Prusa Mk3S IR Filament Sensor Modified Mount

thingiverse

I was struggling with my Original Prusa i3 Mk3S because the filament sensor kept indicating that there was filament present when it had actually run out. The issue turned out to be a common problem caused by a design flaw in the flag inside the extruder assembly, which is pushed by a ball bearing that comes into contact with the filament. To solve this problem, I decided to get rid of the entire flag and ball bearing setup designed by Prusa and simply pass the filament through the IR sensor instead. This new design replaces the top cover with one that holds the IR filament sensor, making it a more reliable option. However, there is a drawback to this arrangement. If you use clear filaments, this design will not detect when the filament is present because the infrared light will pass right through it. Since I don't plan on using clear filaments, this isn't an issue for me, and if I do decide to use them, I can simply disable the filament sensor during printing. When printing out this modification, there are some small parts in the final layers that may deform if they get too hot. To avoid this, it's best to print these parts separately so each layer has time to cool down before moving on to the next one. This design reuses the M3 and M2 screws that hold the cover and filament sensor in place from the original design. However, you will need an extra M2 nut to secure the filament sensor in its new position. I hope this modification will be helpful for others who have experienced similar problems with their Original Prusa i3 Mk3S.