Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:3440278.

Why this extruder? Velleman's K8800 printer comes with an extruder and says being ready for TPU printing. If you ever tried Ninjaflex with it.... Well, you won't be able to. Flexible filaments need very tight leading or the will roll on the pushing wheel resulting in extruder blockage and print failure. The original filament detector is very unreliable as well, and using this endstop technique provides with a very reliable solution. The original mounting solution is also not very clever as you need to unmount the whole extruder, stepper included to change anything. This solution makes the extruder easy to remove and replace.

Enjoy printing not only soft/flexible filaments but also any other 1.75mm filament with this extruder upgrade!