***Update- I'm re-releasing this under the GPL and including the source files.  This last model has a few small improvements as well.  This part was modeled in SolidWorks2018.  Thank you for all the interest!
Long bowden tubes suck!  This was even more apparent after installing a volcano clone heater block on my printer.  You need precise control of the filament to keep blobbing in check.  
Try this experiment-  print out one of the many manual extruder knobs here on Thingiverse and install it on your extruder.  Make sure the filament is fully inserted in your nozzle, and cool down your hot end.  Once it is cool and the filament is fully fused into your hot end, turn the extruder knob back and forth and see how much the filament can move at the extruder with no movement at the hot end.  The longer your bowden tube, the worse this is.
After looking through Thingiverse for a decent direct drive conversion for my CR-10 and not finding anything I liked, I decided to model my own.  This fits on a stock CR-10 using…

So I saw the Pitan and absolutely loved the idea of a printable geared extruder. I gotta admit I was skeptical, but this really works so well!
However, it wasn't exactly easy to make work with the  Ender 3 fitted with a Hero Me when I wanted it to be direct extrusion, so I set out to make some changes.
My goal for this remix was to make it using as many of the parts found on a stock  Ender 3 as I could. And I got pretty close
Features:
Works with the  Ender 3
Compatible with the Hero Me duct
Positioned above the hotend for a straight path from extruder to hotend
Best used with a pancake motor for low weight
Many of the needed parts can be salvaged from an  Ender 3 that has seen upgrades and therefore left spare parts behind
Features remixed direct extrusion adapter that allows for easily taking the extruder off without disassembly
Note: This is best printed in ABS or nylon. PLA can work if you only ever print PLA, but if you plan on occasionally printing PETG, ABS or other higher temp filaments or if…

Клуб обладателей 3D-принтера Ender-3; Ender-3x и  Ender-3 Pro https://ender3.club Если у вас проблема и вы ищете совета то: 1) Распечатайте калибровочную модель:  https://vk.com/album-26626593_269583825  Дефекты лучше всего различимы на сером пластике. 2) Прикрепите несколько фото и/или видео. 3)..