Motor / Extruder Visualizer

You may consider this another visualizer, but it's a bit more than that.

I noticed a lot of visualizer were just gluing large magnets onto their creations, and it all seemed a bit strange.  The design of a Prusa i3 Mk3s extruder means there's a central axel that doesn't move, and inset 0.1mm deeper is the actual rotating ring of the motor.  The design of the visualizers didn't really consider how the motor was constructed.

This example uses an offset magnet.  Just one.  Either 5mm x 3mm or 5mm x 2mm.  It's designed to go 0.2mm deeper into the hole rather than flush, and depending on your print accuracy will push in with a bit of force, then stay there.

An eject pin-hole is provided on the reverse if you need to remove the magnet (something every design should do).

This type of offset design means the magnet effectively pulls with the outer rotating motor ring.  It doesn't impact its print performance, but it does grip very well, meaning you can clearly see retraction and extrusion.

After trying various large magnet designs, I concluded that a single, accurately positioned magnet was more than sufficient.  Other people's extruders may work better with central magnets, but mine specifically, as shipped, does not.  Hence this.