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3.12.0-RC1 Firmware for MK2.5 and MK2.5S  

Same Old Shane
Member Admin
3.12.0-RC1 Firmware for MK2.5 and MK2.5S

Greetings all. We are happy to announce the release of the latest firmware for the MK2 series of printers. Please note that this is a release candidate, so if you run into any issues, please use the link at the end of this article to report any issues. 


  • New thermal model protection
  • NylonPA sheet profile added
  • Updated translations
  • Bug fixes
  • Known issues

This is the first release candidate of firmware 3.12.0 with an extra safety feature.

New thermal model protection

This safety feature was introduced in the previous release 3.12.0-BETA1, see the release notes for more information and in case you are interested in technical details, we recommend reading the dev diary blog. This release further extends the capabilities of this thermal model.

How to calibrate your printer

The Temp model calibration is now part of the menu. Go to the “LCD menu -> Calibration -> Temp model cal.”.

  • Please note that the average calibration time is about 10-12 minutes and your printer will not accept any other input during this time.
  • During the calibration, the LCD status line shows information about the current stage of the process.
  • As soon as you see the Original Prusa MK3S text on the LCD, the procedure is finished and the Temp model is activated.

New default Temp model values

The devs were able to improve the default temp model values after analyzing more data we collected. We would like to thank our community for helping us improve the model even further by reporting positive feedback along with several issues.

Feedback report

Please report positive feedback on the thermal model (with an ✔️ at the end of the release notes). In case you run into issues, start a New issue

  • The report should contain at least following informations
    • Reproducible: Yes/No
    • Printer model: MK2.5/S , MK3/S/+ stock or modified
    • Modifications: Example E3D Revo or Copper block or different Fan shroud (with link)
    • If a specific print causes issues. Please attach the printed model
    • Try to add a serial log of the print failing.

NylonPA sheet profile added

The list of sheet profiles is now extended with the “NylonPA” option. Please note that this is just a name of the profile and there is no difference to other stock profiles (Smooth1, Texture1,...).

Since the list of profiles is limited, the “NylonPA” is replacing the current profile “Satin2”. In order to see this change, a Factory reset is required. Before you do so, please write down the “Live Adjust Z” values for all the calibrated sheets.

Once a Factory reset is performed, the default list is:

  • Smooth1
  • Smooth2
  • Texture1
  • Texture2
  • Satin
  • NylonPA
  • Custom1
  • Custom2

Updated translations

We would like to thank the community members for updating translations with new texts. In case you want to join and help translate the firmware to your language, please visit the following article Community translations.

Based on the feedback from our translators:

  • The translation “.po” files can and should now contain diacritics which will be automatically replaced.
    • This should improve the spell checks in different languages and hopefully make it easier for the translators.
    • At this moment we are still limited by the LCD screen only to show [aA-zZ] and [äöüß] characters.

Bug fixes

  • Parts of the firmware used “Extruder fan”, while the correct name is “Hotend fan”. This is now unified across the entire code base.
  • Some SD cards caused issues, the firmware should handle them correctly from now on.
  • The long button press wasn’t supposed to be active in some locations, this has been fixed now.
  • Minor SD card issue in FARM mode fixed. Sorting and long filenames have not been shown correctly.

Known issues

A feature detecting the filament sensor hardware version is currently not working. Printing process isn't affected, however if the filament sensor is not working properly, the printer is unable to verify it. The devs are aware of this issue and a fix will be provided soon.

Please report any bug here:

Download Link:

How to flash the firmware: (same process for the MK2 series of printers)

Shane (AKA FromPrusa)

Posted : 15/11/2022 7:50 am
Zbigniew Trzepizur
Trusted Member
RE: 3.12.0-RC1 Firmware for MK2.5 and MK2.5S


as the description of the thermal model extension is a bit vague, is it worthwhile for the Revo Six owners to try? IOW, has the behavior with Revo changed in any way since BETA1 that warrants (re)testing?


Posted : 15/11/2022 1:17 pm
Zbigniew Trzepizur
Trusted Member
RE: 3.12.0-RC1 Firmware for MK2.5 and MK2.5S

Meant to post that in MK3S+ subforum, sorry. Please feel free to delete my posts.

Posted : 16/11/2022 3:26 pm