@o_lampe Thanks for the response.

I initially thought that as well, however, after that didn't work, this is what I found in the documentation which clarified that U is the 3rd and V4th axis.

M563:
X, Y The X and Y mapping option is used to create tools on machines with multiple independent X and/or Y carriages. The additional carriages are set up as axes U, V etc. (see M584) and the X mapping option in M563 defines which carriage or carriages are used. Axes are mapped in the order XYZUVWABC, where X=0, Y=1, Z=2, U=3 etc, not by driver number.

Hello all -

Issue:
I am trying to map the Z axis of one of two tools to the V axis (an independent axis operating in the z-direction), however this action appears unsupported. Has anyone found a way around this / or could indicate where I am making an error?

Background:
I have built a custom 3D printer which has two independent X-axes for 2 toolheads (each on its own rail). Each x-rail is controlled by independent Z-stepper motors. The setup has 5 axes:
x-0
Y-1
Z-2
U-3 (powered by stepper driver 6) - parallel to X-axis
V-4 (powered by stepper driver 7) - parallel to Z-axis

The Y-axis is shared between both toolheads (the bed moves).

To move the toolheads independently in the X and Z directions, I've mapped Tool 0 to X0 Y1 Z2 and Tool 2 to X3 Y1 Z4, where axis 3 is the U axis, and axis 4 is the V axis per the duet documentation.

The issue: In the interface, after selecting Tool 2 and moving the 'x' axis, it moves the U axis as expected. However, when moving the 'z' axis, it moves the Z instead of V axis.

I've tried changing the mapping of Z with no effect. The documentation states that mapping of the X and Y axes is possible, but does not indicate whether the Z axis can also be remapped.

Here are the relevant pieces of setup code:
; Drives
M569 P0 s1 ; physical drive 0 goes backwards
M569 P1 S1 ; physical drive 1 goes backwards
M569 P2 S1 ; physical drive 2 goes backwards
M569 P3 S0 ; physical drive 3 goes forwards
M569 P4 S0 ; physical drive 4 goes forwards
M569 P5 S1 ; physical drive 5 goes backwards
M569 P6 S1 ; physical drive 5 goes backwards
M569 P7 S1 ; physical drive 6 goes backwards
M584 X0 Y1 Z2 E3:4:5 U6 V7 ; set drive mapping

M563 P0 D0 H1 F0 X0 Y1 Z2 ; define tool 0
M563 P2 D2 H2 F2 X3 Y1 Z4 ; define tool 2

Thank you for your help!