Filament Guide Stacker

This accomplishes a number of things...

Pulls the filament off of the spools at a constant, low resistance around a gentle arc at a fixed position and angle. Without it, filament pulls off the side of the spool at an extreme tight angle causing the spool to bounce around during reversal and Z movement.

You don't need spool housings around the spool to keep the filament in place. Since it's being pulled off at a fixed angle, the filament no longer has a tendency to fall off the side and get tangled. It also doesn't unwrap when Z homes, the tube rises instead and the spool remains wrapped nicely tight. (which gets really bad when you stack a second spool on top)

Makes switching between the 2 spools really easy since when you pull one out of the extruder, the tube holds the filament in place instead of spinning out of the spool and making a mess.

Provides another place to stash your tools!