Pulse generating jam and runout filament sensor

thingiverse

Note: I removed the cover STL. If people are interested in this sensor, they have to ask for it. This sensor allows for the detection of filament jam or spool end. It uses a multi-pole radially magnetized magnet and a Hall digital sensor (A3144 or equivalent). You can build the circuit yourself or use one similar: KY-003 Hall Effect Magnetic Sensor. Don't use an analog Hall sensor - it requires additional circuitry. Refer to the manufacturer's documentation for details. Instead of ball bearings, this sensor uses short pieces of 4x2 PTFE tube commonly used in 3D printing. I found the magnets (D9X2.2X3) in cheap plug-in mechanical timers. They have five poles pairs. These magnets with even more poles are also available from shops selling servo parts. - Remove any burrs, ensure the mating surfaces are straight and flush. Glue (Cyanolit) or assemble the two parts with two small Phillips screws used for plastic assembly (1.8x8). To glue is fine as you can drill the screw threaded hole to 1.2 and have a perfect alignment thereafter (shaft, screws...). It's easy to break when done. - Drill to 4mm where the PTFE tubes will go. Better done on a drill press.. - Disassemble. - Push the 4mm PTFE tube into the bearing holes, cut flush both sides. Push the bearings a few tenths to prevent the rotor from riding on the housing. Crimp the external sides to prevent the bearings from getting out during operation. - Cut a portion of PTFE tube (about 24), install it in the filament guide hole. Flare both ends and cut flush the filament opening. Rotor: The shaft is 2x18, the rubber roller (D10X6X5) is cut from a D10X6X10 taken from an old printer. It's easy to make a different bushing to accommodate a different inside diameter and even to increase slightly the outside diameter. Rubber is easily "machined" with emery cloth, grinding wheels. There are plenty of ways to make roller the correct size. Could eventually be printed with flexible enough PTFU. Didn't try it here though. Install the shaft in the bushing, center and glue the magnet to both, install the rubber roller (glue eventually). The magnet and rubber roller must run true. Assemble the sensor. Fix the Hall sensor in the cutout, branded face toward the magnet and not touching it. Align and glue the board (or use the screws). Protect the wires with hot glue if you don't use a plug (not done here). Apply power. Check for free rotation and operation (flickering LED). Try with a piece of filament for smooth operation. I personally use RepRap Firmware that supports this kind of sensor. Look at command D591 pulse generating sensor for details in https://duet3d.dozuki.com. Configure the firmware and connect the sensor (GND, Signal, +5V). On a board like the Duet family, an end stop can be used. Should be straightforward. RRF has been ported to different controllers. I use an MSK SBASE 1.3. I use TH4 as input pin. With five pairs of poles, I get five pulses per turn that is about one pulse per six millimeters. An additional 3144 would double this. Note the goal is not to measure the length extruded; it's not a AS5600. It would be easy to adapt it though. This sensor is smaller, simpler, more robust, and impervious to dirt than optical sensors. There's a reason why Hall sensors are used in cars ABS isn't? Note that I integrated this kind of sensor into my direct extruder. It just adds three grams. I found it satisfactory and made this stand-alone version to publish here. Filament used: PETG, no part cooling for max strength. The published STLs are beefier around the filament guide hole than the parts shown. The side holes are also "plugged" to get a better result. It can be mounted close to any direct drive or Bowden extruder. Make sure it turns only when extruding. Here is a video to show it working. It shouldn't be used that way as the filament is moving not just because of the extrusion but the extruder/carriage movement too. This can give false alarms. https://vimeo.com/user79072274/review/395928725/f1927ff35c