A large knob/dial for manually turning the lead screw on the z-axis of your Ender 3 (will also fit CR10 and any other printer that uses a T8 lead screw with 4 starts thread and 8.0mm pitch or 2mm per thread).
I remixed this from the https://www.thingiverse.com/thing:2534990 CR10 lead screw knob as I found it kept coming loose. I recreated thew whole knob in solid works and cut a longer thread.
All the text is inset so the knob will print flat and smooth.
Hobby King PLA
Make sure your print the face of the knob on the print bed so you do not need any supports.
You could print the whole model with 35% infill and 3 or 4 walls and 5 or 6 top and bottom layers but I found this to be a bit wasteful. I used per model settings in Cura to print the shaft with the above settings but the knob with only 15% infill and 2 walls and 4 top and bottom layers. Save a bit of filament and time and still strong enough due to the geometry.
Should take a couple hours at most with all speeds below 60mm/s.
If you have descent filament and are confident to print without brim it will come out neater. I used poor prototyping filament (not the HobbyKing listed) and my logo was pushed off the bed during printing first layer but the rest came out perfectly.