@Kachnik, thanks i did lower the acceleration speed and the lines are much more smoother. As you can see in the picture.
@berainlb, @dean448, @LaserCuttingPro i have tried to tighten or loosening the belts. I also lowered the acceleration speed but none of them did work. As you can see i can engrave “perfect” straight lines and the five boxes next to each other looks fine, but when i add one box on top of another the dimensions are off.
boxes.lbrn2 (8.7 KB)