Pressure advance with BTT SmartFilamentSensor v2
I have a somewhat interesting issue.
Recently I've installed the BTT SFS v2 filament sensor, which detects both if filament is present and if there is a jam or not. The jam detection works with an encoder that spins whenever filament is running through it.
Pressure advance however works by slowing down and speeding up extrusion based on motion of the nozzle to prevent bulging and oozing.
This however triggers false positives in the jam detection. Without pressure advance it works fine.
Does anyone have experience with this? Below is example code of my Klipper config related to the jam sensor. Raising the detection length from 2.88 to 10 did not solve it and I don't want to put excessive numbers there.
[filament_motion_sensor encoder_sensor]
switch_pin: i forgot lol
detection_length: 10
extruder: extruder
pause_on_runout: False
runout_gcode:
PAUSE # [pause_resume] is required in printer.cfg
M117 Filament encoder runout
#insert_gcode:
#M117 Filament encoder inserted
10 replies
PA isn't the issue. Klipper compares the rotation of the sensor to that of the extruder. It's when one is moving and the other isn't that's the issue. You probably need to tweak a setting. I had to bump the filament distance up on mine.
Indeed it was, my PA setting was 10x too high.
Oh, I did that once. Misplaced the decimal on the PA. It took me far longer to figure it out than I care to admit.
Why is your switch_pin not set?
Is your extruder actually named "extruder" in your config?
Actually this isn't exactly my setup. I forgot the pin number and copied the example piece instead.
Ah OK makes more sense then.
As for detection length, default is 7mm for encoder-type sensing according to klipper documentation. So 10mm is far from excessive and you should be able to bump it even more just to check.
Is your extruder direct drive or bowden?
I have a direct drive. Indeed I want the runout length as short as is reasonable.
What did you set your event and pause delays to?Edit: NVM, looking in to the docs shows they have no relevance in this case.
what accelerations, speeds and PA values are you running with?
Ah, I see the problem. I messed up the calculation, instead of .072 PA I used 0.72. The part that got printed looked quite bad as well so that explains a lot. I've entered more normal values and now it looks much better.
Thanks!
Lol yeah 0.72 PA is absolutely insane especially for a direct drive extruder.