An extuder motor indicator made from a 3D Printable Jet Engine's fan by CATIAV5FTW - scaled down to 25%, with a cone or without.

Link to this awesome printable jet engine here: Thingiverse

There are three versions:

1. With an integrated cone - for one color print or use ColorPrint in PrusaSlicer to print the cone in another color
2. With a separate cone and a spiral strip (you can print each with another color)
3. Without a cone

Each of them has a separate version with a brim around blades as the ones without a brim proved not printable for me - as they were lifting from the bed due to not enough surface to adhere (but it seems that it might be the property of the filament I wanted to use).
Versions with a brim have a 0.1 mm high brim helping with the adhesion - set the first layer height to 0.1 mm. You can remove it carefully with an xacto knife later.

There's also a spacer to move the indicator further away from the motor, if your magnet is 3 mm thick (8x3 mm is a standard so you probably need this).

The spacer is supposed to fit inside the little cavity on the base of the Fan for easier positioning ;)

Recommended layer height: 0.05-0.1 mm.

You also need a 8x3 mm magnet and a CA glue (or similar) to glue the magnet, spacer and fan together (just be careful not to glue the fan to the extruder motor ;) ). You will also need to glue the spiral strip to a cone if you choose this version - get a toothpick to apply the glue and a lot of patience ;)

Print instructions

Printer Brand: Prusa
Printer: i3 MK2S
Rafts: No
Supports: No
Resolution: 0,05-0,1