Prusa Research has released firmware 6.6.2 for the CORE One and CORE One+ with the INDX toolchanger, a maintenance update focused almost entirely on the mechanical handshake between the print head and its multi-tool hardware. Released July 10, 2026, the update targets two of the most common INDX complaints since launch: nozzle-cleaner wipes that drift out of position over time, and tool pickups that occasionally eject a strand of filament from the nozzle during pickup.
Neither issue is catastrophic on its own — most owners work around them by re-running calibration or babysitting early layers — but both chip away at the "just hit print" promise that toolchanging is supposed to deliver. A toolchanger's entire value proposition rests on the machine reliably handling tasks a single-nozzle printer never has to think about: parking a tool cleanly, keeping its nozzle wiped, and swapping it back in without leaving a mess behind. When those steps drift even slightly out of tolerance, the owner ends up doing manual babysitting on a machine that was supposed to remove exactly that kind of attention. 6.6.2 is Prusa's attempt to close that gap without requiring owners to touch a single setting.
Nozzle Cleaner: Fixing the Drift, Not Just the Symptom
The nozzle cleaner on CORE One INDX machines is a small brush-and-wipe station that each tool parks against between filament changes to scrape off ooze. According to Prusa's knowledge base changelog, 6.6.2 "adjusted the nozzle cleaner origin position and fixed handling of nozzle cleaner offsets during parking moves" — the brief motion where a tool approaches, wipes, and backs away from the cleaner. Previously, small errors in that calculation could accumulate, nudging the effective wipe position away from where it was originally calibrated.
What makes this fix notable is how Prusa handled the migration. Nozzle-cleaner offsets are stored per-tool in EEPROM, and a naive firmware fix would leave existing stored values calibrated against the old, buggy math — forcing every INDX owner to re-run cleaner calibration by hand after updating. Instead, according to Prusa's changelog, EEPROM-stored nozzle cleaner offsets now adjust automatically post-update, eliminating the need for recalibration. Prusa also added a new option under the Tune menu for fine-tuning the nozzle cleaner's X offset, rather than diving into full recalibration for a minor adjustment.
Tool Lock: Less Filament Left Behind
The second major change addresses tool pickup itself. On an INDX system, each tool sits parked in its own dock, and the print head has to drive over, physically lock onto the tool body, and pull it free before printing can resume. Prusa's changelog lists the tool lock move distance as "refined for better reliability and reduced unintended filament ejection" — an adjustment to the travel path the head follows during that pickup.
That ejection behavior has been a known annoyance: a tool that's been parked for a while can have a small blob or strand of filament hanging at the tip, and if the lock-and-pull motion catches it wrong, it can deposit that strand somewhere it shouldn't be, or leave the nozzle in a state that produces a bad first extrusion after the swap. Tightening the geometry of that move doesn't eliminate priming and purge needs, but it reduces one more variable in an already mechanically complex handoff.
It's a subtle fix in the sense that it's a distance adjustment rather than a new sensor or a redesigned dock, but that's also what makes it low-risk for existing owners: there's no new hardware to install and no new failure mode being introduced, just a refined motion path running through the same mechanism that's already in every INDX-equipped CORE One in the field.
Dock Calibration and a Round of Smaller Fixes
Beyond the two headline fixes, Prusa's knowledge base changelog lists a batch of smaller improvements. Dock Calibration — the routine that teaches the machine exactly where each tool's parking dock sits — no longer requires removing the tool first when the head is empty, trimming a step out of a workflow owners are likely to run after moving a printer or swapping hardware.
The changelog also lists a fix for a waste-bin collision that could occur following a failed mesh bed leveling (MBL) pass, restored support for earlier xBuddy board revisions with inverted pins (including early MK4 boards converted to CORE One), a correction to the feedrate used when transitioning from flexible filament to PLA, a fix for gray Selftest buttons that failed to update once their dependencies were satisfied, a fix for an invisible Abort button on the Y-axis Input Shaper selftest screen, and a fix for Tool Offset Cyphal communication that failed to reinitialize correctly after a board reset.
None of these are headline features on their own, but together they round out a release that reads as pure hardware-reliability housekeeping rather than anything user-facing in the slicer or print settings. The xBuddy fix in particular is a reminder that Prusa is still supporting owners who converted earlier MK4 boards rather than buying a purpose-built CORE One control board — a smaller but real slice of the installed base that firmware updates can easily leave behind if compatibility isn't actively maintained release over release.
What It Means for Makers
None of this is a feature release — there's no new print mode, no speed boost, no headline capability. It's precision maintenance on a machine class that lives or dies by mechanical repeatability: a toolchanger that mispositions a wipe by fractions of a millimeter or ejects filament during a pickup compounds those errors across every tool change in a print, and multi-tool prints can involve dozens of changes. Fixing the underlying math rather than papering over symptoms — and doing it with an automatic EEPROM migration instead of asking owners to redo calibration — is the right call for a fleet of machines already in the field.
The Dock Calibration change is small but practical: not having to pull a tool out of its dock just to recalibrate when the head is already empty removes friction from a task owners are told to run after any physical change to the printer. CORE One and CORE One+ owners running INDX toolchangers should update via Prusa's standard firmware flow; existing nozzle-cleaner calibrations should carry over automatically thanks to the EEPROM migration, but owners who've recently moved or reconfigured their printer may still want to run a fresh Dock Calibration pass as a first move after updating.
