Smart Filament Microswitch Sensor

thingiverse

This is a simple, mostly single piece filament monitor using a cam actuated microswitch. With the hob I used, 34mm is the distance filament travels between clicks, and has worked fine as the configuration for klipper. I just put this together "temporarily" from parts I had lying around, but it proved reliable enough that I didn't bother making a better design, but I hope for remixes of this. The idea is to have a smart filament sensor out of simple parts almost everyone will have lying around from printer maintenance and upgrades. Parts: - 1 x M5 screw (for the axle, long enough, excess doesn't matter) - 1 x M3 screw (for the clamping roller bearing, too long will interfere with the cam) - 2 x M5 nuts - 5mm ID extruder hobbed gear - 1 x 3mm ID, 10mm OD bearing - 2 x 5mm ID, 9mm OD bearings - 1 x microswitch - 2 x 1.5-2mm wood/plastic/self/tapping/M2 screws for the microswitch - wire the switch - 2mm ID, 4mm OD PTFE tube - 4.0mm drill for clearing the mounting holes for the tube Instructions: - Print all the parts, supports aren't required, print the flat side down of the sensor body - Press the 3mm ID bearing into the filament-clicker-roller_pad part - Screw the roller_pad into the upper spring tension arm, make sure it spins freely - Press the two 5mm ID bearings into each side of the sensor body - Press one M5 nut into the cam (filament-clicker-wheel) - Screw the microswitch into the body of the sensor - Drill open the PTFE tube holes to exact dimension - Press a piece of PTFE tube into the microswitch side guide hole - Mount the extruder hobbed gear on the M5 screw, tighten the grub screw tight enough like you would do on a stepper motor - Tread the M5 into the body, help the idle roller clear it. They need to be tightly pressed together for the filament to grab the hobbed gear - Screw the cam on, lock it in place with another M5 nut. - Make sure the cam axle spins freely and triggers the microswitch. Adjust the microswitch arm otherwise - Mount the sensor on the printer, you need a length of PTFE tube between the sensor and the extruder in order for this to work. I included the FreeCAD design document in case you want to adapt this for other parts and mountings.