Quote Originally Posted by m_c View Post
If the machine is using this design - http://www.mycncuk.com/threads/10118...2769#post82769 I'd say it'll be putting quite a lot of leverage on the rails through cutting forces.
Looking at the diagrams, it must be verging on a 2:1 leverage between the lower trucks and the upper trucks, which I'd guess will be pushing 15mm rail to their limits.
However I'd probably look at doubling up the 15mm rails, rather upsizing given the design.
If I remember right there are 3 rails on this Y-axis design with 2 bearings on each rail so I wouldn't expect them to wear out the rails in just over 3yrs. Even the bearings should last that long and they would wear long before the rails.? . . . But you could be right because the Z-axis is a long lever.?.

Matt which rail is worn out and how many does it use.? . . . Also how many hours does the machine have on it.? (mach3 will tell total operating time)