I'm sure I'm not the only one that has given thought to using hydraulics to move the axis on a cnc machine. there are numerous advantages to using a hydraulic cylinder to move the table on a mill as opposed to ball screws. zero backlash, virtually no wear, as fast or slow and as strong as needed. the problem is in getting perfect control.
And price ,, geez hydraulic cylinders are cheap compared to good ballscrews.
on the disadvantage side , a hydraulic pump would need to be running at all times regardless of motion.
I've given some thought to this (about as far as i've got so far) using a stepper or servo to control a spool valve and using glass dro scales to pinpoint actual location of the axis.
Seems doable and by using the glass scale as a reference the axis could be in exact position instead of an assumed position simply because the screw turned x rotations.
wear will always dictate the amount of error on a ball screw machine using an encoder on the drive motor to tell the motor where it should be ,, not so with hydraulics and glass scales . the machine will go to where the glass scales tell it to.
anybody out there with any new thinking novel ideas about how we can control such a system??