Summary

These are some parts i designed to hold 1/4" clear tubing I used to guide my filament. (see photos).
For printing and assembly instructions see the instructions tab

Instructions

1) print one (1) "feeder" and two (2) "Filament tube holder"
2) remove extruder tension screw and spring
3) slide "feeder over the extruder arm until you can see the extrusion gears through the hole in the top. ( some minor sanding or cutting may be required to get a perfect fit, but note the hole does not need to be centered, there just needs to be enough room to fit filament through)
4) slide the "filament tube holder"'s over the tops of the Z bars.
5) string your 1/4" tubing through the holes in the tube holders and into the feeder.
6) push filament from the end of the tube until it emerges at the extruder.
7) Happy printing!

Printrbot Simple Metal filament tube feed system