Needle-nose pliers for tension check.
  • Needle-nose pliers for tension check.

  • 2.5mm Allen key for M3 screws

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WARNING: Printed parts aren't the same! There is a left and right oriented piece. See the pictures. For the following step, please prepare: Z-axis-bottom-left (1x)
  • WARNING: Printed parts aren't the same! There is a left and right oriented piece. See the pictures.

  • For the following step, please prepare:

  • Z-axis-bottom-left (1x)

  • Z-axis-bottom-right (1x)

  • M3x10 screws (6x)

  • Place the printed parts next to the frame. See the picture for CORRECT ORIENTATION (the small circular openings must be facing out).

  • Tighten each printed part with M3x10 screws.

  • Don't use excessive strength during tightening! In case of increased resistance, try to place the screws from the other side to "clean up" the hole. Then return to the front side.

There is a little bit of play in these brackets during tightening. I didn't realize it when I built my mk2s and it caused a slight misalignment. This time, I decided to use a machinist’ square here to ensure these were square with the frame. Worked great.

Steven Underwood - Reply

Thanks for the tip. Mine were quite misaligned until I used a square to align it.

Andreas Sjolund -

Thanks for the comment Steven, I had mounted my right Z-Axis motor and noticed that the leadscrew was not vertical. I took it off, squared up the top of the bracket to be at exactly 90 degrees to the frame side and it corrected the problem with the leadscrew. It would be worth adding this to the instructions. All you need is anything with a right-angle to square it up.

Kevin Gallagher - Reply

Thanks for the feedback guys, we will discuss a way to adjust the design to prevent misalignment.

Jakub Dolezal - Reply

For me a book works well to ensure the right angle to the frame.

Martin Wolker - Reply

The image shows an “A5” label. Mine is labeled “B1”

Øyvind Taknæs - Reply

Hi Øyvind, yes as the parts evolve we are changing labels on them.

Jakub Dolezal -

While your at it, it wouldn’t hurt to make these parts poka-yoke. They look almost identical, and I’m sure plenty of people have switched right/left during installation. Maybe make the hole pattern slightly asymmetrical.

Mahir Abrahim - Reply

Hi,

thank you for the suggestion. I will add a warning to the text.

Jakub Dolezal -

Alternately, it would be a fairly trivial change just to incorporate the orientation into the version number, i.e. print B6R and B6L.

Zachary Loafman -

I received two of the exact same Z-axis bottom right pieces. It looks like I am missing a Z-axis bottom left. The part no. is B6

Austin McLean - Reply

Hi Austin, please contact our support to get the correct one (info@prusa3d.com). Thank you

Jakub Dolezal -

I have the same z-axis motor holders parts (B6). This will cause a problem with assembling the printer / rods.

Any suggestions?

Asad Hindash - Reply

All the parts are labeled B6. Thats a version number. Just make sure the parts are opposite.

phr0ze -

I have the same parts / orientation for the z-axis motor holders. Any suggestions?

Asad Hindash - Reply

The two parts are the same direction. However, I 3D printed the wrong part. Thank you.

Asad Hindash - Reply

Adding to the earlier Poke-yoke suggestion, these parts could easily be made identical without sacrificing function.

Andrew Forsberg - Reply

For the following step, please prepare: Z-axis motor (2x) Note each Z-axis motor has different cable length. The shorter one must be on the left side, longer on the right side.
  • For the following step, please prepare:

  • Z-axis motor (2x)

  • Note each Z-axis motor has different cable length. The shorter one must be on the left side, longer on the right side.

  • Z-screw-cover (2x)

  • Remove the trapezoidal nuts from the motors. DON'T THROW them away, you will need them!

  • Screw the Z-screw covers onto both leadscrews.

  • Covers should be screwed fully to the motor, but not too tight! The motor must be able to spin freely!

My fingers hurt so bad :) … these were so tight it almost made me believe I created the threads as I was turning the leadscrew :) … I would have designed some tabs like those of a wingnut but shorter, 4-5mm deep to be able to grip the covers better. My 2c :)

Florian Ford - Reply

There are 2 extra components here that I have and have not found them in the manual. They are black printed cones shaped things that are loose. I have just scrolled down a bit on this page and see something like them at the end of the lead screws near the motor. Is this them? If so this is a big pain as I have my axes assembled and now need to disassemble them to put these on. Note they were supplied loose in my kit with no instruction as to what to do with them.

Stephen - Reply

Hi Stephen, check the second picture, those are called Z-screw-cover.

Jakub Dolezal -

Ah - apologies - I have now looked properly and see where they are mentioned above. My mistake :(

Stephen - Reply

No problem ;)

Jakub Dolezal -

Could you add a picture showing what “trapezoid nuts” are? Step 4 doesn’t use them and I don’t know what’s meant by this.

Peter Larsen - Reply

Using the pliers to get the z-screw covers started saved this process, it seemed impossible to get thems started by hand.

Sean - Reply

I have one Z-Screw cover that went on easy, and one Z-Screw cover that I had a very difficult time with even using pliers.

Paul Bowers - Reply

Very tough on the fingers, one was easy and the other nearly impossible. Better QC needed here. Also a better description of the covers might help to identify them. I didn’t know until today what a trapezoidal lead screw and nut were.. and I ‘ve only been a (poor) engineer for 50 years….

Alex Geller - Reply

For me it helped to push straight down (not too hard) and then start turning. I couldn’t thread them like a nut like I did with my MK2.

James Becwar - Reply

The photos of the Z-screw covers screwed down against the motors are visible only after knowing what to look for. The black on black makes everything blend in. I got them to screw down pretty easily .. I rotated them in a counter-clockwise direction first before screwing them on. That seemed to align everything.

Edward Traxler - Reply

A photo showing what the “trapezoid nuts” are (especially since they’re not very trapezoidal) would make this step much more clear. The screw covers are identified in the second photo, but there is truly no label for the trap nuts, the term just shows up in the text.

Kalani - Reply

Hi Kalani, thanks for the feedback, I’ve circled the nuts and will think of some update to this step. We call them trapezoid not because of their shape, but because of the function (they move on the trapezoidal rods).

Jakub Dolezal -

Once started it is surprisingly easier to turn the screw and hold the cover in place to work its way down.

Rich - Reply

Agreed - Turn the threaded rod and hold the z-screw cover steady. Much easier.

Corey Dangel -

more accurately

1. place the motor base on your lap with the rod pointing up

2. use one hand to hold the z-screw cover and apply a little downward pressure. This way you aren’t grabbing the fine edge of the z-screw but, rather, the flat tapered surface.

3. turn the threaded rod with the other hand and the screw cover should glide down, easy peasy

Corey Dangel -

For the following step, please prepare: Z motor left (labeled Z axis left, shorter cable) Z motor right (labeled Z axis right, longer cable)
  • For the following step, please prepare:

  • Z motor left (labeled Z axis left, shorter cable)

  • Z motor right (labeled Z axis right, longer cable)

  • M3x10 screw (8x)

  • See the second picture. The motor with the shorter cable (red arrow) is on the left, the motor with the longer cable (orange arrow) is on the right!

  • Motor cables must be oriented towards the frame, there is a small cutout in the frame on the lower edge for each cable.

  • Secure each motor with four M3x10 screws. Tighten evenly and carefully as you might break the printed parts.

Could you add a photo specifically showing the wire exit/orientation of the motors? Thanks!

Kenneth Albanowski - Reply

Agreed or just state the wires exit at the rear and route downwards in the slot used for the bottom fixing screw of the bracket.

Neale Brodie - Reply

Kenneth (@kalbanowski) and Neale (@jnb), thanks for the feedback, step will be updated. Motor wires must be facing the frame and there is a cut out for them on the lower edge of the frame.

Jakub Dolezal - Reply

Motor wires must be facing the frame and there is a cut out for them on the lower edge of the frame.

A suggestion: replace facing the frame with facing the “XY Frame” or the “verticle frame” , to clarify they should be facing it and not facing the aluminum extrusions, which may appear to be "frame” to us laypersons at this stage due to the amount of assembly completed already :)

tim -

To get the threaded rods quite center instead of having them to force into the top ends later it’s not a bad idea to check the alignment of the threaded rod with the two holes at the top of the frame before screwing the motor to the z-axis holders. I had to loosen the holders again and push them a bit while screwing them to the frame to get the threaded rods to be quite straight.

Uli Braun - Reply

Did as Uli to get the threaded rods straight. Just fasten the motor holder to the frame so that could be moved before mounted the motors. Then adjust the shaft in the middle of the two holes on top. Then removed the motors and and tighten the motor holder.

I also had some problem with the one of the threaded rods was leaning away from the frame, it diffed about 3 mm from bottom to top. It looks like the holder is not 90 degrees. I ended up to put washers between the motor and the motor holder (0,8 mm thick) to tilt the rod to the farm. The glue stick that comes with the printer works perfect to compere the distends between the frame and the threaded rod.

Mattias - Reply

At least for the B6 version of the part, if the bottom screw isn’t in all the way then there isn’t enough of a cut-out for the wires. This results in the threaded rod not being straight, but much worse it can crimp the motor wire. (I’ll have to wait until I complete assembly to see if this damaged the wire or just bent the insulation.)

Erik Nygren - Reply

For the following step, please prepare: Trapezoidal nut (2x) M3x10 screw (4x) or M3x18 screw (4x)
  • For the following step, please prepare:

  • Trapezoidal nut (2x)

  • M3x10 screw (4x) or M3x18 screw (4x)

  • Starting X-end version B6 you need longer screws M3x18. In the first batches (February 2018) the screws are in a separate bag.

  • M3n nut (4x)

  • Turn the X-axis upside down and insert nuts into traps on both X-ends.

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

  • Note: Design of your X-end printed parts might slightly differ, but the assembly process is the same.

First, check that there isn't any obstacle in the nut trap.

Keith Manley - Reply

Hi Keith, sentence rephrased, thank you.

Jakub Dolezal -

Why no thread lock! :P

Mr Cookie - Reply

This step has really turned into my first roadblock. The nut just won’t settle far enough into the trap on the left side for the screw threads to catch. I’ve used a pick looking for any obstacle and just don’t find one. Does anyone have a good tool/technique to ream it out an extra millimeter?

Rueben Nilsson - Reply

… Nut trap :D

H4irBear - Reply

I cannot get the nuts to fall in the trap correctly no matter what I do. This entire process has been incredibly frustrating.

Sean - Reply

Pliers to the rescue again. I had to force the nut down in to the trap with the plies by putting an uncomfortable amount of pressure on the nut. Ended up working, however.

Sean -

I’m also having difficulty getting the nut seated correctly into the trap. Printed part version B6.

Paul Bowers - Reply

I got super worried that I would need to use some pliers or something to cut some of the stuff in the nut trap, since the nut did not wanted to get in deep enough.

However, I found the trick, after 1h of random tool testing :)

Tweezers, pliers, allen keys to align from the screw hole and kaboom.

The trick was to not use a lot of force or anything, but to bruteforce the exact rotation of the nut so that it can fit.

Lyubomir - Reply

The deep-set trap on these parts had me stumped and worried for a bit, but then I found a method that worked for me: just shove the nut in as far as it reasonably goes, and then insert the second-smallest hex wrench into the screw hole, just push it into the nut. It’s smaller than the screw, it goes pretty easy. The. Just push the nut in place with the key, and it popped right in, no problem.

Maybe I just got lucky (twice), otherwise this might work for others.

Kalani - Reply

Thank you all for the “align with allen key/ hex wrench” tip!

Jeff Spencer - Reply

Would be helpful if you explicitly called out the orientation of the nut in the trap - I.e., a corner of the nut faces out. Can almost see that in pictures..

Rich - Reply

Hi Rich, the orientation is given with the shape of the opening.

Jakub Dolezal -

OK this was extremely frustrating. Those nuts really didn't want to go al the way in, not even with the tricks mentioned here. In the end I resorted to using a dremel to enlarge the hole. But because of the awkward angle the hole was now too big to actually trap the nut. But with pliers holding the nut in place I was able to make things work. But boy did I so _not_ enjoy this part!

Tako Schotanus - Reply

The slotted nut trap on the left of the assembly allowed the nut to rotate when the screw was inserted. This meant that it was very difficult to tighten one of the screws holding the trapezoidal nut in place - this I suspect is crucial to accurate Z axis layering. I had to put pressure on the nut with the tips of the pliers to stop it rotating and slowly advance and back-off the screw until it was seated. It’s still not as tight as the others and I’m worries. I think a square nut would have been better than a hex nut in this slotted trap, but the instructions clearly state a hex nut.

Jonathan Butters - Reply

I have the same issue as Jonathon, but I haven’t been able to salvage it. Now, every time I try, it gets worse. I’ve just tightened up the one as much as I can and I’ll probably reprint the part, but pause as the trap is finished and put the nut in place.

A better production solution might be to move the trap down a bit so it doesn’t sit inside the hole for the nut, and use a longer screw to reach it.

John Jones - Reply

This step might be better moved to before the rods are inserted during X-Axis assembly. As others have noted, getting the nut properly positioned in the slot is problematic and I’m constantly worried about the possibility of warping the rods while trying to get this part done.

Raymond Toovey - Reply

Hi Raymond, thanks for the suggestion. I was thinking of a solution, but to my opinion it will bring more confusion and even more explanation. You need to take first the Z-axis motors, remove the nuts and then use them on the X-axis. Take an Allen key and check first, whether the nut trap isn't filled with some particles.

Jakub Dolezal -

This is total crap. No matter how I position the nuts in the slots there just isn’t a position that works. I’ve wasted a f’ing hour just on this step. The slot is round so have the nut with one of the hex points poking out just moves the screw thread further out of the hole.

I’m bitterly disappointed having to wait two months and be faced with this crap.

Stephen York - Reply

Hi Stephen, I'm sorry for the issues, in case you won't be able to place the nut in, please contact our support.

Jakub Dolezal -

Very difficult. I got this done but the slot needs a redesign for sure. I’d suggest the square nuts would be better so there could be more clearance without compromising the function.

Tom Fountain - Reply

Hi Tim, thanks for the suggestion. I will discuss it with the devs.

Jakub Dolezal -

After two days I still can't get this nut into this slot. I've tried every suggestion here except for making the slot bigger and the nut still doesn't sit correctly. It doesn't help that it's impossible to see the slot with the black printed. I whole heartedly agree this slot needs some kind of rework.

Ryan Latimer - Reply

Hi Ryan, in case the slot is somehow distorted, please talk to our support team about getting new parts.

Jakub Dolezal -

I did end up getting the nut in. I had to go into the screw hole with a pick at a sharp angle to get inside the nut and then pull the nut into the slot and hold it down with the pliers while I tightened the screw.

Ryan Latimer -

Running into the same issue that everyone here has, my kit has B6 printed parts. I spent over an hour trying to force the nut in. I’ve tried almost every suggestion here other than using a dremel to create more space. There’s no debris in the holes. I’m unable to insert it part way and use a smaller hex wrench to shimmy it into place.

This isn’t even my first issue. The holes for the aluminum extrusions and steel plates for the Y-axis required large effort to get them to all fit nicely. Also could not successfully get my Y-axis perfectly level. Not thrilled with this kit so far.

Mike - Reply

I filed down the nuts on one side and was able to get this in.

Mike -

I solve the issue by grind down(using dremel) two opposite corner(just a bit) of each hex nut. It will fit the slot perfectly. You can use a long needle to guide the nuts into the slot and turn it to fit. It took me few minutes to complete step 5.

W Lai - Reply

I echo all the others who have complained that the slotted nut capture design is extremely hard to use. First, it was hard just to get the nut to enter the slot at all due to the shielding afforded by the cylinder. Then, what I discovered was that - although the nut seemed to be very loose and floating - it actually required a HUGE amount of force to push it into the proper position. Lost an hour on this one step.

Jay Sinnett - Reply

What worked for me here was using the pliers to push the nut into the trap. So stick the pliers down into the hole between the two nuts, then pull the handles apart to push the nut into the trap. After that look in from the bottom to see the alignment of the nut. If you can see a good portion of the nut from the bottom, then you can use the small allen key to center it a bit more.

Also, when i was manipulating the x-axis the square nuts from the extruder housing kept falling out. I agree with others that it would be better to move this step to during the x-axis assembly. It’s not that confusing to have to take out the z motors a phase or two early.

Adam Sbeglia - Reply

I was unable to directly use R2 revision x-end parts I had printed myself in E3D EDGE due to this issue. (These parts are printed on an MK2 at recommended .2 layer height with PrusaControl, and generally seem to be of excellent quality.)

Combining all of the above suggestions (allen key to pull the inner nut into alignment with the trap, and pliers to apply pressure while putting in the screw) worked, but then the hex nuts simply spun in place once the screw caught.

I ‘fixed’ this with some 2-part epoxy dripped into the open side of the nut trap while a screw was already inserted (to keep the threads clear). This appears to have worked without side-effects and I was able to back the screws out with minimal effort. I haven’t reassembled the entire axis yet, but it feels like it’ll hold at least through one assembly.

I wonder if the EDGE is slightly softer than the Prusa PET and the trap edges round off just that little bit more easily. In any case, this part seems to need some redesign if it is this fussy.

Kenneth Albanowski - Reply

I was using the supplied manual to do this step and the image of the nut trap on the left part it was not clear to me that a round nut was needed because all the previous insertion slots were for a square nut. So I inserted a square nut and screwed into it but it wouldn’t get all the way in and then I couldn’t get the nut or the screw out. With the help of a friend I was finally able to get it out and the correct nut and screw in. This cost me two days of stress and searching. I really thought I had screwed up the whole printer.

I think if you are going to switch the type of nut you are going to put in a slot you should highlight the fact. I admit that if I had been following this document instead of the printed manual I wouldn’t have made this mistake.

gritty - Reply

Hi Gritty,

thanks for the suggestion, I understand your point. The nut type is specified in the description and there is also a picture. I will see if I can do more to highlight the correct nut.

Jakub Dolezal -

I also had issues getting the inner most nuts into the traps. I tried the suggestions of trying to guide them in with the allen keys and pliers, but I could never get them seated in far enough.

I found another trick that may help someone else. I noticed that a 3/8” socket extension bar was almost a perfect fit to place into the x-ends’ shafts. This allowed me to gently rotate/wiggle the extension bar around and coax the nut in correctly. Since the extension fills the entire shaft it puts even pressure on the printed part so I was applying much less pressure/stress than trying to force the nut in with the allen key or pliars.

James Shumpert - Reply

I also had issues with this step, particularly the left X axis inside trapezoidal nut. It’s probably human nature to put the easier nut in place first. I realized that if I removed the outer nut, I had a clear path to push the inner nut into place with the screwdriver. I was able to apply sufficient force to the nut to drive it home. Once the inner nut was placed, I was able to then place the outer nut again easily.

Duane Pinkerton - Reply

here’s what worked for me to get the nut seated into the hex opening - I screwed the nut onto the end of a screw and then used the screw as a handle to push the nut straight down into the hole.

jodi buckley - Reply

Righto, I received my kit a few days ago and I’m now a few hours into this assembly and no great problems so far [apart from receiving a VERY dark shade of orange mouldings; so dark in fact that even a blind man would say that they were BLACK!] . . . . . anyhoo, this stage has quite a few comments compared to previously!

I’m on B6 mouldings like a lot of others and with my (very) nearly 60 year-old eyes I’m struggling to see from the recesses in the moulding which way the hex nuts should be orientated - it appears that a correctly inserted nut should present a corner in the middle of the recess (ie the nut needs to go corner first NOT flat first!)

So what worked for me is this:

I gently pushed a nut into the opening and then using an engineers scribe (of about 1.5mm diam but VERY pointy!) from underneath through the screw hole, I located the hole in the nut and physically moved it into place - 2 minutes all sorted and for what it’s worth, my heart goes out to all those who have suffered snags with this stage!

Mark Baker - Reply

I managed to get the nut cross-threaded on the bolt and now it’s turning in the slot. Remains to be seen whether I can get the nut and bolt out at all, and if I can, whether the slot will be ruined and useless. This is not a good design. Perhaps a square slot and square nut would make insertion easier and grip more reliable?

Anne - Reply

Carefully rotate  the X-axis onto its backside. Insert the trapezoidal nuts to each X-end.
  • Carefully rotate the X-axis onto its backside.

  • Insert the trapezoidal nuts to each X-end.

  • Note the correct orientation of the trapezoidal motor nuts!

  • Tighten the nuts with M3x10 screws or with M3x18 screws. Longer screws are needed in case of X-end version B6 and newer.

  • You can use any of all four holes on the trapezoidal nuts.

  • Note: Design of your X-end printed parts might slightly differ, but the assembly process is the same.

Here should be the indication that the outer edges should coincide, otherwise the trapezoidal rods will later touch the upper guide which leads to rattling

Gerhard Kunz - Reply

The nuts that hold these screws in place fell out really easily for me. Perhaps this stage should be done earlier? when you have both of the axis ends still off the rods?

Alistair - Reply

FYI I had overtightened these bolts which caused my Left Z axis motor to have trouble turning and thus caused the calibration to fail. I loosened it a bit and it turned just fine.

Andreas Sjolund - Reply

Dear Prusa. Please stop using the description ‘trapezoidal’ nuts. You have supplied hexagon and square nuts. A trapezoid is a quadrilateral with only one pair of parallel sides. There is no nut like that.

Tom Fountain - Reply

Hi Tom,

several other companies are using this term to describe the same shape (e.g. https://www.mooreinternational.co.uk/Pro...), how else would you call this one?

Jakub Dolezal -

I agree with Tom, just because other companies use a broad term doesn’t mean Prusa should . Take the feedback because its constructive rather than defending the reason. My challenge on this build ids is that I think you guys are rushing production because the resolution isn’t high enough for the square nuts to be properly located. the slots are either too narrow or the hole isn’t deep enough. I have been modeling for 45 years . If you want a yardstick for mold quality and precision fit buy any Tamiya model and spend a weekend assembling it and you will see that wherever there is a square nut located in a slot that part should be max resolution for precision, I was forced to dremel to locate the square nuts to allow the M3 18 mm bolt to meet the nut in alignment so that it could be tightened.

PaulHarris - Reply

Aside from the X-axis, please prepare for the following step: Smooth rod (2x) Carefully slide the X-axis on the trapezoidal lead screws. By rotating both screws simultaneously let the X-axis slide until both trapezoidal lead screws are visible.
  • Aside from the X-axis, please prepare for the following step:

  • Smooth rod (2x)

  • Carefully slide the X-axis on the trapezoidal lead screws. By rotating both screws simultaneously let the X-axis slide until both trapezoidal lead screws are visible.

  • Make sure the top smooth rod of the X-axis and the lower edge of the frame are parallel.

  • NOW, PLEASE BE VERY CAREFUL! Gently insert the remaining smooth rods through the bearings on the X-axis all the way down into printed parts, do not apply too much force and do not tilt the rod!

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

  • Note: Design of your X-end printed parts might slightly differ, but the assembly process is the same.

I missed the smooth rods part here…. …found out after calibrating part

printminion - Reply

Hi Printminion, was it unclear from the text or did you just follow the pictures?

Jakub Dolezal -

I’m having a problem where one the the trapezoid nuts is difficult to put on the threaded rod. Is this ok? I have to use a lot of force to slide the x axis down. I tried printing replacement nuts but those are hard to turn too.

John Helgeson - Reply

I found that sliding the nut up and down on the leadscrew a few times helped loosen up the fit a bit. The one of the left motor was far tighter than the right one in my kit.

Robert Hunt -

Hi John, the trapezoid nuts should be running smoothly and I haven’t encountered issues with them so far. Make sure your X-axis isn’t wider or inclined, this might cause increased friction.

Jakub Dolezal -

For the following step, please prepare:

Smooth rod x2

Robert heller - Reply

Hi Robert, thanks for noticing. Since the rods are already on your working bench (table) and it is the last couple, I assumed to instruct you just to use them.

Jakub Dolezal -

Agree. I would have missed this step. I read it but confused because I didnt realize that the smooth rods were part of this step. Actually, I’m building this thing a few hours at a time here and there so it’s been awhile since I last saw or used smooth rods. So making this extra clear in the steps would be helpful.

Andreas Sjolund -

I agree, and Jakub’s reply makes little sense since all other steps specify exactly the parts needed to complete the step, regardless of whether they are “already on the workbench” or the “last couple” parts. If the instructions are to be clear and trustworthy, they need to be consistent.

Guido Kimble -

Hi Guido, you’re right step instructions will be updated ;)

Jakub Dolezal -

One thing I noticed is that the x axis bearings slid down the plastic holders when I put the rods in. I’m hoping this is ok since the x axis steps indicated that the bearings should be somewhat flush to the top and bottom of the plastic piece holding them (with a gap in between). I pushed the bearings back into place but not sure if they will just fall down again and if it will impact the printer in anyway.

Daniel Lipsky - Reply

Hi Daniel, it the best scenario the bearings should be aligned with both top and bottom edges of the X-ends (printed parts). However, slight movement in the printed part should be ok.

Jakub Dolezal -

You can use your flathead screw to push the bearing back up into place using the slot that exposes it.

Todd Scott Anderson -

We should put the trapezoidal by hand on the rods before screwing them at step 6. Its very easy to damage the trapezoidal nut because they are hard to put on

there is no warning except ‘carefully screw the trapezoidal’.

Is it a problem if the nut is hard to turn ?

Jlevray - Reply

Hi Jlevray, different approach during the assembly might brings issues. Putting on the trapezoidal nuts shouldn’t be hard, it should be smooth. If you have issues, please try to put on the nut without the X-axis. If everything works fine, then your X-axis is either too wide or assembled inclined, which is causing tilt between the nut and the trapezoid screws.

Jakub Dolezal -

I did damage both trapezoidal nuts using the standard instructions as the metal screws can easily cut into the starting thread while trying to find the right alignment. That led to endless debugging about why the Z-axis didn’t work correctly.

I agree with Jlevray and strongly recommend carefully threading the nuts by hand first and screwing them to the X-axis second.

LaurentR -

Add one more to the agree with screwing on the nuts first. This was not an issue with the MK2, but seems harder with the MK3. Perhaps the spacing is slightly different. If you goof up the nut, you will either spend a ton of time trying to recut the threads with the leadscrew, or find an alternate solution such as printing temporary ones or stealing them from another printer as I did in the meantime. Mine was really tight right out of the box, so I am not sure whether it is the part or the process, however there is little left to guesswork if threaded on before being locked in.

Douglas Shelfoon - Reply

I’m also struggling with one of the trapezoidal nuts - it’s far too tight and I suspect it is causing the calibration failures that I’m now seeing. I’ve tried swapping the left nut with the right, and the same problem persists with just the one nut. I don’t recall putting it on awkwardly, but I might have damaged it. Although, it was also quite hard to remove from the screw shaft straight out of the box. It would be great if a spare was included with the kit!

Sean - Reply

I had the same problem. i just chatted with support and they are sending my a new nut.

Joe -

Hi Sean, the nuts are part of the Z-axis motors. In case yours are too tight, please contact our support.

Jakub Dolezal -

Similar problem :-(

I may have damaged my trapezoidal nut.I was having a tough time with step “slide the X-axis on the trapezoid screws. By rotating both screws simultaneously let the X-axis slide until both trapezoid screws are visible. “

After several times attempts i tryed running the nut backwards, and feeling the lip of the nut fall off the thread.

One of them was impossible to start with out putting some torque on it.

Now the left side X-access is very stiff.I removed the nuts from the x axis .

1 nut is very tight fit to the lead screws.

If i need to order new nuts please advise.

Do you guys sell ball caps ?

Joe - Reply

Hi Joe, please discuss this issue with our support team (info@prusa3d.com). The nuts shouldn’t be preventing you from assembling the X-axis.

Jakub Dolezal -

Similar situation here. One of the trapezoidal nuts is way too tight.

Sean - Reply

Same here, one trapezoid nut is too tight, Z-axis motor with faulty trapezoid nut won’t move.

Ivica Petrovic - Reply

I initially had the same problem of getting the trapezoidal nuts started, and not wanting to cause damage as noted above, I stopped. I remembered that the nuts came off the rods back in Step 3 very easily, so I assumed there must be something else going on. What I did was as follows, and they both went on very easily: I sat the X axis on top of the rods (as everyone probably did). Then I rotated one of the rods backwards until I heard/felt a click as the nut dropped onto the thread. But that alone isn’t the trick. I then rocked the end containing the nut away and toward the frame while trying to rotate the rod into the nut - at some point it kind matches up and goes in very easily. I repeated the same thing on the other side with the same results. Seems like the nut needs to be on the exact axis of the screw rod to get it to start easily. NOTE: When I say “rod”, I’m talking about the threaded rod, not the one that the bearings run on. Sorry for the confusion.

Ira Schonfeld - Reply

I had the same experience as Ira. (Post above mine) I got lucky on one side and the nut threaded onto the rod easily. So she. The second side was difficult, I knew something was off. Simply rotating the threaded rod backwards a bit allowed the existing threads to drop into place, and then it was easy from there.

Kalani - Reply

Regarding the tight trapezoidal nut, what I see is the mass of the x motor is tipping the assembly off axis. I simply used one hand to straighten it and the other to start each side, once you get the thread started the assembly sits up straight.

After setting the x axis assembly on top of the lead screws look at the printer from the side, and you will see what I’m talking about.

Scott Carlson - Reply

Do the leadscrews need any kind of lubrication? I’m asking here because I see no mention about the leadscrews in the maintenance guide.

Manolis Agkopian - Reply

Hi Manolis, to my knowledge there is no need. From time to time you can remove dust from the threads and before each maintenance have a look in the online 3D Printing Handbook to read the latest instructions.

Jakub Dolezal -

Same problem with trapezoid nut as reported by other folks here - one nut is *very* tight even when put on a screw rod alone. The other nut is fine - moves easily. There are no visible damage to the nut threads.

Eugene Surovegin - Reply

I’ve had no problem at all with this step . I’m wondering if the people having issues with a tight axis confirmed that the motor mounts were square to the frame . If not , the leadscrews could be leaning in or out and causing binding . Just a guess and another thing to try ….

Marc Thomson - Reply

I had the same problem with one of the trapezoidal nuts being very difficult to rotate. I’m going to try some of the suggestions here once I get back home. Plus, I sent a message to support asking to get a replacement nut.

It seems like it’s VERY easy to cross-thread these [based on all the comments], so maybe a warning in the text to reinforce that the nuts should thread on easily and to check the threading if there’s resistance? I should’ve known better because I remembered the nuts un-threading from the rod nice and smooth in the earlier step. But, I got caught up in the excitement ;-)

Tony Cacciarelli - Reply

I also ran into one of the trapezoidal nuts being way too hard to turn. I put in a request via email to support for a replacement nut. Sigh.

Christopher Dopp - Reply

I know this is a bit extreme, but I too had a trapezoidal  nut that was either miss-threaded or just too tight. I took a blowtorch and lightly heated the end of the lead screw and the nut then screwed it on and off several times. It worked! It now glides as smooth as the other. Good luck!

Lance Jensen - Reply

If anyone makes it this far in the comments and still hasn’t figured out how to make the existing trapezoidal nut work, you might try printing a new one (for permanent replacement or as a temporary fix until a replacement gets shipped):

https://www.thingiverse.com/thing:224650...

This, of course, only works if you have another printer. Good luck.

Darrel Raines - Reply

So I bought the upgrade kit mk2s to mk3 and had to print all the parts, everything went ok however when assembling the z axis i noticed that my x-axis rods are not parallel to the frame, checked everything for many hours and turns out that the x-axis printed parts holes for rods are not 100% perpendicular to the side of the plastic part and I’m having the same issues as the one described on the next link (https://shop.prusa3d.com/forum/prusa-i3-...) however I dont know anyone that could help me by printing a spare part. I am hoping the self calibration process can fix the problem :s

Juan López - Reply

One of the nuts on mine was way too tight too compared with the other one. Caused calibration error right away, Z-axis wouldn’t even move by itself. The nut showed no sign of damage, but I found out where it was binding and used an Exacto knife to gently clean out some threads in that area. Took a little while but I was able to see significant improvement with very little material removed, enough to make it calibrate properly. They should include some spare nuts in the package.

Scott Story - Reply

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

  • Z-axis-top-left (1x)

  • Z-axis-top-right (1x)

  • M3x10 screw (4x)

Add Comment

Place the Z-axis-top-left part on the rods and align it with the frame. Ensure the holes in the printed part are fully aligned with the holes on the frame. Use two M3x10 screws to tighten the Z-axis-top-left part.
  • Place the Z-axis-top-left part on the rods and align it with the frame.

  • Ensure the holes in the printed part are fully aligned with the holes on the frame.

  • Use two M3x10 screws to tighten the Z-axis-top-left part.

  • Don't use excessive strength during tightening. In case of increased resistance, try to place the screws from the other side to "clean up" the hole. Then return to the front side.

  • Repeat this step on the other side of the frame with Z-axis-top-right printed part.

  • Note: Design of your X-end printed parts might slightly differ, but the assembly process is the same.

refering to MK2 manual step 12:

“Check both leadscrews in the upper part of printer, they shouldn't touch the edges of the printed part. If so, release the motor holder at the bottom and slightly move it. “

You cannot see it from the top because the surface is full and solid. My leadscrew hits the edge what causes noise on fast movements of the x-axis.

It is much easier to adjust the motor holder now instead after fully assembled and finished wire management.

Heiko Schultz - Reply

Hi Heiko, the Z-axis design was changed to prevent misalignment of the leadscrews. I will discuss this with devs, thank you for the feedback.

Jakub Dolezal -

it’s not an issue of the design, it’s just the assemble instruction that doesn’t highlight this. From below I can see if it is centered or not.

Heiko Schultz -

Hi Heiko (@predatorjr), the design was changed to align the rod correctly by itself and user shouldn't be checking the position, that is why it is not mentioned in the guide.

Jakub Dolezal -

I had an issue with the screw threads on the frame for the top right Z axis part.  I don’t think they were tapped properly because the screws were extremely tough to get in.  This was not an issue with the 3d printed part as I tried to work the screws in the holes without the 3d parts as well.  Ultimately, I had to carefully use my drill and was able to get the screws to go all the way in.  The top right 3d printed part does not sit tightly onto the smooth and threaded rod but there’s no play if I wiggle them with my hand.

Shouldn’t be an issue but wanted to share my feedback.

Corey Dryja - Reply

Starting mid of February 2018, the MK3 kit is shipped with improved X-carriage.
  • Starting mid of February 2018, the MK3 kit is shipped with improved X-carriage.

  • Compare yours against the picture and choose from following:

  • The old design is on the left side of the photo. Please proceed to Step 19

  • The new design is on the right side of the photo. Please proceed to Step 11

my mid Feb kit showed up with the old design (in addition to the old version of the X end motor)

Eric Harten - Reply

Mine is old yet was shipped near the end of March :(

Does it make much difference? Should I print a new one asap?

Jeff Spencer - Reply

Insert the flat part of the X-GT2 belt (850 mm) into the X-carriage as in the picture.
  • Insert the flat part of the X-GT2 belt (850 mm) into the X-carriage as in the picture.

  • Use a screwdriver or the smallest Allen key to push the belt in.

I can´t manage to insert the belt! Its stuck halfway in, how should I do it?

William@stadheim.com - Reply

Hi William, check the slot for any obstacles first. If it doesn't help please contact our support according to the options in the first chapter of this manual: 1. Introduction

Jakub Dolezal -

My X-axis belt is only 740 mm in length. The Y-axis belt is already installed and was the correct length, so I don’t think I’ve switched them. I’ll probably source a replacement locally but wanted to point out that this happened.

Eric Lee - Reply

Guide the X-axis belt through the X-end-idler, around the 623h bearing with the housing and back. Continue with the belt through the X-carriage. Note there are slots below the belt, those will be used for cables. Guide the X-axis belt through the X-end-motor, around the GT2-16 pulley and back.
  • Guide the X-axis belt through the X-end-idler, around the 623h bearing with the housing and back.

  • Continue with the belt through the X-carriage. Note there are slots below the belt, those will be used for cables.

  • Guide the X-axis belt through the X-end-motor, around the GT2-16 pulley and back.

Add Comment

Before you continue to guide the belt through the X-axis, please release two M3 screws on the X-end. Rotate the X-axis motor as indicated towards the frame.
  • Before you continue to guide the belt through the X-axis, please release two M3 screws on the X-end.

  • Rotate the X-axis motor as indicated towards the frame.

  • Insert the flat part of the X-GT2 belt into the X-carriage as in the second picture.

  • Use a screwdriver or the smallest Allen key to push the belt in.

  • There will be belt overhang on this side, DON'T TRIM IT yet.

Is the motor supposed to pivot on the bottom screw? By “release,” do you mean a half turn looser or fully retracted from the motor housing?

It looks like the screws should be able to move slightly side-to-side on the top two, but the openings are too small to allow that kind of movement.

Evan - Reply

Hi Evan, leave the motor connected just on the bottom screw, the upper two screws can be almost “removed”. Your aim is to rotate the motor as close to the frame as possible.

Jakub Dolezal -

Using right hand rotate the motor to its original position and hold it (tension is applied to the belt). Using two fingers on your left hand push the belt together. Very small force should be needed for bending the belt, BUT the belt shouldn't be bent by its own weight before being pressed with your fingers, it must be straight.
  • Using right hand rotate the motor to its original position and hold it (tension is applied to the belt).

  • Using two fingers on your left hand push the belt together. Very small force should be needed for bending the belt, BUT the belt shouldn't be bent by its own weight before being pressed with your fingers, it must be straight.

  • If you are struggling to rotate the motor back into position the belt tension is too high.

  • Depending on the belt being under or overstretched, adjust the amount of the belt in the X-carriage.

  • When done, rotate the motor to its original position and tighten the M3 screws again.

I would clarify the “original”position is the one where tension is applied to the belt.

Rich - Reply

Good point Rich, description added. Thanks

Jakub Dolezal -

Both top and bottom part of the belt should be parallel (above each other).
  • Both top and bottom part of the belt should be parallel (above each other).

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

  • Tighten both screws on the pulley.

I don’t know what it is, but the belt rubs against the X-axis where the motor is. It rubs on the outside edge, and looks like the X-axis part is not wide enough for the motor. In other words, I cannot push the pulley any closer to the motor without it rubbing, and the belt is against the far side of the X-axis part. Any ideas?

Jason Conaway - Reply

Please disregard my question. I had a moment of poor judgement and put the pulley gear on backwards.

Jason Conaway - Reply

I did that too, but I noticed it during the next few steps and fixed it.

David Thompson - Reply

Does the belt always ride to the left or right? I can’t seem to get my belt to stay precisely in the center. This is true for the idler and motor side of my Prusa mk3 and mk2.

Ludvik Jersbek - Reply

Use the technique described below to test if the belt is properly stretched.
  • Use the technique described below to test if the belt is properly stretched.

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

  • Move the X-carriage towards the X-axis motor. Don't use excessive force.

  • If the belt is stretched properly, you should feel a resistance and the X-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.

  • Belt too loose? Return to step 13 and repeat all steps until now. You have to rotate the motor and retighten the belt in the X-carriage. Shortening the belt length by moving one or two teeth outside X-carriage should be enough.

Add Comment

For the following step we recommend getting a white marker, but you can also trim the belt without it. Measure the part, which must be trimmed and gently take the end of the belt away, from the X-carriage, but make sure at least 3-4 teeth are still in the X-carriage, as you don't want to lose the tension. If possible make a mark, where to cut the belt. Ensure again your mark is in the correct position and the belt is still stretched.
  • For the following step we recommend getting a white marker, but you can also trim the belt without it.

  • Measure the part, which must be trimmed and gently take the end of the belt away, from the X-carriage, but make sure at least 3-4 teeth are still in the X-carriage, as you don't want to lose the tension. If possible make a mark, where to cut the belt.

  • Ensure again your mark is in the correct position and the belt is still stretched.

  • Using pliers cut the belt and push it inside X-carriage. Use screwdriver or Allen key, if needed.

Finding a “proper” belt tension has always been an issue, so if the frame measures are well known (as they are), shouldn’t the belt length be known as well? Why don’t you just say “cut the belt down to X cm and mount it as shown”?

Arsen Torbarina - Reply

Hi Arsen, it is not that easy. All products have a certain tolerance, so you can't give one number of length without testing it for a while. Because for some it might be a bit too long, for some a bit too short. As soon as we have enough data I'm sure we will cut the belt for you.

Jakub Dolezal -

After cutting and pressing in the end of the belt, you may want to check the belt alignment again, in case it was pressed in further than before.

Etienne van Ballegooijen - Reply

In this step, we will finish tensioning the belt. Please read the instructions first, your belt might have proper tension already. First, slightly release all the screws holding the motor, otherwise, the upper "tensioner" won't work (the motor must be able to move). Using Allen key start tightening the M3x18 screw inside the X-end-motor, but after each turn or two check the tension in the belt.
  • In this step, we will finish tensioning the belt. Please read the instructions first, your belt might have proper tension already.

  • First, slightly release all the screws holding the motor, otherwise, the upper "tensioner" won't work (the motor must be able to move).

  • Using Allen key start tightening the M3x18 screw inside the X-end-motor, but after each turn or two check the tension in the belt.

  • In Step 14, you were asked to have the belt a bit less stretched, however, for the optimal performance, the belt must be a bit harder to press with your fingers. Move the X-carriage all the way to the X-end-idler and try the belt tension in the middle of the X-axis.

  • When you achieve optimal tension, please tighten the screws again.

  • In case you experience X-axis failure during calibration or skipped layers in the X direction, you can adjust this screw accordingly. Tightening the screw stretches the belt. Releasing the screw has opposite effect. Each time don't forget to release the screws on the motor first.

  • Ready? Please jump to step Step 25

With regards to the correct tension, won’t it be possible to design a weighted scale, one that hangs on the belt, this might insure that the correct tension is achieved during construction and when doing maintenance further down the line.

Regardt Jordaan - Reply

This step needs MUCH better instructions. “a bit harder” is not a real specific term. Also with the new pieces printed in PET they won’t take as much stress as the ABS parts. At least give a reference to how much deflection the belt should have or some kind of scale as quoted above.

Greg Sargent - Reply

Not understanding the purpose of the X-end-Motor Tensioner Assembly M3x18 screw I over tightened it and broke the assembly. This may cause multiple issues with the X-axis assembly because I don’t know how hard it will be to remove the damaged part from the smooth rods.

I may have to break of the plastic part to get them loose from the rods because that’s a tight fit.

David Thompson - Reply

broke mine :-(

process was definitely improving tension on the belt - but not clear how many turns, or how much slack was acceptable. I was still able to comfortably touch upper and lower belts

scott hansen - Reply

I just broke my X-end-motor bracket. :( Was following printed manual (with errata insert for this step), but this looks to be the same. I have B6 version. I tightened the M3x18 screw and eventually plastic bracket de-laminated close to the nut hole. The belt was nicely tensioned, but it was not tensioning any more, but I kept turning the screw, it probably touched the other screw and just put more stress on the bracket which eventually failed. It would be nice to have: a) more material in the left-top corner, c) much bigger washer, d) some window to see the position of the screw inside, e) a way to measure the tension of the bracket and belt in objective way.

I managed to finish the build anyway, with broken bracket. It works flawlessly actually with perfect print results. I will glue the X-end-motor bracked later back to good shape, and print replacement (possibly with strength improvement modifications), or order new one. :/

Witold Baryluk - Reply

Totally agree with the above. I don’t have a lot of experience with belt tension, so “a bit harder” is a bit of a struggle.

Zachary Loafman - Reply

Ditto. Mine’s broken too. Now what?

James Smith - Reply

Hi James, please contact our support using a live chat, visit shop.prusa3d.com and look for the chat window.

Jakub Dolezal -

Mine broke as well. It didn’t break off completely, but there’s a big crack to the right of the top left screw from top to bottom. Seems to be holding itself together alright, just going to continue and hope it works out. I agree it’s unclear how tight the belt should be.

Clay Smith - Reply

At some point, the square nut trapped in my motor mount got misaligned, so I was never able to use the tensioning screw. But based on seeing how many people had their mount break, I think that the tensioning screw may be a bad idea. I tensioned my belt very easily by hand. Just loosen the three motor-mounting nuts and rotate the motor frame by hand to achieve the desired belt tension, then tighten the bolts. By the way, during Calibration (which comes much later) the electronics will measure the effort required to move the belt and will give you a numerical gauge telling you if you have done it right. So don’t obsess about getting the belt tension “just right” at this step.

Jay Sinnett - Reply

And to add to the list of issues, my x axis motor snapped when tightening the tensioner screw.

I would definitely add a warning in the text of this step as it seems to be a common problem.

Going to continue with the build as things are holding together OK still, but going to print a replacement part (to go with the pair I ordered today) as soon as its all up and running well.

If nothing else, I've learned to read these comments before starting a new step :p

Rob Ryan - Reply

DON'T TRIM THE BELT unless you are asked in the instructions!!! Insert the flat part of the X-GT2 belt (850 mm) into the X-carriage as in the picture. Press the belt all the way in, use a screwdriver or an Allen key.
  • DON'T TRIM THE BELT unless you are asked in the instructions!!!

  • Insert the flat part of the X-GT2 belt (850 mm) into the X-carriage as in the picture.

  • Press the belt all the way in, use a screwdriver or an Allen key.

  • It's very IMPORTANT that the short end of the belt isn't sticking out of the X-carriage.

“Insert the flat part of the X-GT2 belt (longer one) into the X-carriage as in the picture.”

What you mean by “longer one”?

Austin Hampton - Reply

It seems to me the X belt is longer than the Y belt.. so if you unpacked everything all at once and not step by step “longer one” would tell you which is which.. but how you would get to this step with more than one belt from one kit is a mystery =)

Thomas Kasner -

Step description updated with exact length of the belt. It should be a check for those, who switch the belts by accident.

Jakub Dolezal -

I think it’s a mistake to “press the belt all the way in”. I think this is the reason that many people are experiencing belt rubbing on the front shoulder of the pulley and resultant belt twisting. Instead the belt should sit flush with the outer edge of the round mount.

Ken Hackbarth - Reply

Hi Ken, no it is OK as described in the manual. The belt should be completely pressed in. I need to see your printer, to examine the possible cause of the rubbing.

Jakub Dolezal -

Guide the X-axis belt through the X-end-idler, around the 623h bearing with the housing and back. Continue with the belt through the X-carriage. Note there are slots below the belt, those will be used for cables. Guide the X-axis belt through the X-end-motor, around the GT2-16 pulley and back.
  • Guide the X-axis belt through the X-end-idler, around the 623h bearing with the housing and back.

  • Continue with the belt through the X-carriage. Note there are slots below the belt, those will be used for cables.

  • Guide the X-axis belt through the X-end-motor, around the GT2-16 pulley and back.

Add Comment

Before you continue to guide the belt through the X-axis, please release two M3 screws on the X-end. Rotate the X-axis motor down. Insert the flat part of the X-GT2 belt into the X-carriage as in the second picture.
  • Before you continue to guide the belt through the X-axis, please release two M3 screws on the X-end.

  • Rotate the X-axis motor down.

  • Insert the flat part of the X-GT2 belt into the X-carriage as in the second picture.

  • Press the belt all the way in, use a screwdriver or an Allen key.

  • There can be a slight belt overhang on this side, no need to trim it.

When I was doing this step, the belt teeth were slipping over each other, even without significant tension. I concluded that the “pinch points” in the printed part (the X-carriage) were not tight enough. I cut 2 small squares of thin (0.25mm), hard plastic (from the plastic wrapper from the packaging of a 9v battery), and slid them in above the overlapping belt The location is pointed to by the upper green arrow in the second picture. It stopped the slipping and it worked perfectly after that.

Kevin Gallagher - Reply

Same problem, as soon as i try to tight with the motor, it slips…:-(. I agree with Gerhard, even if after trained myself on MK2, it seems easier to use this fixing belt today, when it holds something !

Jeremy -

A sugestion for a Version MK3S or MK4: another fixing for the belt.

It was a pain to get this in in the right position.

Gerhard Kunz - Reply

mk3.jpeg No problem here

Valentin Bulbuc - Reply

Using right hand rotate the motor to its original position and hold it. 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.
  • Using right hand rotate the motor to its original position and hold it.

  • 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.

  • If you are struggling to rotate the motor back into position the belt tension is too high.

  • Depending on the belt being under or overstretched, adjust the amount of the belt in the X-carriage.

  • When done, rotate the motor to its original position and tighten the M3 screws again.

Add Comment

Both top and bottom part of the belt should be parallel (above each other). To adjust the belt position, release the screws on the pulley and move it slightly until you reach the best position.
  • Both top and bottom part of the belt should be parallel (above each other).

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

  • In case you can't make the belt parallel, check if the belt is properly inserted in the X-carriage.

  • Tighten both screws on the pulley.

If the pulley screws are not tightened really properly, it may cause a random x-axis layer shifting later, if they become loose!

Miroslav Piencak - Reply

I am having an issue with the belt touching the printed pat that holds the motor. It catches the side of the printed part away from the motor toward the rod and screw. I have tries pushing the the pulley all the way against the motor but it still will not clear the opening in the printed part as it passes through to the x-carriage. This causes the belt to tilt in toward the front side and away on the back side so it looks like a long V that does not quite connect. I was thinking I might cure this by placing washers between the printed part and the motor to give me additional shaft so I can push the pulley back far enough to clear the opening in the printed part. However, this seems likely to create additional problems later. I suppose a stiff gasket material that covers the top of the motor might be less risky, would need to search for something like that. Is there another adjustment I missed here that might cure this problem? It seems to me this may cause the belt to be unstable and wear badly if not fixed.

Harry Townsend - Reply

Solved my problem, I put the pulley on backwards…

Harry Townsend - Reply

Does the belt always seem to pull to the left or right? I have a Prusa i3 mk2 and mk3 and this happens on both the motor and idler side. I’ve tried to get it to ride in the center but it always drifts to one side or the other. Any help would be appreciated.

Ludvik Jersbek - Reply

IS there a way to accurately check if its parrallel? Is there a tool we can use?

or is it all eyeball?

Brian - Reply

Hi Brian, check the belt with your eyes, it should be enough. You can move the extruder back and forth to see, whether the belt stays parallel.

Jakub Dolezal -

Use the technique described below to test if the belt is properly stretched.
  • Use the technique described below to test if the belt is properly stretched.

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

  • Move the X-carriage towards the X-axis motor. Don't use excessive force.

  • If the belt is stretched properly, you should feel a resistance and the X-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.

  • Belt too loose? Return to step 12 and repeat all steps until now. You have to rotate the motor and retighten the belt in the X-carriage. Shortening the belt length by moving one or two teeth outside X-carriage should be enough.

Small gripe: It should say to return to step 20. Step 12 is for the new design X-carriage.

Torsten Lif - Reply

Z-axis is done! Time for another gummy bear. You still have some right? :)
  • Z-axis is done! Time for another gummy bear. You still have some right? :)

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

  • Checked everything? It's time for: 5. E-axis assembly

Add Comment

Finish Line

379 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

72,479 Reputation

132 Guides authored

20 Comments

One hour, tensioning was a bit time consuming.

Scott - Reply

35 minutes. :D

Zaz - Reply

Difficult to insert the beginning of the belt into the carriage but not the end. Some slight production variation?. Managed anyway. Looking good at this point.

Henry Casson - Reply

Up until this part, I used the printed assembly instruction - because it is easier to have a book on the work table than a computer. But the printed pictures of the black X-carriage and the black belt were impossible to see in any detail, so I had to come here. I think some sketches of the belt path would be a huge improvement.

Torsten Lif - Reply

Step 21 can be a little difficult when trying to place the loop. what i found that helped was to use one of the tie wraps, place the thin end under the top belt to help keep it up and off the bottom. this made the process go a lot quicker with less frustration. once the lower part is engaged sufficiently just remove the tie wrap and press the belt to the bottom.

Philippe Desjardins - Reply

to add to what was said before .. I think some of the black printed parts need to be either printed in a gray or painted gray so they show up better

Edward Traxler - Reply

Hi Edward, thanks for the suggestion, I appreciate it. Using different color leads often to confusion, whether the part is different or new. I will think of a way to adjust the current step, maybe reshoot the pictures.

Jakub Dolezal -

After Z-Axis finished there is material leftoverr:

4 x M3 x 10

1 x ‘M3 x 18 (missing at X-Axis)

1M3nS (missing at X-Axis)

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Werner Zoechling - Reply

The right trapezoidal nut went in after a little finagling, but I’ve spent 20 minutes trying to get the left one to fall into the nut trap(step 5). Anyone have any advice?

Albert Yu - Reply

Hi Albert, always check whether there is some obstacle in the slot preventing you from inserting the nut. You can use sharp tool to get those obstacles away, but be careful ;)

Jakub Dolezal -

use one of the smaller allan keys to go in the screw hole and push it in the hole in the nut (should manage to do that even if the nut is not in all the way). Then you can use the allan key as a lever to slide it fully in.

David Kaufmann -

Step 5 was very difficult.  Inserting the inner M3n in both X ends was problematic.  After getting the nut in I managed to cross thread the screw which allowed the nut to rotate during tightening on both X ends.  I think more detail in needed on inserting these nuts.  I have decided to continue the assembly.  Is this a good idea or should I buy a completed X Assembly?  I don’t think I could get the x rods out of the X ends.

Karl Dickens - Reply

Hi Karl, no need to buy the axis preassembled. Finish the assembly and see how the printer performs. I think rotating M3n won't be an issue. You can print new X-ends yourself, if needed. Removing the rod is possible, but it takes certain force.

Jakub Dolezal -

1.5 hours just on step 5. The design is flawed.

Oh another 20 minutes trying to get my Trapezoidal but to wind back down the lead screw. Gave up and having a replacement sent out. I was ready to bin the kit

Stephen York - Reply

I have 2 printed conical washers left after assembly. These were in bag 4. Didn't see anything in the process to use these. Did I miss something?

Adam - Reply

It’s easy to miss, they are used in step 3. You remove the trapezoidal nuts and then immediately spin the cones down the lead screws until they are next to the motors. They really should make those orange instead of black to make it easier to tell what’s going on in those pictures. In the second picture they aren’t showing the trapezoidal nuts next to the motor, those are the cones.

Dave S -

I made the same mistake. Fortunately it only takes a few minutes to drop the motor and shaft and fit to them on.

DavidNutton -

Both of my Motors have the same length cables where the guide says one is longer than the other [Step 3]. Both about 560mm. Hope not a problem so I have fitted them an finished this axis.

DavidNutton - Reply

45 minutes to assemble, needed to use a thread chaser on two of the threaded holes in the frame, no problem though from experience I know that aluminum threaded holes are easy to muck up if you start the screw a little off. Once again thanks for spare kit.

Ricky Burnett - Reply

You didn’t say to save the gummybears! My gummybears where all consumed by the end of unboxing and inventory of parts! Please warn users to ration the gummy bears…Note this is just a joke, great job so far!

Luke Davis - Reply

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