Something that can be done with screw drives is put them under slight tension. Attach angular contact ball bearings to both ends of the screw in such a way they cannot slip, then make the mounts so they will put a bit of a pull on the screw. Not enough to distort the threads.
The slight tension keeps the screw from bending and whipping at high RPM. It should also twist less when there's rapid accelerations or rotation reversals. A smaller diameter screw can be used because the tension helps support it against sagging under its own weight. Not that a 24 inch long screw is going to whip or sag much. A benefit that a short screw will have with tension is zero lash from end play because it won't have any end play. On Monday, December 25, 2023 at 05:06:20 PM MST, Linden via Emc-users <emc-users@lists.sourceforge.net> wrote: Hello All, In the early stages of converting a 13 x 24 inch manual Chinese lathe to run with Linux CNC. I have 2 questions regarding replacing the Z axis lead screw with a 3205 ball screw: What I am thinking is mounting the fixed end in a pillow block at the head stock end of the lathe and the floating end in a second pillow block at the tail stock end of the bed. The question I have is there any reason I shouldn't drive the ball screw from the floating end? My logic for driving at the floating (tali stock) end is 1 I have more room for belt reduction at this end and 2 with the fixed end of the ball screw at the head stock end is that the ball screw will be in tension when it is pulling the carriage toward the head stock during cutting and less likely to flex or bend. The second question I have is what would be a realistic cutting speed range for the ball screw in RPM? The servo motor I am using has a top speed of 3000rpm and I am trying to figure out reduction ratio that is realistic. Thanks in advance for any help or suggestions. _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
