While I have not had issues with filament tension or the extruder motor not being powerful enough to pull it off the reel I do feel I could improve on my existing path. First a bit of history.....

When I first reflashed my DaVinci to run the Repetier firmware I printed a new spool holder for use inside the machine and the parts required to feed this to the extruder.

http://www.thingiverse.com/thing:592197

This works ok but I cant help but tinker and incrementally upgrade my machine ;)

First up was the spool holder. My first change was to use a remixed version of the spool holder side plate to provide longer fixing lugs and stop the holder moving so much.

http://www.thingiverse.com/thing:1351834

Spool Holder longer lugs

The second was to replace most of the rest of the holder with a version that ran bearings for the spool support and therefore removed any resistance to the spool rotating.

http://www.thingiverse.com/thing:695976

Spool Holder

NOTE: I used this design but kept the longer lugged side plate from the previous.


Next was the filament path. The design I used has the corner bracket and filament guide over the Z-axis lead screw. This works ok but is not resistance free especally at the corner loop where the filament changes direction by 90 degrees in a short space. It is also kinda fiddly to get the filament through the guide cone with the z-axis rodes and lead screw in the way. 

Filament Top Feeder

Filament Corner Feeder

I also wanted the filament to come out in a similar place to the original. I achieved this with a length of PTFE tubing (2mm inside, 4mm outside diametres) running between the spool holder (now on the right side of the machine) up behind the metal work and out of the hole in the plastic casing that would normally be for the second filament cartridge.

Here you see the tube at the spool holder end. There is no need to fix it in place since the extruder motor will try to pull this tube and I have secured it at the other end.

Guide Tube Spool end

Here is a view of the tube running up the back of the machine. Notice the highlighted area, this is where the tube passes through the plastic case to the build area. I have secured a small cable tie around the tube to prevent it from being pulled through the hole. A little rubber gromit would be idealy here but I didnt have one and the cable tie is ALL that is actually needed to keep the tube in place.

Guide Tube Path

Finally you see the hole it passes through from the other side (build chamber side)

Guide Tube Extruder End

This means the filament now comes off a bearing supported roll and passes through a PTFE tube for it's entire run until just before the extruder. This greatly reduces the friction on the filament path and therefore the force required to pull filament through.

For those that noticed the little yellow sponge in the above photo. This is a standard sponge with a small split cut in it. It lives on the filament normally and the filament is pulled through it. This clears off any dust on the filament before it gets into the hotend. I do NOT use any form of lubricant on my filament so this sponge is dry.