At above picture we can see that at left and right of screw rod haven’t same distance. Left side 17 cm, right 17,2 cm. The difference only 2mm but…..that is a problem. This 2mm will make the Y axis moving with not stable and doing zig zag.
Since i haven’t sophisticated machines, i’m only have a small bench drill, so i’ using calibration ring. This ring have 4 screws at 4 sides ( up, bottom, left and right ). with this parts, we can adjust the linear motion guard with same distance.