Kossel 2020 rigid carriage with eccentric wheel axis

thingiverse

After installing SgaboLab's carriage designs on my kossel, I was astonished by a significant drop in my auto calibration standard deviation in Marlin 1.1.8 from around 0.025mm to ~0.05mm due to poor first layers caused by the carriage offset effectively rotating the towers' position. I discovered that the arms were no longer centered with respect to the tower laterally because SgaboLab had included a 1mm offset in the 3x M3 holes to compensate for wheels of different diameters, whereas my wheels all have the same diameter - 21.4mm. I'm impressed by his design as previous reinforced carriages I used wrapped around the entire 2020 extrusion section, but these carriages only cover the front face and are quite rigid. To correct this issue, I remixed SgaboLab's design to shift the 3x M3 holes 1mm over since my measurements showed 24mm and 26mm from the top of the arm retaining bolt head to the respective side of the extrusion. Now both sides measure 25mm. Thanks again to SgaboLab for his awesome carriage designs, which have improved my std deviation back down to 0.023mm with Marlin configured for +/- 0.05mm (MIN_STEPS_PER_SEGMENT = 4, 80 steps per mm). I also added STLs with built-in washers, including 2mm x 9mm and 2.5mm x 9mm, as the original design required additional washers. Using wide washers printed from plastic can deform when tightened, causing issues with rotating bearing dust seals etc.