Multi-tool XL: colours do not line up or tool offset calibration fails

Symptom

On an XL with several tools, what each head prints is shifted relative to the rest, or the offset calibration fails with «Tool offset out of bounds» (#17104) or with «XY probing failed due to the low measurement stability» (#17105, XY probe unstable).

Likely causes, from most to least likely

1. Plastic residue on the nozzle, or filament loaded during calibration, distorting the measurement on the calibration pin.
2. A loose, bent or too-low nozzle: if it sits too low it hits the plastic part of the calibration pin. It matters most on tool 1, which is the reference.
3. The calibration pin is loose or dirty, or the nozzle crashes onto its key.
4. A tool dock is loose or badly calibrated, or the bed frame screws are loose.
5. Vibration reaching the surface the printer stands on (other printers nearby, an unstable surface).
6. After a nozzle crash or with non-original nozzles, the automatic offset needs manual fine-tuning.

Checks to tell which one it is

• Read the message: it says which tool and which axis are out of range.
• Make sure no tool has filament loaded and that the nozzles are clean.
• Check that the calibration pin is firm and clean.
• Swap the hotend of the failing tool with one from a tool that passes the calibration: if the fault follows the hotend, the problem is the hotend.

Before you start

Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.

Step-by-step fix

1. Unload and clean the nozzles

   Unload the filament from all tools. To clean a nozzle, pick the tool with Control → Pick/Park Tool → Pick Tool, heat it at 250 ºC for three to five minutes (the value in Prusa's guide) and remove the plastic with a brass brush. Let it cool before touching anything.

   Check: The nozzles are clean, with no plastic stuck to them.

   If that does not fix it: Check how the nozzles are fixed (next step).

2. Seat and tighten the nozzle

   With the printer off and the nozzle cold, hold the heater block and tighten the nozzle screw with the Torx TX8 key, following Prusa's guide for your setup. If the nozzle sits low, loosen the grub screw, push the nozzle up as far as it goes and tighten the screw again.

   Check: The nozzle does not move and no longer touches the plastic part of the pin.

   If that does not fix it: Check the calibration pin (next step).

3. Calibration pin and bed frame

   Check that the calibration pin is not loose and clean it. If the bed has play, loosen all the bed frame screws and tighten them crosswise: first front right and rear left, then front left and rear right.

   Check: The calibration no longer reports unstable measurements.

   If that does not fix it: Recalibrate the dock position (next step).

4. Recalibrate the tool dock

   Go to Control → Calibrations & Tests → Dock Position Calibration, choose the tool showing the error and follow the screen.

   Check: The tool is picked and parked without rubbing.

   If that does not fix it: Repeat the Tool Offset Calibration with no filament loaded.

5. Avoid vibration

   During calibration, stop nearby printers and place the XL on a stable surface; add damping padding underneath if needed.

   Check: The offset calibration finishes without errors.

   If that does not fix it: Do the manual calibration (next step).

6. Manual offset calibration

   Print the manual calibration model Prusa provides for 2-tool or 5-tool XL (satin sheet and light-coloured PLA), find the best-aligned marks on each pair of combs and add their value to the current offset in Settings → Tool → Tool (number). Tool 1 is the reference and its offset is always zero.

   Check: When you reprint the model, the best-aligned marks are the zero ones (the largest mark).

   If that does not fix it: If the offset drifts again, contact Prusa support.

Prevention

• Always calibrate with no filament loaded and clean nozzles.
• Repeat the offset calibration after a nozzle crash or when fitting different nozzles.
• Keep the XL away from vibrating machines while it calibrates.

Still not fixed?

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Printers it applies to

The Prusa XL family: XL and XL+.

Official sources

This guide summarises the official documentation linked here:

• Multi-tool manual calibration (XL) · Prusa Research
• Tool offset out of bounds #17104 (XL) · Prusa Research
• XY probe unstable #17105 (XL) · Prusa Research
• Selftest failed (XL multi-tool) · Prusa Research