Stuck on change filament loop
Hi,
I want to see if the community could help me diagnose the cause of this weird problem I have with MK3S minus the MMU. I'm on the FW 3.9.0 and PrusaSlicer 2.2.0. Shortly after I removed the MMU from my MK3S, the printer would get stuck in an unprompted filament change loop. Sometime it will happen right after level calibration, other times it will print 10~20 layer before the unprompted filament change loop shows up. Even after I changed the filament (unload and reload) as it prompted, it will start the process again prompting change filament. Please see the video I posted on YT.
Here is a video to the behavior >
Thanks in advance for any help.
RE: Stuck on change filament loop
BTW. It was displaying this unprompted filament change with the previous FW as well.
RE: Stuck on change filament loop
@ten13th
Hi Ten13th,
are you intending to put the MMU2S back on the printer?
If not you have the wrong filament sensor configuration. you currently have the MMU2s, extruder Filament sensor tower option, unfortunately this setup is very likely to give problems when the filament runs out. this is because ( When working correctly) the MMU tower filament sensor will not identify filament out, until the tail end of the filament is leaving the Bondtech hobbed gears. which means it it unlikely to be able to pull the filament stub out of the extruder after the filament has run out...
Putting that aside, the filament sensor is over sensitive at the moment. with luck you can slacken the tower mounting screws and move it over a little bit to make it less sensitive. (that's fine if you intend to put the MMU back, (and the filament sensor being out of adjustment may have given problems with the MMU2)
If you don't intend to put the MMU2 back, it might be better to install the normal filament sensor setup. 
I have both types of filament sensor, and found then a bit difficult to setup because you needed to switch the LCD menu to the sensor status menu to check the status of the sensor.
I resolved this by putting a 5 volt LED in paralell with the sensor output, and this gives immediate sensor status indication.
this picture of the standard mk3S filament sensor was taken when I was testing the setup, I have since made a cover with a hole for the LED.
this is the modified setup for the MMUtower filament sensor
also, your printer is doing 3x3 Mesh bed levelling, there is a 7x7 mesh bed levelling option that tests 49 points on the build plate, giving better results.
I hope this helps.
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Stuck on change filament loop
Hi Joan,
Thanks much for the tip. Indeed, it was the sensor. Once I shift it over, the problem went away.
That LED hack is pretty great, I look forward to add that on mine.
Regards