.5mm Allen key for M3 screws

    • 2mm Allen key for nut alignment

  2. Prepare following parts to build the YZ frame: Aluminum extrusions (4x)
    • Prepare following parts to build the YZ frame:

    • Aluminum extrusions (4x)

    • Aluminum frame (1x)

    • M5x16r screw (16x)

    • You can tighten the M5x16r with included Allen key or with a Torque Wrench. Recommended torque is 4.5 N.m (40 lb-in).

    • Before you proceed further, please place the frame on a FLAT SURFACE (this is crucial).

    I used a “fat wrench torque screwdriver” made by Wheeler and sold on Amazon. The way I see it, this frame is going to see endless hours of stress and should be torqued equally all around.

    Ken.Lotts - Reply

    Step 12 mentions the CRUCIAL “flat surface” which should be mentioned as a requirement here.

    Recommendation: begin with a flat surface as it will help to mitigate alignment problems in the following steps.

    Jake H - Reply

    Hi Jake, good point. We’ll mention it in this step.

    Filip M - Official Prusa CS -

    I am a bit confused. At least from the photos in Steps 3 to 5, we need to place the frame vertically to install the Aluminium extrusions. Why it is crucial to put it on a flat surface? Could anybody please explain?

    pcprusa -

    @pcprusa The flat surface should just serve as a reference for you to mount the frame in a way to minimize wobbling.

    Martin L. - Official Prusa CS -

    Hi,

    The manual tells you to take 16 ‘M5x16r’ screws; but on the smallest plastic bag that contains these screws; this name ‘M5x16r screw’ was not written. This confused me a little bit. Maybe it is a minor point. :-)

    Pieter Vermeersch - Reply

    Mr Vermeersch,

    thank you for reporting this, we’ll make sure to check it.

    Martin L. - Official Prusa CS -

    Hi Pieter,

    the label M5x16r is used on the main bag “2. Y-AXIS”. I will see if we can apply it on the small one as well.

    Jakub Dolezal -

    Yah confused me a bit too. My bag said “3/2 Y-Axis MK3”

    The 3/2 made it a bit more confusing. But the label/picture on the bag 2 (Y-axis) helped clarify it for me.

    david -

    Don't exclude the possibility that I'm doing something wrong, but using a torque wrench set to 4.5 N.m, the screw heads would deform before reaching the recommended torque… I ended up using the provided Allen key and three fingers to tighten.

    David Stosik - Reply

    I have the same issue, using a torque wrench I damaged one screw. Trying to loosen them again to compensate misalignment destroyed half the screws.

    I noticed that the hole in the screws are fairly large. Eg. Not a tight fit to the wrench as one would expect, I tried several wrenches. Measuring gives >3.1mm on average on un used screws (probably some small measurement error in caliper handling). The metal used in the screws seems very soft.

    New supplier?

    Tölander Henrik - Reply

    Hello Mr Henrik,

    Thanks for your feedback, we will check that. If you need some new M5x16r screws, you can either source them locally (fastest option) or you can contact us via email.

    Martin L. - Official Prusa CS -

    “Flat” is a relative term. I wish I had a truly flat surface. My desk where this is being assembled caused wobbling so I turned the frame 90 degrees and the wobbling was gone. I trust the flatness of the printer more than my desk. So I kept going.

    Darrell - Reply

    When mounting the four extensions to the frame how do you prevent wobble when the frame itself sits a few mm below the four extensions . I can remove wobble left to right but not front to back or are is my frame drilled wrong..?

    John LeMoine - Reply

    Hi John, we’ve explained how to get rid of the wobble in Step 12.

    Filip M - Official Prusa CS -

    Hi Prusa, is it recommended to use a torque wrench during the assembly of the printer? Have you figured out what is wrong with the 4.5Nm value as some users reported that setting the wrench to this value damaged the screw heads.

    pcprusa - Reply

    Hello, no, we are not recommending to use a torque wrench, it is an “overkill”, I would say. All you really need are the bundled hex keys and following the instructions word by word.

    Martin L. - Official Prusa CS -

    I too had screw head issues when using my torque wrench, i think the wrench would tilt slightly sideways and twist out of the socket. I ended up using the standard allen wrench and make sure the wrench is held square and just tighten it Gutenteit.

    jim Jacobson - Reply

  3. Take the LONGER aluminum extrusions and place them next to the frame. Make sure the engraved PRUSA logo on the frame (top left) IS  VISIBLE! Note: screws are inserted from the opposite side of the frame. If you need to manipulate with the frame, make sure the extrusions are on the correct side.
    • Take the LONGER aluminum extrusions and place them next to the frame.

    • Make sure the engraved PRUSA logo on the frame (top left) IS VISIBLE!

    • Note: screws are inserted from the opposite side of the frame. If you need to manipulate with the frame, make sure the extrusions are on the correct side.

    • Ensure you are using the correct holes, see the second picture. Use the M5 screws to connect extrusions to the frame. Tighten the screws with the Allen key just slightly!

    • Now, tighten the screws fully, but ON A DIAGONAL, see the last picture. As soon as you finish the first, tighten the second pair. Then proceed to the second long extrusion.

    I have found the bolts to be manufactured to quite poor tolerances. Take care when tightening, as the head of the bolt will not take much pressure to deform. Even using very high quality (both Wera and Wurth) hand tools does make it better.

    Jonny Badley - Reply

    WARNING to all future assemblers: the bolts that come with the kit are made of a very soft material, and they will deform easily if not tightened or loosened carefully.

    I do not recommend FULL tightening to the specified torque in step 2 until you are ready for STEP 12. Use a 3mm allen wrench, with the short end as the torquing handle, until you are ready for the final tightening, for which I recommend the torque wrench mentioned in step 3 by Ken.Lotts

    Heimdall - Reply

    Actually, after Step 10, and then again after steps 11 and 12. Otherwise, the bolts are blocked by the rear plate being in place from most torque wrenches i’ve worked with.

    Joe Corrao - Reply

    I assembled my first i3 MK3 back in October 2018 where I noticed first hand the poor quality of the included M5 bolts [you wil easily destroy the Allen socket in the head of the bolt if you torque it to the recommended specs]. Right now I’m building another printer, the newest and greatest i3 MK3s and to my surprise, the same crappy screws are still there.

    Dear people at PrusaResearch: please fix this as this will surely result in machines that won’t meet the user expectations and will degrade greatly during transport and over time; all this will attract bad reputation to your otherwise awesome product.

    A 2 E - Reply

    Hello!

    Thank you for your kind words, but no worries, you will sure see many comments on this topic here in the manuals, but put into perspective, based on our testing and usage data, the screws aren’t posing too much of a problem, once you figure out how to tighten them correctly.

    Martin L. - Official Prusa CS -

    Crappy screws. Often, I cannot reach the 4.5 N.m torque, before the 3mm Allen key star sliding inside the screw’s head.

    Luca - Reply

    Do yourself a favour and buy new M5x16r screws. I replaced the one in the kit with bolts with an hexagonal head. It’s much more easy to control the torque.

    Luca - Reply

    the M5x16r screws are very soft. Take great care or you WILL strip the heads

    Jack - Reply

    I don’t have a torque wrench. I tightened everything until contact was made, then just a little more. No forcing was needed. Everything turned out wonderfully.

    Darrell - Reply

    OK, so check *all* the pictures carefully! I looked at the first picture, but enlarged the second to do the assembly. Unfortunately, the second picture does not include the “PRUSA”. I used the written instruction (“be sure you see the PRUSA…) along with the second picture. Consequently, when I figured out my mistake (between steps 23 and 24) I ended up having to remove a whole bunch of screws etc to correct my mistake.

    Laurie S - Reply

    Hmm, so far I have not strip the head of the screw yet. I use a Bosch “go cordless” powered screw driver. And tighten manually at the last moment. I find that if I want to strip the screw head, I would probably strip the threads on the aluminum extrusion first.

    So far I only spoil one M3x10 screw because I did not align it properly before tightening.

    so far so good

    Wai Leun - Reply

  4. Take the SHORTER aluminum extrusions and place them next to the frame. Short extrusions must be placed on the side, where engraved PRUSA logo on the frame (top left) IS NOT VISIBLE. Note: screws are inserted from the opposite side of the frame. If you need to manipulate with the frame, make sure the extrusions are on the correct side.
    • Take the SHORTER aluminum extrusions and place them next to the frame.

    • Short extrusions must be placed on the side, where engraved PRUSA logo on the frame (top left) IS NOT VISIBLE.

    • Note: screws are inserted from the opposite side of the frame. If you need to manipulate with the frame, make sure the extrusions are on the correct side.

    • Ensure you are using the correct holes, see the second picture. Use the M5x16 screws to connect extrusions to the frame. Tighten the screws just slightly!

    • Now, tighten the screws fully, but ON A DIAGONAL, see the last picture. As soon as you finish the first, tighten the second pair. Then proceed to the second short extrusion.

    I think it would be best if antivibration feet were put in at this step. Otherwise its hard to put them in and they been falling out. See a video from Thomas Sanladerer bellow

    https://youtu.be/M73uIMDlvvk?t=137

    Vadim D - Reply

    You’ll need to check for wobble in Step 10 and the feet will interfere with that. It’s best to leave them off for now.

    Joshua Gish - Reply

    Two of the aluminum extrusion profiles [one short and one long] have defects on threading: on the long one the bolt will go in without screwing [no thread available] and on the short one, the thread is too tight to allow the bolt to be inserted after a couple of turns.

    A 2 E - Reply

    Hello, if you are sure you are using the correct screws, please make a video of this problem and contact us on email.

    Martin L. - Official Prusa CS -

  5. Before we proceed further, let's make a final check. IT IS VERY IMPORTANT to have extrusions on the correct side of the frame.
    • Before we proceed further, let's make a final check. IT IS VERY IMPORTANT to have extrusions on the correct side of the frame.

    • Long extrusions - must be on the side of the frame with the Prusa logo, also ensure longer extrusions are closer together.

    • Short extrusions - must be on the side of the frame without the Prusa logo, also ensure shorter extrusions are further away from each other.

  6. For the following steps, please prepare: Front plate (1x)
    • For the following steps, please prepare:

    • Front plate (1x)

    • Rear plate (1x)

    • M5x16r screw (16x)

    • PSU holders M3nE (2x)

    • You can tighten the M5x16r with included Allen key or with a Torque Wrench. Recommended torque is 4.5 N.m (40 lb-in).

    Which box are the PSU Holders stored in? I can’t find them in my kit.

    Max Niehaus - Reply

    Hi Max, they are together with other fasteners in bag 2 (Y-AXIS).

    Filip M - Official Prusa CS -

    They are in the bag labeled “2. Y-AXIS". Based on the pictures in the instructions I first thought they were white and much larger. However, they are the same silver color as the screws. They are also much smaller than I originally thought.

    Cal Langford - Reply

  7. Rotate the frame with longer extrusions towards you. Place the front plate on the extrusions and secure it with M5x16r screws, DON'T TIGHTEN them yet!
    • Rotate the frame with longer extrusions towards you.

    • Place the front plate on the extrusions and secure it with M5x16r screws, DON'T TIGHTEN them yet!

    • Now, tighten the screws fully, but ON A DIAGONAL, see the second picture. As soon as you finish the first, tighten the second pair. Then proceed to the second long extrusion.

    Holes on the right far side of the plate (little dimple facing you) are drilled too small. There were two types of M5x16 screws supplied: one with A2-70 stamped on the head, and nothing stamped on the other type. The stamped ones are slightly bigger, but the holes are tight even for the smaller ones. I wish I had metric drill bits lying around. I first screwed the smaller screw into the holes. It threads itself in, then with a little force it would strip the thread (use on the plate only, without extrusion!!!). Repeated the same step with the larger one, and now the hole is big enough to properly fit the smaller screws.

    Alex - Reply

    Same small hole problem on my build. It appears the coating material collected in those holes (possibly due to hanging the part to be painted or dried) reducing the diameter of the hole. In order for the screw to fit easily into the hole I removed the excess coating with an undersized drill bit used as a file. This left a small amount of black coating as a on my build surface and a hole large enough for the screw to easily fit.

    Greg Self - Reply

    Hi Greg,

    Thank you for letting us know, I will let our Quality Control know to check for this.

    Marcin M. - Official Prusa CS -

    Had to chase all holes in one end of both front and back plate by hand with a drill bit.

    Bob Baltz - Reply

  8. There are two types of the PSU with different mounting points. Make sure you are following the correct instructions!!!
    • There are two types of the PSU with different mounting points. Make sure you are following the correct instructions!!!

    • New PSU with black casing (PSU holders are on the side of the extrusion)

    • Old PSU with silver casing (PSU holders are on the top of the extrusion)

    • Find your PSU in the package.

    Why comes my brand-new MK3S with an “old” silver PSU?

    Mauro Casanova - Reply

    Hello,

    The silver PSU is tested and of the same quality as the new black PSU. New PSUs will soon be delivered. If you received PSU silver, it is absolutely fine and you will not need a newer one. The type of PSU has no effect on the printer.

    Martini H. - Official Prusa CS -

    I ordered everything with black parts because I like it that way. Is there a way to receive a black PSU in exchange for the silver one I got?

    Miguel Barroso - Reply

    Hello Miguel,

    It’s not possible to swap the PSU if you have the silver one, however you will be able to purchase it later from our eshop :)

    Marcin M. - Official Prusa CS -

    I agree with the previous comment, as we ordered a brand new MK3S it should come with the new PSU. I wouldn’t be bothered other than the large number of reviews that mention how unreliable the PSU is, I presume this is the reason for you changing it. It would have been better customer service to send out the newer one to all new orders.

    Sam - Reply

    Hey Sam,

    As my colleague has mentioned above, the silver PSU is tested and of the same quality as the new black PSU. In some rare cases the PSUs got damaged during shipping and caused issues, and we were always more than happy to replace them.

    Filip M - Official Prusa CS -

    Customer support says if you get the silver then tough….If you want the black delta you have to buy it for over $100 bucks…The delta black supply is better than the silver PSU. Its very disappointing that the company makes you pay for delta PSU instead of giving you the choice if your unlucky enough to get the phased out supply in order to get rid of them and push them off to the buyer.

    Dale DiDomenico - Reply

  9. THIS IS A VERY IMPORTANT STEP! Incorrect placement of PSU holders will lead to issues later. This step is valid only for the BLACK PSU!!! Take the YZ frame and rotate it with the shorter extrusions towards you.
    • THIS IS A VERY IMPORTANT STEP! Incorrect placement of PSU holders will lead to issues later.

    • This step is valid only for the BLACK PSU!!!

    • Take the YZ frame and rotate it with the shorter extrusions towards you.

    • Place the PSU holders (M3nE) in the extrusion, use the side section, ensure it is the correct extrusion. See the picture.

    • The exact spacing of the PSU holders doesn't matter, we will adjust them later.

    The 2 PSU holders are shown in the picture above as slotted in the side of the short extrusion yet in pictures shown later in the manual show them. Inserted in the top of the short extrusion. I assume the holders should be inserted in the top of the extrusion, yes? Allan

    Allan Bourner - Reply

    Hi Alan, please read the steps 9 and 10. If you have the black PSU, holders should be on the side, silver PSU, holders on the top.

    Martin L. - Official Prusa CS -

  10. THIS IS A VERY IMPORTANT STEP! Incorrect placement of PSU holders will lead to issues later. This step is valid only for the SILVER PSU!!! Take the YZ frame and rotate it with the shorter extrusions towards you.
    • THIS IS A VERY IMPORTANT STEP! Incorrect placement of PSU holders will lead to issues later.

    • This step is valid only for the SILVER PSU!!!

    • Take the YZ frame and rotate it with the shorter extrusions towards you.

    • Place the PSU holders (M3nE) in the extrusion, use the top section, ensure it is the correct extrusion. See the picture.

    • The exact spacing of the PSU holders doesn't matter, we will adjust them later.

    I managed to mess up the placement of the PSU holders. Despite reading the instructions when I got down to it the images of the two possible PSU’s and the Green check and the Red ex’s threw me off. I’d suggest for each given PSU you only show that unit. That way reduces the chance of others doing what I did and scrolling to the wrong one to double check where to put the PSU holders.

    Luckily I was able to loosen things off enough to remove the screws holding that piece of extrusion allowing me to take it out and reposition the holders before putting everything back in place and then re-squaring and re-tensioning the frame and belt.

    Alan Pieroway - Reply

    Hi Alan, we believe the pictures here are OK. Make sure to read the description thoroughly, it also mentions which PSU is this step for.

    Filip M - Official Prusa CS -

  11. Ensure the frame with shorter extrusions is rotated towards you. Place the rear plate on the extrusions and secure it with M5x16r screws, DON'T TIGHTEN them yet!
    • Ensure the frame with shorter extrusions is rotated towards you.

    • Place the rear plate on the extrusions and secure it with M5x16r screws, DON'T TIGHTEN them yet!

    • Now, tighten the screws fully, but ON A DIAGONAL, see the second picture. As soon as you finish the first, tighten the second pair. Then proceed to the second short extrusion.

    Why are the PSU holders (M3nE) now located on top of the short extrusions? This is confusing.

    Koen Verbeeck - Reply

    Hello Koen,

    It seems like you are using the outdated manual, as this one is for stock MK3. For MK3S, the current one, use these instructions: 2. Y-axis assembly

    Marcin M. - Official Prusa CS -

    Hi Marcin, the link you posted points back to this page and I clicked on the mk3s manual to get here.

    Joshua -

    Guide 7 - Step 19 - shows the holders on the side for the black PSU so that’s how I’m continuing.

    Joshua -

    Hi Joshua, the placement depends on the PSU type. You can choose it here: 2. Y-axis assembly

    Filip M - Official Prusa CS -

    Hi Filip.

    They are referring to where the M3nE are located in the picture corresponding to this step, 11.

    I don't know whether it's feasible to branch out the manual with different pictures according to which psu you have?

    Björn Holmér -

    Hi Bjorn, many of our manuals branch in a similar way.

    Filip M - Official Prusa CS -

  12. Before you proceed further, please place the frame on a FLAT SURFACE (this is crucial). All the components are cut or drilled by machine for highest precision, but with uneven tightening, it is possible to warp the frame.
    • Before you proceed further, please place the frame on a FLAT SURFACE (this is crucial).

    • All the components are cut or drilled by machine for highest precision, but with uneven tightening, it is possible to warp the frame.

    • Using your hand, try to wiggle with the frame sides and check, whether some corners are lifting up or not.

    • In case you find some imperfections, release the screws, press the extrusions against the FLAT SURFACE and tighten them again.

    • IMPORTANT INFO: the printer is capable of self-correcting a certain amount of the frame skew. Try getting the geometry as best as possible, however, if one of the corner still keeps lifting up with values up to 2 mm (0.08 inch) you can proceed.

    I’ve torqued, re-torqued, and finagled the long extrusion screws several times, and cannot get the wobble out, with the latest re-torquing, I think it may be worse. The supplied screws are soft and I’ve had a few of the heads strip while using a correctly set torque wrench, one is stripped to the point that I can’t tighten or remove it. The cheap screws are a major issue with this kit, especially since it’s very difficult to get the frame trued.

    William Rigsby - Reply

    Hey Willian,

    Make sure you don’t overtighten the frame screws. If that doesn’t help, you can always ask someone to push both extrusion pairs down with his forearms - afterwards tighten them and you won’t see any wobble.

    Filip M - Official Prusa CS -

    Same issue here. One corner is lifted up for 1 mm or less but I tried to fix it even manual says it is not necessary . The result- corner is still lifted up( I tried to push both extrusion down with all my weight during tightening screws )and one screw is stripped.

    Dmytro Datsenko - Reply

    For those that are having issues with getting parts to stay flat after torquing, mark with masking tape which side of the extrusion that is lifted up, and then remove all the screws in it and make the side with the tape face down (rotating the part 180 degrees) and this may help. All of these parts have tolerances, including the end cuts. They might have a slight angle on them.

    Mark Jurisch - Reply

    Yes! Flipping the extrusions 180 deg helped me removed the approximately 1mm lift I had on one of the legs. Flipping meaning the part originally in contact with the YZ frame is rotated to be in contact with the rear plate instead.

    Eric Lee - Reply

    Geez, first step and I’ve already hit a snag on this, as others have mentioned. The quality of the bolts is sub-par. They are way too soft and when tightening you can feel them give. When I got to this step to check for the geometry i had to loosen and tighten them a few times to get it right and stripped one of the bolts when retightening. Every time you mess with them they lose a little bit of strength in the head. I have no doubt these cheap bolts will all strip if they ever need to be taken apart or reassembled more than a couple of times. Really sad that in the first step there’s already signs of cut corners (no pun intended).

    The note about this being perfectly square to the table should be included BEFORE they are assembled, not afterwards. Makes no sense to have it here.

    Eric - Reply

    Hey Eric,

    It’s important to not overtighten those screws, otherwise they can get stripped.

    The final note is important to make sure you don’t skip it beforehand.

    Filip M - Official Prusa CS -

    The Prusa responce is wrong. THe screws are VERY soft. I stripped two of them using the supplied alen rench to finger tightness

    Jack -

    Just got done with this part. Tried a bunch of loosen, then retighten, and also flipped extrusions 180 degrees (as per Mark’s comment). I think that one helped a bit, and what I think helped most of all: not overtightening. No wobble now. Finally - I’d make sure you test the wobble in the exact spot where the printer will be sitting once operational (not all flat surfaces are truly flat).

    Per Farny - Reply

    I’am assembling on a wooden table and quicky realised that the surface on which you test it needs to be flat as well. Otherwise you will always get wobble or even wrongly “correct” your structure.

    I tested this and indeed it seemd i got different points to wobble in different positions. I moved on to my Compter desk which is made out of 1 piece material and there it didn’t wobble at all.

    TLDR; Make sure to test your wobble on a perfectly flat surface.

    Bryan O'Neil - Reply

    Not a bit of wobble on my first attempt. I had success doing every screw by hand, then allen wrench. Only took about a quarter turn to be really tight. Feels super solid. I also hung the extrusions off the side of the table while I put the screws in.

    Nathan Charlton - Reply

    I think the guide should mention that the screws are soft and finger tightening first is preferable, before using the allen key. Furthermore, already working on a flat surface when performing the previous steps is also key.

    I read the guide and all comments before I started so I knew of this and managed a non-warped frame on first attempt.

    Miguel Barroso - Reply

    I think the guide should mention that before you screw any extrusion to any of three frames you can move it about 0,5-1mm in any direction and screw it in that position. This should be enough to correct any irregularities

    My guide:

    1. First mount shorter extrusions to main frame, gently pushing extrusions to bottom while screwing.

    2. Geometry check, you can hear which one extrusion hit desk first, try to make them equal as possible in point 3

    3. Screw again extrusion which is too low to make it higher (just push top when screwing, if it will be too high you will need to go somewhere between)

    4. Mount longer extrusions to main frame, gently pushing extrusions to bottom while screwing.

    5. Geometry check, try to wiggle

    7. Screw again longer extrusion which is too low to make it higher (just push top when screwing, if it will be too high you will need to go somewhere between)

    8. Mount front and back frames with pushing extrusions to bottom

    9. Geometry check, if not correct, modify screwing from point 8, same method

    gfxstcges - Reply

    Thank you for your feedback.

    We suggest pushing the extrusions down when tightening to avoid rising corners. The geometry check is not necessary in the very beginning, the rear/front plates often can correct it.

    Filip M - Official Prusa CS -

    Reiterating what others have written, the screw heads are too soft and too easily stripped out by the allen wrench. Not having a torque wrench, it is impossible for me to estimate 40 in-lb of torque, even with my 78 years of experience. Some of my screws are in tight but stripped. It would be a bear to replace them with new screws. I hope that is never necessary.

    john brenner - Reply

    Hello John. It is not necessary to use torque wrench, just tighten the screws slowly and carefully, not using force. If your frame holds, you will not need to disassemble it.

    Martin L. - Official Prusa CS -

    To reiterate what “Mark Jurisch - February 21” said, find the position where 3 of the legs are flat with the surface and mark the side that is up. Flipping 180 degrees did not work for me but 90 degrees on the short access removed all the wobble completely. You just have to try different positions with the one extrusion that seems off being careful to just tighten enough with just two fingers on the well seated Allen wrench. This is key, the Allen wrench must be in completely and turn very slowly keeping it parallel or you risk stripping the screw heads.

    Dave Bear - Reply

    When I finished this step, I still had liftup on opposing diagonal corners, which I believe was a result of the torque stress from tightening all the bolts.

    Here is how I corrected this issue:

    (remember to treat the bolts with care when loosening/tightening as they are very soft and will deform easily)

    Completely removed one of the longer arms on the corner that was lifting up, leaving only the other arm and the end plate on that side; loosen the bolts on these remaining parts.

    Re-tighten the bolts while slightly putting pressure to torque on the free end of the end plate in the opposite direction to the original liftoff and roughly an equal amount of distance.

    Re-attach the remaining arm and re-tighten the bolts starting at the central plate and then at the end plate.

    After this, I was able to achieve perfect flatness of the frame to my reference plane, an optical table from ThorLabs (I work with lasers and optics, so I had a small one available to borrow).

    Heimdall - Reply

    If you have a granite kitchen counter top, keep all the frame bolts loose and tighten them with the frame on top of the granite counter top surface. Zero frame wobble achieved with this method.

    Nelson Zambrana - Reply

    The granite counter top works great. My main construction table was plastic that wasn’t totally flat, and I used that to make sure everything was level. Seems to have worked fine, I got the “X/Y axes are perpendicular” result in the end :-)

    Klaus - Reply

    I’ve run into the screw stripping problem as well. Now I’ve got an assembly that’s close-but-not-quite square, and no way to adjust.

    I bought a torque wrench specifically for this occasion (came with its own calibration certificate and everything) and have been torquing precisely to 4.5Nm each time, but on just my second attempt to re-align I’ve already lost it. What is with these screws? Is the 4.5Nm torque inaccurate? Anyone have any tips for removing the stripped screw at this point?

    Charlie - Reply

    Hi Charlie, you might need to remove the stripped screw using a different bit or some other method. You can find more of them in the spares bag.

    Filip M - Official Prusa CS -

    I had some wobble, and couldn't get it fixed after loosening and tightening 10 times. Turns out I wasn't loosening enough, my front plate was slightly skewed, so I had to loosen my screws quite a bit, then push on the plate. It 'clicked' into place, tightened again, zero wobble now. Hope this helps someone.

    Falk Thys - Reply

    Thought I was being clever using loctite. Didn't realise how frequently I was going to be backing the bolts off, and with the known soft heads, so many got rounded off.

    Jamie Williams - Reply

    Recommendations for improvement:

    1. Yes, I also confirm the screws are very soft and the build quality is not great. Keep the Allen key straight to not round them out.

    Please, Prusa, invest some more cents in sturdier screws?

    I’d even sacrifice the gummy bears for it - or just pack a smaller bag of them to recouperate costs.

    2. Please put the warning to check for wobble to THE BEGINNING of the frame building chapter!

    If you bolt down screw after screw you already misalign the extrusions a little because of the play.

    Only after putting on the plates you have reference points for the position of the extrusions since now you have an "end point".

    At first I tried the aforementioned method of only taking out one deviating extrusion and then flipping it around.

    That didn't seem to work (I tried rotating and turning the thing 180° horizontally)

    So in the end I unscrewed ALL 32 screws and did everything all over again.

    Florian - Reply

    Hi Florian,

    Thanks for your comments, your request has been noted.

    Martin L. - Official Prusa CS -

    Tips on doing things:

    The best way for me was to tighten all 32 screws by hand at first until ca. 0.5-1mm from the frame.

    Then I started to tighten the extrusions to the frame, beginning with the long ones.

    I grabbed them besides the frame and gave them a little pull in an upward direction and held them there, not lifting the end plates, of course. Just a nudge since there's about 0.5mm play around the screw holes.

    While holding I tightened the screws to the frame diagonally.

    Then I lay my forearm over both extrusions close to and parallel to the front and rear plates and pushed down on both while tightening the outer screws to the plates.

    So in the end I got the wobble controlled and now I'm at a deviation of 0.5-1mm (lift off in one corner)

    Since I fiddled around with it far too long I think that has to suffice.

    Florian - Reply

    Did you complete the build this way with a functional printer? :)

    I’ve followed your steps, and the deviation is now very minimal, lot better than before (<=1mm). So I’m going to leave it as is for now.

    István Nagy -

    A WORD ON LEVEL SURFACES:

    You won't get this thing completely level unless you have a completely level surface!

    Seems simple but you might be surprised on how "unlevel" most surfaces are which you thought were even.

    If you take a long spirit level, 1 m+ and put it in 2 perpendicular positions on your surface you can wiggle the ends or you can see a small gap between edge and surface.

    Both indicate an uneven surface.

    I tried

    - wooden table

    - wooden kitchen worktop

    - large floor tile in bathroom

    - laminate floor

    - large thick coated MDF wood board

    All are not level!

    Finally I used a glass table with stand in the middle (having one with feet in the corners might "sag" in the middle)

    After assembly I revisited all surfaces and put the fully tightened printer frame on again.

    On all of them it wobbled!

    So you could unknowingly create wobble by making it "flat" with your uneven surface.

    Perfectionists will have to use some kind of concrete workspace or lab workbench.

    Florian - Reply

    Yeah, it’s quite a read ;)

    Just wanted to share since I spent almost 2 h (!) just on this step.

    Only after completion I saw the comment section here with many valuable tips of which a lot of them should be in the official manual!

    Better yet, please make one of your excellent youtube videos just for the frame leveling like the “common mistakes” one or the "MK3 beginner's guide" with the man himself (both are great! Highly informative, to the point and concise)

    It is a very important step since if the frame is crooked you run into problems later.

    It would be especially interesting to see exactly how you tighten the screws manually.

    You say “don’t overtighten” but what’s tight enough, how much is overtightened?

    Without a torque wrench it’s impossible to tell.

    So maybe you could give an estimate like how many degrees shall I further rotate the screw after having it screwed in by hand as far as I can?

    Florian - Reply

    Basically, don’t tighten the screws fully, in a way that you wouldn’t be able to tighten them more. And they must not be loose either.

    Martin L. - Official Prusa CS -

    I have a flat surface—a heavy piece of glass plate. Probably was once a table. My assembly rocked. I tightened, loosened, tightened, loosened. Rotated one long arm 180 on its axis, retightened. Still rocking about the same. Finally I tried padding one high foot. Three layers of electrical tape did the job. Three layers of electrical tape measures 0.29mm, which makes me suspect that maybe we are shooting for too accurate a foot leveling adjustment. Total spent on this step: 2 hours.

    Miles Odonnol - Reply

    Great idea. It was driving g me insane after redoing it so many times. Two layers did the trick for me. I did it all on a glass flat surface, found one of the short extrusion is not perfectly flat… :( You can tell by placing it on a flat surface and trying to slide a sheet of paper under.

    Teo -

    A completely flat surface is key for this part of the construction. Even so I still experienced about a 1-2 mm lift on the one corner of the long extrusion. Loosening all four screws on the front plate, applying down pressure and re-tightening did still not fix the wobble. I suspected that I needed an opposite flex of the metal equal to the amount of lift(wobble). Used flat metal washers 1,5 mm thick as spacers under the other 3 corners and applied a down force using a straight edge placed across the raised(wobble) corner and the corner diagonally across from it and then re-tightened the screws as per the normal instructions. Did the trick no wobble, completely square.

    Uwin Young - Reply

    This step is killing me…the one long extrusions holes were not tapped properly and I am getting about 2mm of wobble. The only way to not get wobble is not having the screws fully tightened. Once I go to tighten, it goes out of square. Two hours on this step already and that’s making me feel a bit uneasy about the rest of the build

    Daniel Clemente - Reply

    The tolerances were so tight on the frame that I trusted it was correct more than I trusted my pressboard desk was scientifically flat. Am done and printing and it’s perfect. I say skip this step. Though “don’t overtighten” are wise words here.

    Darrell - Reply

    The problem I have is that the screws are a very tight fit in the holes, maybe due to a finishing process build up of material, preventing any adjustment.

    The whole idea is to get the 4 flat areas (2 on each end plate) to sit flat on the table surface.  I am using a flat marble work surface and cannot improve on 1.25mm. If the 4 holes in the plates where the 1.25mm clearance gap is, were elongated a tiny amount, vertically upward, then it would be possible to remove the clearance.

    The ‘Y’ axis would be ok because of the fixed length of the square tubes, and the ‘Z’ axis calibrated by the vertical stepper motors. As the linear bearing rods are attached to the plastic carriers that are fixed to the end plates, they would still remain parallel to the mounting surface. I guess I just need PRUSA to confirm it is ok to increase the hole size slightly?

     I agree with others about the screw quality. They seem very soft.

    I will replace with Unbrako Socket head ‘Cap’ screws.

    Laurie Barton - Reply

    Hi Laurie, perhaps some of the screws were overtightened?

    Still, 1.25 mm is acceptable and won’t be noticeable after you add the rubber feet. The printer will correct everything else for you.

    Filip M - Official Prusa CS -

    If I hold the frame in the middle at the top (at the location where the finger is pointed at in the left photo) and wiggle, the entire thing is stable. However, if I hold at either end of the top of the frame and wiggle, some corners are lifted up. Is this acceptable enough to proceed to the next step?

    pcprusa - Reply

    Hello, no worries, that is acceptable, important part is that it is stable in the middle. Remember, the printer is capable of self-correcting.

    Martin L. - Official Prusa CS -

  13. Note this step is optional for now. We recommend mounting the feet to protect the surface on your table (workbench). However, you need to lift the frame up before each turn. There will be extra step at the end of the assembly to remind you of the antivibration feet. Note there are two designs of the feet, your package will have either the new version (marked orange) or the old version (marked yellow).
    • Note this step is optional for now. We recommend mounting the feet to protect the surface on your table (workbench). However, you need to lift the frame up before each turn.

    • There will be extra step at the end of the assembly to remind you of the antivibration feet.

    • Note there are two designs of the feet, your package will have either the new version (marked orange) or the old version (marked yellow).

    • For this step, please prepare:

    • New antivibration feet (4x)

    • Old antivibration feet (4x)

    • Turn the YZ frame on the side and insert the antivibration foot. For the new design, insert and turn 90 degrees to lock it in place. For the old design insert inclined, then rotate the foot until you squish the rim inside the extrusion.

    • Repeat this process on all 4 feet. Place them 2-3 cm from the end of each extrusion.

    What does “you need to lift the frame up before each turn” mean?

    Frank Pape - Reply

    Hello Frank, it’s just a suggestion that you need to lift up the assembly in order to be able to install the rubber feet more easily.

    Martin L. - Official Prusa CS -

    Got it, thank you! I thought it was some warning about why I should wait to install the feet until later.

    Frank Pape - Reply

    Honestly, add the feet at this step like it suggests. It gives your cables a bit more room and you don't run the risk of slicing them by accident.

    Jeffrey Foley - Reply

    Shouldn’t there be two additional feet right next to the center frame? As it it, i’d think that there’s more stress on the frame-to-extrusion connections than necessary. It seems like we could avoid center-sag and distortion by supporting it.

    Robstar - Reply

    Hi Rob, 6 feet aren’t necessary - the printer works perfectly fine with 4.

    Filip M - Official Prusa CS -

    The new feet (rectangular twist-lock) are marked in orange and the old feet (round) are marked in red. However, the instructions say the new feet are marked orange and the old feet are marked in yellow. I double checked with another person and a color picker, so I'm pretty sure this is an error. Additionally, an orange and a possibly orangish red are not easily distinguished for many people and are a poor choice for identification. Please label the different versions of the feet.

    Luke C. Ruppersburg, Jr. - Reply

    Hello Mr Ruppersburg, well spotted, we will correct the instructions. Thank you!"

    Martin L. - Official Prusa CS -

  14. For the following steps, please prepare: Y-rod-holder (4x)
    • For the following steps, please prepare:

    • Y-rod-holder (4x)

    • M3x10 screw (8x)

    • M3nS nut (8x)

    If you think you are missing a nut, check the bearing and pulley carefully - the nuts can hide inside them.

    Steve Lionel - Reply

    The Prusa Cheatsheet (v1.02) appears to label the M3x10 screws wrong. While the “2. Y-AXIS” bag labels them correctly.

    Mike Jouwstra - Reply

    Hey Mike,

    Thanks for the heads up, we’ll check it.

    Filip M - Official Prusa CS -

    My cheatsheet is version 1.03, and it appears to be corrected.

    Nathan Charlton -

    Can confirm previous comment. The included Cheat Sheet v1.02 seems scaled incorrectly. After verifying with calipers the M3x10 screws are included in the 2/2 Y-axis-MK3s bag. They appear to match more closely with the M3x12 diagram however they measure 10mm with calipers.

    Matthew Hall - Reply

    Some of my y-rod holder's slits for the nuts were too narrow. I used the calipers to widen them carefully, this worked for me. Be cautious though!

    Falk Thys - Reply

    I don’t seem to have any Y-axis rod holders. Are they supposed to be in a box with the other printed/plastic parts? Because I just realized that I don’t have any plastic parts. I do have two boxes of filament though…

    Brandi Braschler - Reply

    Hello Brandi,

    You should have received those in a bag labeled Y-axis. If you don’t have it, please go quickly through the rest of the manual and see if anything else is missing. Contact us at info@prusa3d.com or our 24/7 livechat and let us know, we will arrange for everything required to be shipped to you, I’m sorry about the inconvenience.

    Marcin M. - Official Prusa CS -

  15. Take one Y-rod-holder and insert two M3nS nuts. Make sure you've pressed the nuts all the way in. You can use pliers, BUT be careful, you can damage the printed part. In case you can't press the nuts in, don't use excessive force. First, check if there isn't any obstacle in the nut trap.
    • Take one Y-rod-holder and insert two M3nS nuts.

    • Make sure you've pressed the nuts all the way in. You can use pliers, BUT be careful, you can damage the printed part.

    • In case you can't press the nuts in, don't use excessive force. First, check if there isn't any obstacle in the nut trap.

    • Ensure and adjust the alignment of each nut with the 2mm Allen key.

    • Repeat this step for the remaining Y-rod-holders.

    I found that using forceps to securely hold the nut while pressing it into the casting with your finger, helped a great deal.

    Ken biles - Reply

    Might be a little easier to insert the nut if the square openings were slightly chamfered.

    Zack Shivers - Reply

    Hey Zack,

    Adding chamsfer could make them fall out easily - it’s better that way.

    Filip M - Official Prusa CS -

    You can also screw the nut onto the bolt a few threads to hold it aligned and get it started in the hole easier

    lincolntstein@gmail.com - Reply

    Good tip. Thanks for sharing.

    adrian.w7 -

    Solved my problem - what a time saver! Thanks!

    Sophie Bunton -

    Thank you, this is a super tip!

    Lander Benoit -

    Great tip, it really helped me!

    Teo -

    I found that the easiest technique was to 1) sweep out the square openings with a 1.5mm Allen wrench and 2) use @lincolntstein’s technique by screwing the nut a few threads onto a bolt.

    Jack McGwire - Reply

    Agreed that technique works very well. All of the square openings for me required sweeping.

    Charlie Miller -

    I was having lots of trouble with this step. The sweeping technique worked really well for me.

    ashlynwbaum@gmail.com -

    Quickest and easiest way was to first insert the corner bit (so that the corner faces downward. This way i got a bit of leverage but didnt need the tight squeeze to open up the hole and once pressed in a bit i turned them the way they should (flat side facing down) which worked fine for me. I do had to use the allen key to perfectly align them.

    Bryan O'Neil - Reply

    Grab one side of the nut with the end of the pliers and push - it goes right in. Learned that on my sixth nut.

    Neal Rudnick - Reply

    This worked well for me. Thanks!

    Steve Gowin -

    Quick sweep with the second smallest allen key, and then threading the nut on a screw to help get it started worked great. Unscrew, push in, and then finish the last bit the the allen key. Notice, they’ll snap into place, and be slightly recessed when they’re all the way in.

    Nathan Charlton - Reply

    Be prepared to insert a lot of M3n and M3nS nuts into printed plastic parts, and be advised that they do not always sit flush with the surface that the were inserted to. As a precaution, I always test that nuts are seated in the correct place by screwing in a bolt through the hole and then back out. I do this every single time that an M3n/M3nS nut is seated into a plastic part; I recommend this to everyone for all nuts from now on.

    Heimdall - Reply

    The slots ought to be a few thou larger. They still wouldn’t fall out. This is harder than it needs to be.

    David Krauss - Reply

    Useless telling us not to force the parts in when force is the only way to get the nuts into the slots. Better to have a slot that is a tiny bit too loose than having to risk damaging the part.

    Lessian - Reply

    Make sure to press the nuts deep enough, otherwise you’ll have a spinning bolt.

    tim.baetens@gmail.com - Reply

  16. Take the first pair of Y-rod-holders and place them on the longer extrusions, openings for screws must be facing up. Rotate the 3D printed parts towards the front plate. Secure each front holder with two M3x10 screws. Tighten both screws equally, but not completely. We will tighten them fully later on.
    • Take the first pair of Y-rod-holders and place them on the longer extrusions, openings for screws must be facing up.

    • Rotate the 3D printed parts towards the front plate.

    • Secure each front holder with two M3x10 screws. Tighten both screws equally, but not completely. We will tighten them fully later on.

    • Take the second pair of the Y-rod-holders and secure them with M3x10 screws on the rear plate (with shorter extrusions). Tighten both screws equally, but not completely. We will tighten them fully later on.

    • In case the M3nS nuts keep falling out, please flip the frame upside down. Tighten both printed parts and then return the frame to the previous position.

    On the third step here, one of the M3ns nuts just turns loose in the printed part when I try to turn the screw. Theres no way to loosen or tighten it, unless I can somehow jam the nut in place so the screw can turn into the nut, rather than the nut turning around in the printed part. But I risk damaging the part. Any suggestions?

    Falk Thys - Reply

    Hi Falk,

    You could use a dab of glue to keep it in place as a temporary solution. Once the printer is assembled, you can print a new part :)

    Marcin M. - Official Prusa CS -

    Be careful when tightening the bolts, I had a bad M3nS nut and when I tried to screw the bolt it almost started spinning inside the printed part. Replaced it from the spares

    Omer kalitzky - Reply

    Yup, striped thread. No easy way to get this out now. Can’t unscrew it.

    Randy Andrews - Reply

    Hello, try to grab the screw with pliers and pull it out. Or push it from the other side.

    Martin L. - Official Prusa CS -

    One of the screws won’t screw all the way in and I can’t figure out how I would get the nut out to replace it with a spare. Any suggestions on how I can proceed?

    Aaron Russo - Reply

    Well, you have to get it out somehow - maybe use pliers?

    Martin L. - Official Prusa CS -

    i feel like the holes (in the printed parts) are a just a tad too tight. that is, i thought that with captive nut parts, the nut should be doing all the gripping on the thread.

    Robstar - Reply

    (the screw hole, that is; the slot for the nut seemed just great)

    Robstar -

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

    • Y-belt-idler (1x)

    • M3x18 screw (1x)

    • M3x10 screw (2x)

    • M3nN nyloc nut (1x)

    • M3n (2x)

    • 623h bearing housing (1x)

  18. Take the Y-belt-idler and insert two M3n nuts from the  top. Turn the idler to the other side and insert the M3nN nyloc nut. The rubber inside the nut must be facing towards you. BE CAREFUL, don't over tighten the screw, you can break the part!
    • Take the Y-belt-idler and insert two M3n nuts from the top.

    • Turn the idler to the other side and insert the M3nN nyloc nut. The rubber inside the nut must be facing towards you. BE CAREFUL, don't over tighten the screw, you can break the part!

    • Make sure all three nuts are all the way in.

    • In case you can't press the nuts in, don't use excessive force. Take M3 screw thread it from the opposite side of the printed part, as you tighten the screw, it will pull the nut in. Be careful not to break the idler during tightening.

    The parts for this step call for nuts without nyloc but the instructions say “The rubber inside nuts must be facing up.” and the picture looks like nyloc nuts.

    John Merling - Reply

    Hi John, there was a change in the design. Use regular M3n nuts without rubber, the text was fixed. Thanks

    Jakub Dolezal -

    Found that attaching the M3n to the M3x18 one round, then pushing the nut in from the top then unscrewing it makes it easier to place the nut.

    Scruff - Reply

    This tip did it for me. I wish I had read it before fighting with the nuts for about an hour. The nuts were in the slots, but I guess they weren’t in deep enough - every time I tried to attach them to the frame, the m3-10 bolts would just spin and never catch. I took the idler apart again, took the M3-18 bolt, threaded it and pushed down hard and the nuts pushed down further and stopped. Perfect!

    Michael Pennachio -

    I found it easier to align the nuts with the holes by inserting an allen key from the other side then letting the nuts slide along the key into the holes.

    Miguel Barroso - Reply

    Very good tip! You can then use another allen key to push the nut down.

    Lucas Rakoto-Sam -

  19. Insert the prepared bearing in the Y-belt-idler. Bearing housing orientation doesn't matter.
    • Insert the prepared bearing in the Y-belt-idler.

    • Bearing housing orientation doesn't matter.

    • Secure the bearing with the M3x18 screw. Don't fully tighten the screw.

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

    Great instructions so far. A minor issue with the pictures in step 17, they appear to show a M3nN nyloc nut in the base (there is a bit of blue color shown) even though step 16 states using two M3n nuts in the base of this piece. Maybe that pictures can be updated to correct this?

    adrian.w7 - Reply

    Hello Adrian, well spotted. We’ll check this.

    Martin L. - Official Prusa CS -

    thanks for the mentioning it i was so confused until i read the comment :)

    Houssam Abi-issa -

    the picture still shows nyloc nut in the base and not the side.

    david -

    I noticed the same thing.

    Luke Maxcy - Reply

    Same. Confusing :\

    Itamar - Reply

    +1 noticing the same thing XD

    Bradley Heenk - Reply

    going okay so far. beware: I had a nut sneakily find its way inside the side of the bearing in the jumble in the bag. some people might not notice it and try to secure this with the sneaky nut inside the bearing.

    Alan Ostroff - Reply

    Thank you so much for this tip. I too had a sneaky nut lodged in the bearing’s axle hole. Folks, check for sneaky nuts.

    Steve Gowin -

    Sneaky nut here, too. But I happened to notice it.

    Miles Odonnol - Reply

    After I have checked that the bearing can rotate freely, am I supposed to fully tighten the M3x18 screw?

    pcprusa - Reply

    Hi there, no, not fully, that would prevent the bearing from rotating.

    Martin L. - Official Prusa CS -

  20. Rotate the frame with longer extrusions towards you.
    • Rotate the frame with longer extrusions towards you.

    • Take the Y-belt-idler and place it on the front plate. Note there is a mark (circle) on the printed part facing up.

    • Secure the Y-belt-idler with two M3x10 screws. Tighten the screws until the printed part reaches the surface of the plate.

    • This approach is different compared to the previous model MK3, follow the instructions in this step.

    I noticed later on that one of the nuts wasn’t fully inside. (It was kind of at an angle inside). Tried to remove it, and put it inside again, but now its “stuck” inside, as in…the nut has free roam inside the 3d printed part and now I can’t remove the screw+nut from it….

    Be careful with tightening!

    Dominik - Reply

    Same thing happened to me, the nut turns within its plastic hole, I can’t tighten or remove the screw now. Did you end up continuing the build with that one screw not properly tightened? How much of an impact do you think it would have on the belt later?

    Brett Hamm -

    Hey Brett,

    You can try holding the nut with pliers and tightening it. It should allow you to re-print the part later.

    Filip M - Official Prusa CS -

    I have the same issue i over tightened the screw and the nut is free now tried my best to tighten it even by pressing the corners of nut and tightening the screw but no luck. I proceeded with the build for now I am not sure but i guess it is tight enough to print the part later.

    An advice?

    BASSAM MALEH -

    As long as the part holds in place, I agree, continue the build and print a new one later.

    Martin L. - Official Prusa CS -

    With these new R4 parts (I’m upgrading my MK3 to the MK3S parts for the Y belt retention), the 10mm screws only just catch the thread in the nut, with the idler fully against the frame. It would be better if slightly longer screws were used.

    Steve Jones - Reply

    Hello Steve, are you sure the nuts are insterted all the way in?

    Martin L. - Official Prusa CS -

    Was thinking the same thing about the 10mm screws being too short but realized the nuts weren’t fully set. They should be about 2-3mm below the surface of the idler holder. Use the bolt to draw them in a bit first before attaching to the frame.

    Mark Leighton - Reply

    I used screws to seat the nuts in the part first. When assembled and the screws tightened, they just barely stick out the far side of the nut. If yours do not, I would try seating the nuts with a screw again.

    Mark Jurisch - Reply

    I thought the same that the screws were too short. Easiest way i corrected was to thread the screw through and grab the pliers and gently pull the nut and screw through about 2 - 3 mm

    Shain Pipan - Reply

    Tip!

    If you have problem inserting the nut you can use a hex wrench to guide the nut into the bolt like in the image below.

    Image

    Then just use a bigger hex wrench or similar to push it down the hole.

    Hope it helps :)

    Aqua Stealth - Reply

    is there a reason you didnt require to tight the screws fully? since you change the belt tension system, why not tighten them all the way? it feels to me like you change the tension mechanism to a much better one, but why sticking to the old “remains” of the previous system?

    shwekwek@gmail.com - Reply

    Hello there, it’s just that when the printer is assembled, it is easier to tighten/loosen these screws.

    Martin L. - Official Prusa CS -

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

    • Y-axis motor (1x)

    • Y-motor-holder (1x)

    • M3x10 screw (4x)

    • M3n nut (2x)

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

    It would be good to have a mechanism to be able to better align the orientation of the belt. Some washers might do to be able to move the motor in the X axis. For the idler, this is more difficult to do. In my case, tolerances were pretty tight and my pulley was touching the motor, which apparently caused me a number of issues with calibration and layer shift.

    Or mentioning that a pulley touching the motor causes friction (and problems later on) might also be helpful, I think.

    Christoph Hollauer - Reply

    Hello Christoph,

    the description of how to align and tension the belt is at the end of this chapter.

    Martin L. - Official Prusa CS -

    Only 2 m3n nuts in y-axis bag and they got used on the y belt idler. Y-Axis bag even says 2X M3n. Use spares?

    jeff d - Reply

    Hi Jeff,

    Did you make sure that you haven’t used the square nuts instead somewhere? In any case, if you are missing any screws/nuts, that’s why spares bag is included :)

    Marcin M. - Official Prusa CS -

  22. Take the Y-motor-holder and insert two M3n nuts. In case you can't press the nuts in, don't use excessive force. Use an M3 screw from the other side and tighten it.
    • Take the Y-motor-holder and insert two M3n nuts.

    • In case you can't press the nuts in, don't use excessive force. Use an M3 screw from the other side and tighten it.

    • Place the Y-motor-holder on the motor, ensure the correct orientation as in the picture (use the motor cable).

    • Using two M3x10 screws tighten holder and motor together.

    I screwed up here and put the nuts on the wrong side. Still trying to get them out…

    Matthew Niederberger - Reply

    Same thing happened to me. To fix it I put a screw in from the other side and pushed on that.

    Ben M -

    Used some extra nuts. Seems to be holding alright for

    Matthew Niederberger - Reply

    I found it easier to push the screw in from the other side, place the nut on the screw (just so it fastened on the screw) and pull through to get a good alignment.

    Rickard Hermansson - Reply

  23. Take the Y-motor-holder and place it on the rear plate (short extrusions).
    • Take the Y-motor-holder and place it on the rear plate (short extrusions).

    • Ensure the correct orientation, the motor shaft must be facing towards the aluminium extrusion with the PSU holders. Note that their position differs based on the Black or Silver PSU.

    • Secure Y-motor-holder with two screws M3x10.

    Don’t over-tighten the last two screws. The hex nuts can slip their position it seems

    Niall Brown - Reply

    Make sure stepper motor (rather than printed part) is level before tightening.

    Miguel Barroso - Reply

    Photo is for old (silver) PSU. PSU holders for new (black) PSU are in the SIDE section, see step 9.

    Hans G. Schnieder - Reply

    Hello Hans,

    Thank you, we will amend this step.

    Martin L. - Official Prusa CS -

    Hans’ comment caught my attention too, I had to go back up and look; for the Black PSU the holders are on the side, not the top. May want to make a note.

    Zaimor Kai - Reply

    Securing the motor on the plate doesn’t need nuts as well? The instructions reference no nuts there.

    yannisc - Reply

    You secure the motor to the plate using the nuts you inserted in step 22 (the first action in that step, labeled with blue). Or if you’re talking about attaching the motor to the motor holder (the 3D printed part), you don’t need nuts for that.

    Jon Humphreys - Reply

    Motor rotation / cable orientation is not shown or described. I assume cable goes down?

    Nick Gardner - Reply

    Hi Nick, please see Step 22.

    Filip M - Official Prusa CS -

    This has to be updated for the new PSU (Black). I got nearly to the part to finally install the PSU and the PSU holders were positioned for the old. I see it was noted by other users, but this step hasn’t been updated as of June 2019.

    ****Note to those with the new PSU (Black version), slide the PSU holders pointing outwards (So if the PRUSA logo is facing you, the holders will point to the right). You’ll thank me later if you don’t, I had to re-align a lot of parts again.

    Brandon - Reply

  24. For the following steps, please prepare: Y-carriage (1x)
    • For the following steps, please prepare:

    • Y-carriage (1x)

    • U-bolt (3x)

    • Linear bearing (3x)

    • M3nN nyloc nut (6x)

    • The printer's package contains a lubricant, which is intended for maintenance. No need to use it now the bearings are lubricated. There is a dedicated online manual on how to clean the printer and apply the lubricant. See Printer maintenance tips

    • For MK2/S owners, the Y-carriage is now symmetrical in one direction, therefore the dot (countersink, marker) orientation for bearing insertion doesn't matter.

    This step doesn’t include any context about what is meant by “the Y-carriage is now symmetrical”. I have a MK3S and have never owned one of the previous printers. So, what am I comparing this to? Does that mean the next step doesn’t apply to me?

    Doug Hughes - Reply

    Hi Doug, this note was more for MK2/S users that might be building their first MK3S.

    Back then, the MK2/S carriage would require a very specific orientation (there used to be a notch on it).

    Right now you only need to make sure the 2 bearings are on the left.

    Filip M - Official Prusa CS -

    M3nN nylon nut (6x) only 5 left in the bag.

    going to use a spare.

    Love those… THX

    CoC - Reply

    Just nit picking here ,  all the previous pictures show the components require with a white background the positioning of the nuts and to a certain extent, the bearings  should (for continuity ) should possibly be put in front of the y axis carriage  as the nuts look to be part of the y axis .

    Alex - Reply

    Looking at the pictures of the y-carriage, as well as the part in-person, it seems like the 3 holes in the center are not perfectly in-line. Maybe this is an optical illusion, but it seems as if the center hole is out of line with the others. If so, this would mean that which side we place upwards matters.

    In the later steps, I noticed that my belt moves left to right on my motor pulley as I move the carriage forward and back. I think flipping the carriage might fix this for me. I will try soon.

    Meanwhile, any info on if these holes are supposed to be in-line or not?

    Andrei Popescu - Reply

    Hi Andrei, the holes are aligned and will be used later - you don’t need to worry about them.

    You might need to adjust other parts (such as pulley) to properly align the belt.

    Filip M - Official Prusa CS -

    My printer did not come with the lubrificante.

    What is the proper one to use when time comes ?

    Gustavo Voltani von Atzingen - Reply

    Hello Gustavo, generic superlube (with lithium) will do just fine.

    Martin L. - Official Prusa CS -

    My Mk3S kit was also missing it's tube of lubricant. I will purchase some lubricant with lithium later.

    Jonathan Lin -

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

    Could you maybe add a picture on how to NOT do it? I’m not sure if I’m understanding it correctly, haha.

    Dominik - Reply

    Thanks for the suggestion, we’ll see what can be done

    Martin L. - Official Prusa CS -

    Why is there no information about that these bearing should be degreased and greased properly before assembly?

    Asbjorn Mikkelsen - Reply

    Dear Asbjorn, while applying some grease to the rods and bearings is recommended while doing the maintenance every couple months, it is not necessary to do it neither during nor after the assembly.

    Martin L. - Official Prusa CS -

    +1 on Dominik’s comment!

    Per Farny - Reply

    In this step you could try all U-bolts to see if they will fit the holes. If not, you can bend them carefully using a bit of hand power.

    Miguel Barroso - Reply

    Definitely do this! None of my U bolts fit instantly, I just bent them manually, carefully.

    Falk Thys -

    When you say “One of the tracks (row of balls) has to be in line with the cutout for the bearing,” what do you mean by “in line?” Do the rows of balls just need to be parallel with the side of the coutout (the bearing sits in the cutout naturally anyways), or do you mean that one of the lines of balls should be centered down the middle of the cutout so they are at the lowest point? Or do you mean that a row of balls should be as close as possible to an inside edge of the cutout?

    Bryan Bostrom - Reply

    Hi Brian,

    One of the lines should ideally be centered down the middle of the cutout :)

    Marcin M. - Official Prusa CS -

    The picture turns out to be very confusing at first glance. You’re showing the Y-carriage upside down and arbitrarily pointing at the track of bearings. I recommend that you change the blue arrow to indicate that the track of bearings should be oriented in the “UP” position while also making clear which side of the Y-carriage is “UP”.

    Jake H - Reply

    Hi Jake, the “up” or “down” doesn’t matter in this step - it’s only important to make sure that one of the tracks is in line with the cutout.

    Filip M - Official Prusa CS -

    Wasn’t it a good practice, when you’re using 4 rows linear bearings to have them seated at 45degrees in relation to the plane of the bed so that the weight is distributed to 2 rows not just one, as it is in this case?

    Razvan Simionescu - Reply

    Hi Razvan,

    thanks for the suggestion, we've discussed this some time ago with the devs. In case of the heatbed, the load is mostly vertical and to ensure the 100% contact between the bearings (spheres) and the smooth rod, we have decided to rotate them like this.

    Jakub Dolezal -

    Hi. Inserting a rod into one of the bearings 3 balls of the reference line fell out, I did it gently but they fell. I rotated the bearing so a complete row was in reference positios (so to stand vertical force) but I’m not sure: do I have to replace the bearing? How?

    kurtlong - Reply

    Hi Kurt, it’s best to replace the bearing if some of the balls have fallen out. You can simply reverse the instructions to replace it.

    Filip M - Official Prusa CS -

    I still don’t get this. The picture shows the line of bearings at an angle, around 15 degrees, relative to the cutout.

    David Krauss - Reply

    Hi David, the long row of bearings is almost perfectly in the middle of the cutout.

    Filip M - Official Prusa CS -

    I’m not familiar with this kind of bearing, so I just threw it on without checking. Now I finally understand, a diagram rather than photo would have been clearer.

    Darrell - Reply

  26. This is VERY IMPORTANT part of the assembly, which can significantly influence printer's behaviour. PLEASE read following lines carefully! Place the Y-carriage on a flat surface. Orientation doesn't matter. Insert linear bearing in the cutout and secure it by U-bolt.
    • This is VERY IMPORTANT part of the assembly, which can significantly influence printer's behaviour. PLEASE read following lines carefully!

    • Place the Y-carriage on a flat surface. Orientation doesn't matter.

    • Insert linear bearing in the cutout and secure it by U-bolt.

    • Hold thumb on the U-bolt and turn the carriage. Place nyloc nuts on both ends of the U-bolt.

    • Start tightening the nuts, BUT ENSURE you are tightening both nuts equally and AS SOON AS EACH NUT REACHES THE SURFACE OF THE Y-CARRIAGE STOP TIGHTENING!!! We will finish tightening the nuts in the next step.

    • Repeat these steps for the remaining two linear bearings.

    • Over tightening nuts leads to deformation of the bearing and all the issues connected with it. Please follow the instructions.

    Hi

    When inserting the linear bearings and trying to secure it by U-bolt I find the U-bolts about 1mm to small.

     - Measuring the U-bolts from radial centre to centre I get ~18.5mm (~22mm U outsides)

     - Measuring the machined holes in the Y-carriage (radial centre to centre) I get 20mm (~23mm outsides)

    Trying to see if I can apply a bit of force to widen the U-bolt I find that with quite a bit of force I can expand them about all the way, but it looks like the tread might get damaged if I try to force it through. What do you think – should I go for it and use this force?

    Stephan Lindeque - Reply

    I experienced a similar issue where the U-bolts were too small. Using a bit of hand (finger) muscle it was possible to slightly stretch (pull apart) the U-bolt (instead of using a tool that may damage the U-bolt’s threads) to widen each U--Bolt so that it will fit into the machined holes of the Y-carriage.

    adrian.w7 -

    Definitely do use your fingers to pull apart the u-bolts as necessary. I messed up the threads a bit (still worked, but more resistance) by forcing one in.

    Charlie Miller -

    Hello guys, I confirm that it might be necessary to pull the U-bolt ends apart .

    Martin L. - Official Prusa CS -

    Which way should the nylock nuts go? With the nylon facing towards the u-bolt threading or away from it?

    Michael Pennachio - Reply

    Hey Michael,

    Have a look at the pictures, you can always enlarge them.

    Filip M - Official Prusa CS -

    I had a hard time getting the nuts to go very far with just my fingers. I was forced to start using the pliers earlier just to get them to turn. This made it very difficult to judge any sort of resistance against the surface. I also accidentally, slightly scratched the black surface with the pliers from this process. I decided to redo this this part over again since I was so unsure of how tight I actually had the u-bolt.

    I got a 7/32” socket and (WITHOUT THE WRENCH PART!) turned the nuts by hand with it. It gave me so much better control of the tightness with fingertip feedback and was able to get it perfect without any extra leverage from the pliers. Also made tightening both sides evenly much easier, and was able to make small adjustments easier - such as centering the bearing and rotating the bearing into final position.

    Andrew VanHeuklon - Reply

    Socket wrench is very useful for this part (if you have one)

    Please consider adding a small socket wrench/pipe in the kit - does not have to be anything fancy, just a piece of pipe with m3 nut hole on one end and hole to insert allen key in another (for better tightening)

    Roman Tarakanov - Reply

    Hey Roman,

    The wrench is not necessary for this part, and it wouldn’t be useful in all the other steps. Pliers are perfectly fine for this kind of task.

    Filip M - Official Prusa CS -

    Yeah, it’s totally doable with pliers (I did one like that), but a small socket wrench, even a 3D-printed one like this https://www.thingiverse.com/thing:195996... , would make this step a lot easier.

    Plus, as Andrew mentioned above, it is rather easy to scratch the surface when using pliers (I did that as well).

    Again, not a big deal, but would be a welcome addition if you decide to include some sort of tool (even if 3D printed).

    Roman Tarakanov -

    I recommend this as well, just without the wrench. I finger tightened using just a 5.5 mm socket.

    Heimdall -

    Why do you mention flat surface, if later you hold carriage while tightening U-bolts anyway?

    Paul Kozlovitch - Reply

    Hello Paul, it’s to check if the carriage is not bent by some accident.

    Martin L. - Official Prusa CS -

    I was glad for spares. One of my Y-axis u-bolts was “pretzel-like”. With the u-bolt laying flat on the table, the other leg was 3mm off of the table. Also legs were 4mm closer than diameter of hoop part. (like above). So if your u-bolts are too wonky, try the one in the spares bag.

    Bill Brothers - Reply

    A tip for finding out if the nuts have reached the surface or not is to take a piece of paper and hold it underneath the nut while tightening it. As soon as the paper is gripped by the nut - STOP! Yes, don’t tighten it any further as you may fail calibration if you do.

    Miguel Barroso - Reply

    Excellent strategy! I had already tightened the nuts before arriving at this comment, but I used this comment to go back and check the grip of the nuts and found that one of my U-bolts was wildly uneven. Slipping some paper beneath, doing a quarter turn (with pliers), and checking if the paper is gripped by the nut really helped me ensure even tension.

    Prusa — even a tiny stamped-out sheet metal wrench would really improve this step. Using pliers is a frustrating pain in the ass, and prone to scratching up the assembly.

    Wesley Boynton -

    If this step especially

    -) is so susceptible to errors that you have to warn people excessively

    -) is so important for the very basic function

    -) is so inconvenient and fiddly to assemble with the given tools

    -) has so many comments about how you can ease the assembly (over 68 from step 25-28)

    then you REALLY should revise your design!

    Here is a suggestion: include a CNC mill into your manufacturing line that precisely cuts into the slotted holes, so that the linear bearings fit perfectly into the Y-carriage.

    Also decrease the length of the slotted holes. It only impedes the assembly if you can slide your bearings back and forth such an unnecessarily huge distance (2mm).

    Although a rework could solve some problems, in my opinion this clumsy design should be revised in it’s entirety.

    Gabriel Mündl - Reply

    7/32” socket fit these nylock nuts for me. Metric sockets did not fit.

    Miles Odonnol - Reply

    I suspect they are 5.5mm nuts, not in any metric socket set I have. Confirmed that 7/32” works just fine.

    Paul Meyer - Reply

    I’m confused by the confusion. I used an adjustable wrench and it was a breeze. As always, don’t overtighten.

    Darrell - Reply

    my u bolt was also longer on side than the other. what you need is a 3 d printed housing that just screws in from the other side. no crushing of bearing or over tightening. i realize u bolts were the cheapest option.

    julian - Reply

  27. Ensure again the nuts are tightened just to the surface and equally. Check if the bearing is centered in both directions, if not slightly release the nuts and adjust its position. Then retighten the nuts to the previous state.
    • Ensure again the nuts are tightened just to the surface and equally.

    • Check if the bearing is centered in both directions, if not slightly release the nuts and adjust its position. Then retighten the nuts to the previous state.

    • When you are ready, using pliers rotate each nut, but only 90°. This is enough to fix the bearing without deforming it.

    • Repeat these steps for remaining two linear bearings.

    Should the bearing housing spin , or should the u bolt hold the housing in place?

    eli - Reply

    Hey Eli,

    The housing shouldn’t be able to move.

    Filip M - Official Prusa CS -

    Based on Eli and Filip’s comments, it seems I was a little too cautious with mine and the housing was able to rotate inside of the ubolts. I had to turn an additional 90 degrees to keep from being able to turn the housings with my fingers.

    Zaimor Kai - Reply

    Standard metric socket sets don’t have the right size for these nuts, but I found that 7/32” works quite well.

    Steve Lionel - Reply

    A 5.5 mm Husky socket worked for me

    Heimdall -

    For those who like a little old school Tamiya RC fun - their famous little metal wrench works perfectly with these nuts!

    Keith Mizen - Reply

    I screwed this up the first time using the pliers to tighten these nuts, over tightened and ended up with an unpleasant amount of texture and noise when sliding the carriage. If you have a socket set with a 7/32” and simply place the socket on the nut and twist with your fingers you get a much better feel for how much you’re tightening. Just a light twist did it and now I’m sliding smooth!

    Matthew Pugmire - Reply

  28. Take all the smooth rods and compare their lengths. For  Y-carriage you need mid-sized rods (330 mm). NOW, PLEASE BE VERY CAREFUL! Gently insert the rod straight into the bearings, do not apply too much force and do not tilt the rod!
    • Take all the smooth rods and compare their lengths. For Y-carriage you need mid-sized rods (330 mm).

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

    • If you can't slide the smooth rod easily, check the two bearings are aligned properly.

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

    When sliding the rods through the bearings, they slide in easy enough, but there is a degree of roughness when moving the carriage along the rods. Presumably this is supposed to be a very smooth movement, correct? I have check and rechecked the bearing orientation, and all is as per your instructions. No balls have fallen out of the bearings.

    Alan Crystal - Reply

    Hi Alan, you can try to apply some lubricant to the rod. Any soft grease with lithium additives or Super-lube will do the trick.

    Martin L. - Official Prusa CS -

    Two of our bearings are really scratchy/rough compared to the third bearing…

    Paul - Reply

    Hi Paul, see my previous answer. The bearings don’t have to move by themselves on the rod. If in doubt, lube the rod. ;)

    Martin L. - Official Prusa CS -

    My rods slide in easily but the bearings dont seem to be spinning smoothly… i was careful not to overtighten but maybe i did anyway?

    Johnny Appleseed - Reply

    Hi Johnny, these are linear bearings so they are not supposed to spin. Otherwise see the comments above.

    Martin L. - Official Prusa CS -

    My rods slide easily, but the side with a single bearing is more free. For example: if I tilt the carriage, the rod on the side with the single bearing will slide all the way out on it’s own. The side with both bearings requires a slight pressure to move.

    Hopefully this is correct… going to continue with the build!

    Adam - Reply

    Hello, yesm no worries, you can continue. The bearings might have slightly different tolerances but that’s OK.

    Martin L. - Official Prusa CS -

    The side with two bearings will have double the seals providing resistance, so it shouldn’t slide quite as freely as the single bearing side. The two bearings could also be slightly misaligned causing a bit more friction. As long as the both move with little force you should be fine.

    Mark Jurisch -

    I only seem to have 2 different length of rods so there is no middle size? It’s easy to figure out which rods to use, it’s just I now wonder if at a later stage there will be a rod I need that I don’t have.

    Shane Hobson - Reply

    Dear Shane, sorry for this, please contact us on info@prusa3d.com or livechat, provide a photo of the rods you got and we’ll send you the correct rods.

    Martin L. - Official Prusa CS -

    Dear Martin,

    I have applied the bearings as described, including the lube, but I still can’t move the carriage by hand in a completely smooth motion.

    I am in doubt whether to continue or restart with new bolts and bearings

    Is there some way to describe the minimum required smoothness?

    jaapmsier@gmail.com - Reply

    Hello,

    If you have any doubts whether your bearings/carriage are sliding smooth enough, you can send us a video of you moving it to info@prusa3d.com or contact us on our livechat - we’ll have a look :) The bearings should move relatively smooth, you should still be able to hear/feel some mechanical movement in the bearings - it will never be completely silent. Crucial thing here is to make sure later that your U-bolts are not overtightened, as it may cause the bearings to get damaged easily.

    Marcin M. - Official Prusa CS -

    Just mailed you a video, starring me, in a moving action video.

    By the way, I have tried it also with the bolts loosened to the point where the bearings started to move, but it made no noticeable difference.

    Looking forward for your advice

    jaapmsier@gmail.com - Reply

    The movement is really coarse for me too, even after lubing with lithium grease. There is a bit of scraping sound and when I try to move the carriage with my finger in as tiny movements as possible, it “catches” due to the resistance and the movement is jerky. Is this really ok?

    Magnus - Reply

    Hi,

    The bearings should move smoothly on the rods. A bit of scratching is normal. If the pressure on the bearings is greater during motion, try to check that the rods are not scratched or that the bearings are not damaged. If there is a problem with visible damage or rods / bearings are damaged, do not hesitate to contact our technical support on email: info@prusa3d.com.

    Martini H. - Official Prusa CS -

    Any one else experience this anomaly?

    My issue was that one of the U bolts was not threaded, I was Sunday nothing was open. I to cut threads the in the u bolt but was not successful for lack of tools at my disposal

    https://www.dropbox.com/s/yvga77fe63ort7...

    I then noticed a u bolt in the spare parts bag, both sides were threaded.

    The U bolt would not fit the hole pattern at just 1 location. either the bore was drilled to the incorrect size or it was tapped (threaded) I swapped out all the U bolts. everything fit but the 1 location. I will just drill it out suppose.

    Richardjames@gmail.com - Reply

    Hey Richard,

    Please check the spares bag - it should contain a spare ubolt. If it’s not there, then please contact our tech support via email or live chat - we’ll replace it.

    Filip M - Official Prusa CS -

    I also had a u-bolt that had one end short and not threaded. Sent a pic to support (just FYI). The spare bag had a good one, so I’m good to go.

    Paul Meyer -

    After reading most of your comments, I tried to unscrewed that U bolt a little bit to improve movements, and it made a huge difference, if your movement is not fluid, try to loosen up the u bolt, you're welcome

    Pascal Robert - Reply

    Pascal Robert! Thank you so much! your idea of loosening and checking the U bolts worked perfectly!

    Michael Nolte -

    Funny. For me it was exactly the opposite. I had loosened the screws so that I barely could slide the bearings back and forth. Movement wasn’t very smooth. Then I tightened the screws 90° and the movement became smoother.

    What I get from this information: Try various levels of tightening. First in big increments (90°) and then smaller ones.

    Gabriel Mündl -

    The bearings sound horrible! Rechecked everything, Since a “bit of scratching is normal” I am proceeding on. I have never had new bearings make any noise let alone scratching….

    Dave Bear - Reply

    Hey Dave,

    If you believe your bearings are faulty, then please contact our tech support - we can always arrange replacements.

    You can use email (help@prusa3d.com) or livechat (http://shop.prusa3d.com/).

    Filip M - Official Prusa CS -

    have the same scratchy issue. it simply does sound not well, like some metal-dust is scratching inside the bearings or a metal sponge is scratching the rods. support says its ok?

    Martin Diering - Reply

    Hi Martin, please send us a video with the sound - we’ll let you know if there’s anything wrong with your bearings.

    You can do this by email (info@prusa3d.com) or just upload it to youtube and head over to Livechat.

    Filip M - Official Prusa CS -

    Would an m5 tap be a good idea here to use before assembly ?

    Dave Cook - Reply

    Hi,

    Where would you like to use it exactly, Dave? There is no need to use it at all throughout the whole assembly.

    Filip M - Official Prusa CS -

    I was just thinking of using it in the tapped holes in the ends of extrusions, to clean them out, so to speak. Went ahead with assembly without one, all the holes had zero resistance when putting the screws in. Sorry, didn’t notice until now, that I should have posted this in the first couple steps.

    Dave Cook - Reply

    If you hear scratching, try moving onto step 29 and see if you still hear an excessive amount of it. I found lubing the bearing with a little lithium grease and loosing the u bolts (because I had overtightened them ever so slightly) did the trick. Thanks to Pascal Robert’s tip. I knew that I didn’t have them over tightened when I had them just tight enough that I couldn’t turn the bearings by hand anymore.

    Michael Nolte - Reply

    A light coat of oil made the rods slide easily through bearings.

    Bob Baltz - Reply

    Hi Bob,

    What kind of oil did you use? We recommend using PTFE lubes, as other kinds will most often quickly gather and build up dust/micro debris and impact functionality of the bearings.

    Marcin M. - Official Prusa CS -

    How smooth should the robs’ movement be? So smooth to the point that if I start tilting the Y-carriage vertically from the horizontal, the robs start sliding automatically? Alternatively, should I tighten the U-bolts to the point that I need to exert some force in order to slide each rob in and out? In the latter case, how much force do I need to exert to slide each rob?

    pcprusa - Reply

    Hello,

    If before tightening the U-bolts the carriage slides down by itself, it means that the bearings are working correctly. You can find visual guide for screwing the U-bolts in this video:

    https://www.youtube.com/watch?v=Lsa-PXAX...

    Marcin M. - Official Prusa CS - Reply

  29. Take the Y-carriage including smooth rods and place them in YZ-frame. Make sure, that two bearings are on the left side (see the picture). Using your thumb, press the smooth rods inside all four holders. Don't use excessive force.
    • Take the Y-carriage including smooth rods and place them in YZ-frame. Make sure, that two bearings are on the left side (see the picture).

    • Using your thumb, press the smooth rods inside all four holders. Don't use excessive force.

    • Check again the correct bearing orientation!!!

    Mounted the Rods very gently, when I gently push the Y-Carriage I get a scraping Noise.

    I alligned them thouroughly by loosen the screws and pushed the carriage from front to rear still the same scraping.

    And No no balls fell out, It just doesn’t sound as a regular bearing, After finishing the X axes I pushed the Extruder from left to right and that was very smooth, So I’m thinking one of the bearings issn’t in good working order.

    Is this normal, it is facing some friction, will it go away or are these bearings malfunctioning.

    Jan-Willem - Reply

    Hey Jan, try testing each bearing on the rod (remove them from the Y carriage).

    If some of the bearings sound worse, you can replace them with ones from the Z axis (it doesn’t move so much).

    If they bearings are faulty, then please contact our support and we’ll replace them.

    Filip M - Official Prusa CS -

    I have the same problem as Jan-Willem. When I move the Y-carriage, I get a scraping noise also. The movement is not fluid but jerky when applying the same amount of force. It’s like stopping, moving, stopping, moving and so on.

    I haven’t applied lube yet but I’ll try and see how it goes…

    Miguel Barroso - Reply

    [UPDATE]

    Unscrewing the nyloc nuts on the U-bolts had the largest impact as suggested by Pascal Robert in the previous step. Now the Y-carriage is moving smoothly!

    Miguel Barroso - Reply

    Unscrewing the nyloc nuts on the U-bolts?? No way, the bearings starts to wobble then.

    Martin Diering - Reply

    He meant only a little bit. If they are over tightened this can help otherwise it will not. Try some lube and look at comments for previous section. Your welcome. ;)

    Elliott Bridge -

    To test whether there is too much friction between the bearings and the rods: At roughly what angle should the sled start to move by itself due to gravity when you tilt the frame?

    Ludwig Wall - Reply

    I have the same sound

    Charles Paquin -

    Same noise here. Don’t think it will be very silent while printing like this.

    Koen Verbeeck -

    It’s actually perfectly normal for them to sound like that at this point. I think I also heard a bearing hitting the carriage, so perhaps Vaclav forgot to secure all of them.

    Filip M - Official Prusa CS -

    THEY ARE NOT KIDDING.

    Hello from manual chapter 7 (the future). I have two important pieces of information for you:

    1. The extruder (the scary section of the manual) is not that bad, just be patient and take your time.

    2. TRIPLE CHECK YOUR BEARING ORIENTATION HERE (two on the left) JUST LIKE THE MANUAL SAYS. If you don’t, you will not notice it for about another 4-6 hours. Then it will bite you and you will have to disassemble a bunch of this assembly just to flip it around to get your heatbed to mount properly.

    Wesley Boynton - Reply

    The rods on mine don’t fit snugly in place, I have double checked they are the right length [330mm] I pushed them both to the side of one end to make sure they are parallel, is this normal?

    https://i.imgur.com/soJLYMi.jpg

    Thomas Hardman - Reply

    Hello Mr Harman,

    Yes, this is still normal, just make sure to tighten down the zip ties holding the rods.

    Martin L. - Official Prusa CS -

  30. Find the package with zip ties and take out 4 pieces. Slide the zip tie through the holder, there is a slot. Connect the zip tie and tighten it. The &quot;head&quot; should be inside the frame.
    • Find the package with zip ties and take out 4 pieces.

    • Slide the zip tie through the holder, there is a slot.

    • Connect the zip tie and tighten it. The "head" should be inside the frame.

    • Using pliers cut the remaining part.

    • Repeat this step in all four corners.

    If you want the “block” part of the zip tie to end up on the inside, make sure it starts on the outside. And I used scissors…don’t know how you’re supposed to get a clean close cut with the pliers.

    Nathan Charlton - Reply

    Be careful cutting the zip tie by the y-axis motor. I wasn’t paying close attention and almost cut the wires with the zip tie.

    Zaimor Kai - Reply

    Almost did this myself.

    Joseph Finan -

    A small trick I learned in the USAF…. Nail Clippers are PERFECT Ziptie clippers. ;-)

    Justin Valois - Reply

    I wonder about the usage of these plastic zip ties. this does not looks to me like proper engineering. yes, seems to do their job, still it is like improvising…

    Martin Diering - Reply

    Zip ties are perfect for this situation! Try and name me a better temporary (I.e. removable) solution for this. ;) go on have a go

    Elliott Bridge -

    I'm only messing with you. It's because it's easy to make it work with the 3d printed part it goes through and its able to flex around the rod so it has more surface contact and therefore longer lasting.

    Elliott Bridge -

    Hello Martin,

    take it from this side: why replacing and overthinking something that is simple, practical, functional and inexpensive? From our experience, the real-world engineering is always about trade-offs and compromise.

    Martin L. - Official Prusa CS -

    Martin, I would reiterate the points above and include that these parts are reliable enough to get you printing. And now that you have a working printer, you can engineer new and more permanent fixtures! But also remember you might want to be able to easily remove the carriages again for things such as future maintenance and modifications.

    Heimdall - Reply

    I found that this gives better results:

    1) flip the cable over in picture 1, such that the head is facing up,

    2) wrap it over the top, but keep the head on the side shown in picture 1,

    3) tighten it down on the side opposite what is shown in picture 3.

    The zip tie portion you need to cut is now exposed by the angle in the metal. It also reduces the chances of cutting the motor wire because you can cut horizontally with the pliers.

    I don’t mind the zip ties. It is an effective engineering solution and also an impressive use of combining 3d printing and mass produced parts to solve a problem.

    Joseph Finan - Reply

  31. IMPORTANT: proper alignment of the smooth rods is crucial to reduce noise and overall friction. Ensure all M3x10 screws on Y-holders are released, so the printed parts are able to move. Move the Y-carriage back and forth across the entire length of the smooth rods to align them.
    • IMPORTANT: proper alignment of the smooth rods is crucial to reduce noise and overall friction.

    • Ensure all M3x10 screws on Y-holders are released, so the printed parts are able to move.

    • Move the Y-carriage back and forth across the entire length of the smooth rods to align them.

    • Then move the carriage to the front plate and tighten all screws in the front-Y-holders.

    • Move the Y-carriage to the rear plate and tighten all screws in the back-Y-holders.

    Clever alignment technique!

    Zack Shivers - Reply

    There is some drag when sliding the carriage back and forth once I’ve completed this step, i.e. friction will stop the carriage shortly after I stop sliding it - it does not travel freely onward. While pushing it, it seems to go freely while feeling a tiny bit of roughness as noted as normal above. Does it sound like it’s setup correctly?

    Per Farny - Reply

    Hi,

    Perhaps you have tightened the pulley too close to the motor - make sure there’s at least a small gap in between the two.

    Filip M - Official Prusa CS -

    I have the same feeling of drag on mine and had the same question. I assume this is normal. Filip Ms response about the pulley motor makes no sense seeing that at this stage the pulley belt and motor have nothing to do with the glide of the Y- carriage

    Scott -

    Try a bit of light lube on the rods. You dont actually want it to carry on sliding as it needs accuracy unlike something such as an race-car where you want it to keep rolling. ;)

    Elliott Bridge -

    Per Farny and Scott have the same problem as others had above. Loosening of the nuts holding the U-bolts should do the trick.

    Miguel Barroso - Reply

    These Y-holders are one of the more fragile parts. Be careful not to overtighten. I fear that I cracked one of mine and it didn’t take a whole lot of torque to do. When you’ve been torquing down the metal pieces which allow you to put some good pressure on them, it’s easy to forget that you can’t put the same kind of torque on a plastic part.

    Bryan Bostrom - Reply

    By the end of this step you should be able to manually move the carriage back and forth with about 1 lb or less. Bearing noise is normal because they are not perfect but as long as it doesn’t sound like metal scraping metal. And always when it doubt, lube it out.

    Heimdall - Reply

    Maybe I’m weird, but I don’t really understand this step. It feels weird to move the Y-carriage back and forth when it is completely loose in the frame. I don”t understand what should happen.

    Should I unscrew the screws almost completely?

    Pieter Vermeersch - Reply

    Hello there, the point of doing this is, that the rods and the printed holders will “sit down into their ideal position” before you tighten the screws.

    Martin L. - Official Prusa CS -

    I have completed this step and the U-bolt on the side with a single linear bearing is scraping against the YZ frame. I have tightened the two Nyloc nuts on the U-bolt as much as seems appropriate, but it doesn’t help.

    Stephen Trenta - Reply

    Well, I had to file down the U-bolt just a small amount to get it to have enough clearance. Not sure why mine wasn’t aligned on both sides, but it seems the clearance for the Y-carriage is just minimal in general. I really only had to remove the chrome coating on the U-bolt, as it looks visually the same. Hopefully this is the only “jerry-rigging” I have to do

    Stephen Trenta -

    This is not too great  its by far (so far a) a bit of a let down on precision , no one is quite sure about the noise the sliding should make,   noise, lub or nut tightening , maybe Jo Prusa could do a “what it should sound like video.

    Alex - Reply

    I would like a description of exactly how the bearings will allow the Y-carriage to move once mounted on the printer. Should a very gentle flick with the finger cause the carriage to travel from the front of the printer to the back? Should it happen if I tip/tilt the printer towards the front or the back a certain number of degrees? How many degrees should I expect gravity to cause the carriage to move? OR does the carriage only move this freely when the weight of the heated bed and build plate is in place? I know it is a lot of questions but perhaps Prusa officially posting a video of the degree of motion with tipping will help builders understand how much free motion we are talking about. Best regards and thanks to all for all the comments that have helped with the build thus far.

    Dino - Reply

    Hi Dino, we’ll consider adding a video with Y axis sound. It’s hard to describe it, as everyone will assemble the Y axis in a different way, thus slightly affecting the sound.

    Filip M - Official Prusa CS -

    I’m not so interested in the sound. I would like to know “Should a very gentle flick with the finger cause the carriage to travel from the front of the printer to the back? Should it happen if I tip/tilt the printer towards the front or the back a certain number of degrees? How many degrees should I expect gravity to cause the carriage to move?  “. I’m interested in the amount/freedom of motion the carriage should have.

    Dino - Reply

    Hi there Dino,

    - Should a very gentle flick with the finger cause the carriage to travel from the front of the printer to the back? —> Not at all.

    - Should it happen if I tip/tilt the printer towards the front or the back a certain number of degrees? —> It can, but not easily and not all the way.

    - How many degrees should I expect gravity to cause the carriage to move. —> Let’s say 45° but it’s just an estimation.

    You should be able to move the carriage easily by pushing it with your pinkie. A “very gentle flick” should should move it very little, but surely not cause it to travel on its own.

    Martin L. - Official Prusa CS -

    Thank you! Perfect. This is exactly what I was looking for. I cannot thank you all enough for being all over this guide and helping out with these little details. I think everyone just wants to build it as perfectly as possible to achive the amazing results we find online. I cannot thank you all enough for monitoring these posts and being so helpful. Cannot wait to get to the preflight checklist.

    Dino - Reply

  32. There is a flat part on the motor shaft, rotate it similarly to the first picture. See the direction of the arrows. Place a GT2-16 pulley on the Y-motor shaft as shown in the picture. Don't press the pulley against the motor. Leave a gap so the pulley can rotate freely.
    • There is a flat part on the motor shaft, rotate it similarly to the first picture. See the direction of the arrows.

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

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

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

    • Turn the shaft and slightly tighten the second screw.

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

    U didn’t say this part is needed for this stage

    Itamar - Reply

    Which screw is used in this part? There seems to be a missing “parts for this stage” section

    (oh, there are screws in the GT2-16 pulley component, which are tightened via a an allen wrench)

    Tim Harper - Reply

    The screws come with the GT2-16 pulley component

    Heimdall -

    I think it would be useful to specify that these are “grub” screws in this step, or you could be caught looking for them forever like I was.

    Alan Ostroff -

    Agreed with Alan. It would be useful to note that the screws are in the pulley already. They’re tiny and black and hard to see otherwise.

    Kash Lingat -

    I ended up having to put the GT2-16 pulley on in the other direction or it wouldn’t line up with the belt. Did I do something wrong?

    Hakan Lindestaf - Reply

    Hello Hakan,

    Attaching the pulley the other way can cause the XYZ calibration and selftest to not pass. Did you check for a correct orientation of the Y-belt-idler?

    Marcin M. - Official Prusa CS -

    The belt on mine is centered when bed is close to the GT2-16 pulley but then rubs when it’s at the far end away from the pulley. I’ve gotteh is as close as I can to the motor without touching. Seems like I should flip the pulley around as well. Everything seems fine and the frame is flat with no wobble.

    Bill - Reply

    Looking from the side with the allen wrench inserted into one of the two the integrated screws helps orientate the screw to the flat portion because of the hole the flat portion makes between the two surfaces.

    Joseph Finan - Reply

    The Green arrow is not pointing to the motor shaft but to a screw on the Y-axis motor housing.

    John Swope - Reply

    Hi John, good catch! We’ll correct that :)

    Filip M - Official Prusa CS -

    Hi John, the arrow is not pointing, but indicating the inclination of the shaft. I will add another one to make it clear.

    Jakub Dolezal -

    Mine is missing one of the set screws. What size should I get?

    Ross - Reply

    Hello Ross,

    There should be a spare set screw in the spares bag.

    Martin L. - Official Prusa CS -

    Which is the right size allen key to use with the “grub” screw in the GT2-16 pulley? Perhaps this part should be spelled out in the manual for rank beginners such as myself.

    I don’t want to and risk damaging the pulley since I just managed to push 5 bearings out of one of the linear bearings already (and now and to wait for the ebay replacement to continue with the build).

    RichardL - Reply

    Hello Richard,

    There is only one key in the bundle that fits in, it’s the 1.5 mm one.

    Martin L. - Official Prusa CS -

    Missing a “For the following steps, please prepare:” step.

    Kenn Herman - Reply

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

    • Y-belt- holder (1x) smaller of two

    • Y-belt-tensioner (1x) bigger of two

    • Y-axis belt 650 mm (1x)

    • M3x30 screw (1x)

    • M3x10 screw (4x)

    • M3nN nyloc nut (1x)

    • M3n nut (2x)

    My Mk3 was in-transit when the Mk3s was released. I also ordered MMU2S. So I have some 3 and some 3S parts.

    On the 3 the y belt holder is one plastic part instead of 2 and there are less screws included.

    What is the purpose of changing over to the new design and is it worth printing (on my Mk2S) the 3s version?

    Damien - Reply

    Hi Damien, its easier to tension the Y axis properly with the new design. It’s not a necessary upgrade, though.

    Filip M - Official Prusa CS -

    Hello.

    My Y-Axis parts bag has:

    - Y-belt holders (2x)

    - Y-belt tensioner (0x)

    How long will it take to get the tensioner delivered?

    Thank you

    Ron - Reply

    Hi Ron,

    Please contact us either at info@prusa3d.com or our livechat, and we will arrange for the missing parts to be shipped to you.

    Marcin M. - Official Prusa CS -

    I am missing a M3n nut. What shall I do? I recall seeing a post about a box of spare parts. Does it include a M3n nut? Where is the spare parts box?

    pcprusa - Reply

    Hi,

    There is a whole separate bag labeled Spares, not a box. You can find an extra M3n nut there.

    Marcin M. - Official Prusa CS -

  34. Take the Y-belt-holder (smaller of the two printed parts). Insert M3n nut, all the way in.
    • Take the Y-belt-holder (smaller of the two printed parts).

    • Insert M3n nut, all the way in.

    • Insert M3nN nyloc nut, all the way in.

    • Use the screw pulling technique.

    It's not specified whether the nylock bolt's rubber should be facing you or not. It's visible in the picture, but maybe an extra reminder in the text could be helpful.

    Falk Thys - Reply

    Hello Falk,

    If you take a closer look on the picture, you can see the blue rubber bit facing outwards :) If it was the other way, the bit sticking out would be flat on the photo.

    Marcin M. - Official Prusa CS -

    I like the screw technique. I also found it helpful to use a small allen wrench put through the nut to align it with the hole so you can push it down with your fingers; like if the arrow in the picture was an allen wrench.

    Joseph Finan - Reply

    Might I suggest replacing the Jo graphic with something that makes more logical sense, like a diagram of a bolt, nut, wrench and a broken part. All it reminded me of is that I was behind on bear consumption.

    Darrell - Reply

    Wait! We can have bears already?!?

    Laurie S - Reply

  35. Bend one end of the belt around M3x10 screw. Push it in the holder as in the picture. Use an Allen key to push the belt in. Make sure the bent part and the end are within the width of the printed part.
    • Bend one end of the belt around M3x10 screw.

    • Push it in the holder as in the picture. Use an Allen key to push the belt in.

    • Make sure the bent part and the end are within the width of the printed part.

    • Teeth on the belt must be facing up!

    • Tighten the screw until you reach the nut, don't over tighten the screw, you will deform the belt.

    • Hold the nut from the other side until the screw reaches its thread.

    suggestion: have a screw with sharper end for this one so it will be easier to insert into the belt

    Vadim D - Reply

    I pulled the belt out a little, stuck the screw in then pulled the belt in again until the screw lined up.

    Shane Hobson -

    You actually aren't meant to damage the belt. The bolt is just meant to grip it not pierce it.

    Elliott Bridge -

    Or even better, fold the belt on to the tread of the screw body, and insert the belt folded on the screw at the same time on the plastic part.

    Jorge - Reply

    Hello Jorge, thanks for the suggestion, this does make sens.

    Martin L. - Official Prusa CS -

    “Make sure the bended part…” should read “Make sure the bent part…” (Not a big thing, but thought you should know.)

    Douglas - Reply

    Hello Douglas, thanks for noticing, we’ll correct it!

    Martin L. - Official Prusa CS -

    Struggled a bit with this so i screwed a longer 3m bolt, 20mm from the spares. Just started it in the bolt, wrapped belt around the exposed threaded pert and pushed belt home. Then removed the 20mm bolt and replaced it with the correct 10mm bolt. Job done!

    Norman March 13

    Norman Farmer - Reply

    The screw doesn't go all the way through the nut, only partially through the threads. The range between not in the nut and squeezing the belt is pretty narrow. If you're not sure if you've properly got the screw into the nut you can use the smallest Allen key and push on the screw bottom from the nut side to confirm that the threads are holding it in place.

    Daniel Friesen - Reply

    I found the M3n nut kept being pushed out of position by the M3x10 screw, until I held it in place with another M3n nut, this kept it against the printed part while the M3x10 screw engaged with the threads of the first M3n, the second M3N nut was removed at this point and the rest was easy

    Anthony Butler - Reply

    I’d recommend doing step 36 before attaching the belt! Also, @Anthony Butler’s tip of holding the nut in place with another nut was very helpful – there are extras in the spare bag.

    Mila Santana - Reply

    I wasn’t sure how much belt should be looped and did too much. Had to undo and redo. The photos for this step are far too small to be of any use.

    Darrell - Reply

    Hello Darrell, all the pictures are high resolution. You can enlarge them by clicking on the magnifying glass, or on the main picture itself.

    Filip M - Official Prusa CS -

    The picture seems to depict the end of the belt very slightly out of the printed part with five of the upper teeth engaged with the lower portion of the belt. Is this acceptable? Mine looks similar. Having the end of the belt fully inside of the printed part only allowed four upper teeth to engage.

    Luke C. Ruppersburg, Jr. - Reply

    Hello Luke, It is acceptable, but you don’t have to count tooth by tooth. You will do the final tightening in Step 38.

    Martin L. - Official Prusa CS -

  36. Using M3x10 screw fix the Y-belt-holder to the Y-carriage. Tighten the screw and ensure the printed part is parallel with the &quot;axis&quot; between the Y-motor and Y-belt-idler. Use the hole on the left, see the picture. Guide the belt along the Y-axis, around the pulley on the Y-motor and back.
    • Using M3x10 screw fix the Y-belt-holder to the Y-carriage. Tighten the screw and ensure the printed part is parallel with the "axis" between the Y-motor and Y-belt-idler.

    • Use the hole on the left, see the picture.

    • Guide the belt along the Y-axis, around the pulley on the Y-motor and back.

    • Make sure the belt is inside the frame, not under!

    • Push the belt through the Y-belt-idler and back to the "center" of the Y-carriage.

    It helps to use the allen wrench with the rounded end on this screw so you can hold the wrench at an angle.

    ryman1 - Reply

    I would have liked to know how much extra belt needs to go around screw, I left too much in the first block and had to disassemble it to shorten the distance.

    Pascal Robert - Reply

    Hey Robert, have a look at Step 37 - it tells you how much should go there.

    Filip M - Official Prusa CS -

    Had to tap the holes on the table for the m3 bolts. Threads for the belt tensioner clips on the table were damaged.

    W r hubbard - Reply

    Very difficult to tighten the screw. Also, the part seems flimsy; too thin.

    ASelo - Reply

    I attached the Y-belt-holder to the Y-carriage first and then attached the belt. Seemed easier that way.

    Hans G. Schnieder - Reply

    Agreed. I had a much easier time attaching the belt after mounting the holder.

    Wesley Boynton -

    Wouldn’t this step be much easier right before mounting the Y carriage?

    mandic.daniel@gmail.com - Reply

    Hello Daniel,

    Thanks for the suggestion, we will consider this.

    Martin L. - Official Prusa CS -

    This was the first step where I made the cardinal sin of not closely following the directions. Instead of driving the M3x10 screw upwards through the Y-belt holder as directed, I made the hasty assumption that the nut should go into the hole on the Y-belt holder, and that I should drive a screw from the top down. I spent about two minutes being frustrated that the screw was just too short before discovering my mistake.

    Reality check! Read the manual :)

    Wesley Boynton - Reply

    Attaching the Y-belt-holder to Y-carriage was the screw from h3ll. Same complaint as W r hubbard. I finally got it screwed in, but maybe the surface treatment is affecting the threads in the carriage. During the 15 minutes it took to screw it in, I was thinking “Do I have that tap?” If I had known how hard that was going to be, I would have run a screw in and out before things got so hard to access! Sure hope the Y-belt-tensioner, with 2 screws is not a repeat!

    As a pre-emptive measure, I took one of the spare screws and notched the threads with a Dremel grinder to turn it into a poor man’s tap. Ran it in and out of the holes for the belt tensioner.

    Miles Odonnol - Reply

    “Use the hole on the left” is a matter of perspective..

    Jack - Reply

    Hi Jack, that is correct, that is why there is the photo with the arrows for you to see which hole and which perspective we mean.

    Martin L. - Official Prusa CS -

    Much easier to screw if you remove the belt for this step and put it back in after you have attached it to the frame.

    Mila Santana - Reply

    I am finding it increasingly frustrating that so many of these parts do not fit. I’ve spet half an hour tyring to get a nut into a hole. Now I find that the thread into which this screw is supposed to go in this step dows not work. I can see that other people have ha dthe same proboem. It is now stuck and won’t move etiher way. Is this the end????

    Catherine Wykes - Reply

    Hi Catherine. Please contact our tech support if you’re unable to proceed with the build, we’ll help you.

    Filip M - Official Prusa CS -

    Consider rewrite

    Using M3x10 screw fix the Y-belt-holder to the bottom of the Y-carriage. Screw through Y-belt-holder into Y-carriage while lightly folding the Y-belt out of the way. Tighten the screw and ensure the printed part is parallel with the "axis" between the Y-motor and Y-belt-idler.

    Rene Kuipers - Reply

  37. Take the Y-belt-tensioner (bigger of the two printed parts). Insert M3n nut, all the way in. Use the screw pulling technique.
    • Take the Y-belt-tensioner (bigger of the two printed parts).

    • Insert M3n nut, all the way in.

    • Use the screw pulling technique.

    • Bend second end of the belt around the screw and push it in the holder as in the picture. Use an Allen key to push the belt in.

    • Make sure the bent part and the end are within the width of the printed part.

    • Teeth on the belt must be facing up!

    • Tighten the screw until you reach the nut, don't over tighten the screw, you will deform the belt.

    • Hold the nut from the other side until the screw reaches its thread.

    To have a better access to putting the belt on the belt tensioner, I have put the belt out of the pulley on the Y-motor (not the Y-belt-idler) for the duration of this step. It gave me plenty of access and made it a lot easier to put it on.

    Knieza - Reply

    The part of the belt who is folded are very short. For me it would be nice to have 5mm longer belt.

    Patrick Gubelmann - Reply

    If you think the belt is too short, move the Y-carriage toward the motor. Then you’ll have more than enough belt to work with…

    Miguel Barroso - Reply

    My belt was at least 15 cm too long, but I mounted it and cut it of according to the pictures.

    If this is a regular occurence, maybe update the manual to reflect this?

    Björn Holmér - Reply

    Hi Bjorn, are you sure you used the correct belt?

    The X axis belt is 20cm longer.

    Filip M - Official Prusa CS -

    I measured the remaining belt to be around 80 cm.

    Björn Holmér -

    It’s a bit too tight to put it on the small holder, then motor pulley, then idler then big tensioner and screw it on..

    Jamie S - Reply

  38. Using M3x10 screw fix the Y-belt-tensioner to the Y-carriage. Don't tighten the screw completely, we need to adjust the position of the printed part. Use the hole on the right, see the picture.
    • Using M3x10 screw fix the Y-belt-tensioner to the Y-carriage. Don't tighten the screw completely, we need to adjust the position of the printed part.

    • Use the hole on the right, see the picture.

    • Insert the M3x30 screw through both printed parts. Start tightening until you reach the M3nN nyloc nut.

    If you have a long hex driver, it is easier to adjust the tensioner from above the plate. The allen key in this configuration is a little daunting.

    Adam Bavuso - Reply

    i have to wonder if placing a M3 slim washer in the tensioner where the set screw goes might distribute the pressure that the screw places on the printed part - especially when doing the final tightening here.

    Mike Johnson - Reply

    Dear Mike, you can try that, but it is not necessary.

    Martin L. - Official Prusa CS -

    After finishing this section, I would recommend not securing this part yet to the carriage. Instead route the belt, make the second loop, and then hold both parts up to the carriage to make sure you can see both holes, ensuring both loops are correctly sized. Then attach this part to the carriage and proceed as described.

    Mark Jurisch - Reply

    I agree, after you attach the first block, it's hard to installed the second one between every parts…

    Pascal Robert -

    The belt is very tight. Even though both of my loops were exactly within the slots of the printed parts as instructed, it was very hard to have enough slack to install the belt tensioner. I found it pretty easy to take the belt off of the Y-motor pulley to create slack to install the tensioner. Then loosening the mounting screws for the idler and the Y-motor created enough slack to slide the belt back over the Y-motor pulley. Finally, tighten up the mounting screws for the idler and Y-motor.

    Jack McGwire - Reply

    I may try this if my plan to use the screw that joins both belt holders, will let me get the screw for the larger one in.

    Shane Hobson -

    I found it helps a bit to loosen the rear pulley holder - gives you a mm or two of play.

    Steve Lionel - Reply

    deferentially helps *thumbs up*

    Roman Tarakanov -

    The hole that is holding the m3 nut is not holding it tight, spinning and not allowing me to screw the bolt to meet the other nyloc nut. Ideas?

    Paul alvarez - Reply

    Hey Paul,

    You can hold the part with pliers, glue the nut, or re-print the part.

    Filip M - Official Prusa CS -

    How about spending 1 additional cm of belt that would later be cut? I had to turn the tensioner 90° counter clockwise to be able to screw it to the Y-carriage

    Hans G. Schnieder - Reply

    I would suggest that you make sure the belt is pretty tight. The belt tension should be +/- 240. My Y-belt was 298 after first assembly. I was too careful assembling this part and now I’m back to find out of how to adjust it.

    Luckily, it’s pretty easy, at least with the Y-axis…

    Miguel Barroso - Reply

    It seems to be a more logical progression to attach the 2 tensioners to the frame, at the looses setting, insert the belt and tighten accordingly.

    Dave Bear - Reply

    I agree a little more belt length would be helpful I cant get it over the motor shaft and don’t know why

    Don Ferris - Reply

    For this instruction

    *** Using M3x10 screw fix the Y-belt-tensioner to the Y-carriage. Don't tighten the screw completely, we need to adjust the position of the printed part. ****

    Tip

    (1) Take the M3x10 screw ONLY and screw it into the designated hole. This helps start the hole to make it easier to screw in.

    (2) Unscrew the M3x10 screw and place it into the Y-belt tensioner

    (3) With the M3x10 screw inserted into the Y-belt tensioner, find the hole. Once you find the hole, spin the Y-belt tensioner to get the belt out of the way and give you access to securing it to the Y-carriage. Then spin it back before tightening.

    (4) It says don’t tighten completely, but make sure you make it is at least flush or you won’t be able to insert the M3x30 screw through both printed parts.

    Ron - Reply

    I’m really struggling with this - the screw just won’t tighten and it requires a lot of force to get it to go in just a little way.

    I’ve even tried screwing the screw into the hole without the Y-belt-tensioner there (to see where the problem is, and to access it more easily) but it won’t turn more than a couple of turns until it gets too difficult to screw in (I bought a proper driver to use rather than the allen keys, in the hope that would make it easier, but even doing that I can only get a few turns, and the screw is nothing like far enough into the hole).

    Any suggestions?

    Owain - Reply

    Dear Owain,

    What I suggest is to go a few steps back and check whether you have oriented the parts correctly, inserted the correct nut, and if you a re using the correct screw.

    Martin L. - Official Prusa CS -

    Thanks - unfortunately, I went back and checked and hadn’t made any mistakes (that I could see).

    However, I did look inside the hole with a lens, and saw there was quite a bit of swarf there, so used a pipe cleaner to try to clean it out. After I did this, i was able to drive the screw in.

    Owain - Reply

  39. Make sure the belt is placed in the &quot;axis&quot; of the printer. Both top and bottom part of the belt should be parallel (above each other).
    • Make sure the belt is placed in the "axis" of the printer. Both top and bottom part of the belt should be parallel (above each other).

    • To adjust the belt position, release screws on the pulley and slightly move with it, until you reach the best position.

    • Tighten both screws on the pulley.

    My belt rubs against the pulley. It travels to the middle of the pully when the carriage is at one end, then moves towards the motor side of the pulley at the other. Is that ok?

    Ephram cohen - Reply

    Hi Ephram, it usually means the belt hasn’t been adjusted properly. Try moving the pulley or adjusting the belt inside the holder.

    In the end it won’t cause any major problems, but depending on the amount of travel it could cause slightly lower print quality.

    Filip M - Official Prusa CS -

  40. Using a finger on your left hand push the belt down. Some force should be needed for bending the belt, BUT don't try to overstretch the belt as you might damage the printer. You can change the tension in the belt by adjusting the M3x30 screw below the Y-carriage.
    • Using a finger on your left hand push the belt down. Some force should be needed for bending the belt, BUT don't try to overstretch the belt as you might damage the printer.

    • You can change the tension in the belt by adjusting the M3x30 screw below the Y-carriage.

    • Tighten the screw, bring the parts closer and thus increase the overall tension.

    • Release the screw, parts will move apart, the overall tension will decrease.

    I’m updating my MK3 to the MK3S Y belt retention parts. When I install the belt, with the loops retained as per instructions and with the ends not extending out past the printed parts, I run out of adjustment with the long screw. The 2 parts are fully against each other. I assume this is due to a stretched belt. The only option I see is to shorten the belt or alternatively, allow the ends of the loops to extend out past the printed parts a bit - I can’t see why this would be a problem.

    What is recommended in this situation?

    Steve Jones - Reply

    Steve, try a combination of both. Let the ends extend, but not much.

    Martin L. - Official Prusa CS -

    I did need to have my belt extend out of the printed part by 2mm on one end to have some space left between the printed parts (about 3mm) to have some adjustment available.

    Mark Marsula - Reply

    I wonder if it would be possible to add a nut to the y-belt tensioner/holder so that the screw that holds them to the carriage comes from above. This means one could tighten the screw comfortably from above without the belt getting in the way of the allen wrench

    Miquel Martin - Reply

    Hi Miquel, the STL files are available for download - you can always modify the part if you wish :)

    Filip M - Official Prusa CS -

    Sounds like a great idea

    Jorge -

    Why “Using a finger of your LEFT hand”?

    Would it be different if using my RIGHT hand? :)

    Jorge - Reply

    Hey Jorge, we recommend left hand, but right should also do the job ;)

    Filip M - Official Prusa CS -

    I share your concern. I touched the belt with my right hand. Did I ruin my machine? (joke)

    Miles Odonnol -

    my belt is way too long; do I have to cut it to length first?

    Pieter Vermeersch - Reply

    Hi Pieter, no no, cutting should be the last step.

    Martin L. - Official Prusa CS -

    I find it hard to know how much tension I need to put on the belt and what “overstretching” means

    Pieter Vermeersch - Reply

    Yes it somewhat tricky, but no worries you can adjust the tension later too. You should be able to pinch the cables together and also to pluck them as a bass string.

    Martin L. - Official Prusa CS -

    Thanks Martin L. - Official Prusa CS! That last comment was the most helpful for this step.

    Michael Nolte - Reply

    My pleasure to help you, Michael : )

    Martin L. - Official Prusa CS -

    Agreed. Needs to be in the manual!

    Darrell -

    How easy should it be to move the carriage by hand by this point? Mine gets an odd accelerate/brake pattern when I move it by hand. Is this normal?

    Freddy Jay - Reply

    Hello Freddy, you should be able to move the carriage by pushing it with your fingers and the movement should be smooth.

    Martin L. - Official Prusa CS -

    I also had a similar problem but it turned out that the pulley that I had on the stepper motor was too close to the motor itself. After giving it a generous gap I was able to get rid of the weird stiff and non stiff pattern of the carriage.

    Hayato Kato -

    Thanks Hayato, that seemed to do the trick. The belt is now unfortunately all the way to the inner side of the pulley on the stepper motor, and on the Y-belt idler. This doesn’t seem to strain the belt in any way and the carriage travel seems smooth, so I’ll try my chances and continue.

    Freddy Jay -

    It would be nice if you could make belt tensioning less subjective. The free iphone app “Easy Tension” will give you a frequency reading for a plucked belt. If I slide the bed back, put the cell phone mic next to the belt on the right side, pluck the top belt with my *left* hand, I get ~97 Hz. If I tighten it half a turn further, I get ~104 Hz, so seems reasonably sensitive and consistent. Seems about the right tension.This approach would give folks a less subjective measure.

    Paul Meyer - Reply

    Mr Meyer,

    Unfortunately, it would not. We have actually tested a few apps and not only do they not provide stable and reliable results, everyone has a different phone with a diffrent microphone. Plus, I’m sure many users don’t even know where the microphone is on their mobile phone.

    After you finish the assembly and pass the Selftest, the MK3/S is able to determine the tension by itself (Menu-Support-Belt Status).

    Martin L. - Official Prusa CS -

  41. Use the technique described below to test if the belt is properly stretched. Use pliers to hold the Y-axis motor shaft.
    • Use the technique described below to test if the belt is properly stretched.

    • Use pliers to hold the Y-axis motor shaft.

    • Move the Y-carriage with your hand towards the Y-axis motor. Don't use excessive force.

    • If the belt is stretched properly, you should feel a resistance and the Y-carriage won't move at all. If the belt is too loose, it will deform (create a "wave") and jump over the teeth on the pulley.

    • After the proper tension is set, tighten the M3x10 screw.

    can the belt be too tight?

    Vadim D - Reply

    Yes, they can - and that can also cause several problems when printing. Make sure it’s tight enough to pass the pliers test, but don’t overdo it.

    Filip M - Official Prusa CS -

    I’ve followed the recommendation that the belt should sound like a bass guitar string with a low-pitched sound when plucked. If it sounds high-pitched, it may be too tight.

    Klaus -

    I am having a weird problem. When I move the Y carriage, it will periodically get stuck & hard to move. Then it will release. Here is a video trying to explain what is going on. Easier to understand if sound is on. Any suggestions?

    Burak Aktas - Reply

    Hello Burak, try to loosen the belt. If that won’t help, take the belt off and see if it behaves the same way without even without it. Then contact us and report your findings :)

    Martin L. - Official Prusa CS -

    Burak I had that same problem. I resolved it by loosening the belt tension just a bit and then restarting from step 39.

    Heimdall -

    I have the same issue as Burak. The issue goes away if I loosen the set screws on the y-axis motor belt drive gear, and gets worse the more I tighten these screws.

    John Hill - Reply

    Hello John,

    The Y-axis may also get stuck during movement if your U-bolts are tightened too much. You can see how to tighten them properly in one of our videos here:

    https://youtu.be/Lsa-PXAXdKY?t=97

    Marcin M. - Official Prusa CS -

    Except that the whole assembly slides perfectly if the gear drive set screws are loosened. Has anyone else had that issue? Also, I followed the unbolt tightening instructions to a T during original assembly. The assembly slid very smoothly before the belt was added, and still slides smoothly if the drive gear set screws are

    John Hill - Reply

    Corrected the issue by adjusting the gap between the drive gear and the y-axis motor. Couldn't see any rubbing between the two before, but increasing the gap fixed the issue.

    John Hill - Reply

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

    • You need to split the bears into 8 groups according to the upcoming chapters.

    • Each chapter requires specific amount of bears, see the picture.

    • For Y-axis you must eat 15 % of all the bears.

    5% of candies should go just for the belt assembly… actually make that 10% haha

    Vadim D - Reply

    All candies for the fact I used up too much belt making the loop you screw into the y belt holder bits lol. I managed to correct it without undoing it all though.

    Shane Hobson - Reply

    I accidentally ate all of the gummy bears before arriving at this point. Do I have to order a replacement set?

    Andreas Langberg - Reply

    Yup, might be a good idea :)

    Martin L. - Official Prusa CS -

    Umm… I don’t have any greens.

    Bryan Bostrom - Reply

    OMG, its about time…. I thought I would never get here!!!! NOM NOM!

    Justin Valois - Reply

    I'm vegetarian. :(

    Elliott Bridge - Reply

    Just FYI, I lost several of the M3n nuts, and these bears worked perfectly as a replacement! Thanks Prusa!

    Kinsky - Reply

    I had 3 bears left over after laying them out, they don’t belong to a group! What do I do!?

    kimikinsw@comcast.net - Reply

    At this point you will probably have a bit of bearing grease residue on your hands, so you'll probably want to wash your hands first.

    Daniel Friesen - Reply

    Grease residue just adds flavor. Anyone that works with his/her hands knows this.

    Fred -

    4 hours

    Grace - Reply

    In preparation, I made note that there were bears. I have no self discipline with sweets. Therefore I bought a bag of my own just in case. I finished that bag. I’ve only had my allotted amount of the bag that came with the Prusa. I have to say, the bears from the Czech Republic taste better than the ones I got at my bodega here in NYC.

    J. Walter Hawkes - Reply

  43. Y-axis is done, great job!
    • Y-axis is done, great job!

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

    • Note that you should feel some resistance while moving with the Y-carriage. It is due to the tightened belt and also the motor has some resistance.

    • Ready for more? Lets move to 3. X-axis assembly

    How freely should the y-axis move at this point? I feel like there is some resistance and Im paranoid that I messed the bearings up despite being very careful. If a bit of resistance/friction is normal then Im probably safe to move on…

    Johnny Appleseed - Reply

    I have exactly the same question.

    Peter Allday -

    Yes, a bit of resistance is very much OK, as long as the resistance is even all along the rod. If the bearings don’t move by themselves when you incline the rods, it is still OK.

    Martin L. - Official Prusa CS -

    I have the same comments as most everyone on this. the bearings seem gritty and the method of securing the belt is arduous at best. my poor digits are sore from the screw wrangling. I think that a re-think on this belt assembly is in order. it should be way easier than this.

    Scruff - Reply

    this is also my opinion

    capek.vitezslav@seznam.cz -

    I think the resistance that we are feeling at this point is due to the belt being connected to the y-axis motor.

    Eric Lee - Reply

    Exactly my thought. Stating this in the instructions could be helpful.

    Per Farny -

    Hey guys, we’ll add a note about it.

    Filip M - Official Prusa CS -

    I wasn’t satisfied how the Y axis moved (even after carefull adjustments of the U-Bolts) so I ordered Misumi LM8U linear bearings. They will only arrive later so until then I decided to give a simple solution a try. I removed both rods, cleaned the grease off with high quality brake cleaner and gave them a (hand) polish with Autosol metal polish and a rag until they had a nice shine. What a difference! After cleaning and re-greasing the rods, they move MUCH smoother. It’s a simple but very effective way to get a smoother slide.

    Steve - Reply

    Uh oh, you actually need a small amount of mechanical friction for position accuracy.

    Elliott Bridge -

    The Y axis moves terribly.. It was fine and smooth till belt.. It is not smooth, catches and is very rough.. Bearings sound like they will carve grooves in rods.. Resistance is not even but spotty and catchy.. Stopping and took belt off again.. Without belt moves fine.. with belt sounds like a mix master..

    . Hate the sound ..

    Reset pulley further from motor .. reset belt and sounds better.. Smoother .. still friction but nowhere near as bad as before.. added lithium grease to rods and adjusted.. still sounds like scraping .. still feels too tight .. maybe bearings are too tight .. don’t want to go further..

    Gary Sinkowitz - Reply

    Hi Gary, it’s normal for Y axis to sound and move “worse” than before adding the belt. If in doubt, you can always contact our tech support and provide videos, we’ll tell you if it’s OK.

    Filip M - Official Prusa CS -

    I hear some mild grinding sounds while moving the Y carriage after getting to this point. I am guessing it is the ball bearings? Is this an indication that the bearings are too tight or is this normal to hear?

    Mike Altstadt - Reply

    Hi Mike, well it depends on how does it actually sound, it can also be a loose u-bolt. Either way, please check it.

    Martin L. - Official Prusa CS -

    Also make sure the belt isn’t rubbing on something. This can cause the uneven start-stop motion.

    Darrell - Reply

Finish Line

859 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

217 Guides authored

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359 Guides authored

13 Comments

It would be a good investment to purchase a interchangeable head screwdriver outfitted with hex metric bits. This would speed up installation of some of the longer bolts big time.

My mk2s upgrade kit came with a small 3D handle and a drill bit for cleaning up the 3mm holes. I didn’t see that in this kit, but used my old one. I found it very handy.

Allan Albrecht - Reply

important - guide 2 step 9 - PSU holders. Incorrect placement of PSU holders will lead to issues later

same problem you will have, if theese PSU holders do not have thread in them (as in my case) and you will discover it at guide 7 - PSU assembly , step 19. :-)

capek.vitezslav@seznam.cz - Reply

Hey Capek, please contact our tech support - we’ll send you replacement if the part is faulty.

Filip M - Official Prusa CS -

Would it be advised to use a threadlocker like loctite on any of these M5x16r screws once the frame is squared? Or really on any of these fasteners? Not sure if you have products by these names in the Czech Republic. if not, the following URL link should give you an idea of the product: http://www.loctiteproducts.com/specialty... . It stops screws and nuts from vibrating loose over time. I was thinking of using a product like this during assembly.

Paul Ashe - Reply

Hello Paul,

We do have and know these products, but we are not using them, not even on our farm where we run hundreds of printers 24/7. We don’t consider it necessary.

Martin L. - Official Prusa CS -

Great, Thanks for the update. I just want to build my new MK3S Kit the very best that I can. I’ll follow your lead.

Paul Ashe - Reply

Maybe I was just being overly cautious and reading through every comment, and this is my first printer build, but this section took me 3:15. Perhaps you might increase the top end time estimate.

Matt Burrough - Reply

Not my first printer purchased as a kit, but my first expensive kit :)

2 things I would like to point out:

Being that important that you do not overtighten the U-bolts, an indication of how much thread should protrude above the nut would be very helpful. In my case, got them rougly 0.8mm above. 90degrees back from this and the linear bearing would be loose. Is that a correct value? In the manual picture it looks like the thread end is flush with top of the nut.

In the case of the Y motor holder and Y belt idler, the holes for the screws that connect to the frame should be sligtly oversized. The belt rubs on the shoulder of the pulley next to the motor, and there is no more room to move the pulley as it would rub against the motor. The belt holders are as aligned as they can possibly be.

Thats it, off to the next chapter.

Best regards,

Razvan.

Razvan Simionescu - Reply

Hello Razvan,

We have more than one supplier for the screws and bolts and they have slightly different precision tolerances for the lengths, so that is why we can’t indicate how much thread should protrude. As for the belt, it should definitely not rub against anything.

Martin L. - Official Prusa CS -

Getting the tensioner and the holder installed required me to flip the printer over.

Pro Tip - use the box to put the printer upside down in. It’s also much easier to do this with a screwdriver style set of allen keys.

Shane B - Reply

Just my thoughts on the Y-belt holder and tensioner;

Would have been a lot easier if the holder and tensioner had inserts for the nuts and the bolts came through the top of the Y-plate .

If the bolt heads would be a problem, stand-offs could be used. Maybe that would cause issues later in the build ???

Guess I’ll find out ! )

Mark Lamb - Reply

Hi Mark,

Yes that would cause issues later in the build . There is no place on the top of the Y-carriage.

Martin L. - Official Prusa CS -

I had a little bit of difficulty with the belt installation, had to re adjust twice to allow both printed parts to align with the bolt holes without over stretching the belt. Perhaps a description or other photos showing the amount of belt teeth that should overlap after the bolt would come in handy and avoid people, (Like myself), looping too much through and having to go back and adjust after fitting.

Ryan.

Ryan Gwilt - Reply

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