Thank you for the reply Bill, why I asked the previous question (aside for having the need for such a solution) was a video I saw from a fair where the chameleon was featured. Plenty of upgrades and features were discussed for example the reduction of parts and sensors. The motor torque could be used for sensing where the filament was after calibration if I understood things correctly. Here I see a scenario that seems logical at least in my head: A sensor detects a runout upstream from the printers own runout detector. This triggers the chameleon to feed a new strand behind the soon to run out filament for a certain length to assure grip in the printers extruder gears. I have seen an example of such a device on youtube that is spring actuated by mstrwizard1, but the stroke is short and only caters to bowden extruders where the device can be close to the grip gears. I am thinking maybe the chameleon could do this with just some simple code regardless of distance to the extruder gears? Could it push the new filament in behind the old strand while sensing the stop and iterating with short enough pulses/pushes to avoid the printers run out sensor to trigger until the desired length is achieved and the new filament is gripped?