Filament Sensor Readings Strange Result M591

[RogerPodacter]

Using the magnetic filament sensor, i've been getting a negative number over the last 24 hours as i'm running a 24 continuous print. the min % is negative and i dont understand why.

10/17/2022, 6:33:45 AM 	M591 D0
Duet3D rotating magnet filament monitor v4 on pin 121.io1.in, disabled, sensitivity 27.00mm/rev, allow 1% to 199%, check printing moves every 3.0mm, version 4, mag 131 agc 96, measured sensitivity 28.15mm/rev, min -33% max 129% over 60380.6mm

10/16/2022, 6:37:00 PM 	M591 D0
Duet3D rotating magnet filament monitor v4 on pin 121.io1.in, disabled, sensitivity 27.00mm/rev, allow 1% to 199%, check printing moves every 3.0mm, version 4, mag 129 agc 96, measured sensitivity 26.68mm/rev, min -9% max 121% over 2884.3mm

[infiniteloop]

@RogerPodacter

@RogerPodacter said in Filament Sensor Readings Strange Result M591:

the min % is negative

Most common reason for negative readings is filament backslash. This happens if the extruder looses grip or doesn’t have enough torque due to high counter-pressure from the nozzle. Common reasons for that are a clogged nozzle or printing too fast / too cold.

[dc42]

@RogerPodacter as @infiniteloop said. Also, if the distance between the filament monitor and the extruder drive inlet is not short and the filament well-constrained over that distance, then that will also cause inaccuracy, including negative minimum reading.

[RogerPodacter]

@dc42 thanks. so my filament sensor performs beautifully, its just this one complex and long running print that seems to cause this behavior. i have the filament sensor directly on the extruder so only about 5mm of tubing between the sensor and entrance to the orbiter.