From project description:
Extruding natural ABS at 18"/min. The guide limit on the left isn't quite far enough to the edge. The loop seems fairly unstable seen at high speed, but the tolerance was still within .05mm. I fixed the loop near the end by keeping the filament from getting pushed back past the nozzle. As long as the filament leaves the nozzle at a constant angle for the time it takes to get from the extruder to the winder, the shape of the loop will stay consistent for the rest of the job.
Detailed information and downloads:
Here is older v2: