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

  • 3mm Allen key for M5 screws

  • 2.5mm Allen key for M3 screws

  • 2mm Allen key for nut alignment

Add Comment

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

  • Aluminum extrusions (4x)

  • Aluminum frame (1x)

  • M5x16r screw (16x)

The M5x16 screws are labeled as “M5x16r” on the “2. Y-AXIS” pack, the name on this instruction should probably be updated to match what the pack says.

Kevin Gallagher - Reply

Hi Kevin, thank you. Information updated.

Jakub Dolezal -

The inner smaller bag is labeled 3/2. Y-Axis MK3.

Neal Tibrewala - Reply

What type of extrusion are used? V-Slot 2020?

Googliola - Reply

Hi, we are using aluminum extrusions PAR-HWR-MK3-3030

Jakub Dolezal -

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

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

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

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

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

I see there’s no mention of locking washer, is this because theres no perceived need/cost savings, or? I would assume that the frame and bolts are subject to vibration and would need after tightening over time?

Robert Hooper - Reply

I assume there will be issues with vibration over time. I used loctite blue (removeable) for structural metal/metal connections.

Steven Underwood -

Hi Robert, I discussed this with devs some time ago and according to our tests, it was ok. You can recheck them each time doing maintenance, but it should be ok.

Jakub Dolezal -

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

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

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

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

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

looks actually easier if you swapped steps 3 n 4 because the long extrusions interfere the allen key of the closer M5 screws on the short extrusions when tightening them,….

Alex Tutusaus - Reply

Hi Alex,

We've tested several approaches, but thanks for the feedback. I will recheck it again.

Jakub Dolezal -

Better to pitch the allen wrenches all together and get a quality set of hex screw drivers.

Murray Foster - Reply

Any guidance from the devs on torque settings on the screws?

Martin Stoufer - Reply

Hi Martin, no torque is defined for the tightening. I will talk to the devs.

Jakub Dolezal -

Thanks Jakub. I’ve seen a few posts across the forum from wrench heads like myself that would feel better with points of assembly that did call for specific torque settings on bolts/screws. This could even be a range of min torque (enough to seat the bolt) and max (bolt will break, material will strip) From that we can start to get a better idea on how much “a quarter turn after seating” really means. Keep up the great work, we are all pulling for you!

Martin Stoufer - Reply

Thanks Martin ;)

Jakub Dolezal -

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

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

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

Would make sense to me to do step #11 now (anti-vibration feet) BEFORE adding the end pieces.

Mike Womer - Reply

Hi Mike, it is not possible as you need to check the geometry first.

Jakub Dolezal -

Prepare following parts to assemble the front and rear plates:
  • Prepare following parts to assemble the front and rear plates:

  • Front plate (1x)

  • Rear plate (1x)

  • M5x16 screw (16x)

It would be nice if this also mentioned the PSU holders needed in step 8

Ryan Peters - Reply

Hi Ryan, thanks for the suggestion ;)

Jakub Dolezal -

Same thing as in step 2, the M5x16 screws are labelled M5x16r.

Martin Masson - Reply

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

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

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

I used the included filament box placed on the extrusions near the back plate. This helped keep the back down while tightening the front. Helped keep the frame flat. Could include it as a tip.

Joe V - Reply

For all metal on metal joints (screws into metal) I would recommend blue (removable) locktite thread locker.

Jim O'Keane - Reply

This is very IMPORTANT step! Incorrect placement of PSU holders will lead to issues later. Take the YZ frame and rotate it with the shorter extrusions towards you. Find the PSU holders (M3nE) in the package (2x).
  • This is very IMPORTANT step! Incorrect placement of PSU holders will lead to issues later.

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

  • Find the PSU holders (M3nE) in the package (2x).

  • Place the PSU holders in the extrusion, ensure it is the correct one.

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

If you use t-nuts instead slot nut it doesn’t matter if you miss the PSU holders now.

Heiko Schultz - Reply

Hi Heiko, slot nuts were chosen by our devs for certain reasons, but I will forward to them your suggestion ;)

Jakub Dolezal -

The PSU holder is part M3nE

Brandon Oprendek - Reply

Brandon you're right, description updated.

Jakub Dolezal -

My two single PSU holders are physically different from each other in the sense that the screw head beds in the threaded openings, on the outer side, are different in diameter / depth. I cannot tell now whether this matters. It would be good to provide instructions which one goes in first, if that matters.

Stephan Kyutchukov - Reply

Hi Stephan, both PSU holders should be the same. Please check you can insert screw M3x10 in both.

Jakub Dolezal -

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

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

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

Make sure you have enough M5x16 screws. I was shorted 4 screws and had to use all of the available spares.

Paul Betz - Reply

Hi Paul, thank you for the feedback. I will forward this to the production team.

Jakub Dolezal -

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

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

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

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

Im having a problem with step 10. Place it on glass surface and there is about 0.5mm gap uneven between the 2 legs (if you look at 1st the image, leg at the long extrusion nearest from you and the leg at the short extrusion furthest from you). Spent one hours unscrew and screw everything back. but as long as Im tightening the screws, the gap is there. Loosen the screws a bit and the gap show up again…. tried all different ways from swapt left right turn the extrusions around still have the same gap at the same location. Have been google, watched youtube, check forums… seems like not only me but many struggling with this… Hopes you guys should given clearer guidance…eg… if not better design then should there are any tolerance….Spent over 4 hours screw and unscrew without any success

Bill D - Reply

I had similar problems. It’s really tricky to get it perfect. As soon as you tighten the last screw, things are out of whack again. Also, there are surprisingly many surfaces in the house which are NOT actually as flat as you think. Not even all glass.

If you want to know whether a surface is flat, do the wiggle test and then turn the printer 90 degrees, then repeat the wiggle test. If it wiggles more or less after turning then you know that the surface isn’t flat. No point in using that surface since you will not get a straight frame.

In the end I approved a 0.5mm wiggle and we will see if it smoothens out in the auto calibration .

Jos - Reply

I have the same problem. Unfortunately, after loosening and re-tightening the screws about five times (and even turning around some extrusions to see if that might help), I now have a stripped screw (please, please, switch to Torx, Prusa). I’m actually now worse off than I was at the beginning, with more wiggle than initially, but I’m afraid to retry, since I don’t want to strip more screws… I’ll just have to hope it’s good enough.

Lukas - Reply

Tried this on 3 printers using a perfectly flat surface.

There is always a wobble from the front right to the back left. All 3 printers do this.

When screws are loose there is no wobble

Only way I could fix is to expand the screw holes from 5mm to 5.5mm using a drill

Tom - Reply

For clarity, wich screw holes do you mean? The ones in the center frame or the ones in the front and back plates? Haven’t ordered a printer yet, but I want to make sure I know what I’m getting myself into ;-)

Koen -

Front- right to back-left wobbling here also. Normally the front right corner is up in the air. Loosened and retightened all screws multiple times in different order, the result is always the same.

Attila - Reply

Well, after spending more hours than I wanted, trying to figure out what was happening, I had help from support and ended up identifying the problem. Not solving it yet, but identifying it. Remove all extrusions and put them laying on the flat table, check if they rock (rotate them on all 4 sides), if so, you have a bent extrusion. If they don't, move on to the next test, put them standing up on the flat surface, check if they rock, there was one of mine that was rocking a lot while vertical. Smooth sanding with a 1200 grit sand paper revealed a small imperfection, something like a burr on the top of the long extrusion. I was happy at this point, reassembled everything, still out of geometry. Last, I did the rock check with the front plate and it is really bent. They are providing a replacement. Prusa support is awesome.

Giacomo - Reply

Also, one thing that helped me very much was having the frame supported by two woodblocks ( be sure the blocks are the same height ) underneath the extrusions, so I could check if the problem was there before attaching the front plate or not. And that way I could see that it was pretty spot on without the plate and once I tightened just a tiny bit of the plate bolts it would twist the assembly, thus identifying the defective part. I hope it helps you guys out. It was frustrating.

Giacomo -

Since this step is so tricky, I’d recommend modifying the previous instructions to advise against tightening at all. Just take the screws up until flush. Then tighten all of them on a glass surface at this step. I could not get mine perfectly square on a glass table either. I hope a little wobble is OK, if I have to, I’ll just stick a piece of masking tape under a leg.

Ryan Sealy - Reply

Since this step is so tricky, I’d recommend you modify the steps above to not tighten the screws at all. Just make them flush and tighten them all at this step. I couldn’t get mine perfectly square either. I hope a little wiggle is OK. I’ll use a piece of masking tape if I have to.

Ryan Sealy - Reply

I too have had this problem. As soon as the final screws were tightened the frame would then wobble with a 1mm gap.

After much swapping around and many, many tries, I found that reversing the front plate cured the problem. Almost suggesting that either this or the the rear plate were not completely flat but, without a surface plate, I cannot confirm that.

Anyway maybe his will help someone else. Wasted 4 hours on this step.

Neale Brodie - Reply

I too had this problem and no matter what I loosened and tightened I always ended up with a 1mm gap on one diagonal. I checked the extrusions for squareness and the frames for flatness but couldn’t make sense.

In the frustration of many assemblies and dissassemblies, I eventually found by reversing the front plate the problem dissappeared. The plate looked perfectly flat but it wouldn’t take much more than the slightest twist to cause the problem.

Hope thsi helps

Neale Brodie - Reply

Same issue as everyone else (front right, rear left diagonal wobble). Tried reversing front and rear plates and flipping a few of the rails… no luck. No matter what I try, I can’t get rid of the wobble (no obvious defects on front or rear plate when checking for rocking). Engaging support.

D Wellnitz - Reply

I had this problem too, rocking front right-back left. After slacking off, and re-tightening a number of times without removing the wobble completely, I found this process to work,

Loosen all screw and make just finger tight. Place the smallest Allen key under the front left, clamp ( with gentle pressure!) the back left. Apply a weight to the front right. Tighten all screws as previously described. Result =no wobble.

Paul - Reply

Same problem here. Tried several times to loosen screws and retighten, but could not completely remove the wobble. Tried this and found it to work.

Loosen all screws and make finger tight. Place the smallest Allen key under the front left. Clamp (with gentle pressure!) the rear left to your work bench. Place a weight on the front right. Tighten screws as previously described. Result - no wobble.

Paul - Reply

+1 to @frostie (Paul’s) approach. It probably varies printer to printer, but I started with the smallest allen key and found that was enough to reduce, but not remove the wobble. I ended up working my way up to the second largest allen key along with a 35lbs weight. There is still a _very_ slight wobble, but it’s down to .1mm or less (less than a sheet of paper) from ~1mm or more.

D Wellnitz - Reply

I am having the same problem. I’ve tried Pauls approach and that has removed some of the rocking, from about 8 sheets of paper to now 4 but its quite a lot still!

Alistair - Reply

Hi Alistair, in case you can't reach straight frame without significant movements, please contact our support at info@prusa3d.com.

Jakub Dolezal -

And where is Prusa's support ???

Joaquin Villar - Reply

Hi Joaquin, depends on your needs. If you have a problem with the instructions I'm here. In case of faulty parts, please contact our support info@prusa3d.com or by live chat on our eshop.

Jakub Dolezal -

Also had the same problem. wobbled around 2-3 pages.

Did as Paul describe above with the smallest allen key and used clamps with a light pressure to hold left back and front right down on the aluminium extrusions worked perfectly no wobble at all . thanks for the tip Paul

Mattias - Reply

I had the same problem and used Paul’s trick to get the wobble down now to only about 2 pages of paper on a Flattish surface.

It would be extremely helpful to know specifically:

What is the tolerance of this and to what extent will calibration correct for this? Shall I continue building now that I have only 2 pages of wobble or should I invest another 4 hours into getting it perfect. Frankly, on a glass top surface at home when I rotate 90 degrees the wobble goes away (indicating to me that even the flattest surface in my house isn’t actually 100% flat.

Andreas Sjolund - Reply

10mn step, become 1h30 step….1 star…Thanks Paul ;-)

Jeremy - Reply

Note this step is optional for now. We recommend mounting the feet to protect the surface on your table (working bench). However, you need to lift the frame up before each turn. There will be extra step at the end of the assembly to remind you of the antivibration feet. Antivibration feet (4x)
  • Note this step is optional for now. We recommend mounting the feet to protect the surface on your table (working bench). However, you need to lift the frame up before each turn.

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

  • Antivibration feet (4x)

  • Turn the YZ frame on the side and insert the antivibration foot inclined, then rotate the foot until you squish the rim inside the extrusion.

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

I found that using hot melt glue holds the feet well. I saw on several you tube videos that they came off a lot during the build.

James Zimmerman - Reply

I used hot melt glue on the feet and it holds well. I saw on several You Tube videos they came off during the build a lot.

James Zimmerman - Reply

Hi James, the feet come off only if you try to turn the printer without lifting it up first. The friction between the table and each foot is simply to big.

Jakub Dolezal -

ATTENTION: Starting 01/2018 Y-holder-front and Y-holder-back parts are replaced by Y-rod-holder, which has the same shape for all 4 pieces. Please see the second picture. Nut insertion and tightening procedure remains the same. For the following steps, please prepare:
  • ATTENTION: Starting 01/2018 Y-holder-front and Y-holder-back parts are replaced by Y-rod-holder, which has the same shape for all 4 pieces. Please see the second picture. Nut insertion and tightening procedure remains the same.

  • For the following steps, please prepare:

  • Y-holder-front (2x)

  • Y-holder-back (2x)

  • M3x10 screw (8x)

  • M3nS nut (8x)

So is the new “Y-rod-holder” the same part as the old “Y-holder-front”? I could not find the “Y-rod-holder” part on GitHub.

Christoph Stahl - Reply

Take the Y-holder-front and insert M3nS nuts. Make sure you've pressed the nuts all the way in. In case you can't press the nuts in, don't use excessive force. First, check if there isn't any obstacle in the nut trap.
  • Take the Y-holder-front and insert M3nS nuts.

  • Make sure you've pressed the nuts all the way in.

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

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

  • Repeat this step for the remaining Y-holders. At the end, you should have two pairs, front and back.

Take the scewdriver to push it in

Muck - Reply

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

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

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

  • Second, take the Y-holder-back parts and secure them with M3x10 screws on the rear plate (with shorter extrusions). Tighten both screws equally, but not completely. We will tighten them fully later on.

For me the Y-Holders do not fit on top of the long extrusions. I seem to have the “new” version where all 4 are the same. I had to sand the bottom down in order to reach the screws.

Peter - Reply

I just received my Kit yesterday and I seem to have the new pieces. They all fit fine for me. Sorry Peter!

Andreas Sjolund - Reply

Yup they worked for me also.

Donnell - Reply

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

  • Y-belt-idler (1x)

  • M3x18 screw (1x)

  • M3x10 screw (2x)

  • M3 nyloc nut (3x)

  • 623h bearing housing (1x)

Add Comment

Take the Y-belt-idler and insert two M3 nyloc nuts from the  top. The rubber inside nuts must be facing up. Turn the idler to the other side and insert the last M3 nyloc nut. The rubber inside the nut must be facing towards you.
  • Take the Y-belt-idler and insert two M3 nyloc nuts from the top. The rubber inside nuts must be facing up.

  • Turn the idler to the other side and insert the last M3 nyloc nut. The rubber inside the nut must be facing towards you.

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

I’d suggest modifying this step to make it clear that the nyloc nuts should be pushed as far into the idler as possible; without them at full depth, the bolts installed in step 18 don’t have enough range to make a useful tension adjustment once you get to step 36.

Kenneth Albanowski - Reply

Hi Kenneth,

Thanks for the suggestions, I have a general update regarding the nut insertion in mind.

Jakub Dolezal -

i used another similar bolt to help pull in it (probably should’ve had a washer, but didn’t tighten it down)

Jonathan - Reply

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

  • Bearing housing orientation doesn't matter.

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

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

The bolt could stand to be a bit longer. Mine just barely engages the nylock insert. I added a bit of blue Loctite to play it safe.

Scott - Reply

Hi Scott, please check there is nothing blocking the bolt. I've assembled several MK3 printers and it was always about some small pieces of PETG left in the hole.

Jakub Dolezal -

18mm is OK for me

Petr Navrátil -

Agreed. I swapped the 18mm length M3 screw with a 20mm.

18mm is just too short, and 20 is the perfect length.

Patrick Crawford - Reply

Hi Patrick, 18 mm should be enough, please see my comment to Scott (above yours).

Jakub Dolezal -

I agree with Patrick and Scott. The bolt is a bit too short. It doesn’t properly touch the nylock inset and there is nothing blocking the holes.

Guntor H - Reply

Hi Guntor, thanks for the feedback, the 18mm screw should be enough, but I will check it with my colleagues, who are assembling printers.

Jakub Dolezal -

18mm is enough here for me!

Christoph Stahl - Reply

It worked perfectly for me with 18mm screw!

Christoph Stahl - Reply

18 was fine for me, but you need to make sure the nuts are seated all the way down as far as they can go. This turned out to be a bit tricky. In once instance I used a screwdrivers to push the nut in. In another case I used another screw to pull it into place (which is suggested actually in a previous instruction).

Andreas Sjolund - Reply

Rotate the frame with longer extrusions towards you. Take the Y-belt-idler and place it on the front plate. Note there is a mark (circle) on the printed part facing up.
  • Rotate the frame with longer extrusions towards you.

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

  • Secure the Y-belt-idler with two M3x10 screws.

  • DON'T TIGHTEN the screws fully, you will need a "loose" Y-belt-idler to adjust the tension in the belt later on.

I’m not really sure what the red circle with the X in the last picture is suppose to mean but it makes it seem like the circle facing up is wrong. Maybe just putting a arrow pointing at the circle on the part would be better.

Paul Betz - Reply

Hi Paul, the red circle is connected with red text in the description. I've made adjustments to the picture. It is it understandable now? Point is, you shouldn't tighten the screws fully as you need them to adjust the position of the idler later on.

Jakub Dolezal -

Yeah last pic makes no sense!!

Alex Tutusaus - Reply

Hi Alex, picture adjusted. Please let me know, if it is understandable now. Thanks

Jakub Dolezal -

Sorry I was a bit confused also by the last picture. Here are some suggestions which may make it more clear.

1. Maybe add some rotation lines to the pic indicating that you are discussing the tightening.

2. Make sure the red color in the picture is the same color as the red text that goes along with it. In this case the colors seem to be slightly off so I didn’t associate the arrow with the text at all.

3. If possible, reserve the color red for really important information and use a different color for the steps.

Andreas Sjolund - Reply

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

  • Y-axis motor (1x)

  • Y-motor-holder (1x)

  • M3x10 screw (4x)

  • M3n nut (2x)

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

Add Comment

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

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

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

  • Using two M3x10 screws tighten holder and motor together.

I think that the motor mount is a high vibration point why aren’t we using m3nN M3 nyloc nut instead of the m3n nuts it would make more sens,we are installing the m3nN nuts on the y axis idler holder but not on the motor mount . is there a reason ?

Marc Dumoulin - Reply

Hi Marc, thanks for the suggestion. I will talk to the devs.

Jakub Dolezal -

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

  • Ensure correct orientation, the motor shaft must be facing towards PSU holders.

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

The motor mount breaks easily, so be careful!

Jørgen Stokke - Reply

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

  • Y-carriage (1x)

  • Y-belt-holder (1x)

  • U-bolt (3x)

  • Linear bearing (3x)

  • Nyloc nut (6x)

  • M3x10 screw (2x)

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

I think you should add 2. Y-axis assembly Step 14 Correct bearing orientation from the Original Prusa i3 MK2S kit assembly v2.05 instructions.

Waldemar - Reply

Hi Waldemar, thanks for the suggestion. I will confirm this with devs and make adjustment if necessary.

Jakub Dolezal -

Missing 2 Nyloc nuts. Opened spares.

David Wilbanks - Reply

Might want to specify the screws are M3x10.

Bruce Moore - Reply

Bruce, thanks for noticing. Description updated.

Jakub Dolezal -

few balls (3-4) fell of the bag when unpacking one bearing. Still slides on the rail when I tested. Using it anyways.

Juraj Mr. - Reply

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

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

It would be helpful to explain what is meant with ‘orientation’ in this case. First time builders like me only discover what is meant here when assembling the X-Axis step 3 as that step contains a drawing of this bearing. I thinnk it would be beneficial to have that drawing inserted here too.

Jeroen - Reply

It would be helpful to know what is meant by “track”.

JC Wren - Reply

Looking ahead to X-axis step 3 as suggested by @jeroen helped me figure this out, I think. Notice that in the picture there are rows of ball bearings inside, that are facing straight down. I am thinking we will want to mount one with the ball bearings straight down and one with them rotate 45 degrees?

Graham McIntyre -

Jeroen (@jeroen), JC Wren (@jcwren) and Graham (@grahamm78) by the track is meant row of balls inside the bearing casing, step description was updated. For the Y-axis please use same rotation for all the bearings, do not turn them 45°.

Jakub Dolezal - Reply

If you look closely inside the bearing you will see the row of tiny balls is not straight all the way to the ends. At the ends the row of balls bends slightly making it look like a broad grin. I “think” what this instruction is telling us it that the grin all needs to be in the same direction on all 3 bearings when they are mounted on the Y Carriage. Is this correct?

Andreas Sjolund - Reply

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

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

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

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

  • Tighten the nuts, BUT ENSURE both nuts are tightened equally and AS SOON AS YOU REACH THE SURFACE STOP TIGHTENING!!!

  • Repeat these steps for the remaining two linear bearings.

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

The MK2 assembly instruction tells to align the bearings in a special position.

http://manual.prusa3d.com/Guide/embed/29...

Step 14

doesn‘t matter anymore?

Heiko Schultz - Reply

Hi Heiko, you can use the “special position”, it will be added to this manual shortly.

Jakub Dolezal -

Does the countersunck marker facing down no longer matter? I see in the pictures from the next step you have it facing down, so I am doing that. (Since you say orientation does not matter, I suppose that is explicit, but since the the holes in the middle of the carriage are asymmetric left/right, it is confusing. I’m assuming those holes are no longer used.

Paul Meyer - Reply

Hi Paul, looks like you've missed our information at step 22: “For MK2/s owners, the Y-carriage is now symmetrical in one direction, therefore the dot (countersink, marker) orientation for bearing insertion doesn't matter.”

Jakub Dolezal -

The bearings don’t glide easily on the tracks. They sound like metal rubbing against metal and catch a little. All three bearings do this. I noticed this before I tightened up the U-bolts. Is this normal?

Ken Ondo - Reply

Hi Ken, try again step 30 and let me know ;)

Jakub Dolezal -

I used a 7/32 racheting (72 tooth) socket wrench, tightening a quarter turn until they touched the surface, looked at the arch, and made sure it was even. Then I double checked that the bearing is exactly in the center before another quarter turn to tighten the bearing down. Also… I think the IGUS part RJZM-02-08 is a worthy upgrade. :)

Mr Cookie - Reply

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

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

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

  • Repeat these steps for remaining two linear bearings.

There was a suggestion in the forums, to not tighten the bearings until after you’ve inserted the smooth rods in order to ensure aligned bearings. Is this a good idea?

Zaz - Reply

Hi Zaz, if you align the bearings using the cutouts in the Y-carriage you should be fine, you can do visual check as well. I've assembled several printers using the manual and all were fine with no need to readjust the bearings.

Jakub Dolezal -

This Tool for the nuts is very bad to handle

Muck - Reply

Maybe use the “correct” tool to tighten the nut? Pliers is Not that tool ;)

List the Nut spanner size in the manual.

Roger Meldal - Reply

I wrote it in another reply, 72 tooth rachet, with 7/32 inch socket. I tightened by 45 degrees, side to side, to be safe.

Mr Cookie -

I think you should add how many newtons you can tighten the u bolt since some people have access to tork wrench and as a work injurd I get chills down my spin seeing you tighten with a plaer on the picture.

Patrick Larsson - Reply

Place the Y-belt-holder on the Y-carriage. ENSURE THE TEETH are facing TWO BEARINGS!
  • Place the Y-belt-holder on the Y-carriage. ENSURE THE TEETH are facing TWO BEARINGS!

  • Secure the Y-belt-holder with two M3x10 screws. Tighten them fully, there are threads in the Y-carriage.

Zdravím, zbyli mi dvě obyčejné matky. Nepatří sem z druhé strany? Naproti šroubům? :)

Miroslav Novotný - Reply

Zdravím Miroslave, v dílu Y-carriage jsou závity, takže nejsou potřeba. Ty dvě matky M3n jsou navíc, v dalších kitech už nejsou.

Jakub Dolezal -

the hole alignment in the y belt holder was about 1mm short

Mark Abrams - Reply

Don’t be mislead by “tighten fully”. The plastic piece breaks very easily.

Ryan Sealy - Reply

You are correct, my plastic broke a bit - but is it firm

Bozidar - Reply

Easier to just wiggle it a little to determine when it’s tight enough that it won’t move. If your worried about it still moving, maybe threadlock would be a good idea? Hmm.

Mr Cookie - Reply

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

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

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

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

The rod with two bearings wants to rotate counterclockwise several degrees each push and pull cycle. Is that normal?

RWReese - Reply

Hi RWReese, please can you make a video? Bearings should be tightened to prevent their movements, but do not overtighten them ;)

Jakub Dolezal -

how smooth Should the root move. and should the bearing have any influences or artefacts in the movement pattern

Patrick Larsson - Reply

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

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

Add Comment

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

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

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

  • Using pliers cut the remaining part.

  • Repeat this step in all four corners.

I feel like something soft could be used to keep the metal rods from banging the frame if they’re loose. Just a thought.

Mr Cookie - Reply

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

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

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

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

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

Anything I can do if the M3x10 screws on the rear plate (short extruders) holding the rear Y-holders are not tightening all the way? They are stripped and just keep rotating. The rear Y-holders wiggle a little.

Alex Wilkie - Reply

Hi Alex, are you able to release the screws and take them out? Both nuts and screws, can be replaced from spare bag if needed.

Jakub Dolezal -

it would really help if you made a video to show how much force you should use and how it should Glide

Patrick Larsson - Reply

There is a flat part on the motor shaft, rotate it upwards. Place a GT2-16 pulley on the Y-motor shaft as shown in the picture. One of the screws must be facing directly against the pad (flat part) on the shaft. Slightly tighten both screws.
  • There is a flat part on the motor shaft, rotate it upwards.

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

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

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

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

I had to flip the pulley to have the set screws toward the outside of the shaft get the best alignment

Mark Abrams - Reply

I experienced the same thing

Marcus Stenehäll - Reply

I agree. The pulley needs reversed. The pulley was all the way against the motor to align until I reversed it. I should have listened to you guys!

Ryan Matheny - Reply

Guys (@mak3r, @riddlern, @ryan_matheny) The orientation in the picture is correct, can you please take a photo from below your printer and share it here in the “Answers” section? I would like to see the whole Y-axis assembly. Thanks

Jakub Dolezal - Reply

Actually, I think it makes sense to attach the pulley as shown. It will be less prone to wobble the closer the attachment point is to the motor. I think that instead of instructing us to orient the flat part of the motor shaft facing up (since the screw wont go in straight), the more important point to make is that one of the screws should screw directly into the flat part since this is the best way to ensure no slippage.

Andreas Sjolund - Reply

Turn the frame on its "right" side, as shown in the picture. You need access to belt holder, idler and pulley. Use the bottom opening in the extrusion and gently insert the cable from Y-motor. Find the belt for Y-axis (650 mm) and insert one end in the Y-belt-holder. Ensure you are using the upper slot (closer to Y-carriage).
  • Turn the frame on its "right" side, as shown in the picture. You need access to belt holder, idler and pulley.

  • Use the bottom opening in the extrusion and gently insert the cable from Y-motor.

  • Find the belt for Y-axis (650 mm) and insert one end in the Y-belt-holder. Ensure you are using the upper slot (closer to Y-carriage).

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

Add Comment

Insert the belt through the idler as shown in the picture. Guide the belt behind Y-axis motor and ensure following: Don't use the second slot in the Y-belt-holder.
  • Insert the belt through the idler as shown in the picture.

  • Guide the belt behind Y-axis motor and ensure following:

    • Don't use the second slot in the Y-belt-holder.

    • Guide the belt above the aluminum Z frame, NOT below.

    • Guide the belt above the rear plate, NOT below.

  • Turn the printer on its "feet" and guide the belt around Y-motor.

The part “Don’t use the second slot in the Y-belt-idler” might need to be corrected. I’m assuming you mean the second slot in the Y-belt-holder, not idler.

Paul Betz - Reply

Hi Paul, you’re right. Thanks for the feedback :)

Jakub Dolezal -

Hi, the y-belt-holder part which came with my machine is way too loose on the upper slot - the belt slides out while tensioning like in step 36. I printed out a spare part - and guess what it has original the same problem ?

What was wrong with the old belt holder - the way to hold the belt with itself is simply the best solution.

Richard Rohan - Reply

Hold the Y-carriage by hand (prevent its movement) as we need to pull the belt. Ensure the idler isn't tightened completely to the front plate. Otherwise, you won't be able to adjust the tension later.
  • Hold the Y-carriage by hand (prevent its movement) as we need to pull the belt.

  • Ensure the idler isn't tightened completely to the front plate. Otherwise, you won't be able to adjust the tension later.

  • Take the end of the belt, pull the belt with a reasonable force and insert it in the Y-belt-holder. Note you don't have to use the whole length of the slot.

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

  • The belt should be stretched and not easily bent. However, the final tension will be adjusted later.

If you use 14mm (i use 16) screws for the idler on the front plate, you can take the end of your belt easy in, and you will have a lot to screw & tight later ?

Jeremy - Reply

Make sure the belt is placed in the "axis" of the printer. Both top and bottom part of the belt should be parallel (above each other). To adjust the belt position, release screws on the pulley and slightly move with it, until you reach the best position.
  • Make sure the belt is placed in the "axis" of the printer. Both top and bottom part of the belt should be parallel (above each other).

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

  • In case you can't make the belt parallel, check if the belt is properly inserted in the Y-belt-holder (below Y-carriage).

  • Tighten both screws on the pulley.

As a note, there’s no usable adjustment space in my build for alignment; the belt is against the right side of the idler pulley, the motor pulley is up against the motor, and the belts are at full depth in the holder; I had to be careful to leave a small gap between the motor pulley and the motor, it would have been very easy to accidentally tighten the pulley up right against the motor, trying to get the best alignment. (And that would be bad, because they could bind.)

To gain some space to adust, the motor mount would have to position the motor more to the left, and the idler pulley mount needs to be more to the right. These are Prusa-supplied Orange parts.

Kenneth Albanowski - Reply

To avoid eye-balling the perfect alignment I just loosened up both set screws of the motor pulley so that it would rotate freely on the shaft and moved the Y-Carriage back and forth along the full-length Y rods until the belt adjusted itself on the idler and on the motor pulley, on this side also moving the pulley with it along the shaft, as necessary. In my case the belt is flat against the idler on the opposite flange to the Y motor while the idler is also flat against the plastic part so a wider gap on the plastic part could be appropriate.

After I was satisfied with the alignment I moved the Y-carriage until one set screw came just above the motor shaft’s flat side, where I fastened it. Then I fastened the other set-screw.

Florian Ford - Reply

Really struggling to get the belt to align as its rubbing on the pulley lip close to the motor.. It seems like the motor needs to move a few mms (away from the pulley) as you the pulley hits the motor before the belt runs centrally on it.

So I have created a spacer which moves the motor 2mm… And it appears to have done the trick.

Others on teh forum have confirmed this, so I believe Prusa need to consider changing the mount to move the motor slightly, allowing more of the shaft to be useable.

For now I have made a 2mm spacer which appears to have done the trick:

ftp://jweaver.ddns.net/yaxisspacer.stl

Jon Weaver - Reply

Using Allen key tighten/release the screws on the front plate. Try to adjust both screws the same way.
  • Using Allen key tighten/release the screws on the front plate. Try to adjust both screws the same way.

  • 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.

would it be possible to know. the belt tension. and should you leave some room so that you can tighten it when it gets loose over time ?

Patrick Larsson - 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 Y-axis motor shaft.

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

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

Add Comment

Y-axis is done, great job! Open the bag with Haribo gummy bears and treat yourself with few ;)
  • Y-axis is done, great job! Open the bag with Haribo gummy bears and treat yourself with few ;)

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

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

The Y Axis feels somewhat “grainy" and requires a little force to move. Is this expected?

I've been very cautious about how I tighten everything.

Tyler Harding - Reply

No more gummy bears…:-(

Jeremy - Reply

Finish Line

121 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

47,605 Reputation

104 Guides authored

24 Comments

I am left with 2 extra M3n nuts (hexagons)

Alex Tramiel - Reply

Hi Alex, thanks for the feedback. For this chapter you need two M3n nuts to place them in the Y-motor-holder.

Jakub Dolezal -

Same here, two extra nuts.

Scott -

I also have 2 extra M3n nuts.

Brandon Oprendek -

Same here, two extra M3 standard nuts. All nuts are properly inserted in the printed parts, no screws are lacking nuts. Maybe can be put on the opposite side of the y-carriage to lock in the bolts holding the Y belt holder? Not necessary, but maybe optional?

Kaina Cockett -

Hi Kaina (@dracx), there are two extra nuts as a result of a design change. For the future kits it is already sorted out.

Jakub Dolezal -

One of the short extruders lacked threads in one of the holes.

Tried making the threads with a screw and destroyed the screw head. Had to saw off the screw and try again. Not fun.

Also, aligning it perfectly was a pain

Kenneth - Reply

Hi Kenneth, do you mean the aluminium extrusions? In case of a missing thread I doubt you can create it just with the screw. In general, if there is a faulty part, please contact our support at info@prusa3d.com.

Jakub Dolezal -

Took 3hrs on the money. Moving at a casual pace with my sons help.

Scott - Reply

45 minuets for this part.. should be good for 1 hour on estimate time frame for completion.

danbrewster - Reply

2h with reading everything very carefully.

Guntor H - Reply

Is normal a kind of friction of the rods passing through the bearings?

Peter - Reply

Hi Peter, some friction is always present, but it should be smooth and without significant resistance.

Jakub Dolezal -

90 minutes for me. Would have thought the “suggest a time” would actually work up top.

Eric Proces - Reply

80 Minutes here. Two Extra M3n nuts here as well.

Douglas Shelfoon - Reply

2 hrs and spent almost 45min just to readjust ‘on flat surface’ (Step 5), it was just moving very slightly when I tap on it and it bothers me, couldn’t fix that 100% because it’s impossible to adjust them the way the screws are aligned (step 3 and 4). I also have 2 extra M3n nuts.

Cedric Young - Reply

The frame does not perfectly align to flat surface, have verified this on 3 new printers.

The only way i could get it to stop wobbling is to expand the screw holes from 5m to 5.5.

After this it is perfectly flat.

Tom - Reply

Had the same issue with it not being perfectly flat. Instead of expanding the holes I lifted the whole frame up and tightened the screws while bending down the extrusion that had been the culprit before. Got it completely flat using that technique.

Uli

Uli Braun -

Had the same issue with alignment but instead of drilling the holes up I lifted up the whole frame and tightened the screws while pressing / bending down the extrusion that had been the culprit before. Got it completely flat after that.

Uli

Uli Braun -

@tomt, can you call out which holes you opened up? Was this for all holes that the extruded aluminum parts attach to?

Martin Stoufer - Reply

Took about an hour. Leveling to the table involved loosening screws and pressing front and back down fairly hard to level while tightening the screws. Took two people, one to hold the frame flat, the other to tighten the screws. The ‘gap’ was quite small, but I guess I’m a perfectionist. Also, had the same two screws everyone else had.

The linear bearings slide, but there’s a surprising amount of noise and resistance sliding a single linear bearing on the rod compared to my other 3d printers (Ultimaker, FlashForge). i don’t think it’ll cause the printer to not print - it’s not jamming, and I am sure the stepper motors can push through the resistance, it just “feels wrong” - but if it stays this noisy and resistant after it seems some real use, I will probably replace the linear bearings just to quiet the printer down.

Laird Popkin - Reply

Hi Laird, any news on the extra nise from lienar bearings? Mine are noisy too, but i cannot compare it to anything.

Bozidar -

Hi ! I wouldn’t describe the difficulty as ‘Moderate’ - I came home to find that my 9 year old had completed this stage without any help. It was all correct too apart from needing to tighten a few things up.

Lee Massey - Reply

Hi Lee, yes this is quite an easy chapter, I will adjust the level of difficulty.

Jakub Dolezal -

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