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Thermal model calibration

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Last updated 2 months ago
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Starting from firmware 3.12.0, the Original Prusa MK3/S/+ will have Thermal model protection. This will result in better operation when dealing with thermal errors.

How it works

During the print, the printer is constantly comparing the temperature measured by the thermistors to a thermal model of what is expected from the printer. In case the measured temperature does not follow the model, the printer will beep and show the warning THERMAL ANOMALY, but the print will continue. If the anomaly disappears the warning goes away after 20 seconds. In case the anomaly continues, the printer will turn off the heating and activate an error. If you choose to continue the print after it stops, it is recommended to stay near the printer.

This will help in cases where the temperature issue is temporary, like when a window is opened near the printer. Also, in case the printer has a blob that wraps around the hotend, the thermal model should be able to stop the print before any damage is done to the hotend cables.

If you're interested in further details of how the thermal model works, check the Dev diary blog.

The printer knows only that something is wrong, i.e., when the system is not performing as expected. It is up to the user to inspect the printer and check for issues.


When installing the new firmware, the printer will start the calibration. In case it does not go in the printer menu to Calibration -> Thermal Model cal. It takes around 12 minutes, after which your printer profile is automatically saved.

The Thermal model also works for third-party components. Note that if you switch components in your printer often, the Thermal Anomaly error might start to appear more often. If this happens, run the calibration again.

If you are using an enclosure, the Einsy-board needs to be inside the enclosure for the Thermal model to work, or it will cause false triggers.


In case the Thermal anomaly message keeps showing, try first doing a PID tuning using the temperature you normally print at, and then go LCD Menu -> Calibration -> Thermal Model cal., and make the Thermal calibration again

If you still have issues with the calibration after this procedure, make some Photo and video documentation and contact our Customer support.


Since the thermal model was developed on a model of a factory-assembled extruder, it may not work correctly on some modified or after-market extruders. If you have a Revo installed on your printer, make sure you have the specific firmware found in our GitHub page.

If you experience issues during the calibration process, start the process described in Crash dump, and after the logging starts, reset the printer and enter the sequence:

M310 ;report current temp model settings
M155 S1 C3 ;enable advanced temp and fan logging
D70 I1 ;enable temp model debug logging
M310 A F1;run temp model calibration

In case you run into issues during the printing process, use the process described in Crash dump, and after the logging starts run the sequence:

M310 ;report current temp model settings
M155 S1 C3 ;enable advanced temp and fan logging
D70 I1 ;enable temp model debug logging

Disabling the Thermal model protection

The thermal model protection can be disabled by connecting the printer to your computer (Octoprint, PuTTY...), and sending M310 S0. An additional M500 will save the setting and the Thermal model protection will remain disabled after the next restart.

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