Multi-tool XL: a tool is not picked up or parked properly (dock and toolchanger)

Symptom

The XL fails to pick up or drop off a tool at its dock, a tool bumps into a parked one, or a toolchanger error appears, such as «Toolchanger problem» (#17813), which asks you to park all tools in their docks and leave the carriage free, or «Dock position out of bounds» (#17103) during dock calibration.

Likely causes, from most to least likely

1. A dock is loose or not fully seated on the extrusions, or the rear metal profile holding the docks is not all the way to the left.
2. The dock position is not calibrated.
3. Belts too loose or too tight, or the gantry misaligned.
4. Dry or poorly lubricated coupler pins (each tool has three).
5. The cable bundle on the tool head bends or restricts movement.
6. If none of the above fixes it, the toolchanger's electromechanical board (cheese board) may be faulty.

Checks to tell which one it is

• With the printer stopped and the tools cold, try to move each dock by hand: it must not move at all.
• Check that the metal part of the dock is perpendicular to the extrusions and fully seated, with no gaps.
• Check the belt tension with Prusa's guide.

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. Park the tools by hand

   If the printer asks, park the tool on the carriage by hand by sliding it to the right into its dock, and check that the others are parked properly. Careful: the tools may be hot and can burn.

   Check: All tools are in their docks and the carriage is free.

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

2. Tighten and seat the docks

   With the printer off, check that no dock has play. To tighten one, pass a 2.5 mm Allen key through the hole in the rear metal sheet to the middle screw of the dock cable router and tighten it firmly. If the dock is not seated properly, loosen it and tighten it again while pressing it into place, with the rear metal profile all the way to the left (looking at the printer from behind).

   Check: No dock moves when pushed.

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

3. Calibrate the dock position

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

   Check: The calibration ends without the red error cross and the tool is picked up and parked properly.

   If that does not fix it: Check the belts and gantry (next step).

4. Belts and gantry

   Check the belt tension and gantry alignment with Prusa's belt adjustment guide for the XL: both loose and overtight belts hinder movement.

   Check: The gantry moves smoothly and squarely.

   If that does not fix it: Lubricate the coupler pins (next step).

5. Lubricate the coupler pins

   Lubricate the three coupler pins of each tool following Prusa's step-by-step guide.

   Check: The tools couple and release without jerking.

   If that does not fix it: Check that the cable bundle on the tool head does not bend; if everything is fine and the fault persists, the toolchanger board (cheese board) may be damaged: contact Prusa support.

Prevention

• Check from time to time that the docks have no play.
• Keep the coupler pins lubricated as part of Prusa's maintenance.
• Recalibrate the dock after removing or adjusting it.

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:

• Toolchanger problem #17813 (XL multi-tool) · Prusa Research
• Dock position out of bounds #17103 (XL) · Prusa Research
• Selftest failed (XL multi-tool) · Prusa Research