As I mentioned, the originl 4x joiner part had some trouble with some filaments, probably due to having too tight bends inside the part. To fix that, I desgined my own part, trying to have the paths bend as little as possible, while keeping the part relatively small. After few iterations I got a part that has been working without problems for few months now. I printed it with PETG, but ABS might be better as it has higher heat tolerances. Still, PETG seems to be holding up quite well.
Ok the setup seems to be working, printed this gear with 4 colors (ABS, 0.2mm, S3D, Pressure Advance 0.27):
I used logical pins 60-63 for control and 5V from ATX PSU for power as I run whole system with it.
tfreex.g:
M18 E0
tpost0.g:
M116 P0
M42 P60 S255
M42 P61 S255
M42 P62 S255
M42 P63 S255
G4 P300
tpost1.g
M116 P0
M42 P60 S255
M42 P61 S255
M42 P62 S255
M42 P63 S0
G4 P300
tpost2.g
M116 P0
M42 P60 S255
M42 P61 S255
M42 P62 S0
M42 P63 S0
G4 P300
tpost3.g
M116 P0
M42 P60 S255
M42 P61 S0
M42 P62 S0
M42 P63 S0
G4 P300
At first I had some trouble wrapping my head around how to keep E0 as the drive when changing tool, but luckily stumbled upon M563 definition in Duet Wiki and all was clear, just set all tools to use E0. I did my first configuration for Duet with some online configuration generator, so didn't really look it through all of the commands very keenly. Loving how much things can be configured without needing to touch the actual code.