There are a several good options for multi-material units:
- ERCF
- SMuFF
- 3D Chameleon
- Trad Rack
- Bambu AMS
- Prusa MMU
and probably several others. However these all seem somewhat expensive (~$200+) and complicated. They also seem to target serving 4 materials and expand upward from there.
A simple two-material switcher could enable
- two-color printing
- disolvable supports
- same color spool switching on run-out
and would serve the vast majority of my anticipated use cases.
Limiting the design to 2 material potentially simplifies things - and I am embarking on at least a thought exercise for a KISS (keep it stupid simple) switcher.
So far I have compiled what appear to be 3 or 4 viable avenues of pursuit:
- use one drive stepper and a 5mm shaft extension that passes through 2 (or more) direct drive extruders. Add 1 solenoid to engage / disengage each tensioner.
- use one BMG extruder, stepper and solenoid for each material (x2).
- use mirrored BMG extruders, 2 solenoids and a single dual shaft extruder.
I found an implementation of concept 2 on GrabCad: https://grabcad.com/library/cycle-test-prototype-for-automated-filament-loading-system-1
It includes an integrated spool management section which is beyond my initial Scope-of-Work, but it looks like I can just print the feeder drive section and check fitment / function.
At the very least it give me some hardware I can start to try to configure firmware for.
There are several options for firmware, but Happy Hare looks like a good place to start.