Open Platform Geared B'Struder, tailored for Ender 3 mount

thingiverse

The main goal of this design is to create a reliable and compact geared bowden extruder that has a moderate gear ratio, open and accessible mechanism, and a unique look while staying true to the aesthetic of the B'Struder. It's designed for mounting on the Ender 3 (or possibly CR-10) in the same location as the original extruder. As an added bonus, the idler arm is positioned on the opposite side from the Ender 3 original, so you can have a geared extruder without having to flash a boot-loader and change the firmware. I've been printing with this latest version for about two months now, and I'm thrilled with how well it's working. Full-speed retracts (set to 70mm/s in Cura) with no bending and no detectable backlash are fun to watch. It's also working great for TPE. The gear ratio is approximately 2.5, a touch less than the E3D Titan. This design is intended as a Bowden extruder so the stepper motor can be large. The primary purpose of the gear ratio was for accuracy. I haven't heard a single missed extruder step since using this, and it's even managed to pull my spool off the stand and into the air from a tangle. A key difference from other geared B'Struder designs is that the driving gear is supported both above and below, while still not being totally enclosed in a box. The pressure from the extruder spring pushes the gears together. Along with the Wade herringbone gears, the operation is silent - no clacking gear teeth! It's a bit trickier to set up the drive shaft as the gear has to be supported in the middle of the bolt. An advantage to the extruder stepper staying on the opposite side of the gears is that the stepper shaft is now available for an extruder gear cleaning brush such as on the Flexion. It wouldn't take much work to modify the extruder saddle to accommodate that. I find that the B'Struder design lends itself well to flexible filament printing, and I've made an idler arm for the Ender stock U604 idler bearing with a very tight filament path. It uses the same base geometry so any of the other idler arms available will fit as well. As far as durability goes, I've studied several other designs that people have been printing consistently on for extended periods, and I've sized the gear module and thickness to be similar. I expect the gears to last quite some time - if they do wear out, just switch them out.