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6.4.1 Beta Firmware for the Prusa XL  

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Jan Kratochvíl
(@jan-kratochvil)
Member Admin
6.4.1 Beta Firmware for the Prusa XL

Summary

  • Improved phase stepping calibration
  • Fixed homing issues with no tool picked
  • Fixed toolchanger service moves being affected by user feedrate override
  • Relaxed nozzle cleaning checks to prevent false nozzle cleaning failed errors
  • Relaxed print fan selftest thresholds to reduce false failures
  • Known issue - Power panic resulting in a BSOD

This is the beta release of firmware 6.4.1 for the Prusa XL, bringing targeted stability improvements and fixes — most notably addressing several homing and toolchanging reliability issues.

Improved phase stepping calibration

The switch to the new universal phase stepping calibration in the 6.4 release caused a regression in the calibration quality for some XL users. The calibration method has been tuned to mitigate these issues.

Release notes

https://github.com/prusa3d/Prusa-Firmware-Buddy/releases/tag/v6.4.1-beta

Fixed homing issues with no tool picked

Homing without a tool picked could cause audible motor skipping or put the printer into an invalid state under certain conditions. The fix ensures that the axes are properly homed before attempting a tool pick, preventing both issues.

Fixed toolchanger service moves being affected by user feedrate

Tool parking, picking, and alignment moves could be slowed down if a low feedrate was set in G-code beforehand. This could lead to unreliable tool changes. All toolchanger service moves now run at their intended speeds regardless of the user feedrate setting.

Relaxed print fan selftest thresholds to reduce false failures

The print fan selftest could incorrectly report a failure on some units due to tight RPM thresholds that did not account for normal fan-to-fan variation across different fan shroud revisions. The thresholds have been relaxed to reduce false failures.

Posted : 04/03/2026 6:08 am
Nagoya kogei
(@nagoya-kogei)
Member
RE: 6.4.1 Beta Firmware for the Prusa XL

Hi, I updated from 6.2.6 to this beta version, but I'm getting an error during phase-step calibration.

The first problem is that if you run phase-step calibration alone, it will start operation without picking up a tool.

Until now, the tool would always be picked up and calibration would start.

I have confirmed that if I run phase-step calibration with tool (T1) attached, it completes successfully without any errors.

Please check that it works properly.

Posted : 06/03/2026 9:42 am
adesir
(@adesir)
Honorable Member
RE: 6.4.1 Beta Firmware for the Prusa XL

https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/5147

Mes modeles publics
Posted : 06/03/2026 2:26 pm
mgantner
(@mgantner)
Eminent Member
RE: 6.4.1 Beta Firmware for the Prusa XL

6.4 cost me a lot of filament and many multiday print failures. I've lost confidence. I think I'll just remain one release firmware behind at all times. Took way too long to admit 6.4 was a problem.

Posted : 06/03/2026 2:57 pm
JavaBean
(@javabean)
Member
RE: 6.4.1 Beta Firmware for the Prusa XL

one of the problems with them admitting 6.4 was a problem is that many people had no issues with 6.4.  i myself have done several multi-day, multi-tool prints on 2 different xl's both running the 6.4 release.  at this time i have no reason to revert, 6.4 is stable for me.  and many others as well

Posted : 06/03/2026 4:35 pm
BullDog8484
(@bulldog8484)
Active Member
RE: 6.4.1 Beta Firmware for the Prusa XL

So, yeah, of my two XL's, one was completely stable on 6.4.0.  The other had intermittent toolhead crash and homing issues.  Rolling back to 6.2.6 fixed everything.  But I'm now testing 6.4.1 on the problem machine and so far, it's rock solid, and quieter than 6.4.0 was.  I'm not 100% confident, but I'll move to some small production runs to stress it.  6.2.6 is on hot standby just in case.

Posted : 07/03/2026 9:45 am
ErikSimon
(@eriksimon)
Member
RE: 6.4.1 Beta Firmware for the Prusa XL

I installed it to try out, the printer is atleast not trying to break itself apart like on the 6.4.0. However it still won't even get passed the probing. Neither 6.4.0 or 6.4.1 is able to complete the probing. I've tried both dimonback nozzle, Obxidian, Prsua XL PA bed and Prusa xl Satin bed.

I'm going back to 6.2.6.

Posted : 07/03/2026 7:38 pm
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