Hi @mselos ,

I've updated this configuration (specifically mmu_hardware.cfg). Can you try updating and let me know if it works?

Same Error! But now that there is no mentioning of MMU_GEAR_UART_1 - MMU_GEAR_UART_3 in the mmu_hardware.cfg, i removed the Aliases in the mmu.cfg. Now klipper starts and mmu_select gate & mmu_test_move move works...
Looks like the aliases of MMU_GEAR_UART_1, MMU_GEAR_UART_2 & MMU_GEAR_UART_3 where the "trouble maker"

Does removing the aliases, have any consequences I can't see?

If the motors move properly, removing the aliases shouldn't have any other consequences.

Hi @jjonas20088

I answered your question on Discord. Please don't crosspost.

I see there area lot of types of NEMA17 Stepper Motor in Ali Express, but not the specific type you put here in your table.
For example, this one:
https://aliexpi.com/gER9
or this one:
https://aliexpi.com/TA7l
Both are claimed to fit 3d printers.
What is your opinion on using one of them instead the one you put?
I see they are narrower than yours.

Hi @RoyMessinger ,

For some reason, it seems like the second link is dead. From the first link, though, I would say that those are too thin and will likely stall at the torque and speed you'd want on a 3MS. I'd recommend a thicker stepper motor like the one from the docs. 3MS kits also just got released which have everything you need if you don't want to have to source everything.