Edit 1 : inverted gears version. so the direct extruder does almost no extra work
so you need to print large stuff and cant access large filament spools?
say no more.
work in progress. have not the time or the spare filament to test-print this stuff yet
donations welcomed :)
on electronics part of the thing, the idea is to use 2 extra extruders of your 6 drivers board and some endstop who is embeded on the carriage. cheap. no extra electronic stuff.
close to no supports needed while printing the parts.
another idea is to make it stackable. so you can add as many extra filament spools as you want if u have large enough 5mm shafts / screws.
yeah it looks like the new prusa multi material but its just a common problem with a common solution.
it may work as a bowden extruder but i dont plan to use it like that.
the working idea is that when the carriage moves it enables the extruder to feed the material on that port.
first port may be a utility port. to eject leftover material. or not.
when u sense that u dont have more filament left, u move the carriage to the first port and retract with your main extruder. then u pick whats left of the filament on the ptfe tube with the hobbed bolt on the base who need to be runing backwards and eject all the filament... lets say u sense the filament runing out again on the carriage, then retract a bit more.. so you are sure there is nothing left.
now you can procede to load a new filament that needs to be in some other input port.
you can print and add as many ports as u like or desire.
it may work as a a prusa multi material retarded brother who lives in the ceiling but i still dont know exactly how. i think u will need to use a filament input port with a steel flexible wire to purge the extruder, and an ejection port if u plan to use ptfe tubes from the spool holders to feed filament to this thing.
its a work in progress...
you can view and download the model on https://a360.co/2IbFnyX
inverted gears version : https://a360.co/2JqCafO