Prusa Research a.s.
Prusa Research a.s.

1. Belt tensioning

Step 1 of 17 (Chapter 12 of 13)
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This chapter will guide you through calibrating and preparing the printer for its first run. Starting with tensioning the belts:
⬢The left screw adjusts the upper belt.
⬢The right screw adjusts the lower belt.
⬢Double-check that the M3x30 screws in the belt tensioners were lubricated during assembly.
WARNING: Incorrect procedure may result in damage to plastic parts or seizing of screws. Before adjusting the belt tension, read the dedicated article:
⬢Adjusting belt tension (CORE One)
Do not forget to come back here after adjusting the belts.

Contents

Prusa CORE One conversion kit (1.0)

Comments

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OnlyCurves
•
The “adjust belt tension core one” is a hyper link to
https://help.prusa3d.com/article/adjusting-belt-tension-core-one-l-core-one_845048

I know there is led enabled belt tuning in the firmware but I’ve got it roughly right here so there is some tension in the belts, before it starts up. And will find tune after boot, and after first run.
(The is this second coreone I’ve worked on!)
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Slayreman
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Finished this upgrade Feb-2026. The current firmware (6.4) would not detect the changeover to Core One correctly. In the end to fix this, I flashed (downgraded) MK4S firmware version 6.2.6 which finally detected the Core One changes, and once it switched over, i was able to load the most recent version of Core One firmware (6.4). You may also have to disconnect the door sensor and Buddy Board extension jumper cable to bypass error messages. Hope that helps someone. It cost me hours of trouble shooting.
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NiteMarmot
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Prusa, please update this guide to take the built-in belt tuning wizard into account. Right now it asks us to do belt tuning before we even turned the printer on and flashed the firmware. Thanks!
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Kivroth
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Oh man, I was so confused about this. Took me far to long to check out the comments. Glad I wasn't the only one.
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J4N
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We don't have even flashed the firmware, power on the printer, that we are supposed to tune the belt, using a core one firmware feature?
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NiteMarmot
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I'm in the same predicament. What did you end up doing?
My belts are completely loose, so I'm thinking to tighten them a bit and continue with firmware flashing, and afterwards running the built in wizard.
I suppose I will have to skip the self test, as that relies on the belts being correctly tuned(?). Anyway, wish this part of the guide was updated to take into account the belt tuning wizard.
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crn
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This step should be moved to the coreXY part where printer is not fully assembled.
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