Required accessories:
608 bearings — 5 pieces
M3×12mm bolts — 3 pieces
M3 self-locking nuts — 3 pieces
In OpenSCAD, you can enable the animation preview function, which is well supported
This knob is specially designed for the 0.3mm nozzle.
If you encounter difficulties when printing gears, it is recommended to use the "Gear Easy Print" mode
https://youtu.be/kl5woZqSD8c
https://youtu.be/4aZfJV-KTPY
https://youtu.be/GwaYSvkLjy0

Added explanation on February 4, 2017:
During the process of printing the third knob, a small problem was found: there was an extra short support structure in the nut installation hole of Frame B. The repaired file has now been uploaded.