Prusa i3 Mk2 / Mk2S / Mk2.5 PSU spacer

thingiverse

I have a Prusa i3 MK2 kit that was shipped in February 2017. Since then, I've upgraded it to a Mk2S in October 2017 and later to a Mk2.5 in April 2018. The bed-leveling search pattern on this printer has led me to believe that the vertical frame is slightly too far back on the Y-axis threaded rods. This issue causes sporadic problems with XYZ calibration. A proposed solution for this problem was suggested by others who have experienced it. They recommended unbolt the power supply unit (PSU) from its position at the back-right corner of the Y-frame, which would allow the vertical frame to be moved forward as needed. This approach worked, but it resulted in a loss of stiffness in the frame. My solution involves printing a spacer to go between the PSU and the vertical frame. This allows the vertical frame to shift forward on the y-axis while still being securely bolted to the back-right corner. To determine the thickness of the spacer (6.88 mm), I unbolted the PSU from the vertical frame, reattached it to the back right corner of the y-axis foot, and moved the z-axis frame further forward on the y-axis's threaded rods until the bed-leveling search algorithm was centered in the y-axis on the marker points on the heated bed. Then I measured the gap between the vertical frame and the PSU and printed the part accordingly. A more complete description of this issue can be found here: https://github.com/prusa3d/Prusa-Firmware/issues/616#issuecomment-385211047