Waste of time on something like a router. You fit double thrusts on both ends, adjust to get a preload, and all that happens is the end frames deflect inwards so the screw is still whipping even with double bearings.

The design has to take this into account.
Bystronics have realised this on their new range of lasers, they have massive end castings and tension the ball screw to something like 70 tonnes tension [ no typo ] to stop it whipping.

Mind you they are using twin drives with 15 HP servo motors on each drive :whistling:

I feel the OP needs to sit down, count his pennies then come up with something that's workable instead of throwing down pie in the sky figures for his first build.

Why the insane rapids anyway ? The whole idea is to bury the tool and work at feed rate.

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