I have limited experience with this sort of printer, but when I have tried to use one, as soon as I unwrapped the reel of filament the tension that kept it neatly coiled would be released, and the whole thing would go "sproing!", like a torsion spring that's suddenly released from captivity. The result was a loosely coiled mess that would inevitably jam as the filament was used. The fix we tried was to rewrap the filament on another reel, which is where the automatic guide would have come in handy. The rewrapped filament would unspool in a more controlled manner than the original, but it still had problems with tangling. If there was some kind of tensioning mechanism, perhaps a brake and filament retainer, that would keep the filament from loosening on the original reel and dispense it in an orderly manner, the rewrapping process probably wouldn't be required.

Andrew Werby
www.computersculpture.com