With this design you won’t have the problem that your Extruder spring gets too weak over time, parts of the extruder breaking (on my ender3 the Extruder arm broke twice) or trouble at removing the filament.
This design uses a M3 flat head Philips screw (max 12mm long) to clamp the filament to the Extruder Gear (d = 11mm).
To use it, you just must insert a nut in the Base and of course also screw the ball-bearing (witch presses against the Filament) into the lever. Then just change your existing extruder to this one and you are ready to go (No post process needed).
(before you start a print do a test extrusion to be sure that the right amount of material is extruded and recalibrate the e-steps, if needed)
This design is able to print flexible Filament, the only step you have to do is to achieve it is to smooth down the holes, the filament goes through, with a small round file or a drill (d = 2.5mm) for maximal accuracy and minimal drag.
If there is a Problem leave a comment I will see if I can solve it (keep in mind that this design is not finalised, and I will upload better Versions!)