Prusa Firmware Buddy

Summary

• Improvements

  • Improved head LED behavior by synchronizing tool LEDs with the printer state and matching the status indication used by the heated bed LEDs.
  • Added Nozzle Cleaner Y Offset adjustment to the Tune menu for easier calibration directly from the printer interface.
  • Added ringdown decay information to the Sensor Info screen for improved diagnostics and troubleshooting.
  • Improved synchronization of loadcell samples between the toolhead and xBuddy, increasing the robustness of probing and calibration procedures.
  • Optimized motion step calculations to reduce the risk of layer shifts during printing.
  • Streamlined hotend management logic to improve maintainability and reliability.
  • Reduced calibration time by skipping temperature residency during tool offset calibration heating.

• Fixes

  • Reworked nozzle heater self-test validation to use thermal model evaluation during heating, reducing false self-test failures caused by minor deviations in heating performance.
  • Added validation of INDX coil current during heater self-tests to detect abnormal nozzle behavior.
  • Updated INDX nozzle thermal diagnostics to leverage thermal protection results for more accurate fault detection.
  • Fixed an issue where hotend thermal errors could be reported even when no nozzle was installed by verifying nozzle presence before triggering errors.
  • Fixed the Tool Change button incorrectly opening the extruded filament submenu.
  • Fixed an issue where an uninitialized nozzle temperature was displayed as 15 °C in the footer.
  • Removed a redundant cooldown check from the nozzle cleaner calibration process.

This is the stable release of firmware 6.6.3 for the Prusa CORE One+ INDX and CORE One INDX.

Summary

• Improvements

  • Adjusted the nozzle cleaner origin position and fixed handling of nozzle cleaner offsets during parking moves.
  • EEPROM-stored nozzle cleaner offsets are now automatically adjusted after the update, eliminating the need for nozzle cleaner recalibration.
  • Adjusted the tool lock move distance for improved tool pickup reliability and reduced risk of filament being unintentionally ejected from the extruder gears.
  • Added a new option in the Tune menu for fine-tuning the nozzle cleaner X offset.

• Fixes

  • Fixed bumping into the waste bin after an MBL failure.
  • Fixed an issue requiring tool removal during Dock Calibration even when no tool was loaded in the head.
  • Fixed support for older xBuddy revisions with inverted pins (early MK4 converted boards). (Credit: @ScottKolo)
  • Fixed selftest gray buttons not updating after dependencies were met.
  • Fixed incorrect feedrate when loading PLA after FLEX material.
  • Fixed an invisible Abort button on the Y-axis Input Shaper selftest screen.
  • Fixed Tool Offset Cyphal communication not being reinitialized after board reset.

This is the stable release of firmware 6.6.2 for the Prusa CORE One+ INDX and CORE One INDX.

Summary

• Improvements

  • Lower the print bed when a tool is unknown or lost, allowing the user to safely remove the print.
  • During Dock Calibration, users can now choose between Keep, Calibrate, and Invalidate.
  • Added an M109 flag to skip temperature stabilization.

• Fixes

  • Fixed spontaneous INDX Head resets.
  • Fixed incorrect tool assignment after a REDSCREEN reset. The printer now saves the currently selected tool.
  • Removed the extruder filament sensor from the footer and the Sensor Info menu.

This is the stable release of firmware 6.6.1 for the Prusa CORE One+ INDX, CORE One INDX.

Summary

New features and improvements

• First firmware release for the Prusa CORE One/+ INDX
• Full INDX toolchanger support, with automatic tool changes for up to 8 tools
• Contactless nozzle induction heating
• Continuous nozzle presence detection for safety and fault detection
• Contactless tool offset sensor
• Guided INDX calibrations: docks, tool offsets, nozzle cleaner, and more
• Automatic, low-waste nozzle cleaning with a wastebin
• Screen for unloading or changing all filaments at once
• Reworked tool mapping screen supporting up to 8 tools
• Empty Nozzle Cleaner
• Known issues are listed at the end

This is the first firmware release for printers equipped with the INDX toolchanger, and it builds on the current firmware. It adds complete support for the INDX hardware, including automatic tool changes with up to 8 tools, induction heating, and a guided calibration workflow that takes you from assembly to your first multi-material print.

Welcome, INDX!

The INDX toolchanger, developed by Bondtech in collaboration with Prusa Research, transforms your CORE One/+ into a multi-material printer with up to 8 tools. The system combines a single active INDX Head with lightweight passive tools. Each tool consists of a filament path and a nozzle, with no heaters, wires, or electronics. After installing the conversion kit and flashing this firmware, the printer identifies itself as a CORE One+ INDX and guides you through the initial calibrations.

Both the 4-tool and 8-tool kit configurations are supported. The firmware lets you calibrate and enable any number of tools from 1 to 8, so you can run the printer with exactly as many tools as your print requires.

Induction heating with temperature compensation

The INDX Head heats the nozzle of the currently picked-up tool by induction and measures its temperature contactlessly. In addition, the firmware runs a thermal compensation model that accounts for extrusion speed, chamber temperature, print fan speed, and the thermal properties of the loaded filament, keeping the actual melt temperature on target across changing print conditions. The INDX Head also independently monitors its own temperatures, adding an extra layer of safety on top of the printer's standard thermal protections. Because the nozzles heat up in seconds, the time required for temperature stabilization is significantly shorter than on a conventional hotend.

New contactless tool offset sensor

The new inductive sensor mounted on the print bed automatically measures each tool's XY offset, ensuring that every tool prints in perfect alignment. The tools are heated during the measurement process, compensating for slight changes in the thermal expansion of the metal nozzle.

Continuous nozzle presence detection

For safe and reliable multi-tool printing, the INDX Head continuously verifies that the picked-up tool's nozzle is present. It detects the nozzle through its induction system and re-checks it approximately every 100 ms while idle and every 500 ms while heating. If a nozzle goes missing - whether because a tool has fallen off its dock or a pick or park operation did not complete successfully - the printer detects the issue and responds safely instead of heating or extruding without a nozzle in place. Ambiguous readings, such as a nozzle caught halfway, are treated cautiously and resolved by the system's recovery logic.

Guided INDX calibrations

The Calibrations & Tests wizard has been extended with new INDX-specific routines and guides you through the complete setup process in the correct order:

• Homing calibration: Reworked for the INDX toolhead with improved accuracy and repeatability. Invalid probes are detected and retried automatically, and the calibration pattern has been redesigned, which is essential for repeatable tool docking.
• Dock calibration: Fine-tunes the position of each dock to ensure the INDX Head can reliably pick up and park tools.
• Tool offset calibration: Measures the XY offsets of every tool using the new contactless inductive sensor, ensuring all tools print in perfect alignment. This calibration, including Z-offset measurement, runs at the start of every print to eliminate tool-to-tool alignment issues.
• Nozzle cleaner calibration: Aligns the nozzle cleaner and wastebin positions for reliable cleaning and blob ejection.
• Input Shaper and Phase Stepping calibration: Measures vibration compensation using the accelerometer built into the INDX Head.

Automatic, low-waste nozzle cleaning

The printer keeps every nozzle clean automatically. An integrated nozzle cleaner and wastebin handle a range of routines, from a quick wipe during tool changes to deep cleaning and purged-blob ejection, ensuring that color bleed and debris never reach your print. The entire system is designed around minimal waste: tool changes require only a very small purge, and the purged material is collected in the wastebin rather than ending up on the print bed or in a separate purge tower.

Empty Nozzle Cleaner

Allows you to easily empty the wastebin. It can automatically pause prints with a high number of tool changes (configurable under Settings > Nozzle cleaner).

A side filament sensor for every slot

Each tool slot has its own side filament sensor, allowing the printer to detect filament runout on a per-tool basis, which is essential for multi-material printing. A runout event triggers the standard filament-change process for the affected tool only.

New multi-tool filament management screens

Managing up to 8 filaments simultaneously is now easier:

• The filament change screen for multiple tools now offers "Set all to" to assign a filament type to all slots at once, and "Unload all" to clear the printer in a single operation.
• Unloading works even when the loaded filament type is unknown.
• Loaded filaments can be reviewed per slot, including nozzle diameter and high-flow nozzle settings for each tool.

Tool mapping and Spool Join

The features known from the Original Prusa XL are available here as well:

• Tool mapping lets you reassign which physical tool prints each filament from the sliced G-code, directly from the extended tool mapping screen on the printer or remotely via Prusa Connect. The screen is now scrollable to accommodate mapping of up to 8 tools.
• Spool Join automatically continues printing from another slot loaded with the same filament when a spool runs out.

Known issues

Pick / park failures

The INDX toolchanger can perform thousands of tool changes during a single print, and reliable picking and parking depend on accurately calibrated positions. If a pick or park operation fails, the printer automatically re-homes the tool and retries, which usually succeeds. In rare cases (for example, if a tool has fallen off its dock), multiple consecutive failures will pause the print for inspection. Once the print area has been checked, printing can be resumed seamlessly.

Parking in an occupied dock

In rare cases, the INDX Head may fail to park a tool while still passing the subsequent nozzle-presence check. The previously used nozzle may then continue printing until the system detects the issue.

Single-tool auto-load

Filament auto-load is supported, but currently only for the tool that is picked up.

Flexible materials

In some cases, TPU and other flexible filaments can tangle inside the INDX Head, causing the extruder motor to skip steps. We will continue fine-tuning the system to eliminate this issue.

Special materials

The thermal model uses thermal-capacity constants defined for known filament types. Special materials with different thermal properties may trigger a thermal runaway error.

Spontaneous INDX Head resets

The INDX Head may undergo internal resets, even during printing. This has no negative effect on print quality, but in rare cases side-effect errors ("Puppy errors") may occur. We are actively working to resolve this.

Phase Stepping & Input Shaper calibrations

These calibrations may occasionally encounter errors. In most cases, restarting the printer and trying again resolves the issue.

Filament stuck detection

Not available on INDX printers in this release.

Summary

• New features and improvements
  • Improved filament change between different materials
• Fixes
  • Support for older xBuddy board versions
  • Fixed input shaper calibration for CoreXY printers
  • Fixed not loading custom Connect certificates
  • Fixed a crash when printing more than 1024 objects

This is the stable release of firmware 6.5.7 for the Prusa CORE One L, CORE One+, CORE One, MK4S, MK4, MK3.9S, MK3.9, MK3.5S and MK3.5 bringing targeted stability improvements and fixes.

Improved filament change between different materials

The filament change procedure has been improved to better handle switching between materials with significantly different print temperatures.

When loading the new filament, the printer now preheats to the higher temperature of the two materials. Once the filament is in the nozzle, the target temperature is adjusted to match the newly inserted material.

This allows the nozzle to cool down gradually when switching to a lower-temperature material, while the previous filament is purged out.

Fixed input shaper calibration for CoreXY printers

Input shaper calibration on CoreXY printers now correctly uses XY coordinates instead of AB coordinates. This fixes an incorrect excitation pattern that could lead to inaccurate calibration results.

Fixed not loading custom Connect certificates

Our customers can set up their printers to use non-official Connect servers by using the “Load Settings from File” menu item. This should also include loading a custom SSL certificate, which was however not working due to a bug in the firmware that has now been fixed.

Please note that we do not open-source our Connect backend infrastructure.

Fixed a crash when printing more than 1024 objects

We addressed a crash triggered when trying to print a G-Code file with more than 1024 objects.

Summary

• Fixes
  • Fixed not loading custom Connect certificates

This is the stable release of firmware 6.4.2 for the Prusa XL, MINI.

Fixed not loading custom Connect certificates

Our customers can set up their printers to use non-official Connect servers by using the “Load Settings from File” menu item. This should also include loading a custom SSL certificate, which was however not working due to a bug in the firmware that has now been fixed.

Please note that we do not open-source our Connect backend infrastructure.

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 stable 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. In 6.4.1, the calibration method has been refined and further improved by backporting phase stepping fixes from the 6.5 releases. These changes enhance overall calibration reliability and address regressions introduced in earlier 6.4 builds.

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.

Summary

• Fixes
  • Phase stepping fixes from the 6.5 releases

This is the release candidate for the upcoming firmware 6.4.1 for the Original Prusa XL.

For a complete overview of features introduced in firmware 6.4.1, users can refer to the 6.4.1-beta published earlier.

Phase stepping fixes from the 6.5 releases

Phase stepping fixes from 6.5 have been backported to 6.4.1. This improves phase stepping and prevents regressions introduced in earlier 6.4 builds.

Summary

• New features and improvements
  • Massively speed up MMU filament changes [MMU]
  • Updated default input shaper profiles [C1+, C1L]
  • Updated translations (beta didn’t have new texts translated)
  • Bed LED progress indicator [C1L]
  • Tuned parking position during purging [C1, C1+, C1L]
  • Vent grille linked to filament preset [C1+, C1L]
  • AC supply voltage for the AC controller has been increased [C1L]
  • Preload all MMU slots at once [MMU]
  • Bootloader update
  • Lowered chamber safety temperatures [C1]
• Fixes
  • Fixed input shaper axis assignment on CoreXY printers
  • Fixed layer shifts during high-speed curved moves
  • M1704 MMU load test gcode now considers toolmapping [MMU]
  • Fixed MMU sending spurious attention reports to Prusa Connect during normal toolchanges [MMU]
  • Fixed crash/BSOD on M501 (restore settings) (#4912)
  • Fixed gearbox alignment test showing wrong status when skipped
  • Fixed chamber fans showing "Auto" instead of "Disabled" when not in use [C1, C1+, C1L]

This is the stable release of firmware 6.5.3 for the Prusa CORE One L, CORE One+, CORE One, MK4S, MK4, MK3.9S, MK3.9, MK3.5S and MK3.5 bringing targeted stability improvements and fixes.

Massively speed up MMU filament changes [MMU]

A series of improvements have been implemented that massively speed up MMU filament changes by up to 9 seconds. Some changes in the MMU firmware were required as well, so it is necessary to flash a new 3.0.4 firmware to your MMU unit.

The improvements include:

• Parallelized unloading filament from the nozzle and idler engaging.
• The printer does not wait for the final idler disengagement to finish to continue printing.
• Parallelized selector and idler movement.
• FeedingToFinda phase now obeys PulleySlowFeedrate with higher value.
• Optimized idler selection mechanism during filament change.

For more information about MMU improvements and the CORE One L MMU3, check out our blog post.

Updated default input shaper profiles [C1+, C1L]

In 6.5.3-beta, we’ve fixed a bug in the input shaper configuration of our CoreXY printers. If you haven’t changed your input shaper settings, the new values will update automatically.

NOTE: If you have CORE One L or an accelerometer accessory, we recommend re-running your input shaper calibration. If you modified these values in the past we recommend resetting your input shaper profiles to defaults using the Settings → Input Shaper → Restore Defaults.

Bed LED progress indicator [C1L]

The CORE One L bed LED indicator now shows the progress of your print, starting from the left and gradually changing from white to blue.

Tuned parking position during purging [C1, C1+, C1L]

The parking position on CORE One and CORE One L has been adjusted so that purged filament flows unobstructed to the bottom, reducing potential debris on the print bed.

Vent grille linked to filament preset [C1+, C1L]

The vent grille now automatically opens or closes based on the target chamber temperature set in the active filament preset. This ensures optimal thermal conditions during printing.

AC supply voltage for the AC controller has been increased [C1L]

Based on user feedback, we have increased the maximum supported AC supply voltage for the AC controller to 264 V.

Preload all MMU slots at once [MMU]

The new menu item Filament MMU - Preload All now asks for the filament type only once and applies it to all slots. This is handy when you want to load, for example, five PLA filaments.

Bootloader update

The bootloader has been updated to version 2.6.0. This creates the necessary foundation for the upcoming INDX upgrade.

Lowered chamber safety temperatures [C1]

Chamber fans now start to spin at 60 °C and the printer shows a "chamber overheating" warning, pausing the print at 65 °C.

Please note that the maximum chamber target temperature is unchanged at 55 °C, only safety margins for emergency cooling have been adjusted.

Fixed input shaper axis assignment on CoreXY printers

The input shaper X and Y axis parameters were swapped on CoreXY printers, meaning the shaper configured for X was actually applied to Y, and vice versa. This also prevented users from disabling input shaping on only one axis. Both issues are now resolved.

Fixed layer shifts during high-speed curved moves

Layer shifts could occur during high-speed printing with curved moves. The motion system has been improved to address the issue.

Note: Please be aware that not all layer shifts have been caused by this issue.

Summary

• New features and improvements
  • Massively speed up MMU filament changes [MMU]
  • Updated default input shaper profiles [C1+, C1L]
  • Updated translations (beta didn’t have new texts translated)
• Fixes
  • M1704 MMU load test gcode now considers toolmapping [MMU]
  • Fixed MMU sending spurious attention reports to Prusa Connect during normal toolchanges [MMU]

This is the release candidate for the upcoming firmware 6.5.3 for the Prusa CORE One L, CORE One+, CORE One, MK4S, MK4, MK3.9S and MK3.9.

For a complete overview of features introduced in firmware 6.5.3, users can refer to the 6.5.3-beta published earlier.

Massively speed up MMU filament changes [MMU]

A series of improvements have been implemented that massively speed up MMU filament changes by up to 9 seconds. Some changes in the MMU firmware were required as well, so it is necessary to flash a new 3.0.4 firmware to your MMU unit.

The improvements include:

• Parallelized unloading filament from the nozzle and idler engaging.
• The printer does not wait for the final idler disengagement to finish to continue printing.
• Parallelized selector and idler movement.
• FeedingToFinda phase now obeys PulleySlowFeedrate with higher value.
• Optimized idler selection mechanism during filament change.

Updated default input shaper profiles [C1+, C1L]

In 6.5.3-beta, we’ve fixed a bug in the input shaper configuration of our CoreXY printers. If you haven’t changed your input shaper settings, the new values will update automatically.

NOTE: If you have CORE One L or an accelerometer accessory, we recommend re-running your input shaper calibration. If you modified these values in the past we recommend resetting your input shaper profiles to defaults using the Settings → Input Shaper → Restore Defaults.