⬢Insert LM8UU linear bearing into the printed parts (X-end-motor and X-end-idler) as shown in the pictures.
⬢The bearing should be in line with the X-ends as highlighted in the picture.
You can press on the flat surface for easier insertion.
Place two bearings in a way that the inner balls of the second bearing are rotated 45° compared to the first. This way you will achieve greater contact with the smooth rod. See third picture for more details.