Filament runout & jam/tangle sensor

thingiverse

When you finish a spool of filament, one of two things will happen. Either the filament leaves the spool peacefully and your printer runs out of filament, or the filament's end is too bent and the filament gets stuck on the spool or when leaving your drybox, or the like, resulting in a jam (which can break or bend something). This sensor detects both run-out and jam/tangle with just 1 microswitch. The detection occurs before any consequences of the jam/tangle. Video of it detecting a tangle: https://youtu.be/7nQCvjHVrjk If the filament runs out, the switch triggers because it is no longer on the filament. If the filament is stuck prior to the sensor, tension in the filament straightens the path through the sensor and bends two flexure springs, coming away from the switch, triggering the sensor. The sensor works for regular or flexible filament. Print the part out of PETG (it is better for flexure springs, and has a low coefficient of friction for the filament path). Absolutely no supports. I used 0.2mm height. BOM: 1x roller microswitch (I used https://www.amazon.com/gp/product/B07BL33XXT/ ), 2x 10mm m2 bolts (12mm or longer if you want to use nuts, I just rely on the undersized holes). If your printer already has a runout switch, you can simply swap this in and wire exactly as the old switch. Mine did not have a runout switch so here's my setup: I use C and NO positions on the switch (so that the error condition breaks the connection). In Marlin's configuration (For SKR Mini E3 V2), I use this: ``` #define FILAMENT_RUNOUT_SENSOR #if ENABLED(FILAMENT_RUNOUT_SENSOR) #define FIL_RUNOUT_ENABLED_DEFAULT true // Enable the sensor on startup. Override with M412 followed by M500. #define NUM_RUNOUT_SENSORS 1 // Number of sensors, up to one per extruder. #define FIL_RUNOUT_PULLUP // Use internal pullup for filament runout pins. #define FIL_RUNOUT_PIN PA1 // Or any other pin. I am using PA1 because my print head wiring includes wires for bltouch, and I don't use bltouch, so PA1 is free. #define FIL_RUNOUT_STATE HIGH // Pin state indicating that filament is NOT present. #define FILAMENT_RUNOUT_SCRIPT "M600" #endif ``` The sensor should, ideally, be placed immediately before the extrusion drive gears. The feed direction is from the side that the switch is closer to. You can edit the .scad file if you want stiffer or looser spring action. Note: make sure your filament drive is strong enough to trigger the jam/tangle detection.