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  1. 2 and 2.5 mm Allen key
    • 2 and 2.5 mm Allen key

    • Needle-nose pliers

    Clicked on "suggest a time" but that's not allowed. I suggest 2 hours.

    Bruce Boyes - Reply

    same here. Can't suggest time. My suggestion is 40 min. with minimal parallel line adjustments

    Raino Kolk - Reply

  2. Spool holder
    • Spool holder

    • Heatbed cable cover

    There seems to be no need to attach the spool holders anywhere in this step. I would call it a standalone step that can be done when you are done moving the kit around to finalize the electronics assembly. Until you are ready to add the spool of filament they can probably just wait in the box.

    Marianne Davis - Reply

  3. M4x10 with dome head (2 pcs)
    • M4x10 with dome head (2 pcs)

    • 12V/240W Power supply with cover

    The dot colors don't match the circle colors on the photo in both the paper manual and here.

    James Slater - Reply

    This was the worst part of the instructions thus far -

    Nothing happens in this step - it is just a foto of the parts - but it makes it look like the PSU Is supposed to be screwed to something ? because the bed hides things in the foto - REDO the foto with the bed gone and SAY nothing happen in this step. I ruined the PSU-Y nut slots because it was not clear nothing happens in this step.

    Fred Smith - Reply

    Suggestion: this section is 'preparing the PSU'. The next is 'Attaching the PSU'. The two steps could be combined but that would throw off the section numbering, if that is important.

    Marianne Davis - Reply

    Thanks Marianne, Fred, and James.

    Daniel Naas - Reply

  4. Using 2.5mm Allen key, tie the PSU to the frame.
    • Using 2.5mm Allen key, tie the PSU to the frame.

    screw not tie, tie would be if it was with cable ties

    John Cummings - Reply

    Not tightenig theses screws at this stage helps putting the screws on stage 6 - After putting the stage 6 screws, you can then tighten them.

    Andre Laurendeau - Reply

    Before you do this step take a M3x18 screw and capture the nuts for the next operation. I also had to open up the screw hole somewhat for the USA build you can use a 1/8 drill. Put the M#3 screw in and draw the nut into position and then put on the power supply on the frame using the M4x10 button head screw

    Carl W Swanson - Reply

    I think more pictures are needed to clearly show this step. The PSU is suspended and rests atop the black piece connected to the X Axis. Took me a good 5 minutes to realize that.

    Matthew Lozy - Reply

    Since this is where the PSU-Y part is introduced in this chapter (it is what the PSU rests on) it might be better to mention it in this secton of chapter 7. Also, it would be helpful to remind users that the PSU-Y was attached in Chapter 2 (Y-Axis assembly) where it is pictured in Step 2 and placed in Step 3.

    Marianne Davis - Reply

  5. M3x18 screws (2 pcs) M3w washers (2 pcs)
    • M3x18 screws (2 pcs)

    • M3w washers (2 pcs)

    • M3n nuts (2 pcs)

    • Insert M3n nuts in PSU-Y-part nut traps.

    • To insert nuts inside traps, you can use similar "on screw" technique as for the extruder assembly. For more go back to 1. Introduction, Step 7.

    If you've made it this far, you've acquired god-like command of the elements. Use these new skills to suspend the 3D printer upside down in midair. Then, carefully bend the space time continuum in order to make the woefully short screw span the sizeable gap between the plastic parts. If you can do this, you have passed the test and no longer need the 3D printer. Simply discard the printer and enjoy your new ability to shape the world around you in any way you please.

    Perplumblewintz Jonz - Reply

    Hahaha! Thanks for that hilarious comment. It somehow made this step more bearable for me!

    mechaMecha -

    Those nut traps ain't trappin' nuttin'!

    mechaMecha -

    I found this step went easier if you put the nut on the bolt (just barely on, not all the way) and push that into the cavity until it snaps in. Then you can unscrew the bolt and the nut will stay where it can aid the fastening in the next step.

    Kevin Damm - Reply

    I just barely turned the nut on one of the longer screws and used it to push the nut into place, then turned the top screw until it caught the threads of the nut. I could then remove the longer screw from below and continue tightening the top screw.

    Adam Flanders - Reply

    This was a fantastic solution to this stupid step, thanks man!

    Brian Easly -

    I used this trick aswell, the only diference is that i used the corner of my table, suspended the hole, put the screw with the nut from bellow, and used the hex spanner to tighten it.

    João Fortunato -

    I had to loosen the nuts and washers holding frame for the X and Z axis and move the frame closer to the end in order for the mounting holes to line up.

    Ben Jones - Reply

    Use one of the longer bolts from the spares pack to pull the nuts in before fitting the M3x18 ones.

    Ian Horsfall - Reply

    Somehow my bolts were long enough that they just barely caught the nut when I pushed it up from the bottom with my fingers. I also did not yet tighten the M4s, so the plastic parts sat flush at this step. Maybe they updated the kit. (Mine is January '17)

    Tom Capon - Reply

    The nuts are nylock, it's became very easy once I fitting a fastener to the nuts to cut the thread then put them on backwards to place them inside the holder and with a gentle tap it was fully inserted, after fitting the fastener from the correct side you can use the needle nose pliers to keep the nut from turning.

    A VEDADIPOUR - Reply

    Put the printer on the edge of the table to be able to access the nuts holes. Using a long screw from the spare bag I pushed the nut and screwed the top one. Worked fine.

    Charlie Leroy - Reply

    I did as you, putting the printer on the edge of the table, as I didn't want to flip it over risking to misalign the frame.

    The screw nethod didn't work, instead I used the 2.5mm Allen key to keep the nut pushed in.

    The difficult part is to carefully insert the nut while keeping it on top of the Allen. Once in, it was stable, and the screw engaged it fine.

    Paolo Gaiardelli -

    Unfortunate I was not able to bend the space time continuum. Since the frame is perfectly perpendicular, I hesitated to solve the problem. The vertical plate was 2 mm to far from the position it supposed to be. Zipties to the rescue, which I pulled through the wormhole, tighten the psu to the frame :o)

    Lourens - Reply

    My nuts were not nylock and spin freely in the trap. The screws are so tight in the next step that I think the nuts may not be necessary.

    Jordan Munn - Reply

    Would it not have been easier to press these in before we attached it to the frame way back at the beginning? Quite an oversight there I think. My kit delivered Feb.13 did not come with nylock nuts for this step.

    Ronald Bellows - Reply

    Oh nuts! xD Hard time with this step, but im happy ever after.

    Romina - Reply

    In assembling mine, it was clear that the hexagonal holes on the bottom were too large to snap-fit the nuts provided for this step. Thus I threaded the screws in from the bottom and affixed the nuts from the top side where I could clamp them tight with the needle-nose pliers. To compensate for my lack of god-like powers (hence the need for this printer in the first place), I somewhat non-precariously propped up the printer using a digital caliper case under the front of the frame near the LCD cover. I also happened to forget the washers in this step but if I had a nickel for every time I forgot to use washers, I'd have a surplus of nickels and washers.

    Anthony E - Reply

    I loosened up the three screws on the base, left the two m4 bolts put in above loose, and didn't use the nuts. M3 bolts threaded fine into the base piece, as we've done in other steps. My thinking was " where's it going to go ?

    Dave Cook - Reply

    I threaded the nut about halfway onto the screws, screwed it in from the bottom, and when I felt the nut "click" into place, removed the screw. The nut was held in place in the nut traps and I was able to install the screws from the top side without any issues.

    Kyle Ertel - Reply

    Did what Anthony E did above, run the screws in from the bottom, put the nuts on the top - worked fine.

    Fred Smith - Reply

  6. Using 2.5mm Allen key, tie the PSU-Y-part to the PSU-cover. If there is a gap, use the screws to contract it.
    • Using 2.5mm Allen key, tie the PSU-Y-part to the PSU-cover.

    • If there is a gap, use the screws to contract it.

    The upgrade kit does not work like this - the supplied 'support' for PSU makes it sit too high, not allowing for alignment with frame holes. quite a bad issue to find after gluing the support on...

    Martin - Reply

    There is a gap between the PSU support and frame. I considered placing some spacers or nuts there to bridge the gap but instead I used the flathead screwdriver to pop the support off the PSU (undo the glued bond). I then tightened the support to the frame, meaning the support was flush with the frame. I removed the lower M4x10 with dome head from the PSU/frame so that I could rotate the PSU out of the PSU support piece in order to apply a new layer of glue. I applied glue to 2 of the 3 inner walls of the PSU support piece, but I did not apply any glue to the "floor" of the PSU piece because the PSU would not make contact with it due to the gap. Therefore the PSU has additional horizontal support, but less vertical support. Where the M4x10 with dome head screws provide substantial frame support, I have no concerns about this small gap in the support piece (which could be bridged later with a small printed piece).

    Adam Flanders - Reply

    Despite taking great care to get the 100mm dimension right in step 2.3, the two parts did not align, and I had to drill out 3mm. I did this from the part attached to the frame, so the captive nuts were in the right place.

    Howard Watkins - Reply

    I also had to use a drill, but I find it a lot easier just to invert the nut and bolt, and have the nut be on the top with the washer instead.

    Rex Lu -

    Rex, thanks. I did just that ( nuts on the top )and it worked like a charm. The spacing went away as well with little effort.

    Raul Vidal -

    Thank you Rex and Howard, I did invert and those were fine!

    takashi ufugushiku -

    After installing the PSU to the frame, there is a 1 mm gap between the PSU and PSU-Y-part. Will use a spacer to fix, but PSU-Y-part could be 1 mm higher to fix. Or the mounting holes for PSU in the frame 1 mm lower.

    Jerry Koniecki - Reply

    Agreed. I used a 1.5mm spacer between the bottom of the PSU plastic cover and the PSU-Y-part. Also - while most of my parts have been excellent in fit and finish, the nut PSU-Y nut traps needed a lot of filing to allow the nuts to fit in.

    John O'Shaughnessy -

    Can't edit previous comment. I have a better measurement of the gap now, about 1.5 mm.

    Jerry Koniecki - Reply

    screw not tie

    John Cummings - Reply

    I also have a gap

    John Cummings - Reply

    Maybe say something like ' the gap between the two parts will disappear when they are screwed together'

    John Cummings - Reply

    At this point I found out I must have been using the wrong size millimetres at the stage where you position the nuts at "100mm". There was a good 3mm gap between PSU and frame.

    I undid the nuts then attached the PSU, then redid the nuts at the new frame position. Hope this is an okay thing to do...

    Innes MacKenzie - Reply

    This stage of assembly would be much easier if the clearance holes in the PSU-cover were made into slots. The 100mm distance noted in step 2.3 is not critical to the functioning of the printer. It's also not entirely accurate. I nailed that 100mm dimension exactly but the holes were offset by 2mm in this step. Through much time and effort I was able to move the frame the extra 2mm I needed to get these holes to allign. What should be noted in step 2.3 is that the distance needs to be the same for both Y-axis rods to keep the X-axis square to the Y-axis. Keep the dimension 100mm, but make the slots 4 mm long.

    Bill Catherall - Reply

    I also had a short gap between the PSU and the black printed part but there's no need for spacers. Just gently loosen the nut holding the Y-stage support part and rotate it upwards until it sits flush with the PSU. This fixed my problem, but I had only ~2mm max of space.

    Jon Jordache - Reply

    This was the first real hassle for me. I had trouble getting the nut into the slot - wish I had done it before mounting the PSU. I ended up double nutting a separate M3 screw, so that the end nut was only on for maybe one thread. I used this to hold the nut in place while I balanced the frame sideways (resting on the PSU) and screwed the M3-18 in. I screwed until I felt it catch in the nut. Then I backed out the other screw and finished tightening. Probably better ways to do this - it took a couple of tries, but worked for me.

    Bruce Crowder - Reply

    First, yes the 100mm spacing in one of the first steps is off, so what I did is gently flip the printer over, loosen up the nuts holding the frame together and aligned the frame to the holes for this PSU. Once the holes lined up I tightened the frame back in place making sure that the frame was seated all the way down into the slots (since it was upside down).

    The next issue. The nuts that slip in to the holes are just not the greatest solution. I mentioned this in another comment that perhaps having a longer bolt and have the nuts closer to the surface would be easier. That being said I didn't change any of that. Here's a trick:

    While the printer is upside down - Put the bolt in (screw it in, it doesn't move freely). Screw it in almost all the way. Then take the nut and place it into the hole. Take the backside of another screw and use it to hold the nut against the bolt and push gently on it while screwing the bolt from the other side. It should catch and start threading.

    Daniel Lipsky - Reply

    The nut traps did not trap the nuts at all. I was finally able to get this step done by screwing the screws in most of the way, then holding the nut in place at the end of the screw by pushing on it with another screw, and continuing to screw the screw in. It managed to screw into the nut properly.

    mechaMecha - Reply

    I think this is the point where we discover if we've learned anything at all from assembling the printer, and are able to overcome small challenges. As noted above, the 100mm is not correct in all cases, and you might have to actually move your upright frame a few mm. to get the screws to fit into the wholes in the PSU-Y piece at the corner. For me, the magic distance was 96.7mm. and "Oh My", that was a job moving the frame to get it to fit.

    A decent set of calipers are a great tool to have around at this point. Even an indecent set would be great... Remember to acquire some.

    Bjoern Hoejte - Reply

    3.3mm seems like a lot... that just can't be counted within printing tolerances. Have you checked that your frame is perfectly square? I thought mine was, it wasn't until I relaxed the 4 external couples of small nuts and re-tightened it while measuring withe caliper all the sizes. That was a few stages before this one though.

    Paolo Gaiardelli -

  7. Guide the low voltage cables from the PSU under the threaded rods to the other side of the frame as shown in the picture. Tie the low voltage power cables to both threaded rods.
    • Guide the low voltage cables from the PSU under the threaded rods to the other side of the frame as shown in the picture.

    • Tie the low voltage power cables to both threaded rods.

    • Do not tighten them too much, otherwise you can damage cable insulation.

    it would be helpful to have a more zoomed out image here to make sure I understand which way the cables are going

    John Cummings - Reply

    Exactly what I need !!

    Andre Laurendeau -

    Yes it would wonderful +1

    Ghislain -

    Yep, agree as well these pictures are inadequate.

    Brian Easly -

    Yes , wider view please. also the images with black ( throughout all images ) could be brighter. Also I cannot tie wrap wires to sharp bolt threads. I wrap the wires to protect them, and is a good idea to protect wires from tie wraps. Most tie wraps will damage wire insulation when tight.

    Frank Hubbard -

    The images are fine. Its clear if you have been paying attention that the cables are going over to where the Rambo is. So if the PSU is on the back right... the cables need to go over to the back left.

    Chris Bishop -

    Chris not everyone knows where the Rambo board ends up being located (myself included, although I had an idea. I'm new to 3D printers). Thank you for the explanation.

    Matthew Lozy -

    I found that it helps to move the Y-Axis bed forward so you can easily access the threaded rod and cables. I struggled with too much stuff in the way, then had a face-palm moment.

    Kevin Hawke - Reply

    haha, yes me too. I realized it when I was having troubles engaging the M3x18 PSU screws.

    Paolo Gaiardelli -

    I wrapped some black electrical tape around threaded rods everywhere wires are zip-tied to them. This protects the wires from the relatively sharp threads on the rods. I will send on some photos (once I am done and sure it is all correct).

    Bruce Boyes - Reply

    Wider view with some annotation would be helpful

    Timothy Lee Russell - Reply

    Attaches to the left threaded rod on the right z axis/PSU side and then to threaded rod on the other side accross.

    A VEDADIPOUR - Reply

    I wrapped the cables in electrical tape to protect them from the rods' threads.

    Trevor Vannoy - Reply

    I used paper tape, and thank you for the tape suggestion :)

    Paolo Gaiardelli -

  8. Check the switch position on the side of the PSU if it's in correct position. Make sure that the power supply is not connected to mains!
    • Check the switch position on the side of the PSU if it's in correct position.

    • Make sure that the power supply is not connected to mains!

    • Correct position means that the switch is on the side with your mains voltage. (If you have 110/120 V mains [mostly America] the switch has to be on the left, if you have 220/230 V [Europe and the rest of the world] the switch should be on the right ).

    • You can change the switch position with flathead screwdriver.

    • This is very important part, if the power supply is configured incorrectly it can be damaged!

    Probably a good note too, is to make sure the power supply on/off switch is in the off position.

    Kevin Hawke - Reply

    Kevin Hawke thanks for that reminder.

    I thought that step 8 was a weird place to put this step. It seemed more appropriate right at the start when you can just pick up the PSU and look it over without the printer attached. Once the switch is found and figured out it is a simple matter to double check before turning everything on to ensure the switch is still in the correct position. By that point the switch is clearly visible when you turn your printer so you look at it from the back.

    Marianne Davis - Reply

  9. If you assembled the optional nuts on the  Y-belt holder screws, you have to remove them.
    • If you assembled the optional nuts on the Y-belt holder screws, you have to remove them.

    • Remove the M3 nuts highlighted in the picture.

    This step and the following one are confusing to me - I figured that when you remove the helper nuts, you should also back out the bolts a bit so they are flush with the surface of the carrier. Then after you mount the bed (following step) you come back and re-tighten these 2 center bolts to pull the bed down tight against the carrier in the middle.

    Anthony - Reply

    At this stage the two bolts holding the Y axis belt holder should be unscrewed until flush with the bed. Otherwise there is a danger of bending the bed as the corner bolts are tightened.

    Ian Horsfall - Reply

    These are good observations. I was concerned about the zip tie heads being in the way, so why make these screws flush? It's because the bottom of the print bed has spacer nuts on it, into which, all these screws will insert.

    Kevin Hawke - Reply

    Thank you for this - I was wondering exactly the same!

    Michael Wheeldon -

    I don't know if it's been changed on my newer kit, but I didn't have to back off the screws because the holes they're in are not threaded - I just pushed them down with my finger. I suppose that's why you have the temporary nuts there -to hold these screws in place during the earlier assembly steps.

    Robert Wallace - Reply

    In my end-december kit, I had threaded holes requiring to remove the nuts. May be they should explain that 2 different heatbeds are distributed.

    Thierry Paché -

    In my January 2017 kit I found that the screws barely went beyond the Y-belt plate and the nuts were held on only by 1 thread. This assembly process of tying into two standoffs on the heated plate through two blind mates with the 2 short Y-belt holder screws is impossible!! You are unnecessarily cutting some screw length tolerances way to close, as in this case. All screw/nut matings should be of 3 threads, minimum.

    Jay McIntosh - Reply

  10. M3x8r screws (4 pcs)
    • M3x8r screws (4 pcs)

    • Heatbed comes with the print surface (yellowish foil) already sticked on so DO NOT REMOVE IT and take extra care to prevent damaging the surface.

    would be helpful to show the top of the screws so we know they are the domed ones

    John Cummings - Reply

    Unless you are mixing your screws, the dome head screws are your only option.

    Chris Bishop -

    On my bed the powder coating has closed up the holes so I used a 3mm (.177) drill to open the holes so the screws moved freely and could engage the threaded hole

    Carl W Swanson - Reply

  11. Using 2mm Allen key, tie the heatbed to the Y-carriage. Tighten the screws with care. The threads inside the heatbed can be easily broken!
    • Using 2mm Allen key, tie the heatbed to the Y-carriage.

    • Tighten the screws with care. The threads inside the heatbed can be easily broken!

    • The screws should fit directly to the threads, if not, you could have turned the Y-carriage upside down, see Chapter 2 for the correct assembly.

    I screwed the screws in the nuts underneath the heatbed in very gently but I think that the thread of one of the nuts broke or mayber the screw is too short. Any recommendations on what to do? Is it possible to replace the nuts? Thanks for the support.

    David - Reply

    I resolved my problem. I changed the screw and now it is keeping the bed locked in place. Maybe this problem appeared because the screw was slightly too short or maybe the thread of screw or nut not perfect.

    I also came to realize that I made a mistake with the assembly:

    I started the assembly following the instructions online and in chapter "2. Y-axis assembly" there is Step 24 — [OPTIONAL] Y-belt holder nuts but later on I followed the instructions in the assembly instructions booklet where unfortunately in chapter 7. PSU & Heatbed assembly Step 9 — [OPTIONAL] Y-belt holder helping nuts removal" is missing. Therefore the heatbed was sitting on two hex nuts and it was all bend.

    I hope I can get started printing lots of things now I'm very excited about my prusa printer. I hope that all the booklets in the future will include these instructions and maybe for the old one you should stick in a note or so.

    Thanks and all.

    David -

    do I need to unscrew the two screws in the carriage a bit so they are flush with the carriage?

    John Cummings - Reply

    yes you should

    Radek Migula -

    I think I figured out the "problem" the holes of the carriage are a tiny bit tight causing the bolts to get threaded into it. Actually, I think the holes should be larger to allow the bolts to pass through more easily and they can be tightened individually. Otherwise, you will need to carefully press-fit the bed and the carrier together while you try to screw them together without any gap.

    Anthony - Reply

    1. M3x10/12 would be nicer to give a little extra bite and make fixing easier.

    2. They're using a different hex driver so I'm using two different drivers to assemble the bed

    3. My "white dot" was on the wrong side (my mistake) but it looks like alignment is different by a tiny amount suggesting a CAD error like a centre-line not being used?

    4. Can you stick some bubble wrap or polythene over the bed surface to protect it during assembly? I didn't know PEI was such an oil magnet!


    Mark H - Reply

    Latex or nitrile gloves would solve the fingerprint/oil issue.

    Trevor Vannoy -

    Holes in the side were ok for me. I have drilled up most of my holes (3mm) in the frame since the paint easily get stuck in the holes and makes the screws thread in the hole and therefor difficult to sense how hard you are tightening it.

    Andreas Engkvist - Reply

    My mounting nuts under the heatbed were crooked, I had to flip the bed and loosen them a little to get them straight

    David Hayes - Reply

    I drilled the Y axis mounting plate to remove the powder coat from the holes. Used a 2.8mm drill. Mounted easily. January 2017 model

    Frank Hubbard - Reply

    If the holes dont align try flipping the bed frame with out rotating it. Worked for me!

    A VEDADIPOUR - Reply

    The screws that hold the heat bed must pass freely through the holes in he y-axis mounting plate. Until I lightly drilled out the powder coating that filled the holes, the heat bed would not align for all screws to fit. Once I did that, all 6 screws tightened perfectly

    Frank Bonelli - Reply

    +1 on flipping the carriage. I had gotten step 13 on the Y-axis assembly wrong. The dot on the carriage should face up when looking from the top (opposite side from the bearings). Undid 3 zipties and the belt and flipped the carriage and now everything aligns properly.

    Jordan Munn - Reply

  12. Tighten the Y-belt holder to the heatbed using the supplied 2.5 mm Allen key. Make sure that the screws are screwed into the heatbed and no space is left between the nut on the heatbed and the Y-carriage.
    • Tighten the Y-belt holder to the heatbed using the supplied 2.5 mm Allen key.

    • Make sure that the screws are screwed into the heatbed and no space is left between the nut on the heatbed and the Y-carriage.

    • Tighten the screws with care. The threads inside the heatbed can be easily broken!

    • If you have the Y-belt-holder with a slot, make sure that the screws are in the middle as shown in the picture.

    Look under the heated bed to check that metal nuts attached are pulled down and touch the frame to make sure the bed is completely flat.

    Jurgen B - Reply

    Note added. Thanks!

    Josef Prusa -

    Hi, I'm upgrading from the Original i3 to the MK2, so far everything went fine, except the bed. the 4 corner nuts are not aligned with the holes on the carriage! Only the 2 screws in the middle can be tightened. What can I do?

    I think I might have 1 of 2 options:

    1- Drill the corner holes to make them bigger, or

    2- tighten the 2 center screws only - not sure of this will be enough though.

    please advise.

    Mohammad AlGammal -

    I'll second the "CHECK ITS FLAT", mine had a 0.3mm dip at the center screws. Check the diagonals with a straight edge. I used foil tape to shim the two center screws.

    Marten Hutchison -

    On my kit one of the screws in the y-carriage is loose, looks like an issue with the nut on the heatbed

    Cristian Sandu - Reply

    On second thought, seems like an issue with the printed part

    Cristian Sandu -

    The nuts on the heated bed are not lining up with the holes on the y-carriage. I've tried moving it around, fastening it in a different order, and nothing seems to work. Any help??

    Oswaldo Ferro - Reply

    I had the same problem - solved by removing the X-plate & turning it over (should have paid more attention to step 11 way back on the Y axis assembly). Easy enough to do as it only involved removing the 3 cable ties and the Y belt holder. While the X-plate was out I drilled out the holes for the Y belt holder so the bolt was a loose fit. The powder coating must have reduced the hole sizes enough that the bolt was cutting its own thread.

    Howard Watkins -

    howard watkin's method is an easy fix! thanks!

    Rex Lu -

    Can't attach heat bed .Carriage holes do not line up with heat bed nuts and screws too short . A lot of work now to uninstall, modify and reinstall carriage and source proper length screws. This fitment should be verified at the beginning of chapter 2 .

    Earl Brooks - Reply

    You should follow exactly what's written in Chapter 2/Steps 11, 13 and 22.

    Josef Prusa -

    Josef - Earl is correct, you need to redesign this engagement of the Y carriage and the heated bed, the required tolerances here are too tight, and I guess sometimes it works and sometimes not - but this is not a robust design. Please rethink this stage of conneting the heated bed.

    Assaf Weiss -

    I don't meet the threads. I also tried to do first step 11 and then 12, but it still not works. what should I do?

    Niklas Arnold - Reply

    Should there be any vertical play at the ends of the "X" when this is sitting flat? I can see and hear slight movement when trying to move the end of the support and and down gently. I'm not sure if this is from the zip ties not being tight enough on the bearings from the Y-axis assembly or if the bed isn't tightened properly. I'm not sure if what I'm seeing will affect future prints or not.

    Scott Walhovd - Reply

    It was easier to tighten the Y-Belt holder when the print bed was slid to the center of the track. Then the belt tension allowed enough movement to get the hex wrench in place.

    Kevin Hawke - Reply

    The explanation should explain the role of helping nuts. In my case, the Y-bed holder screw were threading the bed carrier. So the nut were not necessary. Then, in this step, I had to unscrew them. I understand now that bed carrier holes were probably too tiny in my case. So, the remark about the no-space-to-left is important because the screw is crossing two threads. Also, suggest to untighten the belt by release the Y-motor.

    Thierry Paché - Reply

    This blind mating of 2 standoffs to 2 holes and screws through a 3 d printed belt holder and the Y-axis plate is impossible, especially since my 2 screws only show 1 thread clear beyond the plate- not nearly enough to mate with the 2 standoffs on the back of the heat plate. I am trying to use two longer screws, but that has not worked because the 2 standoffs do not line up exactly with the screws-close but not close enough. I am going to remove the heat plate 4 mounting screws and try to mate the 2 standoffs 1st (loosely) with the longer screws, then remount the heat plate with the 4 corner screws.

    Jay McIntosh - Reply

    Definitely - the screws has to be longer (less than 2 threads are free to engage with the bad in my case). Secondly - in order for 6 screws to fit exactly in a ~200x200 mm length - you need very (very) tight tolerances which are not met in the current heated bed / Y carriage. This is OK but at least do some proper engineering - and have one of the holes keyed such that it allows for some play for one of the middle screws, or else this taks is quite impossible.

    Assaf Weiss - Reply

    Agreed. My bed actually went together pretty well, but I really think the screws could be a mm or two longer.

    Trevor Vannoy -

    there must be a reason for this precise length of the screws. Actually, when one of them won't engage the threads it probably means something's gone wrong and needs some fixing before you go on.

    Paolo Gaiardelli -

    is it okay to leave the two middle standoffs unattached? as noted by others, holes don't align and screws are too short...

    Michael Fox - Reply

    In my opinon, it would be best to review the build. Leaving them unattached you could damage or deform the bed when pulling a print off it.

    If they are off by a fraction of a mm it would be best to slightly enlarge the carriage holes manually with a 3mm drill bit so that the screws can fit freely.

    Paolo Gaiardelli -

    I found it easier to thread the screws in flush on all four holes, the place the board on and gently turn each one until the board is secure and then go back and GENTLY tighten them all the way on.

    Charles - Reply

    Couldn't get the two middle nuts to engage because they didn't line up with the two screws coming from the y axis plate. Ended up swapping out the two screws from the centre for shorter screws so that they still gave the belt holder a solid connection to the x-plate without protruding and bowing the buildplate. There was no way those two screws were going to line up with the nuts once the build plate was secured at the edges. Even tried attaching it at the middle and then attaching at the edges. Still no go.

    The tolerances just aren't good enough for that particular part.

    Astridash - Reply

    All this confusion is a result of a clusterfuck of orientation markers. Turns out when you don't get the "White Dot" on your model, you're 1000x more likely to get &&^&@@ here. I ASSUMED that the white dot was directly on the other side of the recessed hole. The image in Ch2 Step 13 Fig 1 LOOKS like the zip tie knots are oriented on the side with the white dot, yet in step 22, the zip tie knots are on the side with the recessed hole. TURNS OUT CH2 STEP 13 IMAGE 1 IS BLATANTLY WRONG WHEN COMPARED TO STEP 22 IMAGE 1. The orientation of the stage is the EXACT SAME between these images in both steps' (the bearings are underneath, with the double bearings at the top AND YET THE ORIENTATION MARKERS CHANGE FROM WHITE DOT TO RECESSED HOLE MAGICALLY!


    Andrew H - Reply

  13. M3x8r screw (1 pc)
    • M3x8r screw (1 pc)

    • M3 nut (1 pcs)

    • Note the white cable from the heatbed can be also in black version, however their function is the same (see the second photo).

  14. Insert M3n nut in place.
    • Insert M3n nut in place.

    It is very possible that there might be some filament clumping that prevents the nut from sitting flat. Clean it out if necessary.

    Chris Bishop - Reply

    Tried to clean it with the screwdriver. Didn't make much difference. So I just used the M3x8 screw from the internal side to pull the nut in the receptacle by screwing it fully in. That worked very well and the nut is now sitting firmly in the receptacle.

    Paolo Gaiardelli -

  15. Take the piece of filament that came with the parts ( length cca 30 cm ).
    • Take the piece of filament that came with the parts ( length cca 30 cm ).

    • Push it all the way down in the filament holder hole in the heat bed cable cover. If you experience difficulties when inserting the filament use pliers to make a sharp tip on the filament.

    • The filament is for whole harness support. Don't cut it, it'll go all the way with the wires to the electronics.

    My 3d part had a lot of infill stuck in the middle of this, I highly suggest taking the smallest hex spanner and clearing out the hole first.

    Daniel Lipsky - Reply

    The filament was having difficulties sliding in, but since I wanted to stay quite firm I didn't enlarge the hole. Rated, I pushed it in while twisting and rotating it back and forth. That worked well, and after a few twists it reached the nut receptacle.

    Paolo Gaiardelli -

  16. Tighten the part to the heatbed using 2 mm Allen key.
    • Tighten the part to the heatbed using 2 mm Allen key.

    And don't forget to put the white cable !

    Ghislain - Reply

    +1 - Thanks for pointing out the white wire. I totally missed that.

    Kevin Hawke -

    careful with the heatbed power cables, their solder points appear to be a weak point, I can see some broken strands already and I've just removed it from the package

    Greg - Reply

    I used a short piece of adhesive tape to keep the thermistor wire into the bundle. It kept falling off while I was trying to center the nut and the screw.

    Paolo Gaiardelli - Reply

    Yeah, white wire was being dificult , so a little electrical tape kept it all together. I was a little concerned that the white wire was real close to the solder joints. One of my solder joints looks a little week. If I have issues I'll try to remember to check it out.

    Daniel Naas - Reply

  17. Use the spiral wrap and wrap nylon with the cables from the heatbed. DO NOT cut the filament, you'll need the full length.
    • Use the spiral wrap and wrap nylon with the cables from the heatbed.

    • DO NOT cut the filament, you'll need the full length.

    • Note the white cable can be also in black version, see Step 13. second picture.

    Just a note. DO NOT cut off excess 3mm filament , it is used later in cable management (wish i knew that before :P)

    rabidninjawombat - Reply

    Reminder added. Thanks for giving us feedback :)

    Josef Prusa -

    There was no more spiral wrap left. I had one small piece for the X motor cables and one larger for the extruder cables. Was there supposed to be a third piece?

    Bill Waggoner - Reply

    I thought I was the only one. I am upgrading and I'm short one piece of wrap as well.

    Bob Smith -

    Be sure to include the heat bed thermistor (small white wires) in the spiral wrap. This was not obvious in the printed manual. Here it is easier to see the thermistor wires wrapping along with the heat bed wires.

    Bruce Boyes - Reply

    The heatbed thermistor cable (coming out from the bottom of the heating bed) is now BLACK (Feb 2017), not white, and because of that, determined it must not go into the spiral wrap. Wrong! I find out near the end of the build.

    Greg Boyd - Reply

  18. Slide spiral wrap into the holder in the heatbed cable cover and secure it in place using a ziptie. Slide spiral wrap into the holder in the heatbed cable cover and secure it in place using a ziptie.
    • Slide spiral wrap into the holder in the heatbed cable cover and secure it in place using a ziptie.

  19. Take a look on the printer from the top side and make sure that lines on heatbed are perfectly parallel with the X axis rods as shown in the picture. If they are not in parallel position, use 17 mm wrench to adjust the M10 nuts to get it correct. Use nuts only on the side close to left Z axis motor.
    • Take a look on the printer from the top side and make sure that lines on heatbed are perfectly parallel with the X axis rods as shown in the picture.

    • If they are not in parallel position, use 17 mm wrench to adjust the M10 nuts to get it correct. Use nuts only on the side close to left Z axis motor.

    • This is extremely important, if the things are not in parallel, you'll have huge troubles calibrating later on!

    • If you'll adjust the nuts, make sure that the M10 threaded rod is all the way down in the slot.

    The Z frame is square with the y axis frame but not the bed - I'm assuming it is correct to take the z axis out of square with the y axis in order to bring it into alignment with the bed.

    Innes MacKenzie - Reply

    +1 same question. My frame itself was rather square considering I had used calipers to precisely measure distances throughout BUT it appears as if the orientation of the printing on the heatbed and/or the headbed itself is not square to the Y-axis carriage. That or there is too much play in how the linear bearings are attached to the y-axis carriage to insure desired orthogonality of the heatbed to the rods.

    Matt Paul -

    Just a suggestion that this squaring step could be done much earlier if a white line were printed on the Y-Carriage (which would also help with orientation in Step 2.13). Then in Step 4.15 for the Z-Axis assembly, squaring could be done against the white line, and would be easier without all the wires, extruder, LCD, and print bed in the way.

    Kevin Hawke - Reply

    There should be a note to only adjust the left side (as shown in the picture). At this stage, the right side is already bolted to the power supply, so changing its M10 nuts does not actually change the Z frame location.

    Tom Capon - Reply

    !!! Most important step to get your printer perpendicular!!!

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

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

    Waldemar - Reply

    This method is better than eyeballing it like the manual suggests. I took a square, lined it up with 155 line on the bed, then moved the bed until the square hit the x-axis; I did this on both sides, and adjusted the M10 nuts until both sides were even. The most frustrating parts of this build have been getting things square and level; since squareness and levelness are critically important to the build, it'd be nice if the kit came with some jigs to help.

    Trevor Vannoy -

    J'ai dans un premier temps réglé la cote de 100 mm à l'aide d'une cale étalon des deux côtés.

    le résultat a été que l'axe Z n'était visiblement pas parallèle aux lignes blanches du lit chauffant.

    le bloc alimentation étant monté, j'ai agi sur les écrous côté moteur axe X.

    La cote finale était de 95,8 mm lorsque l'équerrage est devenu correct.

    Roland Franclet - Reply

    Just a quick tip for step 19: use a flashlight. Shine the light from the top down and look at the shadow that is cast by the linear rail. You can easily see even the tiniest misalignment because the shadow will diverge from the grid printed on the heated.

    Alan - Reply

    Great tip Alan ! got my bed 100% using that - light doesnt lie!

    Mark Saint -

    Well that is frustrating. I made sure my rods were always square and 100mm. Apparently we never square up the carriage. The carriage is what is off by 3mm. If there were 4 bearings instead of 3 that might help. grrrr.

    Daniel Naas - Reply

    ...... I just relooked at it. I guess I could have been off too. Thank you Waldemar and Tom. It is just frustrating to have it all line up, then not at the end. I guess also thank you for the recheck step.

    Daniel Naas - Reply

  20. Assemble the Spool-holders to the top of the frame as shown in the picture.
    • Assemble the Spool-holders to the top of the frame as shown in the picture.

    • Almost there! You're one step before finish! Continue by connecting the electronics in the next chapter - 8. Electronics assembly

    should the holders be apointing towards the lcd side or the backside?

    william utriainen - Reply

    Toward the back as seen in many other photos. You'll notice the filament lines up nice with the extruder if it's correctly placed.

    Martin Forsberg -

    One spool holder broke when I tried to put it on :-( I'll print a new one...

    DJ Roberts - Reply

    yep, me too. saw some good alternates on thingiverse. I may try those.

    Brad -

    I soaked the lower part of the spool holders in hot water for a minute to soften then up then it was easy to put them on

    Eirikur - Reply

    To anyone reading this before buying the printer like I did and you're worried about breaking parts, the spool holders I received in the latest kit are injection molded (*gasp*) in a very durable plastic.

    Jason Spencer - Reply

    Comme Jason Spencer, les supports de bobine de mon kit sont des pièces injectées.

    Temps passé sur cette étape: 0h 35'

    Roland Franclet - Reply

    March 8 kit, spool holders are injection molded plastic and do not fit. Needed to file always plastic to make them fit!

    Jim Jacques - Reply

    the trick for me is to engage the upper part, then push down firmly but gently. The lower part can then snap-in with low effort.

    Paolo Gaiardelli - Reply

Finish Line

218 other people completed this guide.

Josef Prusa

Member since: 01/05/2015

142 Guides authored


Prusa Research Member of Prusa Research


3 Members

377 Guides authored


There seems to be a kind of protection on top of the heat bed I don't see on th pictures, but I don't dare to remove it... Wh do I have it ad don't see it mentioned?

Michael Bock - Reply

The steps about the frame being 100mm down the threaded rods should make it clear that if the PSU bracket doesn't line up they will have to move it. Perhaps suggest using the PSU as a guide to check the alignment. Maybe even temporarily bolting it on while they line up the frame.

Mitch Allen - Reply

This was my problem too. I thought I'd measured out 100mm properly, but I was off by a decent amount, which meant unbolting the frame, adjusting the ribbon cables from the LCD screen, and making some pretty significant movements

Dustin Woodward -

I just don't see the switch inside that hole. And the picture is not showing anything either. Am I missing it? I don't know whether the PS is set on 220 or 110V.

Retel Tulio - Reply

Photo showing the 110 - 220V switch is useless. The switch is quite hidden inside that hole. You can easily move something that is not the switch. I did. Bummer.

Retel Tulio - Reply

There is a need for a couple of zoomed out pictures in that section. A zoomed-in picture does not give us a good sense of what has to be done.

Andre Laurendeau - Reply

Useful tip !! Save the pictures and increase the contrast / brightness levels, so you can see details more clearly

Linda Bachmann - Reply

Here's the links again that I posted at the end of the last chapter:

Hey Josef and everyone else, I documented my experience with figuring out how to build this and put it into separate videos for each chapter. I'll post the appropriate video links in the comments as I think this could help others if they get stuck, and it can definitely help Josef get an understanding of what went well and what did not for a complete rookie with no knowledge of 3D printing during the assembly.

Hopefully this doesn't get flagged :)

Chapter 2: Y-axis assembly:

Chapter 3: X-axis assembly:

Chapter 4: Z-axis assembly:

Chapter 5: Extruder assembly:

Chapter 6: LCD assembly:

Chapter 7: PSU & Heatbed assembly:

Chapter 8: Electronics assembly:

Chapter 9: Preflight check:



Darian Grant - Reply

This section, 7. PSU & Heatbed Assembly, took me 50-minutes.

Todd McDermaid - Reply

Took my daughter and I 50 minutes too!

Andrew Purcell - Reply

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