Original Auto-Rewind Spool Holder

Update Dec 1, 2018: Alternative design available: [Parametric Auto-Rewind Spool Holder](https://www.thingiverse.com/thing:3252111)

Filament load/unload issues? MMU2 taking too much space? Not with this Auto-Rewind spool holder! It keeps filament on the spool during unloading, up to two full revolutions.

The secret is a spring element which keeps some amount of rotational tension on the spool hub while unwinding. The weight of the spool plus friction of the surfaces define the slipping point; nearly-empty spools will rewind less but that is no problem thanks to the high ridges of the (empty) spool.

Hub_Standard is suitable for standard 750g spools, Hub_Wide is used for the wider 1kg spools.

Two bearings are needed, type 608ZZ with outer diameter 22 mm, inner diameter 8 mm and thickness 7 mm. These are the dimensions of the MMU bearings as supplied by Prusa.

If you have different bearings or spools with a different centre diameter, you can customize your own hub with the [