i3 y-idler with tensioner

thingiverse

To resolve belt tension issues on my i3 printer, I designed an improved y-axis idler with a built-in tensioner. While an OpenSCAD version is possible upon request, I opted to create the design from scratch. The part prints in PLA with .25 layer height and 60% infill. Slicing was done using Slic3r 0.9.9, which performed well. Assembly requires a M4 bolt for the idler (similar to previous versions), a 624 bearing, and bearing guides. The tensioner utilizes a M3x20 bolt and two M3 nuts. Additionally, two nuts are added on the support rail to secure the idler while allowing movement during tensioning. I modified the shape to octagonal to avoid overhang issues before a big bridge. The y-idler designs accommodate 3mm and 4mm bearing holes for 623 and 624 bearings, respectively. Interestingly, a similar design exists in the box_frame repository at https://github.com/josefprusa/Prusa3/blob/master/box_frame/y-drivetrain.scad.