In the first part of this story I theorized about a potentially much simpler extruder system for multi-material 3D printing.

I have proceeded to iterate a bit on the idea and this is what I got:

Initially I wanted to either wrap a GT2 timing belt around the drive gear, or print a simple wrap around it. It turned out to be much simpler to print the whole gear out of TPU with 100% infill.

The drive gear has some identations to make sure it does not slip vertically (there’s also a place for a set screw, but it does not work that well with TPU):

Initially, I was thinking about creating a separate sensor/switch to understand where extruder is, to make parking/unparking possible. However, it looks like I will be able to simply turn the motor off and let the main printing extruder to rotate the drive gear until it’s parked.

Anyway, since that works I’ll now continue creating an extremely minimalistic MMU unit. It will have 2 lanes, something for rewinding (have not decided whether to try Filamentalist or try to create my own active respooling system).