IR Filament Sensor not working properly.  

New Member

I'm having a lot of trouble with the IR filament sensor of my MK3S. With my original MK3 sensor I had no problem over thousands of hours of printing. When I upgraded to the MK3S the filament sensor just became completely useless. So much so that I'm actually considering downgrading because the sensor wasted two days of printing (so far, I've upgraded just a few weeks ago). It just gets stuck, always in the "1" (closed) position. I troubleshooted the problem and found that the sensor was sitting too low and fixed the problem temporarily by adding a nylon washer to the screw. That fixed the problem for a while, but now it got stuck again.

Has anyone encountered this problem with the IR sensor? I usually run large prints and really depend on the sensor working.

Posted : 11/09/2019 1:27 am
Noble Member

I swear I saw a printable replacement flag that worked better - but I can't find it.

Keep watching for one. See if there is a related Bear upgrade.

Posted : 11/09/2019 2:17 am
Rodrigo liked
New Member

I had something very similar with my printer (new MK3S kit, assembled about 1 month ago), where the filament sensor would always read "1" regardless of whether filament was present or not.

Two things to note first - make sure the IR sensor is seated correctly and be careful with the torque on the bolt (also ensure it is the correct length, from memory I think it's meant to be M3x18 but I mistakenly used M3x20 at first). I found that it should not be too-tight or it starts to skew the lever.

That aside, when manually looking at the "flag" (i.e. the part that blocks the IR) I could see it was never getting far enough out of the slot.
I cut a very small portion off the corner of the "flag" and it hasn't given me any issues since.
To be fair though, I only ran it for about 3 weeks before installing the MMU, which uses a different sensor setup.

Posted : 11/09/2019 1:02 pm
New Member

After troubleshooting again the problem, and thinking I had a solution, some other problems started. Extrusion problems, idlers skipping. Extruder motor overheating... So I solved all the problems downgrading to the old MK3 extruder. Now everything works as expected. It may be my frustration, but it works even smoother than before. Thanks for the help trying to fix this.

Posted : 23/09/2019 10:23 pm

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