Spannerhands rewinder spool

This is an auto-rewinding spool which fits the beautiful and useful [Spannerhands spool system](https://www.thingiverse.com/thing:2119644) (of which I have published a [remix](https://www.thingiverse.com/thing:4005831)).

It allows the PTFE tube from a Spannerhands box to be directly connected to an MK3S/MMU2S printer PTFE tube without a filament buffer.

This thing is a remix of Vincent Groenhuis [Integrated Auto-Rewind Spool Holder](https://www.thingiverse.com/thing:3781815) where I've used his parameterized SCAD file to make an 88 mm spool holder without rims and have added an axle and mounts which fit the Spannerhands box.

The mounts are supposed to be printed in a flex material and diameter. The length of mounts and axle are chosen such that they are locked in place in the box.

In addition, two (or four) flex rubber rings can be slid over the roll to produce increased friction against the spool (see below why you would want to do this). UPDATE 2020-06-26: After some expe