MK3S Filament Sensor Malfunctions
A bit of a PSA for any new MK3S owner who is suffering from an apparently non functional/glitchy filament sensor, this is a known (though seemingly fairly rare) problem. It appears to be solved with a replacement sensor (in my case, at least), which would seem to suggest a defect.
To verify that you're seeing the same problem (as has been reported by a few of us in the "Original Josef Prusa i3/MK2/S/3 Owners" facebook group, check the following:
1) Check the filament sensor status in Support -> Sensor info on your printer. Those suffering from this problem see it stuck 1.
2) Try loosening the front panel of the extruder assembly (the piece with the extruder motor attached). When the part is still connected but loose (gap between front and back panels at the top, at least. Probably variable by case), the sensor will start reporting 0 and function properly when filament is inserted.
3) Verify that the filament sensor arm and metal ball are installed properly, and that they move freely (remove the front panel of the extruder assembly and verify that the magnets are repelling each other such that the ball rests in the filament path, and that you can easily push the lever to the left)
4) Verify that the IR sensor wiring is correct against the assembly manual.
If you are seeing this behavior, I recommend you contact support (online chat is pretty good and relatively speedy), describe your problem and go through all the debugging steps they recommend. I suggest that anyone else encountering this problem comment here simply for purposes of documentation (and to aid future debuggers).
Re: MK3S Filament Sensor Malfunctions
Did you print the upgraded extruder parts, or are they from Prusa?
Re: MK3S Filament Sensor Malfunctions
Did you print the upgraded extruder parts, or are they from Prusa?
Mine was a full MK3S kit. The problem appears to have been the sensor itself, though, rather than the printed bits.
Re: MK3S Filament Sensor Malfunctions
I got the same issue with my sensor.. No reaction and under Sensor state it does not change even if I lift it and put a filament between the sensor.
Wiring are good (triple checked)
Guess I need to check with support.
Re: MK3S Filament Sensor Malfunctions
Did you verify the sensor arm was moving freely before final assembly?
Step 6 of the E-Axis Manual:
The Mk3S sensor is mechanical. The filament pushes a bearing which pushes an arm into the IR sensor light path. If all of the parts don't move freely it can't work.
Re: MK3S Filament Sensor Malfunctions
Tim, the problem I'm referring to does not appear to be linked with the lever component of the sensor system. The MK3S's filament sensor is actually a hybrid. The filament pushes a ball which actuates the arm which triggers an infrared sensor.
When was debugging the problem for myself (with Prusa Support) we determined that the sensor was assembled correctly. We spent some two or three hours checking various possibilities. In the end, they decided to send a new sensor (the IR sensor specifically) which I installed yesterday and which resolved the problem. I posted here as an advisory for others of this known issue (there are at least a couple others on the one facebook user group that I'm in).
I will modify my OP to recommend verifying physical assembly, however.