Kossel 2020 rigid carriage with eccentric wheel axis

thingiverse

After fitting SgaboLab's carriages to my kossel I was surprised that my auto calibration in marlin 1.1.8 standard deviation fell from around 0.025mm to ~0.05mm with very poor first layers due presumably to the carriage offset effectively pseudo rotating the position of the towers. I noticed that the arms were no longer centred with respect to the tower (from side to side / laterally not closer/further from the centre of the bed) because apparently he had some wheels that were bigger than the others so he had included a 1mm offset in the 3x M3 holes to compensate whereas my wheels are all the same diameter! (21.4mm) I really like his design as the previous reinforced carriages I used had a section which wrapped around the entire 2020 extrusion where as these carriages only cover the front face. They also are quite rigid. I've remixed his design to shift the 3 x M3 holes 1mm over as I measured 24mm and 26mm from the top of the arm retaining bolt head to the respective side of the extrusion. I can now measure 25mm on both sides. Thanks again SgaboLab for your design! I now have awesome carriages and my std deviation is back down to 0.023mm with marlin configured to do +/- 0.05mm. ( MIN_STEPS_PER_SEGMENT = 4, 80 steps per mm) N.B. I also added stls with 2mm x 9mm washers built in as well as 2.5mm x 9mm as the original design required the use of additional washers. If the washers are too wide and printed out of plastic they can deform when you tighten the wheels up and start to contact the rotating bearing dust seals etc.