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Andreas Perlitz
(@andreas-perlitz)
Member
Belt replacement

Hi there,

i recently bought a Core One Update Kit for my MK4s, assembled it and it didn't work. The printhead always bumped at the right front corner. After disassembling the printhead, checking the belt and fighting with the belt tensioners, i broke one of them and now i have to order a replacement for this to give it another try. While ordering i thought, it would be a good idea to order also a replacement belt, since it is so short dimensioned that i really have the fear that i will break it by accident. But i could not find a replacement belt for the core one in the shop. Where could i get one? I don't want any used belts or something similar to the belt, but i want the original belt to be sure that future print failures are not based on the wrong parts in the printer. It would be really great, if anybody could tell me where i can get an original belt for the Prusa Core One or give me the exact metrics i have to search for to find a useful replacemant.

kind regards

Andi

Posted : 11/08/2025 12:07 pm
SgtCaffran
(@sgtcaffran)
Estimable Member
RE: Belt replacement

I don't think you really need a replacement belt until you printed for several years...

Maybe read some user experiences and tips on how to properly build, square and tension the XY system.

Posted : 11/08/2025 5:49 pm
2 people liked
nhand42
(@nhand42)
Estimable Member
RE: Belt replacement

 

Posted by: @andreas-perlitz

i recently bought a Core One Update Kit for my MK4s, assembled it and it didn't work. The printhead always bumped at the right front corner. After disassembling the printhead, checking the belt and fighting with the belt tensioners, i broke one of them and now i have to order a replacement for this to give it another try. While ordering i thought, it would be a good idea to order also a replacement belt, since it is so short dimensioned that i really have the fear that i will break it by accident. But i could not find a replacement belt for the core one in the shop. Where could i get one? I don't want any used belts or something similar to the belt, but i want the original belt to be sure that future print failures are not based on the wrong parts in the printer. It would be really great, if anybody could tell me where i can get an original belt for the Prusa Core One or give me the exact metrics i have to search for to find a useful replacemant.

The belts are near indestructible but I agree it is odd they don't sell replacement Core One belts on the store. 

It should be 6mm 2GT belt same as other Prusa printers. You could buy a Prusa XL belt and cut it to length.

Posted : 12/08/2025 10:56 am
1 people liked
newprinter
(@newprinter)
Active Member
RE: Belt replacement

Have you tried reaching out to support? Surely they'll sort you out

Posted : 18/08/2025 10:41 am
Andreas Perlitz
(@andreas-perlitz)
Member
Topic starter answered:
RE: Belt replacement

Thanks for the hints and tips. Meanwhile I got my belt tensioner replacement from Prusa and will dive into the reassembly in the next days. I managed to reconnect the belts, but they are so exactly cut to length, that there is no room for failure when fixing them to the nextruder. So i ordered a belt from amazon with the specifiactions you gave me. Thanks a lot for this 🙂 The belt will be my fallback, if my assembly fails and I have to adjust the belts or have to disassemble the nextruder again. It is really a pita to fix the belts to the nextruder. But I am looking happyli forward to have my Core One running within the next days.

Posted : 18/08/2025 12:40 pm
SgtCaffran
(@sgtcaffran)
Estimable Member
RE: Belt replacement

Just disconnect the tensioners and you can easily place the belt ends in the Nextruder carriage. Make sure to leave the same amount of teeth sticking out for the best result. I have five teeth sticking out for each belt end.

Posted : 19/08/2025 12:55 pm
Jürgen
(@jurgen-7)
Noble Member
RE: Belt replacement
Posted by: @sgtcaffran

Make sure to leave the same amount of teeth sticking out for the best result. I have five teeth sticking out for each belt end.

I still think that's superstition. As long as you clamp enough teeth to hold the belts securely, how is the printer ever going to know whether you have clamped five teeth left and right, vs. four on the left, six on the right? Or whether you have clamped two teeth less for the lower belt and then compensated that via the belt tensioners?   

Posted : 20/08/2025 11:38 am
2 people liked
Andreas Perlitz
(@andreas-perlitz)
Member
Topic starter answered:
RE: Belt replacement

Just disconnect the tensioners and you can easily place the belt ends in the Nextruder carriage. Make sure to leave the same amount of teeth sticking out for the best result. I have five teeth sticking out for each belt end.

I think, this would have been a really good idea, if I had it, when trying to fiddle the short tails of the belts in the beltclamp. A hint in the documents to do this would have been also helpful. When I need to redo the beltfixing, I hope I can remember this hint. Thanks for this 🙂

 

Meanwhile I have everything connected, the calibration went nearly through and I stumbled at the next hurdle: As said before, I bought the Update-Kit for the MK4S. So far everything is running, except for the filament sensor. Reason: my MK4S had a MMU3 unit and the nextruder has therefore no filament sensor. I was not aware of this until I remembered, that I had to rework the whole extruder when updating my MK4S with the MMU3 unit. So the wait continues. Now I need the MMU3 Update Kit for the Core One, which has a delivery time from 5 to 6 weeks. Thanks for the hints. I will continue my setup when the parts arrive.

Posted : 20/08/2025 12:22 pm
Mercur12
(@mercur12)
Trusted Member
RE: Belt replacement

Hi Andreas,

if you want to use your MMU3 on the Core One also, you need no extra parts for the nextruder.  Use your Idler Lever, Heatsink assembly, PG-Assembly, Idler-swivel and so on as before. The only parts to change are the nextruder spacer and the Fitting (now M5-4).

Any questions. Just contact me...

Posted : 01/09/2025 5:36 pm
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