Duet3D Magnetic Filament Monitor Mod

/// Update: I have an alternate version of this modification located here https://www.prusaprinters.org/prints/41444-duet3d-magnetic-filament-monitor-mod-v2. ///

Do you have a Duet Magnetic Filament Monitor, and wish it was more reliable, well your wish has come true!

I was about ready to give up on my monitor, I had it disabled 90% of the time because it would give me false filament runout detection constantly. So, I decided to open it up and check the spring tension, but I found that the bearing had shifted inside the housing instead. There is a lot of space for the idler assembly to move around, and if it moves to high up, the bearing no longer presses against the filament.

The photos show where I originally found the bearing, and how much space is in the cavity once I pushed it back down. So, I made a simple little spacer that fits on top of the idler assembly, and it's small enough that it just floats around and it doesn't press on the bearing, so from what I can tell the bearing is still allowed to spin, but it now stays in place and remains on the filament.

Normally I would get a false filament runout detection every 10 to 30 minutes, sometimes I would go to bed with a print running just to wake up the next morning to see that the printer is paused because it detected a filament runout shortly after I went to bed, but there was plenty of filament, and it wasn't jammed.

Since putting this spacer in, I've been printing for the last 2 days without one false trigger.

We are in the process of designing a better idler assembly, and when we come up with one that is reliable, I'll post it here.

So, if you have a Duet Magnetic Filament Monitor stuck in a drawer someplace because it just didn't work well, dig it back out and give this little mod a try!

Print instructions

It's a pretty straight forward print, I printed it with .2mm LH, and I think it took 2 to 3 mintues to print.