Prusa Compact Extruder rework

youmagine

My printer is a Prusa i3 box-frame, but I'm not entirely satisfied with the printed parts that came with it. Specifically, the x carriage and Wades extruder from http://www.thingiverse.com/thing:119616 aren't ideal for me. I've tried various adjustments to get better tramming than 0.1 mm, but the issue persists. Upon further investigation, I discovered that the problem lies with the flex in the (8 mm) x rods and the positioning of the heavy Wades extruder's center of mass. To solve this issue, I decided to design a new extruder mount that would move the nozzle closer to the bottom x rod and redistribute the weight more evenly. Since I'm using 3 mm filament and a lightweight stepper (250 gm), I need a large gear ratio (1:4) and a Mk8 hobbed gear for sufficient torque. Prusa's compact extruder from the prusa-vanilla repo caught my attention due to its simplicity and light weight (M5 rod and 625ZZ bearings). However, it still requires a big stepper, so I redesigned it with an 8 to 32 gear ratio (up from 8 to 24) to accommodate my needs. To further minimize the center of mass's distance from the x rods, I raised the motor so that it could extend over the top of the x carriage. Since I didn't want to alter the smooth and slop-free x carriage, I designed a mount (based on http://www.thingiverse.com/thing:148536) to attach my E3D v6 directly to the carriage as high as possible. I offset the mount to keep the center of mass close to the center of the carriage in the x direction and then bolted the extruder to this mount using normal 50 mm spaced groovemount holes on the extruder. One of the M4 bolts used to attach the mount to the carriage also holds the hot-end in place. I can now tram accurately across my entire 200x200 build plate, thanks to these modifications. I print parts with Kisslicer medium support (in ABS), and the mount is designed to be a tight fit on an E3Dv6. However, it might be too tight for an E3Dv5, which would require adjusting the extruder_cyl2_height parameter. When assembling the extruder, don't over-tighten the nuts on either side of the front-most bearing against the bearing. The bearing ID will likely be larger than the shaft diameter, causing the bearing to wobble as it rotates. Instead, leave the front bearing a bit loose, like the back one needs to be. I also pack out the shaft where the hobbed gear is with a few layers of aluminium foil before mounting the gear to center it properly. You can find more information and sources at https://github.com/spinorkit/Prusa3-vanilla.