MK2.4S Bear extruder using hobbed pulley from MK2S

thingiverse

UPDATE 08.06.2019 - Clogging was due to a faulty PTFE Tube, so no problem with the design. Feel free to try it. I also added body and idler parts for the original 625 bearing from MK2S extruder. READ FIRST! If you decide to try this - print the original extruder spare parts just in case you have problems and you have to go back!!!! This is a remix of the latest Bear extruder design for the "S" Prusa printers by Grégoire Saunier (awesome work Greg!!). The original design is still in testing phase, but fully working. It can be found in the dev tree on his Github: https://github.com/gregsaun/bear_extruder_and_x_axis/tree/dev I named this one MK2.4S since it's using the hobbed pulley from MK2S. I was always suspicious about the Bondtech gears on the new MK3/S causing the "inconsistent extrusion" issue (https://github.com/prusa3d/Prusa-Firmware/issues/602) That's why I decided to remix the Bear extruder. I'm still not sure if this fixes the issue (needs some expert testing), but feel free to test and share your results. Since the original MK2S hobbed pulley has smaller diameter, I had to modify the extruder body, bearing idler, and the X-carriage. In short, the motor had to go right 0.65mm. I also found out that the trapezoidal nuts on my MK2S X ends have 13mm diameter, while the MK3 ones have 13.5mm diameter. So I also edited the X ends to fit the older nuts. This design is made for the MK2.5S firmware, but should work for MK3S also. What you will need for MK2.5S to MK2.4S Bear extruder: 1. MK2S hobbed pulley (https://shop.prusa3d.com/en/spare-parts/126-mk2-extruder-hobbed-pulley.html) 2. Original 625 bearing from MK2S extruder OR 623zz bearing for the idler (https://www.amazon.com/623ZZ-Double-Precision-Bearing-Bushing/dp/B01FE2EWO8) - I highly recommend the original 625 bearing and dowel pin. If you decide to use 623zz bearing then for dowel pin just use 3mm screw and cut it to the needed length. 3. 50mm PTFE tube (if coming from MK2.5S or MK3S) (https://shop.prusa3d.com/en/spare-parts/736-PTFE-mk3-mk25-mk2s-mmu2-hotend.html) I highly recommend to use the original MK2S PTFE tube since it has slightly larger internal diameter and will be more "clog resistant". 4. The modified X ends if your trapezoidal nut's diameter is 13mm. Otherwise, use the original X ends from the Bear extruder github. 5. All left parts for the bear extruder (https://github.com/gregsaun/bear_extruder_and_x_axis/tree/dev/printed_parts/stl) 6. Modified MK2.5S firmware for XYZ calibration (https://vmod.wordpress.com/2019/05/26/mk2-5s-bear-extruder-and-firmware-3-7-1-xyz-calibration/) 6.1 You also need to modify the E steps in the firmware to match those on your original extruder. You can calibrate your value using this guide: https://mattshub.com/2017/04/19/extruder-calibration/ What you will need for MK3S to MK2.4S Bear extruder: Same as above, you just need to use my modified X carriage for MK3S and the Bear X ends for MK3S from Greg's github. Also, use the MK3S firmware with the same modifications (E steps, XYZ calibration). Note that I haven't tested this on MK3S and I can't confirm it's working. If you test it, please share your experience. FINAL RECOMMENDATION! Tighten the idler screw a lot! It's only one screw compared to the MK2S and it needs tension to grab the filament right. Once again, I would like to thank Grégoire Saunier for all his work on the Bear frames and extruder and for sharing it all with the community! Use at your own risk and have fun! Best place for comments: https://www.facebook.com/groups/prusabearupgrade/