Easy exchange filament extruder

For a new printer I needed an extruder setup.

Because I print with ABS a lot this one is designed to do just that (but it also works with other filaments).
With ABS printing you do not want to have airflow passing the printed parts.
Therefor the air is inhaled from above. Then passed through to the Hot-end and then back out at the top. The same airflow construction is also made for de motor. This way the printed part never gets cooled by these 2 fans. For the dimensions of these snail house fans, see picture.

Also I wanted an extruder on which changing filament is easy. On most extruders you can’t see the filament wire and that can make it hard to change filament. If you run out of filament due the print, you are in big trouble. Therefor I made this one in such a way that you can always see the filament wire.

Because I have 3 different sizes of Filament (1.75mm, 2.85mm & 3mm) this extruder can use them all.
To do this I have made an exchangeable filament wire guide. For th