A working 3D printed friction shifter!
See video at youtu.be/fLMA-8aSsDM
While friction shifters don't "click" into gear like index shifters - they have advantages. A friction shifter is much more tolerant of minor problems like slightly bent derailers or worn cables / housings.
Heavily tested with 7-speed setup - but should work with any number of speeds (front or rear derailer).
I just biked from Seattle to Portland using this shifter (204 miles) without any problems.
With 300+ miles on same shifter - I'm reasonably confident it's pretty solid and should last a while.