Zaribo MK3 Indirect Filament Sensor Mod

thingiverse

The new laser filament sensor included with the MK3 is less reliable than I would have liked, especially when printing with shiny transparent filaments. Some clever designs have been circulating that utilize a ball bearing as an indirect filament sensor indicator for the stock mk3 extruder. Take a look at these innovative designs here: https://www.thingiverse.com/thing:3091625 (Firmware modding instructions are provided on this page) and https://www.thingiverse.com/thing:3129921. I was inspired by these creative designs to upgrade the R3 version of the Zaribo MK3 Extruder by vekoj. Since I was in the process of a full extruder rebuild, I decided to integrate it directly into the body rather than create an addon like the original designs. I also incorporated my flex mod and chamfered the filament entry into the sensor area to enhance loading and unloading filament. This upgrade has been running smoothly for about two weeks now with no issues! It has detected 2 jams caused by bad filament diameter, and the filament autoload works flawlessly. No false sensor triggers have occurred yet, and I've mostly been printing in shiny black or clear filament. I used a 623zz bearing that I had lying around from an old project, which you can find here: http://a.co/d/a8SzAqF. If you're using the bowden cover, it requires these pneumatic connectors: http://a.co/d/6tg03sJ. Make sure to print the Sensor Pin with supports; it's the only part that needs to be printed with supports. Instructions: 1. Print the parts in PETG at minimum; PLA will cause issues with hotend heat. I used 0.2mm layers, 4 perimeters, and 10% gyroid infill, but feel free to adjust as needed. 2. After printing the body, ensure that you remove the two thin supports marked as "CUT" in photo 3. No other supports are necessary to print this part; you can use pliers to easily remove these supports as they're only 0.4mm thick. 3. Assemble the extruder as usual until it's mounted on the X-Carriage (make sure to use the one from this page). 4. Secure the 623 bearing with an 18 or 20mm M3 screw into the top of the extruder body; rough up the bearing surface using a metal file to ensure grip. 5. Insert the filament sensor into the diagonal slot on the top of the extruder body and use the Sensor Pin to secure it in place. Plug in the sensor cable. 6. Place either the Normal or Bowden Sensor Cover on top of the extruder and secure with a 10mm screw; you may need to clear out the alignment grooves on the front bottom of the cover to fit the two bumps from the body. 7. Modify your firmware as stated on this page: https://www.thingiverse.com/thing:3091625, and you're good to go! This modification is necessary because you have to change the direction that the sensor expects for filament movement. Compiling Firmware Notes: - If you're using Windows, modify platform.txt here: C:\Users\USERNAME\AppData\Local\Arduino15\packages\arduino\hardware\avr\1.6.11\platform.txt The github instructions are confusing, and this was my biggest issue when getting compiling errors; make sure to add the flag line from step 3 on the prusa firmware github. - The version of the AVR Boards library MUST BE 1.6.11 or less; newer versions are not supported. - Only this change is necessary: Flip the signs in the pat9125.c file, changing the '-=' to '+=' for the Y value; there are three places in the file where this occurs: pat9125_y += iDY; //negative number, because direction switching does not work - Sensitivity changes in the firmware are not necessary for this mod since it uses a larger and wider bearing that's placed closer to the sensor.