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

thingiverse

Modified X End Idler plastic part for the Prusa i3 MK3 to fix the common problem of the X belt twisting and rubbing. The original part (both initial and improved R2 marked version) provides too little support for the belt roller axle screw which, as a consequence, is getting pulled askew by belt tension. This part completely fixed 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 https://github.com/prusa3d/Original-Prusa-i3/blob/MK3/Printed-Parts/stl/x-end-idler.stl Modifications: -> Axle screw head bore reduced from 6 to 5.6 mm (for press fit). -> Axle screw shaft bore reduced from 3.1 to 3.0 mm (for press fit). -> Axle screw head bore chamfer removed (for increasing surface area supporting screw head). -> Axle screw head support protrusion raised by 1 mm (for increasing surface area supporting screw shaft). This reduces the clearance between screw head and Z lead screw to about 0.5 mm (see photo), make sure that there's no collision. As weight is not critical here, you might want to use a higher than usual infill percentage to further improve mechanical stability.