Hi ! I saw this Prusa Filament Changer and I think it is worth to have a look at.
Previously, they used 4 extruders that was feeding a single hotend through a join coupler.
They had issues especially with the coupler and also jam.
https://shop.prusa3d.com/en/printer-upgrades/118-original-prusa-i3-mk2s-multi-material-upgrade-kit.html#
I like the new system. It is a filament changer.
It has 3 parts:
- You have have the hotend linked to a mobile coupler that is having a cutting blade, the coupler is moved by a lead screw and a stepper motor. The cutting blade is mandatory because the filament end will be larger and you cannot put it back safely in the hotend.
- You have the filament driving stage, that is a collection of 5 hobbed gears for the 5 driven filaments.
- And you have the most interesting part which is the filament selector implemented with a "revolver" holding 5 bearings where each bearing is set at a specific position to engage only one filament. Probably there is a free wheel position, once the filament has been grabbed by the extruder of the hotend.
I do not yet have all the details regarding the filament detection and other tricks.
It seems to be a sound approach, that can be also implemented by DIY.
Sources: