This is a super simple filament presence and jam sensor.

Sensing filament is simple, and is often done with just a simple microswitch. However, many spools of filament have an annoying kink at the end of the roll where the filament is fastened to the spool. This often jams at the filament sensor, resulting in the printer chewing up the filament at the extruder, and resulting in failed prints.

This mod adapts the simple microswitch filament sensor to also include detection of jams due to kinks in the filament. In addition, it will detect other problems such as oversized filament, and potentially when filament gets jammed on the spool, depending on the spool holder.

It is very simple and uses just a single spring. Any spring with a diameter between 4 - 6.5mm and a length of ~10mm should work. Other than that you need a square nut and some m3 and m4 nuts and bolts. This mod is designed to bolt to 2020 but can be adapted to other mounts.

Update: Added a variant of the level designed to hold a length of PTFE tube to minimise filament wearing away at the entrance port.