Ender3 (pro) X belt aligner

thingiverse

The printers in the Ender3 series have a slightly bad design on the X belt. It might have become a bit better on newer iterations, but according to the images I've seen it's still there. The belt is not aligned with the X movement. This result in varying tension in the belt, and non-linear x-coordinates. It's not a big deal in many cases, but when printing things with pressure fit, then it can be a deal breaker. The leftmost 50 mm of the bed will be stretched a few tenths of a mm. This simple model will push the belt up, so it's aligned with the stepper motor pulley. When mounting it, loosen the belt, hook in the aligner on the left side, and snap in the right side. There's some play in Y direction, jiggle it so you feel that it isn't in contact with the V-slot. Then tension the belt again. There's not as big problem on the right side. Partly since the hotend is mounted asymmetrically, and the carrier doesn't come as close to the right side pulley. But most importantly, it's possible to adjust the pulley on the right side up and down (at least for early models without fancy tensioning). If the right pulley is adjusted to be in the lowest position, the right part of the belt will be well aligned. It will also be in a position where it's easy to “play it” to check tension.