This is a remix of the spring used in VincentGroenhuis' awesome Universal Auto-Rewind Spool Holder.

I use 5 of these on my Prusa i3 mk3s MMU2.0 setup as a replacement for the prusa fiber buffer. They reliably rewind fiber onto the spools each time the MMU tool changes which fiber is going into the extruder.

The remix replaces the spring and housing.
I found the bi-directional spring to be too fragile for the long rewind lengths my setup required. This replacement only acts in a single direction, you want it oriented so that the spring winds up into a tighter and tighter bundle as the spool unwinds. This is more robust.

Print each part individually. I use PetG material. The Customizer should let you change the thickness of the spring to make it apply more or less force.

Print instructions

Category: 3D Printer Accessories Summary

This is a remix of the spring used in VincentGroenhuis' awesome Universal Auto-Rewind Spool Holder.

I use 5 of these on my Prusa i3 mk3s MMU2.0 setup as a replacement for the prusa fiber buffer. They reliably rewind fiber onto the spools each time the MMU tool changes which fiber is going into the extruder.

The remix replaces the spring and housing.
I found the bi-directional spring to be too fragile for the long rewind lengths my setup required. This replacement only acts in a single direction, you want it oriented so that the spring winds up into a tighter and tighter bundle as the spool unwinds. This is more robust.

Print each part individually. I use PetG material. The Customizer should let you change the thickness of the spring to make it apply more or less force.

Print Settings

Printer Brand: Prusa

Printer: i3 MK3 MMU 2

Rafts: No

Supports: No

Resolution: 0.3 mm layers

Infill: No

Filament: generic PetG any
Notes:

Print with enough perimeters so that the spring is solid all the way through.
I think I used 5 or 6 perimeters.

Post-Printing

The housing and spring should assemble pretty easily. Push the end of the spring into the receiver on the housing with a screwdriver to ensure it is fully inserted.

How I Designed This

This was designed in OpenScad. Souce file included.