6.3.4 Firmware for Prusa CORE One

Summary

• Smarter heat absorption logic
• Retuned heatbed PID for thermal stability
• Automatic display refresh rate fallback
• Additional updates, improvements, and fixes

This is the stable release of firmware 6.3.4 for the Prusa CORE One, addressing several improvements and bug fixes.
This release focuses on enhancing reliability and fine-tuning the user experience based on recent feedback and internal testing. Users can expect smoother operation, better thermal stability, and quality-of-life improvements across multiple areas of the firmware.

Smarter heat absorption logic

The heat absorption logic has been significantly improved to make your printer smarter — and your workflow faster. The firmware now continuously tracks recent heatbed activity and dynamically adjusts the required stabilization time before printing. If the bed has already been heated, such as when printing multiple objects in succession, switching materials, or using preheat, the usual heat absorption delay is automatically shortened — or even skipped entirely.
This leads to a noticeably faster transition into printing, especially during reprints or tightly timed jobs, helping you save time, stay productive, and get the most out of every print session.

Retuned heatbed PID for thermal stability

PID values for the CORE One heatbed have been fine-tuned to provide more stable temperature regulation and improved print consistency.

Automatic display refresh rate fallback

If repeated display anomalies (such as flickering) are detected, the printer now shows a prompt offering to switch to a lower refresh rate. To ensure the dialog remains readable even if the display is unstable, the system temporarily applies the lower refresh rate before displaying the prompt. If the user selects "No," the original (higher) refresh rate is restored.
The display refresh rate can also be adjusted manually at any time in Settings → Hardware → Display Refresh Speed.

Additional updates, improvements, and fixes

Progress reporting during filament auto-retract

The progress bar is now updated during the auto-retract phase of filament load or change, instead of remaining stuck at 99% in the "Loading" phase.

Option to disable grille check warnings

The ventilation grille warning now includes a “Disable” button. The warning can also be managed under Settings → Hardware → Check Ventilation Grilles.

N/A entries removed from print carousel

Print screen carousel now omits entries marked as “N/A” to reduce clutter and improve readability.

Increased retraction after filament change

Retraction during filament unparking has been increased from 2 mm to 4 mm to minimize oozing.

Extended post-print filtration limit

The maximum setting for post-print air filtration has been extended from the previous limit to 90 minutes.

Phase stepping calibration option

A calibration option is now available to fine-tune phase stepping on the CORE One. The feature requires a PRUSA Accelerometer Set and is intended for advanced users who enjoy exploring deeper tuning options and experimenting with motor behavior.

Chamber lights stay on with the camera enabled

When the integrated camera is active, chamber light dimming is now disabled by default to maintain optimal visibility. This behavior can still be manually changed in the settings.

Lights settings

The lighting settings have been reworked to offer more precise control over the printer’s status and chamber illumination.
Chamber dimming behavior can be set to one of three modes:

• Always – dimming is active even during printing
• On Idle – dimming only occurs when the printer is not printing
• Never – dimming is completely disabled, regardless of other settings

Additionally, the chamber light settings have been expanded. You can now fine-tune both the standard and dimmed brightness levels separately, allowing for more flexible lighting behavior during different printer states. The option to toggle the RGB status bar under the heatbed on or off has also been moved into this menu.

Nozzle no longer heats unnecessarily on unload

The nozzle will no longer be heated unnecessarily during filament unload if the filament has already been auto-retracted and only needs to be deretracted for gear clearance.

Nozzle now cools properly after unloading

After filament unload, the nozzle now properly begins the cooldown process.

Corrected door sensor calibration instructions

Corrected the wording in the door sensor calibration wizard. The prompt now properly instructs the user to loosen the tensioning screw, not tighten it.

Release notes:  https://github.com/prusa3d/Prusa-Firmware-Buddy/releases/tag/v6.3.4