yes... hard to find a small tension spring then... using rubber band as a temporary workaround.

This is a model of a direct drive dual extruder with a single nozzle and a single stepper motor. A switching between extruders (filaments) is done by a servo mechanism. To drive this mechanism, I used a HS-225 mini servo that is as strong as bigger and heavier HS-422 servo. The model is designed for DyzEND-X hotend by Dyze Design.
See video of the first print: https://youtu.be/STZg94co8CI
Advantages:
No filament oozing from the second nozzle.
No nozzle misalignment.
When printing from one filament on almost empty spool, it is possible to schedule switch to the new spool in the middle of the print.
Disadvantages:
Wasted filament by every filament change.
Can print only with temperature compatible filaments.
Needs some retraction calibration before the first use.
I just rarely use the dual printing with this extruder because DyzEND-X hotend has a big melt-zone so there is a lot of wasted filament by switching. It is worth to print just bigger parts with large layer height to minimize the wasted filament ratio.…