Strange filament sensor behaviour
Good afternoon folks,
I'm getting some strange behaviour with my Prusa MK3S+ - it was assembled by Prusa and delivered mid March. I've been printing fairly successfully and its been pretty much non-stop.
I think this is linked to light coloured filament, its always prusament and it's happened to me on grey based filaments but possibly also galaxy black where the print head will move to the front of the bed and prompt for a filament change. There's no blockage, there's no problem with the reel, it just wants me to unload, then load the filament.
The last few times this has happened, its been around midnight, about 3 hours or so into a print, it happened sunday night and I lost 7 hours or so of printing. I unloaded, snipped the filament to 45 degrees, reloaded and it carried on printing for another 16 hours without stopping.
Overnight it did the same thing again on a new print, 3 hours in, stops and asks for a change. Did the same, working again. I set it back off again at 7:30am and it stopped and did the same thing about 15 mins ago. So I've turned off the filament sensor.
I've checked through the troubleshooting docs, I've loosened off the screw at the back a little but that doesn't appear to have made a difference. I've double checked the gcode for a colour change and there's nothing there.
Has anyone encountered anything similar? It can print for days and days and days and be fine, then it'll just decide it needs a filament swap.
At the moment I think I'll just disable the sensor before bed.
Thank you very much in advance.
Best Answer by FoxRun3D:
The two most frequent reasons are a malfunctioning sensor or an inadvertently inserted color swap (but that one would happen always at the same place). I would take the sensor out and reseat it. Could be a broken sensor but I've never seen one personally.
RE: Strange filament sensor behaviour
Some people say the filament hole wears oval and that re printing the extruder top cap. Resolves the issue. I would consider re printing the top cap and the adapter printer block that. Holds the ball bearing
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: Strange filament sensor behaviour
Thanks Joan - I changed the top cap to the one that came with the enclosure that supported the PTFE tube. I might see if I can order a spare one as a first point of failure https://www.prusa3d.com/product/filament-sensor-cover/
RE: Strange filament sensor behaviour
The two most frequent reasons are a malfunctioning sensor or an inadvertently inserted color swap (but that one would happen always at the same place). I would take the sensor out and reseat it. Could be a broken sensor but I've never seen one personally.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: Strange filament sensor behaviour
Thanks fuchsr, that was my first thought too - The 2nd overnight stop was within about 3 mins and I noticed that when it went back to the print it went back to a different leg (printing 10 legs for a boardgame table) that it was different to the other night. Also double checked the gcode for an M600.
I'll give the reseat a go too thank you so much!
RE: Strange filament sensor behaviour
Another potential issue is metal fatigue in the wiring due to constant motion.
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
One possibility is something interfering the sensor - a whispy fragment of stringing or even cat hair ... ?
Cheerio,
RE: Strange filament sensor behaviour
To exclude other causes you can of course also turn the sensor off and see if prints complete successfully.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: Strange filament sensor behaviour
To exclude other causes you can of course also turn the sensor off and see if prints complete successfully.
That’s the current state of play. The print is due to finish in ten mins 🙂
Another potential issue is metal fatigue in the wiring due to constant motion.
I would hope not, the printer is only a month old!
One possibility is something interfering the sensor - a whispy fragment of stringing or even cat hair ... ?
Cheerio,
No cats and the dog doesn’t molt thankfully. The printer is in a Prusa enclosure but it’s probably worth me checking again for some whispy filament.
I’ll do some digging around the sensor and the whole unit tomorrow morning when I get up.
Thanks for all the suggestions I really appreciate it!
RE: Strange filament sensor behaviour
Contact prusa through live chat it's all under warranty they will send new parts of needed
Please help me out by downloading a model it's free and easy but really helps me out https://www.printables.com/@Hello_474427/models
RE: Strange filament sensor behaviour
Thanks everyone.
I contacted live chat but they wanted me to take the extruder apart and carry out some checks before they'd send out any spare parts. They thought it was probably an over tightening of the lever. They gave me the option of sending the printer back for repair or taking it apart myself - which I'm happy to do so at the weekend if required. I said I was a little disappointed that the issue was happening on a paid for assembled unit and they gave me a £10 voucher for some spare parts should I need to purchase them which I'm more than happy with.
I re-seated the sensor and used some compressed air around the ingress points and things whilst I had the filament out, turned off the auto load and poked a little filament in and out to test the 1/0 reading on the filament sensor. All looks fine, it hasn't skipped a beat since then and has been printing for around 48 hours straight now on that same filament.
Thank you very much for getting back to me, fingers crossed it'll be okay going forward and if not, I know where to check next.
RE: Strange filament sensor behaviour
Just wanted to update that since reseating the IR sensor and blowing out the dust with some compressed air I haven't had this issue reoccur. It was intermittent which means it could still happen at any moment but I've printed with galaxy black, azure blue, gravity grey and a fair bit of esun brown the last two weeks with no issues whatsoever.
Thanks again for all your help.