Bowden Extruder

This is a quite simple bowden extruder, albeit for a very specific mounting case. I couldn't find a ready-to-use solution so I designed this one from scratch.

My 3D printer is placed in an Ikea housing (Stuva box with glass door) on which I have several of my filament dispenser boxes (https://www.thingiverse.com/thing:2754979). The filament ix fed through the top into the direct drive extruder. This is working fine but I always wanted to try a bowden extruder, just to get familiar with it. This extruder is specifically designed to be mounted on top of the housing, as shown in the images.

Update

I added a bowden extruder body for the original Prusa i3 MK2/S. It's basically the original part with the motor mount trimmed away. I also added an additional hex nut to keep the top mounting spot (the second one I added was a mistake, ignore it ;-) ).

Since the extruder uses a different drive gear I had to recalibrate the steps/mm for the extruder motor. You can do this with the M503, M92 and M500 commands. There's some excellent documentation on the Marlin website. For the Prusa i3 I adjusted the extrusion from 161.3 steps/mm to 142.1 steps/mm.

Furthermore I modified the retraction settings in the Slic3r settings to 5 mm retraction length and 100 mm/s retraction speed. This just a start though and will probably be refined later on.

The first print is shown in the images above. I really did not expect it to work so well right out of the box. It still needs some fine tuning though. It appears there's some over-extrusion and the bed height offset is not quite right.
Another issue I noticed is the extruder motor skipping some steps on high load situations. I used a different motor with higher torque, so maybe the current settings are inappropriate. I probably will just switch to the original Prusa motor.

Other than that it works suprisingly well. :-)

ChangeLog

• 2018-03-10
  Original Prusa motor and drive gear mounted. No more stalls or skipped steps, works fine. Fine-tuning of Slic3r can begin...

• 2018-03-03
  Extruder assembled and tested.

• 2018-03-02:
  Original upload

Print instructions

Parts list

The extruder uses/requires the following parts:

• 1 E3D Hobb-Goblin 5mm drive gear
• 1 E3D groove mount bowden adaptor
• 1 quick connector for Teflon tube
• 1 push fit M5 thread
• 1 625 ball bearing
• 1 5x14 mm cylinder rod
• 2 M6x40 screws
• 5 M3x35 screws
• 1 M3x40 screw (+ spring and washers)
• 2 hex nuts M6
• 1 hex nut M3
• 1 square nut M3