Quote Originally Posted by Desertboy View Post
When you start worrying too much about rigidity in the printer then you need to ditch the shit 8mm smooth rod lol and go hiwin route. But for home printer stupid overkill.
Understanding the engineering and physics involved will show the elegance of the Prusa design, this is that the 8mm unsupported rods are not loaded dynamically the way they would be in a router or mill, the carriage acceleration loads are transferred by the drive belts, motors and motor mounts to the frame with the rails simply supporting carriage weight.
Failure to understand this might lead to over engineering the rails and under engineering the frame when it is the frame which supplies the required rigidity for this style of machine, if you sensibly move to a tube feed system with the reel off the machine the only significant loads experienced by the 6mm Aluminium plate upper frame are in the + & - X travel directions where a planar frame performs extremely well indeed.

- Nick