fnoxib

I suggest having the filament pass through an opto interrupter or a micro switch to detect its presence or absence. Locate this detector on the supply side of the feeder mechanism. As soon as no-filament is detected during printing, which would be *while* the feeder still had a grip on and thus could still retract what's in the Bowden tube, automatically go into pause with an option to change filament. This is pretty basic software and hardware stuff which should be easy to implement. It could even be offered as an after-market feeder assembly and would make a bunch of people very happy to not have half their prints made of air because they didn't realize their filament roll did have enough material on it. Also: it maximizes the use of the end of the roll. There's still a little waste between the feeder & the Bowden tube, but except for that span, the entire roll could get used no matter the size of the print. The auto-advance phase for material loading could become smart by starting when filament is detected rather than when the button is pressed. On my UM2Go, it's difficult to get the filament in position AND press the button at the same time. With a filament detector, I could just press the button and then only when the filament was properly in place, the auto advance phase would begin.