Original Prusa i3 MK2S is a successor to Original Prusa i3 MK2 with small hardware tweaks for easier assembly and improved reliability.

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Re-tighten the y-axis belt

Hey everyone,

I just assembled my Prusa i3 MK2s kit a few days ago and it is running not perfectly but pretty well. Nevertheless I am quite sure that the y-axis belt is not tight enough. Compared to the x-axis belt it appears to be very loose. The x-axis belt does the mentioned "bass guitar sound" when picked, but the y-axis doesn't make any sound at all.

My question is: Is there any possibility to re-tighten the belt without disassembling the whole printer? I couldn't find any tutorials or similar.

Some advice would be great!

Answered! View the answer I have this problem too

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I realize this is an older post but I had issues with the Y-axis making seemingly random slips. I spent a lot of time examining belts and looking for anything that might intermittently cause a slip. This is extra frustrating because it would print fine 90% of the time. Here's what I found (and it's so easy to fix).

If the set screw which holds the gear on the Y-axis motor is loose or missing the gear will intermittently slip. in my case it would only slip during really quick movements.

1) Loosened the lower bolt holding the Y-motor in place

2) Rotate the motor up (like a hinge) and slip the belt off

3) Spin the gear on the axle until the screw hole aligns to the flat part of the axle

4) Tighten the axle screw

5) Put the belt back on

6) Rotate the motor back in place and tighten the lower retention screw

I have pictures if anyone needs them.


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Hi Sören,

yes, you can do that quite easily, the Y-axis motor is fixed by two screws, so:

1) release the bottom one and create "a hinge"

2) rotate the motor towards the centre to loosen the belt

3) adjust the belt in the Y-belt-holder part

4) rotate the motor back (don't tighten)

5) check the tension in the belt

6) Is it ok? Yes? Proceed. No? Go to point 3

7) Tighten the motor

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Thanks alot!


You are welcome ;)


These directions are right on.

Set screws were missing on my MK2 Y axis drive motor but I did not notice, causing random slipping. Replaced setscrews and tightened Y axis drive belt as explained above.

Note to Prusia QC - some Loctite on the setscrews might prevent this - seems to happen to others also.

Thanks for posting - very helpful.

Jack E


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I had a loose belt and did as Jakub suggested, it worked well.

Loosen the bottom bolt on the motor. Turn the motor to loosen belt. Tighten the belt by pulling a side out under the carriage and then tightening a few "steps of gears" before putting it back. Then pull the motor back and tighten the bolt again. Done!

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Hi Charlie, great to hear it worked for you ;)


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Sören Intemann will be eternally grateful.
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