Filament runout sensor for Ender 3

thingiverse

I have made a copy of the excellent two roller filament sensor by Bodroi. I wanted to use the top roller as a filament guide to help the filament path, and so it is designed verticaly, which unfortunately adds weight to the moving part, trying to keep the microswitch closed. To overcome this I have added a small (0.3*4*20mm) spring. The unit is designed to be held in place by a tie wrap. This tie wrap is strong enough to hold the device in place when a filament break is detected and the filement is retracted, - when it will probably fail to re-align with the hole!. So the "rewound" filament will probably be found in a tangle between the sensor and the drive. (update- added render of the device with transparent "top". )