What's up when the filaments ends?

[simmonsstummer 0]

I was wondering... when the filament is going to end and you are printing, based on the lenght of the bowden tube and the fact that the motor who pull the filaments is at his ends... how a smaller filaments in the bowden tube can go on?

 

[illuminarti 18]

It can't. Once there's no longer any filament touching the motor drive bolt, (controlled) extrusion stops. You can try to feed in a new piece of filament behind the first one, so that the new filament pushes the old one along. That can work, but you'll lose the ability to do retraction, as only the new filament will move back and forth - nothing will move the old piece of filament back out of the head; you can only keep pushing it forwards until it is all used up.

 

[simmonsstummer 0]

as i suspected.

What if the nozzle is stuck? what i have to do? Opened this post http://umforum.ultimaker.com/index.php?/topic/3801-always-blocked-nozzle-filament-change/ tried everything but the new filament seems to not move forward..

 

[illuminarti 18]

I had it fail to extrude properly 1 time so far, when changing filament on the UM2. I just backed the filament all the way back out, cut off the plastic that had already been through the Bowden, so that I had a clean straight end, and no damage to the filament, and then reloaded it, and it worked fine the second time.