Short version: How fast are you setting speed/acceleration on the c-beam with the 8mm leadscrew, particularly the 500mm or longer ones?
Long version: I just put a 250mm across the top of a 500mm, and turned my lathe into CNC.
Unplugged, turning the lead screws by hand there is no end-play and it is smooth.
Powered it up with LinuxCNC , and if I set acceleration to any setting faster than "arthritic turtle" both axes sound terrible and on the 500mm length the 8mm lead screw starts whipping...
C-Beam w/8mm lead screw - how fast are you going?
Long version: I just put a 250mm across the top of a 500mm, and turned my lathe into CNC.
Unplugged, turning the lead screws by hand there is no end-play and it is smooth.
Powered it up with LinuxCNC , and if I set acceleration to any setting faster than "arthritic turtle" both axes sound terrible and on the 500mm length the 8mm lead screw starts whipping...
C-Beam w/8mm lead screw - how fast are you going?