Prusa i3 MK3 X End Idler to fix belt rubbing and twisting

thingiverse

Modified X End Idler plastic part for the Prusa i3 MK3 fixes common problem of the X belt twisting and rubbing. The original part, whether initial or improved R2 marked version, provides insufficient support for the belt roller axle screw which gets pulled askew by belt tension as a direct result. This part completely resolves the problem on my printer. The original part can be found here: https://github.com/prusa3d/Original-Prusa-i3/blob/MK3/Printed-Parts/scad/x-end-idler.scad, and https://github.com/prusa3d/Original-Prusa-i3/blob/MK3/Printed-Parts/stl/x-end-idler.stl. Modifications include: Axle screw head bore reduced from 6 to 5.6 mm for a press fit. Axle screw shaft bore reduced from 3.1 to 3.0 mm for a press fit. The chamfer on the axle screw head bore is removed, increasing surface area supporting the screw head. A 1 mm protrusion is added to the axle screw head support to increase surface area supporting the screw shaft. This reduces clearance between the screw head and Z lead screw to about 0.5 mm; ensure there's no collision. As weight is not a concern here, consider using a higher infill percentage than usual to further enhance mechanical stability.